U.S. patent application number 11/117701 was filed with the patent office on 2006-04-20 for multi-component particles comprising inorganic nanoparticles distributed in an organic matrix and processes for making and using same.
This patent application is currently assigned to Cabot Corporation. Invention is credited to David Dericotte, Mark J. Hampden-Smith, Ned Jay Hardman, Scott Thomas Haubrich, Toivo T. Kodas, Ralph E. Kornbrekke, Klaus Kunze, Aaron D. Stump, Karel Vanheusden, Heng YU.
Application Number | 20060083694 11/117701 |
Document ID | / |
Family ID | 36180992 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060083694 |
Kind Code |
A1 |
Kodas; Toivo T. ; et
al. |
April 20, 2006 |
Multi-component particles comprising inorganic nanoparticles
distributed in an organic matrix and processes for making and using
same
Abstract
Multi-component particles comprising inorganic nanoparticles
distributed in an organic matrix and processes for making and using
same. A flowing aerosol is generated that includes droplets of a
precursor medium dispersed in a gas phase. The precursor medium
contains a liquid vehicle and at least one precursor. At least a
portion of the liquid vehicle is removed from the droplets of
precursor medium under conditions effective to convert the
precursor to the nanoparticles or the matrix and form the
multi-component particles.
Inventors: |
Kodas; Toivo T.;
(Albuquerque, NM) ; Hampden-Smith; Mark J.;
(Albuquerque, NM) ; Haubrich; Scott Thomas;
(Albuquerque, NM) ; YU; Heng; (Albuquerque,
NM) ; Hardman; Ned Jay; (Albuquerque, NM) ;
Kornbrekke; Ralph E.; (Albuquerque, NM) ; Stump;
Aaron D.; (Albuquerque, NM) ; Kunze; Klaus;
(Albuquerque, NM) ; Dericotte; David;
(Albuquerque, NM) ; Vanheusden; Karel; (Placitas,
NM) |
Correspondence
Address: |
CABOT CORPORATION;c/o Jaimes Sher, Esq.
5401 Venice Avenue, NE
Albuquerque
NM
87113
US
|
Assignee: |
Cabot Corporation
Boston
MA
|
Family ID: |
36180992 |
Appl. No.: |
11/117701 |
Filed: |
April 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60599847 |
Aug 7, 2004 |
|
|
|
Current U.S.
Class: |
424/46 ; 424/490;
977/915 |
Current CPC
Class: |
B01J 13/0043 20130101;
C08J 3/203 20130101; C08J 2339/06 20130101; B01J 13/0095
20130101 |
Class at
Publication: |
424/046 ;
424/490; 977/915 |
International
Class: |
A61K 9/14 20060101
A61K009/14; A61K 9/50 20060101 A61K009/50 |
Claims
1. A plurality of multi-component particles, each particle
comprising: a plurality of inorganic nanoparticles distributed in
an organic matrix, wherein the plurality of multi-component
particles has a d50 particle diameter, based on volume, of greater
than about 0.1 .mu.m and less than about 150 .mu.m.
2. The particles of claim 1, wherein the plurality of
multi-component particles are substantially spherical.
3. The particles of claim 1, wherein the plurality of
multi-component particles has a d50 particle diameter, based on
volume, of greater than about 0.5 .mu.m and less than about 25
.mu.m.
4. The particles of claim 1, wherein the nanoparticles have a
number average particle diameter of from about 10 nm to about 150
nm.
5. The particles of claim 1, wherein a majority of the
multi-component particles have a morphology that is hollow, rod,
flake or platelet.
6. The particles of claim 1, wherein a majority of the inorganic
nanoparticles have a morphology that is spherical, hollow, rod,
flake, platelet, cubed or trigonal.
7. The particles of claim 1, wherein the inorganic nanoparticles
comprise one or more of silver, copper, nickel, platinum,
palladium, rhodium, ruthenium, cobalt, gold, iridium, or a metal
oxide thereof.
8. The particles of claim 1, wherein the organic matrix comprises
one or more of a polycyclic polymer, an organic polymer, an organic
salt, an organic compound, or a bioactive compound.
9. The particles of claim 1, wherein the organic matrix comprises
polyvinylpyrrolidone.
10. The particles of claim 9, wherein the inorganic nanoparticles
comprise silver.
11. The particles of claim 1, wherein an additive is distributed
within the organic matrix, the additive comprising one or more of a
surfactant, a reducing agent, a fluxing agent, an adhesion promoter
or a hardening agent.
12. The particles of claim 1, wherein the matrix comprises a first
matrix material and a second matrix material, the first matrix
material being selectively removable from the multi-component
particles relative to the second matrix material.
13. The particles of claim 1, wherein the organic matrix has a
glass transition temperature of from about 30.degree. C. to about
400.degree. C.
14. The particles of claim 1, wherein the organic matrix has a
melting point of from about 30.degree. C. to about 600.degree.
C.
15. The particles of claim 1, wherein the organic matrix has a
molecular weight of from about 50 to about 1,000,000.
16. The particles of claim 1, wherein the nanoparticles are
dispersable in a liquid medium to form dispersed nanoparticles
having from about 1 to about 10 monolayers disposed thereon,
wherein the monolayers are formed from the organic matrix.
17. The particles of claim 1, wherein the nanoparticles are
dispersable in a liquid medium to form a dispersion having a
surface tension greater than 5 dynes/cm and a viscosity greater
than about 1 centipoise.
18. The particles of claim 1, wherein the multi-component particles
have a multi-modal particle size distribution.
19. The particles of claim 1, wherein each multi-component particle
comprises at least two types of inorganic nanoparticles having
different compositions distributed in the matrix.
20. The particles of claim 1, wherein the nanoparticles are coated
with a surface modifying agent.
21. The particles of claim 1, wherein the organic matrix comprises
a surface-modifying material, and wherein the nanoparticles are
dispersable to form a dispersion of nanoparticles comprising
dispersed nanoparticles, wherein at least a portion of the
surface-modifying material being disposed on and modifying a
surface of the dispersed inorganic nanoparticles.
22. The particles of claim 1, wherein the nanoparticles have a d40
particle diameter, based on volume, and a d60 particle diameter,
and wherein the difference between the d60 particle diameter and
the d40 particle diameter is from about 5 nm to about 50 nm.
23. The particles of claim 1, wherein the multi-component particles
have a d40 particle diameter, based on volume, and a d60 particle
diameter, and wherein the difference between the d60 particle
diameter and the d40 particle diameter is from about 1 .mu.m to
about 80 .mu.m.
24. The particles of claim 1, wherein the average distance between
adjacent inorganic nanoparticles is less than the number average
particle diameter of the inorganic nanoparticles.
25. The particles of claim 1, wherein the average distance between
adjacent inorganic nanoparticles is less than half the number
average particle diameter of the inorganic nanoparticles.
26. The particles of claim 1, wherein the average distance between
adjacent inorganic nanoparticles is less than about 10 nm.
27. The particles of claim 1, wherein the average distance between
adjacent inorganic nanoparticles is greater than the number average
particle diameter of the inorganic nanoparticles.
28. The particles of claim 1, wherein the average distance between
adjacent inorganic nanoparticles is greater than twice the number
average particle diameter of the inorganic nanoparticles.
29. A multi-component particle, comprising: a plurality of
inorganic nanoparticles distributed in an organic matrix, wherein
the multi-component particle has a particle diameter of greater
than about 0.1 .mu.m and less than about 100 .mu.m.
30. The particle of claim 29, wherein the multi-component particle
is substantially spherical.
31. The particle of claim 29, wherein the multi-component particle
has a particle diameter of greater than about 0.5 .mu.m and less
than about 25 .mu.m.
32. The particle of claim 29, wherein the nanoparticles have a
number average particle diameter of from about 10 nm to about 150
nm.
33. The particle of claim 29, wherein the multi-component particle
has a morphology that is hollow, rod, flake or platelet.
34. The particle of claim 29, wherein a majority of the inorganic
nanoparticles have a morphology that is spherical, hollow, rod,
flake, platelet, cubed or trigonal.
35. The particle of claim 29, wherein the inorganic nanoparticles
comprise one or more of silver, copper, nickel, platinum,
palladium, rhodium, ruthenium, cobalt, gold, iridium, or a metal
oxide thereof.
36. The particle of claim 29, wherein the organic matrix comprises
one or more of a polycyclic polymer, an organic polymer, an organic
salt, an organic compound, or a bioactive compound.
37. The particle of claim 29, wherein the organic matrix comprises
polyvinylpyrrolidone.
38. The particle of claim 37, wherein the inorganic nanoparticles
comprise silver.
39. The particle of claim 29, wherein an additive is distributed
within the organic matrix, the additive comprising one or more of a
surfactant, a reducing agent, a fluxing agent, an adhesion promoter
or a hardening agent.
40. The particle of claim 29, wherein the matrix comprises a first
matrix material and a second matrix material, the first matrix
material being selectively removable from the multi-component
particles relative to the second matrix material.
41. The particle of claim 29, wherein the organic matrix has a
glass transition temperature of from about 30.degree. C. to about
400.degree. C.
42. The particle of claim 29, wherein the organic matrix has a
melting point of from about 30.degree. C. to about 600.degree.
C.
43. The particle of claim 29, wherein the organic matrix has a
molecular weight of from about 50 to about 1,000,000.
44. The particle of claim 29, wherein the nanoparticles are
dispersable in a liquid medium to form dispersed nanoparticles
having from about 1 to about 10 monolayers disposed thereon,
wherein the monolayers are formed from the organic matrix.
45. The particle of claim 29, wherein the nanoparticles are
dispersable in a liquid medium to form a dispersion having a
surface tension greater than about 5 dynes/cm and a viscosity
greater than about 1 centipoise.
46. The particle of claim 29, wherein the multi-component particle
comprises at least two types of inorganic nanoparticles having
different compositions distributed in the matrix.
47. The particle of claim 29, wherein the nanoparticles are coated
with a surface modifying agent.
48. The particle of claim 29, wherein the organic matrix comprises
a surface-modifying material, and wherein the nanoparticles are
dispersable to form a dispersion of nanoparticles comprising
dispersed nanoparticles, wherein at least a portion of the
surface-modifying material is disposed on and modifies a surface of
the dispersed inorganic nanoparticles.
49. The particle of claim 29, wherein the nanoparticles have a d40
particle diameter, based on volume, and a d60 particle diameter,
and wherein the difference between the d60 particle diameter and
the d40 particle diameter is from about 5 nm to about 50 nm.
50. The particle of claim 29, wherein the average distance between
adjacent inorganic nanoparticles is less than the number average
particle diameter of the inorganic nanoparticles.
51. The particle of claim 29, wherein the average distance between
adjacent inorganic nanoparticles is less than half the number
average particle diameter of the inorganic nanoparticles.
52. The particle of claim 29, wherein the average distance between
adjacent inorganic nanoparticles is less than about 10 nm.
53. The particle of claim 29, wherein the average distance between
adjacent inorganic nanoparticles is greater than the number average
particle diameter of the inorganic nanoparticles.
54. The particle of claim 29, wherein the average distance between
adjacent inorganic nanoparticles is greater than twice the number
average particle diameter of the inorganic nanoparticles.
55. A process for making multi-component particles comprising
inorganic nanoparticles distributed in an organic matrix, the
process comprising the steps of: (a) generating an aerosol
comprising droplets, wherein the droplets comprise a liquid
vehicle, an inorganic nanoparticle precursor and an organic matrix
precursor; and (b) removing at least a portion of the liquid
vehicle from the droplets under conditions effective to convert at
least a portion of the organic matrix precursor to the organic
matrix and to convert at least a portion of the inorganic
nanoparticle precursor to the inorganic nanoparticles distributed
in the organic matrix.
56. The process of claim 55, wherein step (b) comprises heating the
droplets to a maximum temperature of from about 50.degree. C. to
about 800.degree. C. for a period of time of at least 1 second.
57. The process of claim 55, wherein the droplets further comprise
a reducing agent and wherein step (b) comprises reacting the
reducing agent with the inorganic nanoparticle precursor to form
the inorganic nanoparticles.
58. The process of claim 55, wherein the liquid vehicle is a
reducing agent and wherein step (b) comprises reacting the liquid
vehicle with the inorganic nanoparticle precursor to form the
inorganic nanoparticles.
59. The process of claim 55, wherein the aerosol comprises the
droplets distributed in a gas phase, the gas phase comprising a
reducing agent, and wherein step (b) comprises reacting the
reducing agent with the inorganic nanoparticle precursor to form
the inorganic nanoparticles.
60. The process of claim 55, wherein the aerosol comprises
droplets, the droplets comprising the inorganic nanoparticle
precursor and/or a reducing agent.
61. The process of claim 55, wherein the process further comprises
the step of: (c) collecting the multi-component particles in a
liquid medium.
62. The process of claim 61, wherein the process further comprises
the step of: (d) quenching the multi-component particles within
about 0.001 seconds of step (c).
63. The process of claim 55, wherein the process further comprises
the step of: (c) contacting the multi-component particles with a
liquid medium to release the nanoparticles from the matrix and form
a colloidal solution.
64. The process of claim 63, wherein the process further comprises
the step of: (d) surface-modifying the inorganic nanoparticles with
a surface-modifying agent during or after step (c).
65. The process of claim 55, wherein the multi-component particles
have a d50 particle diameter, based on volume, of greater than
about 0.1 .mu.m and less than about 150 .mu.m.
66. The process of claim 55, wherein the multi-component particles
have a d50 particle diameter, based on volume, of greater than
about 0.5 .mu.m and less than about 25 .mu.m.
67. The process of claim 55, wherein the nanoparticles have a
number average particle diameter of from about 10 nm to about 150
nm.
68. The process of claim 55, wherein a majority of the
multi-component particles have a morphology that is spherical,
hollow, rod, flake or platelet.
69. The process of claim 55, wherein a majority of the
nanoparticles have a morphology that is spherical, hollow, rod,
flake, platelet, cubed or trigonal.
70. The process of claim 55, wherein the inorganic nanoparticles
comprise one or more of silver, copper, nickel, platinum,
palladium, rhodium, ruthenium, cobalt, gold, iridium or a metal
oxide thereof.
71. The process of claim 55, wherein the organic matrix comprises
one or more of a polycyclic polymer, an organic polymer, an organic
salt, an organic compound, or a bioactive compound.
72. The process of claim 55, wherein the organic matrix comprises
polyvinylpyrrolidone.
73. The process of claim 72, wherein the inorganic nanoparticles
comprise silver.
74. The process of claim 55, wherein an additive is distributed
within the organic matrix, the additive comprising one or more of a
surfactant, a reducing agent, a fluxing agent, an adhesion promoter
or a hardening agent.
75. The process of claim 55, wherein the matrix comprises a first
matrix material and a second matrix material, the first matrix
material being selectively removable from the multi-component
particles relative to the second matrix material.
76. The process of claim 55, wherein the organic matrix has a glass
transition temperature of from about 30.degree. C. to about
400.degree. C.
77. The process of claim 55, wherein the organic matrix has a
melting point of from about 30.degree. C. to about 600.degree.
C.
78. The process of claim 55, wherein the organic matrix has a
molecular weight of from about 50 to about 1,000,000.
79. The process of claim 55, wherein the nanoparticles are
dispersable in a liquid medium to form dispersed nanoparticles
having from about 1 to about 10 monolayers disposed thereon,
wherein the monolayers are formed from the organic matrix.
80. The process of claim 55, wherein the nanoparticles are
dispersable in a liquid medium to form a dispersion having a
surface tension greater than about 5 dynes/cm and a viscosity
greater than about 1 centipoise.
81. The process of claim 55, wherein the multi-component particles
have a multi-modal particle size distribution.
82. The process of claim 55, wherein each multi-component particle
comprises at least two types of inorganic nanoparticles having
different compositions distributed in the matrix.
83. The process of claim 55, wherein nanoparticles are coated with
a surface modifying agent.
84. The process of claim 55, wherein the organic matrix comprises a
surface-modifying material, and wherein the nanoparticles are
dispersable to form a dispersion of nanoparticles comprising
dispersed nanoparticles, wherein at least a portion of the
surface-modifying material is disposed on and modifying a surface
of the dispersed inorganic nanoparticles.
85. The process of claim 55, wherein the nanoparticles have a d40
particle diameter, based on volume, and a d60 particle diameter,
and wherein the difference between the d60 particle diameter and
the d40 particle diameter is from about 5 nm to about 50 nm.
86. The process of claim 55, wherein the multi-component particles
have a d40 particle diameter, based on volume, and a d60 particle
diameter, and wherein the difference between the d60 particle
diameter and the d40 particle diameter is from about 1 .mu.m to
about 80 .mu.m.
87. The process of claim 55, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is less than the number average particle diameter of the inorganic
nanoparticles.
88. The process of claim 55, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is less than half the number average particle diameter of the
inorganic nanoparticles.
89. The process of claim 55, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is less than about 10 nm.
90. The process of claim 55, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is greater than the number average particle diameter of the
inorganic nanoparticles.
91. The process of claim 55, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is greater than twice the number average particle diameter of the
inorganic nanoparticles.
92. A process for making multi-component particles comprising
inorganic nanoparticles dispersed in an organic matrix, the process
comprising the steps of: (a) generating an aerosol comprising
droplets dispersed in a gas phase, wherein the droplets comprise a
liquid vehicle, the inorganic nanoparticles and an organic matrix
precursor; and (b) removing at least a portion of the liquid
vehicle from the droplets under conditions effective to convert at
least a portion of the organic matrix precursor to the organic
matrix and to disperse the nanoparticles within the matrix.
93. The process of claim 92, wherein step (b) comprises heating the
droplets to a maximum temperature of from about 50.degree. C. to
about 800.degree. C. for a period of time of at least 1 second.
94. The process of claim 92, wherein the droplets further comprise
a reducing agent and wherein step (b) comprises reacting the
reducing agent with the organic matrix precursor to form the
matrix.
95. The process of claim 92, wherein the liquid vehicle is a
reducing agent and wherein step (b) comprises reacting the liquid
vehicle with the organic matrix precursor to form the matrix.
96. The process of claim 92, wherein the aerosol comprises the
droplets distributed in a gas phase, the gas phase comprising a
reducing agent, and wherein step (b) comprises reacting the
reducing agent with the organic matrix precursor to form the
matrix.
97. The process of claim 92, wherein the process further comprises
the step of: (c) collecting the multi-component particles in a
liquid medium.
98. The process of claim 97, wherein the process further comprises
the step of: (d) quenching the multi-component particles within
about 0.001 seconds of step (c).
99. The process of claim 92, wherein the process further comprises
the step of: (c) contacting the multi-component particles with a
liquid medium to release the nanoparticles from the matrix and form
a colloidal solution.
100. The process of claim 99, wherein the process further comprises
the step of: (d) surface-modifying the inorganic nanoparticles with
a surface-modifying agent during or after step (c).
101. The process of claim 92, wherein the multi-component particles
have a d50 particle diameter, based on volume, of greater than
about 0.1 .mu.m and less than about 100 .mu.m.
102. The process of claim 92, wherein the multi-component particles
have a d50 particle diameter, based on volume, of greater than
about 0.5 .mu.m and less than about 25 .mu.m.
103. The process of claim 92, wherein the nanoparticles have a
number average particle diameter of from about 10 nm to about 150
nm.
104. The process of claim 92, wherein a majority of the
multi-component particles have a morphology that is spherical,
hollow, rod, flake or platelet.
105. The process of claim 92, wherein a majority of the
nanoparticles have a morphology that is spherical, hollow, rod,
flake, platelet, cubed or trigonal.
106. The process of claim 92, wherein the inorganic nanoparticles
comprise one or more of silver, copper, nickel, platinum,
palladium, rhodium, ruthenium, cobalt, gold, iridium or a metal
oxide thereof.
107. The process of claim 92, wherein the organic matrix comprises
one or more of a polycyclic polymer, an organic polymer, an organic
salt, an organic compound, or a bioactive compound.
108. The process of claim 92, wherein the organic matrix comprises
polyvinylpyrrolidone.
109. The process of claim 108, wherein the inorganic nanoparticles
comprise silver.
110. The process of claim 92, wherein an additive is distributed
within the organic matrix, the additive comprising one or more of a
surfactant, a reducing agent, a fluxing agent, an adhesion promoter
or a hardening agent.
111. The process of claim 92, wherein the matrix comprises a first
matrix material and a second matrix material, the first matrix
material being selectively removable from the multi-component
particles relative to the second matrix material.
112. The process of claim 92, wherein the organic matrix has a
glass transition temperature of from about 30.degree. C. to about
400.degree. C.
113. The process of claim 92, wherein the organic matrix has a
melting point of from about 30.degree. C. to about 600.degree.
C.
114. The process of claim 92, wherein the organic matrix has a
molecular weight of from about 50 to about 1,000,000.
115. The process of claim 92, wherein the nanoparticles are
dispersable in a liquid medium to form dispersed nanoparticles
having from about 1 to about 10 monolayers disposed thereon,
wherein the monolayers are formed from the organic matrix.
116. The process of claim 92, wherein the nanoparticles are
dispersable in a liquid medium to form a dispersion having a
surface tension greater than about 5 dynes/cm and a viscosity
greater than about 1 centipoise.
117. The process of claim 92, wherein the multi-component particles
have a multi-modal particle size distribution.
118. The process of claim 92, wherein each multi-component particle
comprises at least two types of inorganic nanoparticles having
different compositions distributed in the matrix.
119. The process of claim 92, wherein the nanoparticles are coated
with a surface modifying agent.
120. The process of claim 92, wherein the organic matrix comprises
a surface-modifying material, and wherein the nanoparticles are
dispersable to form a dispersion of nanoparticles comprising
dispersed nanoparticles, wherein at least a portion of the
surface-modifying material is disposed on and modifies a surface of
the dispersed inorganic nanoparticles.
121. The process of claim 92, wherein the nanoparticles have a d40
particle diameter, based on volume, and a d60 particle diameter,
and wherein the difference between the d60 particle diameter and
the d40 particle diameter is from about 5 nm to about 50 nm.
122. The process of claim 92, wherein the multi-component particles
have a d40 particle diameter, based on volume, and a d60 particle
diameter, and wherein the difference between the d60 particle
diameter and the d40 particle diameter is from about 1 .mu.m to
about 80 .mu.m.
123. The process of claim 92, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is less than the number average particle diameter of the inorganic
nanoparticles.
124. The process of claim 92, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is less than half the number average particle diameter of the
inorganic nanoparticles.
125. The process of claim 92, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is less than about 10 nm.
126. The process of claim 92, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is greater than the number average particle diameter of the
inorganic nanoparticles.
127. The process of claim 92, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
is greater than twice the number average particle diameter of the
inorganic nanoparticles.
128. A process for making multi-component particles comprising
inorganic nanoparticles dispersed in an organic matrix, the process
comprising the steps of: (a) generating an aerosol comprising
droplets dispersed in a gas phase, wherein the droplets comprise a
liquid vehicle, an inorganic nanoparticle precursor and an organic
matrix precursor; (b) removing at least a portion of the liquid
vehicle from the droplets; (c) converting the organic matrix
precursor to the organic matrix; and (d) converting the inorganic
nanoparticle precursor to the inorganic nanoparticles distributed
within the matrix.
129. The process of claim 128, wherein steps (b), (c) and (d) occur
simultaneously.
130. The process of claim 128, wherein step (b) occurs, at least in
part, before steps (c) and (d).
131. The process of claim 128, wherein step (c) occurs, at least in
part, before step (d).
132. The process of claim 128, wherein step (d) occurs, at least in
part, before step (c).
133. A process for forming a dispersion, the process comprising the
steps of: (a) providing a plurality of multi-component particles,
each multi-component particle comprising a plurality of inorganic
nanoparticles distributed in an organic matrix, wherein the
plurality of multi-component particles has a d50 particle diameter,
by volume, of greater than about 0.1 .mu.m and less than about 150
.mu.m; and (b) contacting the plurality of multi-component
particles with a liquid medium under conditions effective to
disperse the inorganic nanoparticles from the matrix and form the
dispersion.
134. The process of claim 133, wherein the dispersion is ink
jettable.
135. The process of claim 133, wherein the dispersion comprises a
colloidal solution.
136. The process of claim 133, wherein the process further
comprises the step of: (c) surface-modifying the inorganic
nanoparticles with a surface-modifying agent during or after step
(b).
137. The process of claim 133, wherein the multi-component
particles provided in step (a) have a d50 particle diameter, by
volume, of greater than about 0.5 .mu.m and less than about 25
.mu.m.
138. The process of claim 133, wherein the nanoparticles have
number average particle diameter of from about 10 nm to about 150
nm.
139. The process of claim 133, wherein a majority of the
multi-component particles provided in step (a) have a morphology
that is spherical, hollow, rod, flake or platelet.
140. The process of claim 133, wherein a majority of the
nanoparticles have a morphology that is spherical, hollow, rod,
flake, platelet, cubed or trigonal.
141. The process of claim 133, wherein the inorganic nanoparticles
comprise one or more of silver, copper, nickel, platinum,
palladium, rhodium, ruthenium, cobalt, gold, iridium or a metal
oxide thereof.
142. The process of claim 133, wherein the organic matrix comprises
one or more of a polycyclic polymer, an organic polymer, an organic
salt, an organic compound, or a bioactive compound.
143. The process of claim 133, wherein the organic matrix comprises
polyvinylpyrrolidone.
144. The process of claim 143, wherein the inorganic nanoparticles
comprise silver.
145. The process of claim 133, wherein an additive is distributed
within the organic matrix, the additive comprising one or more of a
surfactant, a reducing agent, a fluxing agent, an adhesion promoter
or a hardening agent.
146. The process of claim 133, wherein the matrix comprises a first
matrix material and a second matrix material, the first matrix
material being selectively removable from the multi-component
particles relative to the second matrix material.
147. The process of claim 133, wherein the organic matrix has a
glass transition temperature of from about 30.degree. C. to about
400.degree. C.
148. The process of claim 133, wherein the organic matrix has a
melting point of from about 30.degree. C. to about 600.degree.
C.
149. The process of claim 133, wherein the organic matrix has a
molecular weight of from about 50 to about 1,000,000.
150. The process of claim 133, wherein the dispersed nanoparticles
have from about 1 to about 10 monolayers disposed thereon, the
monolayers being formed from the organic matrix.
151. The process of claim 133, wherein the dispersion has a surface
tension greater than about 5 dynes/cm and a viscosity greater than
about 1 centipoise.
152. The process of claim 133, wherein the multi-component
particles provided in step (a) have a multi-modal particle size
distribution.
153. The process of claim 133, wherein the multi-component
particles provided in step (a) comprises at least two types of
inorganic nanoparticles having different compositions distributed
in the matrix.
154. The process of claim 133, wherein the nanoparticles are coated
with a surface modifying agent.
155. The process of claim 133, wherein the organic matrix comprises
a surface-modifying material, and wherein at least a portion of the
surface-modifying material is disposed on and modifies a surface of
the dispersed inorganic nanoparticles.
156. The process of claim 133, wherein the nanoparticles have a d40
particle diameter, based on volume, and a d60 particle diameter,
and wherein the difference between the d60 particle diameter and
the d40 particle diameter is from about 5 nm to about 50 nm.
157. The process of claim 133, wherein the multi-component
particles provided in step (a) have a d40 particle diameter, based
on volume, and a d60 particle diameter, and wherein the difference
between the d60 particle diameter and the d40 particle diameter is
from about 1 .mu.m to about 80 .mu.m.
158. The process of claim 133, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
provided in step (a) is less than the number average particle
diameter of the inorganic nanoparticles.
159. The process of claim 133, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
provided in step (a) is less than half the number average particle
diameter of the inorganic nanoparticles.
160. The process of claim 133, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
provided in step (a) is less than about 10 nm.
161. The process of claim 133, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
provided in step (a) is greater than the number average particle
diameter of the inorganic nanoparticles.
162. The process of claim 133, wherein the average distance between
adjacent inorganic nanoparticles in the multi-component particles
provided in step (a) is greater than twice the number average
particle diameter of the inorganic nanoparticles.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Provisional Patent
Application Ser. No. 60/599,847, filed on Aug. 7, 2004, the
entirety of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to inorganic nanoparticles.
More particularly, the invention relates to multi-component
particles comprising inorganic nanoparticles distributed in an
organic matrix, and to processes for making and using such
multi-component particles.
BACKGROUND OF THE INVENTION
[0003] Nanoparticles, and processes for making nanoparticles, have
been the subject of recent interest and research because of the
advantages provided by nanoparticles over larger sized particulate
materials. One advantage of nanoparticles is they have a greater
surface area and surface energy, which is useful in a variety of
applications, including catalysis, electrocatalysis, absorbance,
chemical separations and bio-separation applications. Nanoparticles
are also useful in the formulation of inks, pastes and tapes that
are used in depositing thin or thick films, such as optically
transparent conductors for use in displays, magnetic coatings for
storage media and printed circuitry for electronic applications.
Inks and pastes with nanoparticles have improved rheology
characteristics (e.g., flowability), which allow thinner layers to
be applied and allow deposition of features with smaller
dimensions. Lighting applications also benefit from the properties
of nanoparticles; for example, semiconductor nanoparticles, in
addition to other uses, are useful because of their "quantum dot
effect," which allows the luminescent color of a semiconductor
nanoparticulate to be tailored according to the size of the
nanoparticulate. In addition to the examples above, nanoparticles
are being used, or considered for use, in many other applications
including pharmaceutical formulations, drug delivery applications,
medical diagnostic aids, abrasives, pigments, phosphors for
lighting, displays, security applications, dental glasses,
polymeric fillers, thermal interface materials and cosmetics.
[0004] As a result of the large number of applications for
nanoparticles, a variety of processes have been developed for
making and processing nanoparticles. One common problem faced by
these processes is the tendency of the nanoparticles to agglomerate
because of their high surface area and surface energy. Once the
nanoparticles have agglomerated, often they do not provide the same
advantages achieved when the individual nanoparticles are in a
dispersed state. Consequently, the tendency of nanoparticles to
agglomerate makes the forming, processing, handling, transporting
and use of nanoparticles difficult. Further, it is extremely
difficult to separate or redisperse agglomerated nanoparticles.
[0005] A wide variety of synthetic methods exist for producing
nanoparticles. Another common problem is to produce unagglomerated
nanoparticles at such scales as to meet commercial needs.
[0006] Thus, there is a need for additional processes for forming,
processing, handling, transporting, dispersing and using
nanoparticles and new nanoparticulate products that alleviate some
or all of these problems.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to multi-component
particles comprising inorganic nanoparticles distributed in an
organic matrix and to processes for making and using same. In one
embodiment, the invention is to a plurality of multi-component
particles, each particle comprising a plurality of inorganic
nanoparticles distributed in an organic matrix, wherein the
plurality of multi-component particles has a d50 particle diameter,
based on volume, of greater than about 0.1 .mu.m and less than
about 150 .mu.m. The multi-component particles preferably are
substantially spherical.
[0008] The inorganic nanoparticles optionally comprise one or more
of silver, copper, nickel, platinum, palladium, rhodium, ruthenium,
cobalt, gold, iridium, or a metal oxide thereof, and the organic
matrix optionally comprises one or more of a polycyclic polymer, an
organic polymer (e.g., polyvinylpyrrolidone (PVP)), an organic
salt, an organic compound, or a bioactive compound. An additive may
also be distributed within or form a portion of the organic matrix,
the additive comprising, for example, one or more of a surfactant,
a reducing agent, a fluxing agent, an adhesion promoter or a
hardening agent.
[0009] Desirably, the nanoparticles may be dispersable in a liquid
medium to form dispersed nanoparticles having from about 1 to about
10 monolayers disposed thereon, wherein the monolayers are formed
from the organic matrix. In one aspect, the dispersion has a
surface tension greater than 5 dynes/cm and a viscosity greater
than about 1 centipoise. In one aspect, the dispersion is ink
jettable.
[0010] In another embodiment, the invention is to an individual
multi-component particle, comprising a plurality of inorganic
nanoparticles distributed in an organic matrix, wherein the
multi-component particle has a particle size (e.g., diameter) of
greater than about 0.1 .mu.m and less than about 100 .mu.m.
[0011] In another embodiment, the invention is to a process for
making multi-component particles comprising inorganic nanoparticles
distributed in an organic matrix, the process comprising the steps
of: (a) generating an aerosol comprising droplets, wherein the
droplets comprise a liquid vehicle, an inorganic nanoparticle
precursor and an organic matrix precursor; and (b) removing at
least a portion of the liquid vehicle from the droplets under
conditions effective to convert at least a portion of the organic
matrix precursor to the organic matrix and to convert at least a
portion of the inorganic nanoparticle precursor to the inorganic
nanoparticles distributed in the organic matrix. In this aspect,
step (b) optionally comprises heating the droplets to a maximum
temperature of from about 50.degree. C. to about 800.degree. C. for
a period of time of at least 1 second.
[0012] Optionally, the process further comprises the step of: (c)
contacting the multi-component particles with a liquid medium to
release the nanoparticles from the matrix and form a colloidal
solution. Additionally, the process optionally further comprises
the step of: (d) surface-modifying the inorganic nanoparticles with
a surface-modifying agent during or after step (c).
[0013] In another embodiment, the invention is to a process for
making multi-component particles comprising inorganic nanoparticles
dispersed in an organic matrix, the process comprising the steps
of: (a) generating an aerosol comprising droplets dispersed in a
gas phase, wherein the droplets comprise a liquid vehicle, the
inorganic nanoparticles and an organic matrix precursor; and (b)
removing at least a portion of the liquid vehicle from the droplets
under conditions effective to convert at least a portion of the
organic matrix precursor to the organic matrix and to disperse the
nanoparticles within the matrix.
[0014] In another embodiment, the invention is to a process for
making multi-component particles comprising inorganic nanoparticles
dispersed in an organic matrix, the process comprising the steps
of: (a) generating an aerosol comprising droplets dispersed in a
gas phase, wherein the droplets comprise a liquid vehicle, an
inorganic nanoparticle precursor and an organic matrix precursor;
(b) removing at least a portion of the liquid vehicle from the
droplets; (c) converting the organic matrix precursor to the
organic matrix; and (d) converting the inorganic nanoparticle
precursor to the inorganic nanoparticles distributed within the
matrix. Steps (b), (c) and (d) optionally occur simultaneously. In
various aspects, step (b) occurs, at least in part, before steps
(c) and (d); step (c) occurs, at least in part, before step (d);
and/or step (d) occurs, at least in part, before step (c).
[0015] In another embodiment, the invention is to a process for
forming a dispersion, the process comprising the steps of: (a)
providing a plurality of multi-component particles, each
multi-component particle comprising a plurality of inorganic
nanoparticles distributed in an organic matrix, wherein the
plurality of multi-component particles has a d50 particle size
(e.g., diameter), by volume, of greater than about 0.1 .mu.m and
less than about 150 .mu.m; and (b) contacting the plurality of
multi-component particles with a liquid medium under conditions
effective to disperse the inorganic nanoparticles from the matrix
and form the dispersion, which preferably is ink jettable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The present invention will be better understood in view of
the following non-limiting figures, wherein:
[0017] FIG. 1 generally illustrates features of a multi-component
particle manufacturable using the process of the present
invention;
[0018] FIG. 2 shows one embodiment of a porous multi-component
particle manufacturable using the process of the present
invention;
[0019] FIG. 3 shows one embodiment of a multi-component particle
including two matrix materials that is manufacturable using the
process of the present invention;
[0020] FIG. 4 shows one embodiment of a multi-component particle
including two matrix materials that is manufacturable using the
process of the present invention;
[0021] FIG. 5 shows one embodiment of a multi-component particle
with an interconnected network of nanoparticles that is
manufacturable using the process of the present invention;
[0022] FIG. 6 shows one embodiment of a multi-component particle
with two nanoparticles that is manufacturable using the process of
the present invention; and
[0023] FIG. 7 shows one embodiment of a multi-component particle
with two nanoparticles that is manufacturable using the process of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
I. INTRODUCTION
[0024] The present invention is directed to multi-component
particles, each particle comprising a plurality of inorganic
nanoparticles, e.g., metallic, metal oxide or main group
nanoparticles, distributed in an organic matrix. The
multi-component particles preferably are "microparticles," defined
herein particles having a size smaller than about 500 .mu.m, e.g.,
in the range of from about 1 .mu.m to about 500 .mu.m. In contrast,
the term "nanoparticles" is defined herein to mean particles having
a size smaller than about 500 nm, e.g., in the range of from about
1 nm to about 500 nm. The invention is also directed to processes
for making and using the multi-component particles.
[0025] The processes for making the multi-component particles
according to one aspect of the present invention are highly
desirable in that they provide the ability to form inorganic
nanoparticles having highly desirable characteristics.
Specifically, the present invention provides a highly flexible
route for synthesizing inorganic nanoparticles, as compared to
standard wet chemical synthesis processes. This flexibility is
derived from the ability of the present processes to include
various components, e.g., surfactants, various polymers, and/or one
or more additives, within the organic matrix. The presence of these
components in the organic matrix provides the ability to synthesize
inorganic nanoparticles having unique characteristics and
properties (e.g., solubility in a variety of solvents, air or
moisture stability, dispersion stability, etc.), independent of the
actual synthesis conditions of the nanoparticles. In contrast,
during conventional wet chemical synthesis processes, one is highly
limited in the choice of surfactants, polymers and/or additives
that may be implemented in the synthesis process due to the fact
that the use of these compositions in wet chemical synthesis
processes will usually be involved in controlling the nanoparticle
growth to a much greater extent than in the processes of the
present invention.
II. COMPOSITION OF THE MULTI-COMPONENT PARTICLES
A. Overview
[0026] In one embodiment, the present invention is directed to a
multi-component particle, comprising a plurality of inorganic
nanoparticles distributed in an organic matrix, wherein the
multi-component particle has a particle size (e.g., diameter) of
greater than about 0.1 .mu.m and less than about 100 .mu.m, e.g.,
greater than about 0.5 .mu.m and less than about 25 .mu.m, based on
electron microscopy.
[0027] In a similar embodiment, the invention is to a plurality of
multi-component particles, each particle comprising a plurality of
inorganic nanoparticles distributed in an organic matrix. In this
embodiment, the plurality of multi-component particles has a number
average particle diameter of greater than about 0.1 .mu.m and less
than about 100 .mu.m, e.g., greater than about 0.5 .mu.m and less
than about 25 .mu.m, based on electron microscopy. The plurality of
multi-component particles has a d50 particle diameter, based on
volume, greater than about 0.1 .mu.m and less than 150 .mu.m, e.g.,
greater than about 0.5 .mu.m and less than 50 .mu.m or greater than
about 0.7 .mu.m and less than about 25 .mu.m, as determined by
light scattering techniques.
[0028] That is, the present invention, in one embodiment, is
directed to one or more multi-component particles. As used herein,
the term "multi-component particle" means a particle comprising at
least two distinct material components or phases. Specifically, the
multi-component particles comprise the inorganic nanoparticles that
include at least a first material phase and the organic matrix that
includes at least a second material phase that is different than
the first material phase. Such particles may be formed, for
example, by any of the processes of the present invention,
discussed below. It is also contemplated, however, that these
particles may be formed by other heretofore undiscovered
processes.
[0029] FIG. 1 generally illustrates one non-limiting example of a
multi-component particle according to the present invention.
Specifically, FIG. 1 shows a multi-component particle 108 generally
comprising distributed inorganic nanoparticles 110 and organic
matrix 112, with the distributed nanoparticles 110 maintained in a
distributed state within the particle 108 by matrix 112. The matrix
112 therefore functions to keep the nanoparticles 110, at least
partially and preferably completely, separated to inhibit or
prevent agglomeration or coalescense of the nanoparticles 110 after
final formation of the nanoparticles 110.
[0030] In the multi-component particles 108 of FIG. 1, the matrix
112 and the distributed nanoparticles 110 are of different
compositions, although they may have one or more components in
common. Also, although the nanoparticles 110 and the matrix 112 are
each shown including only a single material phase, the invention is
not so limited. The particles may include one or more of the
following features: nanoparticles each comprised of one or more
different material phases; one or more different compositions of
nanoparticles; and matrix comprising one or more different material
phases. Moreover, it is not necessary that the matrix or the
nanoparticles be comprised of only a single material phase, or that
any material phase of the matrix be a continuous phase. For
example, the matrix may be made of many different material phases
that together provide a structure for maintaining the nanoparticles
in a distributed state. Likewise, for example, multi-component
particles made according to the invention may include nanoparticles
of only a single type or may include two or more different
nanoparticles (e.g., nanoparticles of different compositions).
Also, for example, the composition of a nanoparticle may comprise
only a single material phase or may comprise two or more distinct
material phases. More specific examples of some possible matrix and
nanoparticulate features are provided below.
[0031] With reference to FIG. 1, the composition of the matrix 112
may be designed to be wholly or partially permanent for use in a
final application. Alternatively, the composition of the matrix 112
may be designed to function as a storage, handling or processing
aid, which is wholly or partially removable prior to final use of
the nanoparticles. The matrix may also serve some function, for
example in aiding the redispersion of the nanoparticles in a
liquid.
B. Composition and Properties of the Matrix
[0032] As noted previously, the multi-component particles of the
present invention include inorganic nanoparticles distributed in an
organic matrix. As used herein, the term "organic matrix" means a
composition comprising one or more organic compounds capable of
supporting the nanoparticles therewithin. By "organic compound" it
is meant a compound that comprises carbon other than elemental
carbon. In one embodiment, the organic matrix comprises one or more
organic compounds in an amount greater than about 50 weight
percent, e.g., greater than about 60 weight percent, greater than
about 70 weight percent, greater than about 80 weight percent or
greater than about 90 weight percent, based on the total weight of
the matrix. It is contemplated that the organic matrix, as a whole,
may also include one or more inorganic components (e.g., additives)
in addition to the one or more organic compounds. In one
non-limiting example, the organic matrix, as defined herein, may
comprise PVP (polyvinylpyrrolidone, an organic polymer) in an
amount less than 50 weight percent, and an organo-metallic additive
such as silver trifluoroacetate in an amount less than 50 weight
percent. Optionally, the organic matrix comprises one or more of a
polycyclic polymer, an organic polymer, an organic salt, an organic
compound, a bioactive compound, or PVP.
[0033] The glass transition temperature as well as the melting
point of the organic matrix can greatly affect the formation of the
nanoparticles within the matrix. Essentially, the properties of the
matrix may effect the growth rate, size morphology and the
distribution of the nanoparticles within the matrix. In one aspect
of the invention, the organic matrix has a glass transition
temperature of at least about 30.degree. C., e.g., from about
30.degree. C. to about 600.degree. C., from about 30.degree. C. to
about 400.degree. C., from about 40.degree. C. to about 250.degree.
C., or from about 100.degree. C. to about 200.degree. C. The
organic matrix also preferably has a melting point of greater than
about 30.degree. C., e.g., from about 30.degree. C. to about
600.degree. C., from about 100.degree. C. to about 350.degree. C.,
or from about 150.degree. C. to about 300.degree. C.
[0034] As indicated above, the organic matrix comprises an organic
compound or a combination of two or more organic compounds that
function to maintain the nanoparticles at least partially and
preferably completely separated in a distributed state within the
multi-component particles. Examples of some general types of
organic materials that may also be included in the matrix (or may
form the matrix) include organic salts, polymers, organic
compounds, organometallic compounds, surfactants, and biological
organic material (such as amino acids, proteins, lipids, DNA,
enzymes, etc.).
[0035] In one particular implementation of the invention, the
matrix comprises one or more than one organic salt material. Matrix
organic salt materials are preferred, for example, for many
applications when it is desired to have a matrix that is partially
or wholly removable, because the organic salt material of the
matrix can be selected to be dissolvable in a liquid medium that is
not detrimental to the nanoparticles. For water soluble organic
salts, a convenient choice for the liquid medium is water or an
aqueous solution, which may be neutral, basic or acidic depending
upon the specific application and the specific matrix organic salt
material to be dissolved. The matrix salt material may comprise a
minor amount of an inorganic salt optionally in addition to an
organic salt.
[0036] In one particular implementation of the invention, the
matrix comprises one or more than one polymer. It may be desirable
to include a polymer material in the matrix for a variety of
reasons. For example, a polymer may be selected for easy
dissolution in a liquid medium to release (disperse) the
nanoparticles for further processing or use. A polymer material
that is soluble in an organic liquid may be selected when it is
desired to disperse the nanoparticles in the organic liquid during
subsequent processing or use. A polymer material that is soluble in
water may also be selected when it is desired to disperse the
nanoparticles in water during subsequent processing or use, as
described in more detail below.
[0037] As another example, a polymer may be selected as a permanent
matrix material for use in some application. When used as a
permanent matrix, the polymer of the matrix may simply provide a
structure to retain the nanoparticulate in a desired distribution
without interfering with proper functioning of the nanoparticles in
the application. Alternatively, the polymer may itself also provide
some function for the application. The polymer may, for example,
have a function that is different than that of the nanoparticles,
have a function that compliments that of the nanoparticles, or have
a function that is the same as that of the nanoparticles. Examples
of some specific combinations of materials for the nanoparticles
and polymer materials for the matrix materials and their
applications are described in more detail below. As yet another
example, the polymer may be selected for its surface modifying
properties to beneficially surface modify the nanoparticles in a
way that is useful in some subsequent processing or use of the
nanoparticles. The invention is not limited to use of any
particular polymers in the matrix. Some non-limiting examples of
organic polymers that may be used in the matrix include:
fluorinated polymers, thermal curable polymers, UV curable
polymers, appended polymers, light emitting polymers,
semiconducting polymers, electrically conductive polymers (e.g.
polythiophenes, poly (ethylene dioxy thiophene), hydrophobic
polymers (siloxanes, silicones, silanes, polyacrylonitrile,
polymethylmethacrylate, polyethyleneterephthalate), hydrophilic
polymers (polythiophenes, sulfonated polymers, polymers with ionic
functional groups), polyaniline & modified versions, poly
pyrroles & modified versions, poly pyridines & modified
versions, polycarbonates, polyesters, polyvinylpyrrolidone (PVP),
polyethylene, epoxies, polytetrafluoroethylene, Nafiong, Kevlarg
and Teflon.RTM.). The polymers included in the matrix may have any
structure, some non-limiting examples of polymeric structures
include: dendrimers, long single chain polymers, co-polymers
(random or block, e.g. A-B, A-B-A, A-B-C, etc.) branched polymers
and grafted polymers.
[0038] As mentioned above, some or all of matrix in the
multi-component particles may be designed to be permanent for some
applications of the nanoparticles. In one example of an application
using a permanent matrix, particles may be made for use as a
thermally conductive barrier layer, such as for use in computers.
The nanoparticles could be of a metal with high thermal
conductivity, such as silver or copper. The matrix could be of an
electrically insulating material, such as an electrically
insulating polymer. The combination of electrically insulative
polymer matrix and thermally conductive metal nanoparticles is
useful for making thermal interface layers, such as may be used
underneath computer chips, permitting rapid dissipation of heat
without significant risk of an electrical short through the
thermally conductive metal. Another example is use of a matrix as a
protective barrier to protect nanoparticles from degradation. A
protective organic matrix may be useful for protecting
nanoparticles comprising inorganic pigments and/or light emitting
materials such as phosphors from the ambient environment (e.g.,
moisture or oxidation). Other non-limiting examples of
multi-component particles that may include a permanent matrix
material are shown in Table 1, along with exemplary applications
for use of those particles. TABLE-US-00001 TABLE 1 EXEMPLARY
PARTICLES WITH PERMANENT MATRIX MATERIAL NANOPARTICLE MATRIX
MATERIAL APPLICATION Photoluminescent Light emitting polymer
Organic light phosphor Polymer emitting diode (OLED) displays,
lighting applications Electroluminescent Light emitting polymer
Electroluminescent (EL) phosphor Polymer (EL) displays/lamps Red,
Green, Blue Polymer Lighting (RGB) phosphors all in one layer
Cathodoluminescent Light emitting polymer Field emission (CL)
phosphor Polymer display (FED) Color Pigment Polymer Colored
coatings Hard materials such Polymer Anti-scratch, anti- as oxides
or nitrides abrasion, dental glass Hard materials such Surfactants
Anti-scratch, anti- as oxides or nitrides abrasion, dental glass
Semiconductor Polymer Solar cell Semiconductor Polymer Solar cell
Semiconducting metal Polymer Resistors oxides UV absorbing Polymer
UV protection High dielectric Polymer Capacitor High dielectric Low
melting point Capacitor material, insulating polymer Conductor
Non-conductor Electromagnetic shielding Absorbent Polymer
Protective barrier Light absorber Light emitter Production of
monochromatic light High dielectric Polymer dielectric Dielectric
layer in polymer transistor Semiconductor, n Polymer Semiconductor
in type, p type semiconductor, n type, polymer transistor p type
Semiconductor, n Insulating polymer Transistor type, p type Silicon
Polymer Transistor electrochromic Polymer Electrochromic display
Thermochromic Polymer Display, visual output device Thermochromic
Inorganic material Display Photochromic Polymer Display, visual
output device Ion conductor Polymer Battery Lithium containing
Polymer Lithium ion battery Metals, electrical Polymer, silicone
Thermal interface conductor material Refractive index Refractive
index Reflective coating matching polymer UV absorber Biologically
inactive Cosmetics materials, polymers, Sorbent Porous organic
Absorbents polymer (dissolving away partially), chemical
separations, bio- separations Low k oxides Porous organic Low k
material polymer Anti-fouling Porous organic Anti-fouling (marine)
polymer Catalytically active Porous organic Self cleaning polymer
surfaces, membrane electrode assemblies Dissolvable material
Polymer Time release Magnetic material Organic Magnetic
applications Pigments Polymer Pigments Color
[0039] The organic matrix optionally comprises one or more silicon
containing polymers and/or compounds, such as polysilanes,
polysiloxanes, polysilicones, polysilsequioxanes, polysilazanes,
polycarbosilanes, siloxanes, silanes or silicones.
[0040] The organic matrix may include one or more surfactant
compounds, such as anionic surfactants, cationic surfactants, or
nonionic surfactants. Examples of anionic surfactants include alkyl
sulfates, alkyl sulfonates, alkyl benzene sulfates, alkyl benzene
sulfonates, fatty acids, sulfosuccinates, and phosphates. Examples
of cationic surfactants include quanternary ammonium salts and
alkylated pyridinium salts. Examples of nonionic surfactants
include alkyl primary, secondary, and tertiary amines,
alkanolamides, ethoxylated fatty alcohols, alkyl phenol
polyethoxylates, fatty acid esters, glycerol esters, glycol esters,
polyethers, alkyl polygycosides, and amineoxides. In addition,
Zwitterionic surfactants (surface active additives with a cationic
and anionic functional group on the same molecule) may be included
within the matrix. Examples include betaines, such as alkyl
ammonium carboxylates (e.g., [(CH.sub.3).sub.3N.sup.+--CH(R)COO--]
or sulfonates (sulfo-betaines) such as
[R--N.sup.+(CH.sub.3).sub.2(CH.sub.2).sub.3SO.sub.3.sup.-]).
Examples include: n-dodecyl-N-benzyl-N-methylglycine
[C.sub.12H.sub.25N.sup.+(CH.sub.2--C.sub.6H.sub.5)(CH.sub.3)CH2COO.sup.-]-
, N-allyl N-benzyl N-methyltaurines
[C.sub.nH.sub.2n+1N.sup.+(CH.sub.2C.sub.6H.sub.5)(CH.sub.3)CH.sub.2CH.sub-
.2SO.sub.3.sup.-], Amido Betaine C (Zohar Dallia)--Coconut amido
alkyl beatine, Amphosol CB3 (Stepan Europe) alkyl amido propyl
betaine, Amphoteen 24 (Akzo Nobel) C.sub.12-C.sub.14
alkyldimethylbetaine, Betadet SHR (Kao Corporation, S.A.),
Cocoamidopropyl hydroxysultaine, and Dehyton MC (Cogis IB) sodium
cocoamplioacetate. A more complete list of surfactants that may be
used as part of the organic matrix (including ionic, nonionic
polymeric and those with a variety of functional groups) may be
found in McCutcheons Emulsifiers and Detergents Vol. I, Int. Ed,
2002, The Manufacturing Confectioner Publishing Co. (ISBN
944254-84-5).
[0041] The organic matrix optionally comprises one or more
bioactive compounds such as amino acids, peptides, polypeptides,
proteins, enzymes, carbohydrates, nucleic acids, polynucleotides,
lipids, phosolipids, steroids, vitamins, hormones or glucose
phosphates.
[0042] The organic matrix may comprise low or high molecular weight
organic compounds, e.g., having a molecular weight ranging from
about 50 to about 1,000,000, e.g., from about 100 to about 100,000
or from about 500 to about 10,000. Non-limiting examples of low
molecular weight organic compounds that may be used in the present
invention as matrix material include fatty acids, in particular,
fatty acids having at least about 8 carbon atoms. Low molecular
weight compounds may ultimately be removed from the nanoparticles
by sublimation or by being dissolved away. In addition, they may be
ideal for surface passivation and redispersing the nanoparticles.
Non-limiting examples of oligomers/polymers for use as the matrix
material in the process of the present invention include homo- and
copolymers (including polymers such as, e.g., random copolymers,
block copolymers and graft copolymers) which comprise units of at
least one monomer which comprises one or more oxygen atoms and/or
one or more nitrogen atoms. A non-limiting class of preferred
polymers for use in the present invention includes polymers that
comprise at least one monomer unit having at least two atoms that
are selected from oxygen and nitrogen. Corresponding monomer units
may, for example, comprise at least one hydroxyl group, carbonyl
group, ether linkage and/or amino group and/or one or more
structural elements of the formulae: --COO--, --COC--,--O--CO--O--,
--CO--O--CO--, --O--C--O--, --CONR--, --NR--CO--O--,
--NR.sup.1--CO--NR.sup.2--, --CO--NR--CO--, --SO.sub.2--NR-- and
--SO.sub.2--O--, wherein R, R.sup.1 and R.sup.2 independently
represent hydrogen and an organic radical (e.g., an aliphatic or
aromatic, unsubstituted or substituted radical comprising from
about 1 to about 20 carbon atoms).
[0043] Non-limiting examples of corresponding polymers include
polymers comprising one or more units derived from the following
groups of monomers:
[0044] (a) carboxylic acids of from about 3 to about 8 carbon atoms
and salts thereof. This group of monomers includes, for example,
acrylic acid, methacrylic acid, dimethylacrylic acid, ethacrylic
acid, maleic acid, citraconic acid, methylenemalonic acid,
allylacetic acid, vinylacetic acid, crotonic acid, fumaric acid,
mesaconic acid and itaconic acid. The monomers of group (a) can be
used either in the form of the free carboxylic acids or in
partially or completely neutralized form. For the neutralization
alkali metal bases, alkaline earth metal bases, ammonia or amines,
e.g., sodium hydroxide, potassium hydroxide, sodium carbonate,
potassium carbonate, sodium bicarbonate, magnesium oxide, calcium
hydroxide, calcium oxide, ammonia, triethylamine, methanolamine,
diethanolamine, triethanolamine, morpholine, diethylenetriamine or
tetraethylenepentamine may, for example, be used;
[0045] (b) the esters, amides, anhydrides and nitriles of the
carboxylic acids stated under (a) such as, e.g., methyl acrylate,
ethyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl
acrylate, hydroxyethyl acrylate, 2- or 3-hydroxypropyl acrylate, 2-
or 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, 2- or
3-hydroxypropyl methacrylate, hydroxyisobutyl acrylate,
hydroxyisobutyl methacrylate, monomethyl maleate, dimethyl maleate,
monoethyl maleate, diethyl maleate, maleic anhydride, 2-ethylhexyl
acrylate, 2-ethylhexyl methacrylate, acrylamide, methacrylamide,
N,N-dimethylacrylamide, N-tert-butylacrylamide, acrylonitrile,
methacrylonitrile, 2-dimethylaminoethyl acrylate,
2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl acrylate,
2-diethylaminoethyl methacrylate and the salts of the
last-mentioned monomers with carboxylic acids or mineral acids and
the quaternized products;
[0046] (c) acrylamidoglycolic acid, vinylsulfonic acid,
allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid,
3-sulfopropyl acrylate, 3-sulfopropyl methacrylate and
acrylamidomethylpropanesulfonic acid and monomers containing
phosphonic acid groups, such as, e.g., vinyl phosphate, allyl
phosphate and acrylamidomethylpropanephosphonic acid; and esters,
amides and anhydrides of these acids;
[0047] (d) N-vinyllactams such as, e.g., N-vinylpyrrolidone,
N-vinyl-2-piperidone and N-vinylcaprolactam; and
[0048] (e) vinyl acetal, vinyl butyral, vinyl alcohol and ethers
and esters thereof (such as, e.g., vinyl acetate, vinyl propionate
and methylvinylether), allyl alcohol and ethers and esters thereof,
N-vinylimidazole, N-vinyl-2-methylimidazoline, and the
hydroxystyrenes.
[0049] Corresponding polymers may also contain additional monomer
units, for example, units derived from monomers without functional
group, halogenated monomers, aromatic monomers, etc. Non-limiting
examples of such monomers include olefins such as, e.g., ethylene,
propylene, the butenes, pentenes, hexenes, octenes, decenes and
dodecenes, styrene, vinyl chloride, vinylidene chloride,
tetrafluoroethylene, etc. Further, the polymers for use as matrix
material in the processes and compositions of the present invention
are not limited to addition polymers, but also comprise other types
of polymers, for example, condensation polymers such as, e.g.,
polyesters, polyamides, polyurethanes and polyethers, as well as
polysaccharides such as, e.g., starch, cellulose and derivatives
thereof, etc. Other non-limiting examples of polymers which are
suitable for use as matrix material in the present invention are
disclosed in, e.g., U.S. patent application Publication
2004/0182533 A1, the entire disclosure whereof is expressly
incorporated by reference herein.
[0050] Other preferred polymers that may be used according to the
invention include water soluble polymers, such as
poly(propylenoxide) amines, polyamines, polyalcohols, polyoxides,
polyethers, polyacrylamides and polyacrylates.
[0051] Preferred polymers for use as matrix material in the present
invention include those which comprise units derived from one or
more N-vinylcarboxamides of formula (I)
CH.sub.2.dbd.CH--NR.sup.3--CO--R.sup.4 (I) wherein R.sup.3 and
R.sup.4 independently represent hydrogen, optionally substituted
alkyl (including cycloalkyl) and optionally substituted aryl
(including alkaryl and aralkyl) or heteroaryl (e.g., C.sub.6-20
aryl such as phenyl, benzyl, tolyl and phenethyl, and C.sub.4-20
heteroaryl such as pyrrolyl, furyl, thienyl and pyridinyl). R.sup.3
and R.sup.4 may, e.g., independently represent hydrogen or
C.sub.1-12 alkyl, particularly C.sub.1-6 alkyl such as methyl and
ethyl. R.sup.3 and R.sup.4 together may also form a straight or
branched chain containing from about 2 to about 8, preferably from
about 3 to about 6, particularly preferably from about 3 to about 5
carbon atoms, which chain links the N atom and the C atom to which
R.sup.3 and R.sup.4 are bound to form a ring which preferably has
about 4 to about 8 ring members. Optionally, one or more carbon
atoms may be replaced by heteroatoms such as, e.g., oxygen,
nitrogen or sulfur. Also optionally, the ring may contain a
carbon-carbon double bond.
[0052] Non-limiting specific examples of R.sup.3 and R.sup.4 are
methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl, sec-butyl,
tert-butyl, n-hexyl, n-heptyl, 2-ethylhexyl, n-octyl, n-decyl,
n-undecyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl and
n-eicosyl. Non-limiting specific examples of R.sup.3 and R.sup.4
which together form a chain are 1,2-ethylene, 1,2-propylene,
1,3-propylene, 2-methyl-1,3-propylene, 2-ethyl-1,3-propylene,
1,4-butylene, 1,5-pentylene, 2-methyl-1,5-pentylene, 1,6-hexylene
and 3-oxa-1,5-pentylene.
[0053] Non-limiting specific examples of N-vinylcarboxamides of
formula (I) are N-vinylformamide, N-vinylacetamide,
N-vinylpropionamide, N-vinylbutyramide, N-vinylisobutyramide,
N-vinyl-2-ethylhexanamide, N-vinyldecanamide, N-vinyldodecanamide,
N-vinylstearamide, N-methyl-N-vinylformamide,
N-methyl-N-vinylacetamide, N-methyl-N-vinylpropionamide,
N-methyl-N-vinylbutyramide, N-methyl-N-vinylisobutyramide,
N-methyl-N-vinyl-2-ethylhexanamide, N-methyl-N-vinyldecanamide,
N-methyl-N-vinyldodecanamide, N-methyl-N-vinylstearamide,
N-ethyl-N-vinylformamide, N-ethyl-N-vinylacetamide,
N-ethyl-N-vinylpropionamide, N-ethyl-N-vinylbutyramide,
N-ethyl-N-vinylisobutyramide, N-ethyl-N-vinyl-2-ethylhexanamide,
N-ethyl-N-vinyldecanamide, N-ethyl-N-vinyldodecanamide,
N-ethyl-N-vinylstearamide, N-isopropyl-N-vinylformamide,
N-isopropyl-N-vinylacetamide, N-isopropyl-N-vinylpropionamide,
N-isopropyl-N-vinylbutyramide, N-isopropyl-N-vinylisobutyramide,
N-isopropyl-N-vinyl-2-ethylhexanamide,
N-isopropyl-N-vinyldecanamide, N-isopropyl-N-vinyldodecanamide,
N-isopropyl-N-vinylstearamide, N-n-butyl-N-vinylformamide,
N-n-butyl-N-vinylacetamide, N-n-butyl-N-vinylpropionamide,
N-n-butyl-N-vinylbutyramide, N-n-butyl-N-vinylisobutyramide,
N-n-butyl-N-vinyl-2-ethylhexanamide, N-n-butyl-N-vinyldecanamide,
N-n-butyl-N-vinyldodecanamide, N-n-butyl-N-vinylstearamide,
N-vinylpyrrolidone, N-vinyl-2-piperidone and
N-vinylcaprolactam.
[0054] Particularly preferred polymers for use in the present
invention include polymers that comprise monomer units of one or
more unsubstituted or substituted N-vinyllactams, preferably those
having from about 4 to about 8 ring members such as, e.g.,
N-vinylcaprolactam, N-vinyl-2-piperidone and N-vinylpyrrolidone.
These polymers include homo- and copolymers. In the case of
copolymers (including, for example, random, block and graft
copolymers), the N-vinyllactam (e.g., N-vinylpyrrolidone) units are
preferably present in an amount of at least about 10 mole-%, e.g.,
at least about 30 mole-%, at least about 50 mole-%, at least about
70 mole-%, at least about 80 mole-%, or at least about 90 mole-%.
By way of non-limiting example, the co-monomers may comprise one or
more of those mentioned in the preceding paragraphs, including
monomers without functional group (e.g., ethylene, propylene,
styrene, etc.), halogenated monomers, etc.
[0055] If the vinyllactam (e.g., vinylpyrrolidone) monomers (or at
least a part thereof) carry one or more substituents on the
heterocyclic ring, non-limiting examples of such substituents
include alkyl groups (for example, alkyl groups having from 1 to
about 12 carbon atoms, e.g., from 1 to about 6 carbon atoms such
as, e.g., methyl, ethyl, propyl and butyl), alkoxy groups (for
example, alkoxy groups having from 1 to about 12 carbon atoms,
e.g., from 1 to about 6 carbon atoms such as, e.g., methoxy,
ethoxy, propoxy and butoxy), halogen atoms (e.g., F, Cl and Br),
hydroxy, carboxy and amino groups (e.g., dialkylamino groups such
as dimethylamino and diethylamino) and any combinations of these
substituents.
[0056] Non-limiting specific examples of vinyllactam polymers for
use in the present invention include homo- and copolymers of
vinylpyrrolidone which are commercially available from, e.g.,
International Specialty Products <www.ispcorp.com>. In
particular, these polymers include:
[0057] (a) vinylpyrrolidone homopolymers such as, e.g., grades K-15
and K-30 with K-value ranges of from 13-19 and 26-35, respectively,
corresponding to average molecular weights (determined by
GPC/MALLS) of about 10,000 and about 67,000;
[0058] (b) alkylated polyvinylpyrrolidones such as, e.g., those
commercially available under the trade mark GANEX.RTM. which are
vinylpyrrolidone-alpha-olefin copolymers that contain most of the
alpha-olefin (e.g., about 80% and more) grafted onto the
pyrrolidone ring, mainly in the 3-position thereof; the
alpha-olefins may comprise those having from about 4 to about 30
carbon atoms; the alpha-olefin content of these copolymers may, for
example, be from about 10% to about 80% by weight;
[0059] (c) vinylpyrrolidone-vinylacetate copolymers such as, e.g.,
random copolymers produced by a free-radical polymerization of the
monomers in a molar ratio of from about 70/30 to about 30/70 and
having weight average molecular weights of from about 14,000 to
about 58,000;
[0060] (d) vinylpyrrolidone-dimethylaminoethylmethacrylate
copolymers;
[0061] (e) vinylpyrrolidone-methacrylamidopropyl trimethylammonium
chloride copolymers such as, e.g., those commercially available
under the trade mark GAFQUAT.RTM.;
[0062]
vinylpyrrolidone-vinylcaprolactam-dimethylaminoethylmethacrylate
terpolymers such as, e.g., those commercially available under the
trade mark GAFFIX.RTM.;
[0063] (g) vinylpyrrolidone-styrene copolymers such as, e.g., those
commercially available under the trade mark POLECTRON.RTM.; a
specific example thereof is a graft emulsion copolymer of about 70%
vinylpyrrolidone and about 30% styrene polymerized in the presence
of an anionic surfactant; and
[0064] (h) vinylpyrrolidone-acrylic acid copolymers such as, e.g.,
those commercially available under the trade mark ACRYLIDONE.RTM.
which are produced in the molecular weight range of from about
80,000 to about 250,000.
[0065] In a preferred embodiment of the present invention, the
matrix material implemented in the multi-component particles is
wholly removable, or partially removable to a sufficient extent, to
release the nanoparticles for further processing or for use. In one
variation of this example, the matrix may comprise only material(s)
designed to be removed at the same time. In another variation of
this example, the matrix may include a material that is selectively
removable relative to another material to provide enhanced access
to the nanoparticles for intermediate processing prior to removal
of other matrix material(s) to effect release of the nanoparticles.
As another example, all or part of the matrix may be designed for
permanent use. In one variation of this other example, the matrix
is originally formed during the formation of the particles and may
be designed to permanently maintain the nanoparticles in a fixed
dispersion for some final application. In another variation of this
other example, a portion of the matrix may be selectively removable
relative to another portion of the matrix designed to be permanent,
providing enhanced access to the nanoparticles for purposes of
intermediate processing prior to final use or for purposes of a
final use.
[0066] An important aspect of the present invention is that the
process allows for control of the ratio of distributed
nanoparticulats relative to the matrix material in the final
multi-component particle. This is important (along with other
processing parameters) for the determination of the properties of
the final multi-component particles. For example, in one
embodiment, a minimal amount of matrix material is used to prevent
the connecting or contacting between adjacent nanoparticlulates.
The prevention of the nanoparticle from agglomerating may be
important for final applications wherein the nanoparticles will be
released (dispersed) from the matrix to form a dispersion of
nanoparticles. In general, the smaller the size of the
nanoparticles, the larger the surface area of the nanoparticles,
and the more matrix material that is desired for complete coverage
of the nanoparticles.
[0067] Depending on the matrix material used, one can make some
simple assumptions regarding the thickness of a monolayer of matrix
material that covers the surface of the nanoparticles. In addition,
one may also assume that a minimum of one monolayer of an
adsorptive substance around a metal core is needed to allow for
complete disconnection of the nanoparticles. As used herein, the
term "monolayer" means a two-dimensional film, one molecule (or
monomer unit of a polymer) thick, situated at the surface of a
nanoparticle. In a preferred embodiment, the nanoparticles are
dispersable in a liquid medium to form dispersed nanoparticles
having from about 1 to about 10 monolayers (e.g., from about 2 to
about 8 or from about 3 to about 6 monolayers) disposed thereon,
wherein the monolayers are formed from the organic matrix.
Preferably, the monolayer(s) comprise at least one component (e.g.,
the major component) of the organic matrix.
[0068] For example, for silver nanoparticles distributed in a PVP
matrix, usually not more than about 10 monolayers (and often not
more than about 5 monolayers or even not more than about 2
monolayers) of adsorptive substance are desired to allow for
subsequent dispersion and stabilization of the metal nanoparticles
in solution. With this simple model one may estimate the amount of
adsorptive substance that is needed to disperse metal nanoparticles
of any size. For example, for PVP as the matrix material, one may
assume that the thickness of a monolayer thereof is about 1 nm.
Using the densities of silver (10.5 g/cm.sup.3) and PVP (1.0
g/cm.sup.3) one skilled in the art can calculate the weight percent
of PVP relative to the weight percent silver for any diameter of
silver particle at any number of monolayers of PVP coating the
silver particle. Based on this model, for a PVP coated spherical
silver core having a diameter of 20 nm, the minimum amount of PVP
needed to disperse a dry particle is about 19% by weight.
Preferably, not more than 10 monolayers or 41% by weight of PVP
will be used. More preferably the PVP forms from about 2 to about 8
monolayers on the nanoparticle core. Most preferably, about 4 to
about 8 monolayers or about 14.8% to about 32.5% by weight of PVP
will be formed. For a 50 nm PVP-coated sphere-shaped silver
nanoparticle core, a minimum of about 1.3% by weight of PVP will be
needed to cover the nanoparticle completely with a monolayer. No
more than about 14.8% by weight or 10 monolayers will usually be
needed. Most preferably, about 5.3 to about 11.5% by weight of PVP
is used (for about 4 to about 8 monolayers).
[0069] In most implementations of the invention, the
multi-component particles will comprise a volume percentage of
matrix in a range having an upper limit selected from the group
consisting of 99 volume percent, 95 volume percent and 90 volume
percent and having a lower limit selected from the group consisting
of 1 volume percent, 20 volume percent, 60 volume percent, 70
volume percent and 75 volume percent. One particularly preferred
implementation is for the matrix to comprise at least 70 volume
percent and more preferably at least 75 volume percent of the
multi-component particles, but also preferably with no greater than
95 volume percent and even more preferably no greater than 90
volume percent of matrix. In this discussion concerning volume
percent, the pore volume in the multi-component particles are
ignored, so that the volumes of the matrix and nanoparticles are
included in determining the total volume of the multi-component
particles used to determine the volume percentages of the
nanoparticles and the matrix. On this basis, the sum of the volume
fractions of the nanoparticles and the matrix add up to 100. It
should be appreciated, however, that in some instances the
multi-component particles resulting from the particle forming may
contain significant porosity.
C. Composition and Properties of the Nanoparticles
[0070] As indicated above, the multi-component particles of the
present invention include inorganic nanoparticles distributed in an
organic matrix. As used herein, the term "inorganic nanoparticle"
means a nanoparticle comprising at least one inorganic element,
which optionally is a part of a larger chemical compound. In one
embodiment the "inorganic nanoparticle" excludes carbon. It is
contemplated, however, that the inorganic nanoparticle may include
one or more organic components in addition to the inorganic
element. For example, an inorganic nanoparticle may include one or
more organometallic compounds or even one or more organometallic
compounds in a mixture with one or more organic compounds.
[0071] In various embodiments, the size of the nanoparticles may
vary widely. Optionally, the nanoparticles have a number average
particle diameter of from about 1 nm to about 500 nm, e.g., from
about 10 nm to about 150 nm or from about 30 nm to about 100 nm,
based on electron microscopy. The nanoparticles have a d50 particle
diameter, based on volume, greater than about 1 nm and less than
600 nm, e.g., greater than about 40 nm and less than 200 nm, as
determined by light scattering techniques.
[0072] The distance between adjacent nanoparticles in the
multi-component particle may vary widely depending on the desired
end use for the multi-component particles. In one embodiment, the
average distance between adjacent inorganic nanoparticles is less
than the number average particle diameter of the inorganic
nanoparticles, e.g., less than half the number average particle
diameter based on electron microscopy. In terms of absolute
numbers, the average distance between adjacent nanopartricles in
the multi-component particles optionally is less than about 150 nm,
e.g., less than about 100 nm, less than about 50 nm, less than
about 10 nm, less than about 5 nm or less than about 1 nm. In terms
of higher range limitations, the average distance between adjacent
inorganic nanoparticles optionally is greater than the number
average particle diameter of the inorganic nanoparticles (e.g.,
greater than twice the number average particle diameter). In terms
of absolute numbers, the average distance between adjacent
nanoparticles in the multi-component particles optionally is
greater than about 1 nm, e.g., greater than about 5 nm, greater
than about 10 nm, greater than about 50 nm, greater than about 100
nm or greater than about 150 nm.
[0073] In one embodiment, the nanoparticles may touch or even neck
or sinter together. In one aspect of this embodiment, on average,
at least about 10 percent, at least about 25 percent, at least
about 50 percent, at least about 75 percent, at least about 90
percent or at least about 99 percent of the nanoparticles are
touching at least one adjacent nanoparticle. In other aspects,
optionally in combination with any of the above-disclosed lower
range limitations, less than about 99, less than about 90, less
than about 75, less than about 50, less than about 25, less than
about 10, less than about 5, less than about 1, or less than about
0.1 percent of the nanoparticles are touching at least one adjacent
nanoparticle.
[0074] The nanoparticles also may have a variety of particle size
distributions. In one embodiment, the nanoparticles have a
monomodal particle size distribution, meaning the particle size
distribution has a generally Gaussian or log normal form.
Alternatively, the nanoparticles have a multi-modal particle size
distribution, meaning there are several modes of particle formation
and growth, having two or more distributions of particle
populations. For example, the particle size distribution optionally
is bimodal, trimodal, etc. Depending on the desired application, a
multi-modal particle size distribution may be desired over a
monomodal distribution. For example, in layer formation the
combination of different sizes will be more efficient at filling
voids between particles and thus increase packing density.
[0075] If the nanoparticles have a monomodal particle size
distribution, the Gaussian form may have a short, narrow
distribution or a broad distribution. The sharpness or broadness of
a particle size distribution may be determined by determining the
difference between two different dx values (e.g., d30, d40, or d50
values, based on volume) for a given population of nanoparticles.
In general, the smaller the difference between the two dx values,
the sharper the distribution. Conversely, the greater the
difference between the two dx values, the broader the distribution.
In one aspect of the invention, the nanoparticles have a d40
particle size (e.g., particle diameter) and a d60 particle size
(e.g., particle diameter) and the difference between the d60
particles size and the d40 particle size is from about 1 nm to
about 400 nm, e.g., from about 2 to about 200 nm, from about 5 to
about 50 nm, or from about 5 to about 10 nm. A narrow size
distribution is useful when properties are affected by size, and a
single type of property is desired. For example, a narrow particle
size distribution may be desired when the nanoparticles are to be
used as seeds for nanowire growth. Conversely, a broad particle
size distribution may be desired for coatings or for dense film
formation. The specifically desied particle size distribution of
the nanoparticles may be controlled by selectively varying certain
spray processing parameters, e.g., temperature, flow rate,
nanoparticle precursor concentration, etc.
[0076] In one aspect, the nanoparticles of the present invention
are spheroidal, meaning that they are generally of spherical shape,
even if not perfectly spherical. Optionally, a majority of the
nanoparticles have a morphology that is spherical, hollow, rod,
flake, platelet, cubed or trigonal.
[0077] In a preferred embodiment, the inorganic nanoparticles in
the multi-component particles comprise one or more metals, metal
oxides, main group elements, metal mixtures or alloy materials or
mixtures or combinations of these materials. Examples of inorganic
materials for possible inclusion in nanoparticles include metallic
materials, (including single metals, alloys and intermetallic
compounds), ceramics, main group elements, such as Si, Ge and mixed
main group materials or mixed metal/main group materials, such as
CdSe, GaAs, and InP. Some examples of metallic materials for
inclusion in nanoparticles include one or more of elemental silver,
platinum, zinc, palladium, ruthenium, gold, copper, rhodium, tin,
molybdenum, cobalt, iron, nickel, metal alloys including one or
more of the foregoing and metal elements, and inter-metallic
compounds including one or more of the foregoing metal elements. In
a preferred embodiment, the inorganic nanoparticles comprise one or
more of silver, copper, nickel, platinum, palladium, rhodium,
ruthenium, cobalt, gold, iridium or a metal oxide thereof.
[0078] Some examples of ceramic materials for optional inclusion in
the nanoparticles include one or more of oxides, sulfides,
carbides, nitrides, borides, tellurides, selenides, phosphides,
oxycarbides, oxynitrides, titanates, zirconates, stannates,
silicates, aluminates, tantalates, tungstates, glasses, doped and
mixed metal oxides. For example SiC, and BN are ceramics with high
heat transfer coefficients and can be used in heat transfer fluids.
Specific examples of some preferred oxides include silica, alumina,
titania, magnesia, indium oxide, indium tin oxide and ceria.
Moreover, the composition of the nanoparticles may be designed for
any desired application. For example, alloy nanoparticles could
include materials for hydrogen storage, such as LaNi, FeTi, Mg2Ni,
ZrV.sub.2; materials for magnetic applications, such as, CoFe,
CoFe.sub.2, FeNi, FePt, FePd, CoPt, CoPd, SmCo.sub.5,
Sm.sub.2CO.sub.17, Nd/B/Fe. For example, the nanoparticles could be
core shell particles, such as, metals coating metals (Ag/Cu,
Ag/Ni), metals coating metal oxides (Ag/Fe.sub.3O.sub.4), metal
oxides coating metals (SiO.sub.2/Ag), metal oxides coating metal
oxides (SiO.sub.2/RuO.sub.2), semiconductors coating semiconductors
(ZnS/CdSe) or combinations of all these materials.
[0079] In another implementation, the nanoparticles comprise very
small particles (less than 100 nm) having a high reflective index,
such as TiO.sub.2, BaTiO.sub.2 and ZnO. These particles are
incorporated in a polymer matrix and will increase the bulk
refractive index of the polymer and therefore the use of the
composite material for optical applications. Another application
for these composite materials is in personal care products
(sunscreens, etc.), where these materials will absorb UV
radiation.
[0080] For example, the nanoparticles could include materials such
as a semiconductor, a phosphor, an electrical conductor, a
transparent electrical conductor, a thermochromic, an
electrochromic, a magnetic material, a thermal conductor, an
electrical insulator, a thermal insulator, a polishing compound, a
catalyst, a pigment, or a drug or other pharmaceutical
material.
[0081] In one particular implementation of the invention, the
nanoparticles comprise phosphor materials. This embodiment may be
desirable for applications in which the nanoparticles are to be
used as phosphors in a display application. Phosphors are
substances that are capable of luminescence. The luminescence
involves emission of radiation in response to a stimulus or
excitation. Preferred luminescence of phosphors for use with this
implementation of the invention includes emission of visible light
for use in display applications. Such phosphors may, for example,
be cathodoluminescent, electroluminescent, photoluminescent or
x-ray luminescent. Inorganic phosphor compositions typically
include a host material and one or more dopants, also referred to
as activator ions. Examples of host materials include yttrium
oxides, yttrium oxysulfides, yttrium fluorides, gadolinium
oxysulfides, sulfides (such as for example zinc sulfide, calcium
sulfide and strontium sulfide), silicates (such as for example zinc
silicate and yttrium silicate, thiogallates (such as for example
strontium thiogallate and calcium thiogallate), gallates (such as
for example zinc gallate, calcium gallate and strontium gallate),
aluminates (such as for example barium aluminate and barium
magnesium aluminate (BAM)), thioaluminates (such as for example
barium thioaluminate), nitrides and oxynitides (such as
Ba.sub.2Si.sub.5N.sub.8 :Eu, Ca.sub.xSi.sub.yN.sub.z:Eu,
Sr.sub.xSiyNz:Eu,CaAlSiN.sub.3:Eu, LaEuSi.sub.2N.sub.3O.sub.2), and
borates (such as for example yttrium-gadolinium borate). Table 2
lists some non-limiting examples of inorganic phosphor materials,
including host material and exemplary activator ions, and the type
of excitation for luminescence. TABLE-US-00002 TABLE 2 EXEMPLARY
INORGANIC PHOSPHOR COMPOSITIONS FOR NANOPARTICLES EXCITATION HOST
MATERIAL ACTIVATOR ION(S) MECHANISM Y.sub.2O.sub.3 Eu, rare earths,
Tb Cathodoluminescent, Photoluminescent Y.sub.2O.sub.2S Eu, Tb
Cathodoluminescent ZnS Au, Al, Cu, Ag, Cl, Cathodoluminescent, Mn
Electroluminescent SrGa.sub.2S.sub.4 Eu, Ce Cathodoluminescent,
Electroluminescent Y.sub.3Al.sub.5O.sub.12 Tb, Cr
Cathodoluminescent, Photoluminescent Y.sub.3(Ga,Al).sub.5O.sub.12
Tb, Cr Cathodoluminescent, Photoluminescent Zn.sub.2SiO.sub.4 Mn
Cathodoluminescent, Photoluminescent Y.sub.2SiO.sub.5 Tb, Ce
Cathodoluminescent BaS Eu, Ce Electroluminescent CaS Eu, Ce
Electroluminescent SrS Eu, Ce Electroluminescent CaGa.sub.2S.sub.4
Eu, Ce Electroluminescent ZnGa.sub.2O.sub.4 Mn, Cr
Electroluminescent CaGa.sub.2O.sub.4 Eu, Ce Electroluminescent
SrGa.sub.2O.sub.4 Eu, Ce Electroluminescent Ga.sub.2O.sub.3 Dy, Eu
Electroluminescent Ca.sub.3Ga.sub.2O.sub.6 Eu, Ce
Electroluminescent Zn.sub.2GeO.sub.4 Mn Electroluminescent
Zn.sub.2(Ge,Si)O.sub.4 Mn Electroluminescent (Y,Gd)BO.sub.3 Eu, Tb
Photoluminescent BaMgAl.sub.10O.sub.17 Mn, Eu Photoluminescent
BaAl.sub.xO.sub.y Mn Photoluminescent Gd.sub.2O.sub.2S Tb X-ray
(Y,Gd).sub.2SiO.sub.5 Tb, Ce X-ray
[0082] In one particular implementation of the invention, the
nanoparticles comprise luminescent lanthanide complexes, such as
lanthanide B-diketonates, acetophenone complexes and cryptates.
[0083] In one particular implementation of the invention, the
nanoparticles comprise catalyst compositions. Catalysts are
substances that affect the rate of chemical reactions without
themselves being consumed or undergoing chemical change.
Nanoparticulate catalysts have an advantage of very large specific
surface area, providing a large amount of catalytic surface area
per unit mass of catalyst material. Preferred catalysts for use in
nanoparticles of the invention include inorganic catalytic
material, which may be either supported or unsupported. By a
supported catalyst, it is meant that the catalytic material is
supported by a support material, which imparts structural integrity
to the composition. The support material may or may not affect the
catalytic performance of the composition. By unsupported catalyst,
it is meant that the catalytic material itself imparts structural
integrity to the composition. Unsupported catalysts are also
referred to as being self-supporting. Catalyst compositions may
include only one catalytic material or may include multiple
different catalytic materials. Supported catalyst compositions may
include only one type of support material or may include multiple
different types of support materials. In addition to catalytic
material, and optionally support material, catalyst compositions
may also optionally include one or more than one additive, such as
one or more than one promoter.
[0084] The catalysts may be of any composition. For example, the
nanoparticles could include an electrocatalyst material, some
non-limiting examples of which include perovskite phase metal
oxides (such as for example
La.sub.1-xSr.sub.xFe.sub.0.6Co.sub.0.4O.sub.3 or
La.sub.1-xCa.sub.xCoO.sub.3); and oxygen deficient Co--Ni--O
spinels of the form AB.sub.2O.sub.4 where A is selected from
divalent metals such as Mg, Ca, Sr, Ba, Fe, Ru, Co, Ni, Cu, Pd, Pt,
Eu, Sm, Sn, Zn, Cd, Hg or combinations thereof and B is selected
from trivalent metals such as Co, Mn, Re, Al, Ga, In, Fe, Ru, Os,
Cr, Mo, W, Y, Sc, lanthanide metals and combinations thereof. Other
examples include catalyst materials for water-gas shift reactions,
auto-thermal reforming, steam reforming and hydrodesulfurization
processes, some non-limiting specific compositional examples of
which are shown in Table 3. Table 3 lists both supported and
unsupported (self-supporting) catalyst materials. In the
compositions of Table 3, .gamma.-alumina (.gamma.-Al.sub.2O.sub.3),
magnesia (MgO), silica (SiO.sub.2) and ceria (CeO.sub.2) function
as support materials. In Table 3, the first column identifies the
general catalyst formulation(s), the second column identifies a
catalytic application in which a catalyst of that formulation might
be used, the third column provides some examples of specific
catalyst compositions, the fourth column summarizes exemplary
reaction temperatures during use of the catalyst in the identified
catalytic application, and the fifth column notes general
variations in catalyst manufacture conditions, to effect changes in
the properties of the resulting catalyst composition.
[0085] In another particular embodiment of the invention, the
nanoparticles comprise CaO. The CaO may be used to adsorb CO.sub.2
and be used to shift the equilibrium of methane gas steam reforming
to produce hydrogen more effieciently.
[0086] In another particular embodiment of the invention, the
nanoparticles comprise Pt or Pt/Ru. The matrix in this case
optionally comprises Nafion. The mutiphase particle of Pt or Pt/Ru
as nanoparticles and Nafion as the organic matrix could be used,
for example, as electrocatylists in fuel cell applications.
TABLE-US-00003 TABLE 3 EXEMPLARY CATALYST COMPOSITIONS FOR
NANOPARTICLES Representative Catalytic Catalyst Catalytic Reaction
Variations in Formulations Rxn Composition Temps. Catalyst
Synthesis AuNi/.gamma.-alumina SR/HT A) 10 wt. % Ni 650.degree.
C.-700.degree. C. Time, temperature of AuNi/MgO WGSR 0.2 wt. % Au
synthesis to vary AuNi/SiO.sub.2 B) 15 wt. % Ni, dispersion and
alloy 0.3 wt. % Au stoichiometry Ru/.gamma.-alumina SR/HT 0.1-0.3
wt. % 650.degree. C.-700.degree. C. Time, temperature of WGSR Ru
synthesis to vary dispersion Ni/CeO.sub.2/ ATR 5-15 wt. % Ni
650.degree. C.-750.degree. C. Time, temperature of .gamma.-alumina
synthesis to vary dispersion NiRu/CeO.sub.2/ ATR A) 10 wt. % Ni
650.degree. C.-750.degree. C. Time, temperature of .gamma.-alumina
0.3 wt. % Ru synthesis to vary (or other oxide B) 15 wt. % Ni,
dispersion and alloy ion conducting 0.5 wt. % Ru stoichiometry
support) Pt/CeO.sub.2/ LT 0.1-0.3 wt. % 200.degree. C.-300.degree.
C. Time, temperature of .gamma.-alumina WGSR Pt synthesis to vary
dispersion PtRu/CeO.sub.2/ LT 0.1-0.3 wt. % 200.degree.
C.-300.degree. C. Time, temperature of .gamma.-alumina WGSR PtRu
synthesis to vary Pt:Ru = 50:50 dispersion and alloy stoichiometry
NiMo/.gamma.-alumina HDS 15.0 wt. % 400.degree. C. Time,
temperature of MoO.sub.3 synthesis to vary 3.0 wt. % NiO dispersion
and alloy stoichiometry NiMo high HDS 85.0 wt. % 400.degree. C.
Time, temperature of surface area self- MoO.sub.3 synthesis to vary
supporting oxide 15 wt. % NiO PSD, porosity, surface area ZnO high
HDS/ 100% ZnO 400.degree. C. Time, temperature of surface area
self- Sulfur synthesis to vary supporting oxide removal PSD,
porosity, surface area NiMo/ZnO HDS/ 3 wt. % MoO.sub.3, 400.degree.
C. Time, temperature of Sulfur 0.6 wt. NiO synthesis to vary
removal 96.4 wt. % PSD, porosity, ZnO surface area WGSR = water gas
shift reaction ATR = auto-thermal reforming SR = steam reforming LT
= low temperature HT = high temperature HDS =
hydrodesulfurization
[0087] In one implementation of the invention, the nanoparticles
comprise pigments. The pigments may be used in a variety of
industries including but not limited to displays (AMLCD), ink jet
applications, electrophoretic applications, household
cleaner/brighteners, printing documents, etc. Table 4 lists some
non-limiting examples of inorganic pigment materials and the color
imparted by the material. The development of pigments with particle
sizes (e.g,. diameters) below 50 nm would be desirable in order to
produce images that have photo quality (high gloss), because the
particle sizes are smaller than the wavelength of light. In
addition, particles of this size will form more stable dispersions.
TABLE-US-00004 TABLE 4 EXEMPLARY PIGMENTS FOR NANOPARTICLES
MATERIAL FORMULA COLOR Iron Oxide (Hematite) Fe.sub.2O.sub.3 Red
Lead Molybdate PbMoO.sub.4 Red Cobalt Arsenate
Co.sub.3(AsO.sub.4).sub.2 Violet Iron Oxide (Magnetite)
Fe.sub.3O.sub.4 Black Iron-Chromium Oxide (Fe,Cr).sub.2O.sub.3
Brown Zinc Ferrite ZnFe.sub.2O.sub.4 Tan Iron oxyhydroxide FeOOH
Yellow Lead Antimoniate Pb.sub.3(SbO.sub.4).sub.2 Yellow Lead
Chromate PbCrO.sub.4 Yellow Zinc Chromate ZnCrO.sub.4 Yellow
Strontium Chromate SrCrO.sub.4 Yellow Nickel Titanate NiTiO.sub.3
Yellow Chrome Titanate CrTiO.sub.3 Yellow Cadmium Sulfide CdS
Yellow Chrome Oxide Cr.sub.2O.sub.3 Green Cobalt Chromite
CoCr.sub.2O.sub.4 Green Cerium Sulfide CeS Red Cobalt Aluminum
CoAl.sub.2O.sub.4 Blue Oxide Rutile TiO.sub.2 White Zinc Oxide ZnO
White Lead Carbonate PbCO.sub.3 White Zinc Sulfide ZnS White
Antimony Trioxide Sb.sub.2O.sub.3 White Cobalt Stannate CoSnO.sub.3
Blue Ferrocyanide Fe(CN).sub.6 Blue Carbon (in C Black combination
with one or more inorganic pigments)
[0088] In one particular implementation of the present invention,
the nanoparticles comprise a combination of pigment materials. For
example, the nanoparticles may comprise a combination of two or
more of the inorganic pigments listed in Table 4 in order to create
a color that cannot be created with a single inorganic pigment. As
another example, the nanoparticles may contain an inorganic
pigment, such as those listed in Table 4, combined with an organic
pigment. A layer of organic pigment on an inorganic pigment may
also aid dispersion of the pigment nanoparticles into a polymer,
organic liquid or other organic medium.
[0089] In one particular implementation of the invention, the
nanoparticles comprise semiconductor materials. Semiconductor
materials in nanoparticulate form have a variety of uses including
applications in solar cells and phosphors for diagnostic
applications. Some examples of types of semiconductor materials
include doped and undoped: IV semiconductors, II-IV semiconductors,
II-VI semiconductors, III-V semiconductors and rare earth oxides.
Specific non-limiting examples of semiconductor materials that may
be used in the nanoparticles include silcon alloys, germanium
alloys, PbS, PbO, HgS, ZnS, CdSe, CdTe, CdS:Mn, InP, InN, Ge, Si,
CeO.sub.2, Cs.sub.2O, Eu.sub.2S.sub.3, Eu.sub.2O.sub.3, ZnO, GaP,
and GaN.
[0090] In one particular implementation of the invention, the
nanoparticles comprise inorganic compounds, inorganic coordination
complexes, organometallic complexes or a combination thereof. For
example, inorganic pharmaceuticals or bioactive metal complexes
maybe incorporated as the nanoparticles. Examples include
cisplatin, carboplatin, DWA-2114R (2-aminomethylpyrrolidine(1,1
-cyclobutanedicarboxylato)Pt(II), or JM-221 (cis, trans,
cis-[Pt(NH.sub.3)(C.sub.6H.sub.11NH.sub.2)(OC(O)C.sub.3H.sub.7).sub.2Cl.s-
ub.2]). The matrix for these types of materials may be selected for
its ability to readily dissolve in the body, preferably in a
controlled manner, so as to release the inorganic active ingredient
(as nanoparticles) in a time-controlled manner.
[0091] In one particular implementation of the invention, the
nanoparticles comprise magnetic materials. Magnetic materials in
the nanoparticals have a variety of uses including applications in
magnetic memory devices, magnetic inks, and magnetic fluids.
Specific non-limiting examples include Fe.sub.2O.sub.3,
Fe.sub.3O.sub.4, Co.sub.2O.sub.3, Co.sub.3O.sub.4, Ni, and Co.
[0092] In one particular implementation of the invention, the
nanoparticles comprise super conductor materials, such as
Y.sub.2Ba.sub.2Cu.sub.3O.sub.7, La.sub.2Ba.sub.xCuO.sub.4,
Bi.sub.2Sr.sub.2Ca.sub.2Cu.sub.3O.sub.10,
Ti.sub.2Ba.sub.2Ca.sub.2Cu.sub.3O.sub.10 and MgB.sub.2.
[0093] In one particular implementation of the invention, the
nanoparticles comprise materials that have non-linear optical
properties, such as LiNbO.sub.4.
[0094] In one particular implementation of the invention, the
nanoparticles comprise lasing materials, such as Nd:YAG,
Mg:ZnO.
[0095] In one particular implementation of the invention, the
nanoparticles comprise materials that have negative coefficients of
expantion, such as YbGaGe, TaO.sub.2F, ZrW.sub.2O.sub.8,
ZrMO.sub.2O.sub.8 and ZrV.sub.2O.sub.7.
[0096] In one particular implementation of the invention, the
nanoparticles comprise a transparent electrical conducting
material. Transparent electrical conductors are useful in a variety
of applications, such as for example in manufacturing displays and
in photovoltaic cells. Table 5 lists some non-limiting examples of
transparent conducting metal oxides that may be included in the
nanoparticles. TABLE-US-00005 TABLE 5 EXEMPLARY TRANSPARENT
ELECTRICAL CONDUCTORS FOR NANOPARTICLES MATERIAL FORMULA Zinc Oxide
ZnO Indium Oxide In.sub.2O.sub.3 Tin Oxide SnO.sub.2 Indium-Tin
Oxide (ITO) Antimony-Tin Oxide (ATO) Cadmium-Oxide CdO Indium-Zinc
Oxide In.sub.2Zn.sub.2O.sub.5
[0097] It should be understood that the materials listed above are
non-limiting examples of materials that may be included in the
nanoparticles, either as a sole material phase or as one of
multiple material phases in the nanoparticles. In other
embodiments, the nanoparticles may contain materials other than
those previously noted that may be useful in a desired application
of the nanoparticles. For example, in chemical mechanical polishing
applications the nanoparticles may contain one or more hard
materials such as metal oxides (e.g. silica, alumina, zirconia and
ceria) carbides and nitrides. For absorbent applications, the
nanoparticles may contain compounds such as zinc oxide, magnesium
oxide, barium oxide, calcium oxide, copper oxide, silver oxide,
barium carbonate, nickel oxide, iron oxide, zirconium oxide,
manganese oxide and lithium oxide. Other non-limiting examples of
applications for materials included in the nanoparticles include:
anti-abrasive, electrochromic, thermochromic, electrically
conductive, electrically resistive, dielectric, moisture absorbent,
cosmetic, pharmaceutical and magnetic.
[0098] In most implementations of the invention, the
multi-component particles will comprise a volume percentage of
nanoparticles within a range having in any combination a lower
limit selected from the group consisting of 1 volume percent, 5
volume percent and 10 volume percent and an upper limit selected
from the group consisting of 99 volume percent, 80 volume percent,
50 volume percent, 30 volume percent and 25 volume percent. One
particularly preferred implementation is for the nanoparticles to
comprise up to 30 volume percent and more preferably up to 25
volume percent of the multi-component particles, but preferably
also with at least 5, at least 10, at least 50, at least 60 or at
least 75 volume percent nanoparticles. These lower volume fractions
tend to favor formation of well distributed and more completely
separated nanoparticulate domains in the multi-component particles.
As the volume percentage of nanoparticles increases, the separation
of the nanoparticulate domains tends to be less complete. For
example, with greater than about 50 volume percent of nanoparticles
in the multi-component particles, an interconnected network of the
nanoparticles may often be favored, such as is described below with
respect to FIG. 5.
[0099] D. Properties of the Multi-Component Particles
[0100] As indicated above, the multi-component particles may have a
variety of different particle sizes. In one embodiment, the
plurality of multi-component particles has a number average
particle diameter of greater than about 0.1 .mu.m and less than
about 100 .mu.m, e.g., greater than about 0.5 .mu.m and less than
about 25 .mu.m, based on electron microscopy. The plurality of
multi-component particles has a d50 particle diameter, based on
volume, greater than about 0.1 .mu.m and less than 150 .mu.m, e.g.,
greater than about 0.5 .mu.m and less than 50 .mu.m or greater than
about 0.7 .mu.m and less than about 25 .mu.m, as determined by
light scattering techniques.
[0101] The multi-component particles also may have a variety of
particle size distributions. In one embodiment, the multi-component
particles have a monomodal particle size distribution, meaning the
particle size distribution has a generally Gaussian form or log
normal.
[0102] Alternatively, the multi-component particles have a
multi-modal particle size distribution, meaning there are several
modes of particle formation, and therefore producing 2 or more
distributions of particle populations. For example, the particle
size distribution optionally is bimodal, trimodal, etc. Depending
on the application a bimodal size distribution may be desired over
a monomodal distribution. For example, in layer formation the
combination of different sizes will be more efficient at filling
voids between particles and thus increase packing density.
[0103] If the multi-component particles have a monomodal particle
size distribution, the Gaussian form may have a short, narrow
distribution or a broad distribution. The sharpness or broadness of
a particle size distribution may be determined by determining the
difference between two different dx values (e.g., d30, d40, or d50
values based on volume) for a given population of multi-component
particles. In general, the smaller the difference between the two
dx values, the sharper the distribution. Conversely, the greater
the difference between the two dx values, the broader the
distribution. In one aspect of the invention, the multi-component
particles have a d40 particle size (e.g., particle diameter) and a
d60 particle size (e.g., particle diameter), and the difference
between the d60 particles size and the d40 particle size is from
about 0.5 .mu.m to about 100 .mu.m, e.g., from about 1 .mu.m to
about 80 .mu.m or from about 5 .mu.m to about 10 .mu.m. The
desirability of having a broad or narrow particle size distribution
will vary depending on the application. A narrow size distribution
is useful, for example, when properties are affected by size, and
where a single type of property is needed. A broad particle size
distribution may be desired, for example, for coatings or for dense
film formation.
[0104] In one embodiment of the invention, the matrix of the
multi-component particles comprises multiple materials. FIG. 2
shows one embodiment of the multi-component particle 108 in which
the matrix 112 includes different matrix materials in two different
material phases 112A and 112B of the matrix 112. The two different
material phases 112A and 112B together function to maintain the
nanoparticles 110 in a distributed state. This particular
embodiment of the multi-component particle 108 contains significant
porosity 138 between the different material phases 112A and 112B of
the matrix 112. The different material phases 112A and 112B, may be
for example different organic salt materials, organic compounds,
different polymers, or a surfactant and a polymer, or any other
combination of different materials. The different material phases
112A and 112B may or may not be selectively removable from the
multi-component particle 108. One of the material phases 112A and
112B may comprise a surface-modifying material that modifies a
surface of the nanoparticles 110 when the multi-component particle
108 is decomposed to release the nanoparticles 110.
[0105] FIG. 3 shows another embodiment of the multi-component
particle 108 in which the matrix 112 comprises the two different
material phases 112A and 112B. The material phases 112A and 112B in
the embodiment of FIG. 3, however, have different morphologies than
in the embodiment of FIG. 2. Unlike FIG. 2, occurrences of the
material phase 112A tend to be in elongated bands, while the other
material phase 112B is more continuous. Again the material phases
112A and 112B may each be of any composition. For example, matrix
phase 112A could be a polymer and the more continuous phase 112B of
matrix 112 could be an organic salt.
[0106] FIG. 4 shows yet another embodiment of the multi-component
particle 108 in which the matrix 112 comprises the two different
material phases 112A and 112B. In the embodiment shown in FIG. 4,
the material phase 112A acts as a substrate for the nanoparticles
110 and the other material phase 112B of matrix 112 helps to keep
the nanoparticles 110 separated. Again, the material phases 112A
and 112B may be of any organic composition. For example, material
phase 112A could be a polymer and the other material phase 112B
could be an organic compound.
[0107] FIG. 5 shows another embodiment of the multi-component
particles in which the nanoparticles 110 are interconnected in a
network. In the embodiment shown in FIG. 5, the matrix 112
maintains the nanoparticles 110 in a partially distributed state.
The volume fraction of nanoparticles 110 in particle 108 is high
enough that the nanoparticles 110 touch (i.e. are slightly necked)
to form an interconnected network of nanoparticles 110. The
particle morphology shown in FIG. 5 may be useful for making
nanoparticles to be used in applications requiring large surface
area, such as catalysts, sorbents or separation applications. As
described above, matrix 112 may be used as an aid for delivering
the interconnected network of nanoparticles 110 into a final
product or application, and then removed to reveal the large
surface area provided by the interconnected network of
nanoparticles 110.
[0108] FIG. 6 shows another embodiment of the present invention
with a multi-component particle 108 having matrix 112 and
nanoparticles 110 with two nanoparticles 110A and 110B. In the
embodiment shown in FIG. 6, one material of the nanoparticles 110A
is a collection of particles that have combined into a single
amorphous unit. The second material of the nanoparticles 110B is
dispersed on the first material 110A. The first material 110A of
the nanoparticles acts as a substrate or a support for the second
material 110B. The nanoparticles 110 shown in FIG. 6 could be
formed for example if a first precursor to the nanoparticles reacts
prior to reaction of a second precursor, so that the first
precursor forms particles that combine to form the first material
110A, then a second precursor reacts to form the second material
110B on the first material 110A.
[0109] FIG. 7 shows another embodiment of multi-component particles
with a matrix 112 and nanoparticles 110 with two materials 110A and
110B. The first material 110A of nanoparticles 110 is a core that
is covered with a shell of the second material 110B. The
nanoparticles 110 shown in FIG. 7 could be formed if a first
precursor to the nanoparticles 110 reacts prior to reaction of a
second precursor, so that the first precursor forms the core
material 110A, then a second precursor reacts to form the shell
material 110B that covers the first material 110A.
[0110] It will be appreciated that FIGS. 2-7 are only non-limiting
examples of some embodiments of multi-component particles of the
invention having multiple matrix materials and nanoparticles. Other
morphologies are possible. Moreover, although the embodiments of
FIGS. 2-7 show only two material phases in the matrix or in the
nanoparticles, the matrix or nanoparticles could include three or
more material phases. Also, the particulate product of the
invention comprising two or more materials in the matrix or in the
nanoparticles need not comprise multiple material phases in the
matrix. The multiple matrix and nanoparticles may be present in a
single material phase. Also, the multi-component particles may have
little or may have significant porosity, and the porosity may be
open or closed and may comprise mesoporosity or microporosity.
[0111] Typically, the multi-component particles of the present
invention are spheroidal, meaning that they are generally of
spherical shape, even if not perfectly spherical. Optionally, a
majority of the multi-component particles have a morphology that is
spherical, hollow, rod, flake or platelet.
[0112] In another variation of the multi-component particles of the
invention, some or all of the nanoparticles in the multi-component
particles comprise one or more precursors that are reactable to
modify the nanoparticles while the nanoparticles are maintained in
the distributed state. The modification may involve surface
modification of the nanoparticles, such as functionalization.
Alternatively, the modification may involve compositional
modification. As one example, the matrix could comprise monomers
that are polymerizable and surround nanoparticles. As another
example, the nanoparticles could comprise a metal oxide that is
reducible to form metallic material in the nanoparticles. The
reduction could be accomplished, for example, by thermal treatment
at an elevated temperature and/or by introduction of a reducing
agent, such as hydrogen gas that is infiltrated into the matrix or
the matrix itself to contact the nanoparticles.
[0113] In another variation, the multi-component particles comprise
a surface-modifying material, which may be present in the matrix,
nanoparticles, or elsewhere in the multi-component particles. The
multi-component particles are decomposable to release the
nanoparticles, with at least a portion of the surface-modifying
material associating with the nanoparticles to modify the surface
of the nanoparticles. As one example, the surface modifying
material may be a residual surfactant or dispersing agent that
adheres to the surface of the nanoparticles. In another example,
the surface-modifying material is reactable with a surface of the
nanoparticles, before, during or after decomposition of the
multi-component particles, to attach functional groups to the
surface of the nanoparticles through chemical bonding.
[0114] In another variation, some portion or substantially all
material of the matrix in the multi-component particles is
removable by a technique other than by dissolution in a liquid.
Matrix material may be removable, for example, by sublimation,
melting, decomposition or chemical removal (e.g., by reacting the
material away).
III. PROCESSES FOR MAKING THE MULTI-COMPONENT PARTICLES
A. Overview
[0115] Several embodiments of the present invention are directed to
processes for making multi-component particles comprising inorganic
nanoparticles distributed in an organic matrix. In one embodiment,
for example, the process includes a first step in which an aerosol
comprising droplets is generated. The droplets comprise a liquid
vehicle, an inorganic nanoparticle precursor and an organic matrix
precursor. In a second step, at least a portion of the liquid
vehicle is removed from the droplets under conditions effective to
convert at least a portion of the organic matrix precursor to the
organic matrix and to convert at least a portion of the inorganic
nanoparticle precursor to the inorganic nanoparticles distributed
in the organic matrix. In another embodiment, the removing of at
least a portion of the liquid vehicle occurs, at least in part,
before the organic matrix precursor is converted to the organic
matrix and before the inorganic nanoparticle precursor is converted
to the inorganic nanoparticles distributed within the matrix.
[0116] In another embodiment, the nanoparticles are formed prior to
the step of generating the aerosol. In this embodiment, the
droplets comprise a liquid vehicle, inorganic nanoparticles and an
organic matrix precursor. In this aspect of the invention, the
removing of at least a portion of the liquid vehicle from the
droplets occurs under conditions effective to convert at least a
portion of the organic matrix precursor to the organic matrix and
to distribute the nanoparticles within the matrix.
B. Preparation of the Precursor Medium
[0117] In each of the processes for forming the multi-component
particles, an aerosol is formed from a "precursor medium," defined
herein as a flowable medium comprising: (1) a sufficient amount of
a liquid vehicle to impart flowability to the medium; and (2) one
or more precursors. As used herein, the unmodified term "precursor"
means a compound that has a first form in the precursor medium, at
least momentarily, which may be converted to a second form (which
may be different from the first form) in the final multi-component
particles of the present invention. Two preferred types of
precursors, either, neither, or both of which may be present in the
precursor medium, include: (1) an inorganic nanoparticle precursor;
and (2) a matrix precursor. As their names suggest, the inorganic
nanoparticle precursor is converted to inorganic nanoparticles in
the final multi-component particles, and the matrix precursor is
converted to the matrix in the multi-component particles. The
precursor medium may comprise one or more than one precursor (e.g.,
matrix precursor, nanoparticle precursor, or other precursor
composition), and/or one or more additives.
[0118] In one preferred embodiment, the precursor medium includes
at least two precursors, and even more preferably at least one
precursor for a material to be included in the nanoparticles and at
least one other precursor for a material to be included in the
matrix. The relative proportions of the nanoparticulate
precursor(s) and matrix precursor(s) in the precursor medium will,
therefore, vary depending upon the relative proportions of
nanoparticle(s) and matrix material(s) in the final particles and
also on the nature of the particular precursors to those materials
that are included in the precursor medium. The precursors should be
included in the precursor medium in relative proportions to provide
the proper relative proportions of the nanoparticle and the matrix
material in the particles made during the forming particle. The
amount of a precursor included in the precursor medium will be
selected to provide the desired amount of the final material in the
multi-component particles. For example, if the multi-component
particles are to contain certain weight percentages respectively of
a nanoparticle and a matrix material, then the relative quantities
of nanoparticle precursor and matrix precursor should be properly
proportioned in the precursor medium to provide the proper weight
fractions, taking into account any reactions that are involved in
converting the nanoparticulate and matrix precursors into the
respective nanoparticulate and matrix materials in the resulting
multi-component particles.
[0119] The precursor medium should also have properties that are
conducive to efficient formation of the desired droplets of the
precursor medium during the step of generating the aerosol. The
desired properties of the precursor medium for droplet generation
may vary depending upon the specific composition of the precursor
medium and the specific apparatus used to generate droplets for the
aerosol. Some properties that may be important to droplet
generation include the viscosity and surface tension properties of
the liquid vehicle, the proportion of liquid vehicle and solids,
when present, in the precursor medium, and the viscosity,
flowability and density of the precursor medium. Some properties,
such as viscosity and flowability of the precursor medium, may be
affected by the temperature of the precursor medium. Accordingly,
if it is desired to reduce the viscosity of the precursor medium to
achieve more effective droplet generation, the precursor medium may
be preheated to an elevated temperature at which the precursor
medium has a reduced viscosity. Alternatively, if a higher
viscosity is desired, the precursor medium could be pre-cooled to
an appropriate depressed temperature at which the precursor medium
has an increased viscosity. Typically, when the droplets are
generated, the precursor medium will have a viscosity of less than
1000 centipoise and usually less than 100 centipoise. If the
precursor medium contains a particulate precursor, the precursor
medium should be sufficiently viscous enough to avoid significant
settling of particles in the precursor medium during
processing.
[0120] 1. Liquid Vehicle
[0121] In a preferred embodiment, the precursor medium comprises a
liquid vehicle, which imparts flowability to the medium. The liquid
vehicle may be any liquid that is convenient and compatible for
processing precursor(s) and reagent(s) that are to be included in
the precursor medium to make the multi-component particles. The
liquid vehicle may comprise a single liquid component, or may be a
mixture of two or more liquid components, which may or may not be
mutually soluble in the proportions of the mixture. The use of a
mixture of liquid components is useful, for example, when the
precursor medium includes multiple precursors (e.g., an organic
matrix precursor and an inorganic nanoparticle precursor), with one
precursor having a higher solubility in one liquid component and
the other precursor having a higher solubility in another liquid
component. As one example, a first precursor may be more soluble in
a first liquid component of the liquid vehicle and a second
precursor may be more soluble in a second liquid component of the
liquid vehicle, but the two components of the liquid vehicle may be
mutually soluble so that the liquid vehicle has only a single
liquid phase of the first liquid component, the second liquid
component and the two dissolved precursors. Alternatively, the
liquid vehicle may have two liquid components that are not mutually
soluble, so that the liquid vehicle has two, or more, liquid phases
(e.g., an emulsion) with one precursor dissolved in one liquid
phase, for example a continuous phase, and a second precursor
dissolved in a second liquid phase, for example a dispersed phase
of an emulsion.
[0122] In some cases, the liquid vehicle may be selected to act as
a solvent for one or more than one precursor to be included in the
precursor medium, so that in the precursor medium all or a portion
of the one or more than one precursor will be dissolved in the
precursor medium. In other cases, the liquid vehicle will be
selected based on its volatility. For example, a liquid vehicle
with a high vapor pressure may be selected so that the liquid
vehicle is easily vaporized and removed from the droplets to the
gas phase of the aerosol during the formation of the particles. In
other cases, the liquid vehicle may be selected for its
hydrodynamic properties, such as viscosity characteristics of the
liquid vehicle. For example, if one or more than one precursor is
to be included in the precursor medium in the form of dispersed
particulates (such as for example colloidal-size particles
dispersed in the liquid vehicle), a liquid vehicle having a
relatively high viscosity may be selected to inhibit settling of
the precursor particles. As another example, a liquid vehicle with
a relatively low viscosity may be selected when it is desired to
produce smaller droplets of precursor medium during the generating
of the aerosol. In still other cases, the liquid vehicle may be
selected to reduce or minimize contamination of the multi-component
particles and/or production of undesirable byproducts during the
generating of the aerosol or the formation of the multi-component
particles, especially when using organic components in the liquid
vehicle.
[0123] The liquid vehicle may be an aqueous liquid, an organic
liquid or a combination of aqueous and organic liquids. Aqueous
liquids are generally preferred for use as the liquid vehicle in
most situations because of their low cost, relative safety and ease
of use. For example, water has the advantage of being
non-flammable, and when vaporized during the formation of the
particles does not tend to contribute to formation of byproducts
that are likely to complicate processing or contaminate particles.
Moreover, aqueous liquids are good solvents for a large number of
precursor materials, although attaining a desired level of
solubility for some materials may involve modification of the
aqueous liquid, such as pH adjustment.
[0124] In some situations, however, organic liquids are preferred
for the liquid vehicle. This might be the case, for example, when
it is desired to dissolve a precursor into the liquid vehicle in
situations when the precursor is not adequately soluble in aqueous
liquids, or when aqueous liquids are otherwise detrimental to the
precursor. For example, an organic liquid vehicle might be
necessary to solubilize a number of organic or organometallic
precursor materials.
[0125] 2. Matrix Precursor
[0126] Additionally, the precursor medium preferably comprises a
matrix precursor. As used herein, a "matrix precursor" is a
composition that can be converted to or forms the matrix in the
multi-component particles. In a preferred embodiment, the matrix
precursor undergoes a reaction to provide the matrix for the
multi-component particles. For example, the matrix precursor
optionally is thermally decomposed at elevated temperature or is
reduced to form the matrix in the multi-component particles. In
another embodiment, the matrix precursor could process without
reaction. For example, the matrix precursor optionally is initially
dissolved in the liquid vehicle, and a matrix precipitate of the
matrix precursor is formed as the liquid vehicle is removed from
the droplets, e.g., as the multi-component particles are formed.
This might be the case, for example, when the matrix precursor
comprises an organic salt, organic compound or a polymer dissolved
in the liquid medium, which organic salt, organic compound or
polymer precipitates out to form all or part of the matrix when the
liquid vehicle is vaporized during the formation of the
multi-component particles. As another example, the matrix precursor
could volatilize, e.g., with the liquid medium, during the
formation of the multi-component particles and then condense to
form part of the multi-component particles. One particular
implementation of this example is the use of a organic salt or
organic compound precursor for the matrix that sublimes or
vaporizes and then condenses onto the nanoparticles after formation
of the nanoparticles. In another particular implementation of this
example, the precursor medium comprises a matrix precursor and a
nanoparticle precursor, both of which may volatilize, react if
necessary, and then condense to form materials for inclusion in the
multi-component particles.
[0127] Another example of a matrix precursor that may be processed
without reaction comprises a solid matrix material suspended in the
liquid vehicle. For example, the matrix precursor could be in the
form of colloidal-size matrix particles in the precursor medium,
which colloidal particles become part of the multi-component
particles made during formation of the multi-component particles.
This might be the case, for example, when the precursor medium
contains colloidal polymer particles, which colloidal particles
then form all or part of the matrix, with or without fusing
together of the colloidal particles. When the precursor medium
comprises colloidal-size particles, e.g., matrix particles, as
discussed above, the precursor medium preferably comprises no more
than 60, no more than 40 or no more than 20 weight percent of such
colloidal-size particles. Moreover, such colloidal-size particles
preferably having a weight average size of no larger than about 100
nm and more preferably having a weight average size of no larger
than about 50 nm.
[0128] Additionally, if useful for subsequent processing or for use
in a final application, the colloidal particles in the precursor
medium could be surface modified or functionalized. By
"functionalized," it is meant that chemical functional groups have
been attached to the surface of the colloidal particles to provide
some specific chemical functionality. Such chemical functionality
may be designed to aid in the processing of the matrix precursor,
to aid in subsequent processing of the multi-component particles,
or for some purpose related to the application for which the
multi-component particles are intended. Also, particulate matrix
precursors may be in a form other than colloidal particles, such as
for example in the form of fibers, nanotubes or flakes.
[0129] 3. Inorganic Nanoparticle Precursor
[0130] In one embodiment, the precursor medium further comprises an
inorganic nanoparticle precursor. As used herein, the term
"inorganic nanoparticle precursor" means a compound that is
dissolved or dispersed in the liquid vehicle, and which may be
converted, at least in part, into inorganic nanoparticles in the
final multi-component particles.
[0131] In a preferred embodiment, the nanoparticle precursor
undergoes a reaction to provide the nanoparticles in the
multi-component particles. For example, the nanoparticle precursor
optionally is thermally decomposed at elevated temperature or is
reduced to form the nanoparticles in the multi-component particles.
In another embodiment, the nanoparticle precursor could be
processed without reaction to form the nanoparticles. For example,
the nanoparticle precursor optionally is initially dissolved in the
liquid vehicle, and a nanoparticle precipitate of the nanoparticle
precursor is formed as the liquid vehicle is removed from the
droplets, e.g., as the multi-component particles are formed. This
might be the case, for example, when the nanoparticle precursor
comprises an inorganic composition, e.g., inorganic salt, dissolved
in the liquid medium, which inorganic composition precipitates out
to form all or part of the nanoparticles when the liquid vehicle is
vaporized during the formation of the multi-component particles. As
another example, the nanoparticle precursor could volatilize, e.g.,
with the liquid medium, optionally during the formation of the
multi-component particles and then condense to form all or a
portion of the nanoparticles. One particular implementation of this
example is the use of an inorganic salt or inorganic compound
precursor for the nanoparticles that sublimes or vaporizes and then
condenses to form the nanoparticles, preferably before or during
the formation of the matrix.
[0132] Table 6 shows some non-limiting examples of some compounds
that may be used as nanoparticle precursors, and that would
normally undergo reaction to form the nanoparticles during
formation of the multi-component particles. The target material for
which a listed nanoparticle precursor provides a component is also
listed in Table 6. TABLE-US-00006 TABLE 6 EXEMPLARY NANOPARTICLE
PRECURSORS TARGET MATERIAL EXAMPLES OF PRECURSORS Platinum Platinum
hydroxide, chloroplatinic acid (H.sub.2PtCl.sub.6.xH.sub.2O);
tetraamineplatinum (II) nitrate
(Pt(NH.sub.3).sub.4(NO.sub.3).sub.2); hydroxoplatinic acid
(H.sub.2Pt(OH).sub.6); platinum nitrates; platinum amine nitrates;
platinum diamine nitrates (e.g.
Pt(NH.sub.3).sub.4(NO.sub.3).sub.2); platinum tetrachloride
(PtCl.sub.4); sodium hexahydroxyplatinum (Na.sub.2Pt(OH).sub.6);
potassium hexahydroxyplatinum (K.sub.2Pt(OH).sub.6) and
Na.sub.2PtCl.sub.4 Palladium palladium (II) chloride (PdCl.sub.2);
palladium (II) nitrate (Pd(NO.sub.3).sub.2); H.sub.2PdCl.sub.4;
Na.sub.2PdCl.sub.4; Pd(NH.sub.3).sub.4Cl.sub.2;
Pd(NH.sub.3).sub.2(OH).sub.2 and palladium carboxylates Ruthenium
ruthenium .beta.-diketonates; ruthenium nitrosyl nitrate
(Ru(NO)(NO.sub.3).sub.3); potassium perruthenate
(K.sub.3RuO.sub.4); sodium perruthenate (Na.sub.3RuO.sub.4);
(NH.sub.4).sub.3Ru.sub.2O.sub.7; NH.sub.4Ru.sub.2O.sub.7;
Ru.sub.3(CO).sub.12 and ruthenium chloride (RuCl.sub.3) Gold gold
chloride (AuCl.sub.3) and ammonium tetrachloroaurate
((NH.sub.4)AuCl.sub.4) Copper copper carboxylates; copper
acetate(Cu(OOCH.sub.3).sub.2); copper chloride (CuCl.sub.2); copper
nitrate (Cu(NO.sub.3).sub.2), and copper perchlorate
(Cu(ClO.sub.4).sub.2) Rhodium rhodium chloride hydrate
(RhCl.sub.3.xH.sub.2O); ammonium hexachlororhodium hydrate
((NH.sub.4)3RhCl6.xH.sub.2O) and rhodium nitrate
(Rh(NO.sub.3).sub.3) Titanium titanium (III) chloride (TiCl.sub.3);
titanium (IV) chloride (TiCl.sub.4) and tetrachlorodianimmo
titanium (TiCl.sub.4(NH.sub.3).sub.2) Vanadium vanadium (III)
chloride (VCl.sub.3); vanadium (IV) chloride (VCl.sub.4); vanadium
fluoride (VF.sub.4) and ammonium vanadium oxide (NH.sub.4VO.sub.3)
Manganese manganese (II) acetate hydrate
(MN(OOCCH.sub.3).sub.2.xH.sub.2O); manganese (III) acetate hydrate
(Mn(OOCCH.sub.3).sub.2.xH.sub.2O); manganese chloride hydrate
(MnCl.sub.2.xH.sub.2O); manganese nitrate (Mn(NO.sub.3).sub.2) and
potassium permangate (KMNO.sub.4) Iron iron acetate
(Fe(OOCCH.sub.3).sub.2); iron chloride hydrate
(FeCl.sub.2.xH.sub.2O); iron chloride hydrate
(FeCl.sub.3.xH.sub.2O); iron nitrate hydrate
(Fe(NO.sub.3).sub.3.xH.sub.2O); iron (II) perchlorate hydrate
(Fe(ClO.sub.4).sub.2.xH.sub.2O) and iron (III) perchlorate hydrate
(Fe(ClO.sub.4).sub.3.xH.sub.2O) Cobalt cobalt acetate hydrate
(Co(OOCCH.sub.3).sub.2.xH.sub.2O); cobalt chloride hydrate
(CoCl.sub.2.xH.sub.2O) and cobalt nitrate hydrate (Co(NO.sub.3)
xH.sub.2O) Tungsten tungsten oxychloride (WOCl.sub.4) and ammonium
tungsten oxide ((NH4).sub.10W.sub.12O.sub.41) Zinc zinc acetate
(Zn(OOCCH.sub.3).sub.2.xH.sub.2O); zinc chloride (ZnCl.sub.2); zinc
formate (Zn(OOCH).sub.2) and zinc nitrate hydrate
(Zn(NO.sub.3).sub.2.xH.sub.2O). Zirconium zirconium chloride
(ZrCl.sub.4); zirconium hydride (ZrH.sub.2) and zirconium dinitrate
oxide (ZrO(NO.sub.3).sub.2.xH.sub.2O) Niobium niobium chloride
(NbCl.sub.5) and niobium hydride (NbH) Molybdenum molybdenum
chloride; molybdenum hexacarbonyl (Mo(CO).sub.6); ammonium
paramolybdate ((NH.sub.4)Mo.sub.7O.sub.24.xH.sub.2O); ammonium
molybdate ((NH.sub.4).sub.2Mo.sub.2O.sub.7) and molybdenum acetate
dimer (Mo[(OCOCH.sub.3).sub.2].sub.2) Tin SnCl.sub.4AxH.sub.2O
Osmium OsCl.sub.3 Silver complex silver salts
([Ag(RNH.sub.2).sub.2].sup.+, Ag(R.sub.2NH).sub.2].sup.+,
[Ag(R.sub.3N).sub.2].sup.+ where R = aliphatic or aromatic;
[Ag(L).sub.x].sup.+ where L = ziridine, pyrrol, indol, piperidine,
pyridine, aliphatic substituted and amino substituted pyridines,
imidazole, pyrimidine, piperazine, triazoles, etc.;
[Ag(L).sub.x].sup.+ where L = ethanolamine, glycine, gormamides,
acetamides or acetonitrile); Silver nitrate (AgNO.sub.3); Silver
nitrite (AgNO.sub.2); Silver oxide (Ag.sub.2O, AgO); Silver
carbonate (Ag.sub.2CO.sub.3); Silver oxalate
(Ag.sub.2C.sub.2O.sub.4); Silver trispyrazolylborate
(Ag[(N.sub.2C.sub.3H.sub.3).sub.3]BH); Silver
tris(dimethylpyrazolyl)borate
(Ag[((CH.sub.3).sub.2N.sub.2C.sub.3H.sub.3).sub.3]BH); Silver azide
(AgN.sub.3); Silver tetrafluoroborate (AgBF.sub.4); Silver acetate
(AgO.sub.2CCH.sub.3); Silver propionate (AgO.sub.2CC.sub.2H.sub.5);
Silver butanoate (AgO.sub.2CC.sub.3H.sub.7); Silver ethylbutyrate
(AgO.sub.2CCH(C.sub.2H.sub.5)C.sub.2H.sub.5); Silver pivalate
(AgO.sub.2CC(CH.sub.3).sub.3); Silver cyclohexanebutyrate
(AgO.sub.2C(CH.sub.2).sub.3C.sub.6H.sub.11); Silver ethylhexanoate
(AgO.sub.2CCH(C.sub.2H.sub.5)C.sub.4H.sub.9); Silver neodecanoate
(AgO.sub.2CC.sub.9H.sub.19); Silver trifluoroacetate
(AgO.sub.2CCF.sub.3); Silver pentafluoropropionate
(AgO.sub.2CC.sub.2F.sub.5); Silver heptafluorobutyrate
(AgO.sub.2CC.sub.3F.sub.7); Silver trichloroacetate
(AgO.sub.2CCCl.sub.3); Silver
6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5- octanedionate (AgFOD);
Silver lactate (AgO.sub.2CH(OH)CH.sub.3); Silver citrate
(Ag.sub.3C.sub.6H.sub.5O.sub.7); Silver glycolate
(AgOOCCH(OH)CH.sub.3); Silver benzoate
(AgO.sub.2CCH.sub.2C.sub.6H.sub.5); Silver phenylacetate
(AgOOCCH.sub.2C.sub.6H.sub.5); Silver nitrophenylacetates
(AgOOCCH.sub.2C.sub.6H.sub.4NO.sub.2); Silver dinitrophenylacetate
(AgOOCCH.sub.2C.sub.6H.sub.3(NO.sub.2).sub.2); Silver
difluorophenylacetate (AgOOCCH.sub.2C.sub.6H.sub.3F.sub.2); Silver
2-fluoro-5-nitrobenzoate (AgOOCC.sub.6H.sub.3(NO.sub.2)F); Silver
acetylacetonate (Ag[CH.sub.3COCH.dbd.C(O--)CH.sub.3]); Silver
hexafluoroacetylacetonate (Ag[CF.sub.3COCH.dbd.C(O--)CF.sub.3]);
Silver trifluoroacetylacetonate
(Ag[CH.sub.3COCH.dbd.C(O--)CF.sub.3]); Silver tosylate
(AgO.sub.3SC.sub.6H.sub.4CH.sub.3); Silver triflate
(AgO.sub.3SCF.sub.3); Silver sterate; Silver oleate; Silver
dodecanoate Nickel Ni-nitrate (Ni(NO.sub.3).sub.2); Ni-sulfate
(NiSO.sub.4); Nickel ammine complexes ([Ni(NH.sub.3).sub.6].sup.n+
(n = 2, 3)); Ni- tetrafluoroborate (Ni(BF.sub.4).sub.2);
Ni-oxalate; Ni- isopropoxide (Ni(OC.sub.3H.sub.7).sub.2);
Ni-methoxyethoxide (Ni(OCH.sub.2CH.sub.2OCH.sub.3).sub.2);
Ni-acetylacetonate ([Ni(acac).sub.2].sub.3 or
Ni(acac).sub.2(H.sub.2O).sub.2); Ni- hexafluoroacetylacetonate
(Ni[CF.sub.3COCH.dbd.C(O--)CF.sub.3].sub.2); Ni-formate
(Ni(O.sub.2CH).sub.2); Ni-acetate (Ni(O.sub.2CCH.sub.3).sub.2);
Ni-octanoate (Ni(O.sub.2CC.sub.7H.sub.15).sub.2); Ni-ethylhexanoate
(Ni(O.sub.2CCH(C.sub.2H.sub.5)C.sub.4H.sub.9).sub.2); Ni-
trifluoroacetate (Ni(OOCCF.sub.3).sub.2) Chrome Oxide
K.sub.2Cr.sub.2O.sub.7; chrome carboxylates; and chromium oxalate
Manganese KMnO.sub.4; manganese nitrate; manganese Oxide acetate;
manganese carboxylates; manganese alkoxides; and MnO.sub.2 Tungsten
Na.sub.2WO.sub.4 and W.sub.2O.sub.3 Oxide Molybdenum
K.sub.2MoO.sub.4 and MoO.sub.2 Oxide Cobalt Oxide cobalt-amine
complexes; cobalt carboxylates and cobalt oxides Nickel Oxide
nickel-amine complexes; nickel carboxylates and nickel oxides
Copper Oxide copper-amine complexes; copper carboxylates and copper
oxides Iron Oxide iron nitrate Carbon (in carboxylic acid; benzoic
acid; polycarboxylic combination acids (e.g., terephthalic,
isophthalic, trimesic with inorganic and trimellitic acids);
polynuclear carboxylic nanoparticles) acids (e.g., napthoic acid)
and polynuclear polycarboxylic acids
[0133] Because of their lower cost, some preferred precursors from
Table 6 include nitrates, acetates and chlorides. Not listed in
Table 6 are precursors for phosphor materials, which include
nitrates, hydroxides and carboxylates of yttrium, gallium, barium,
calcium, strontium, germanium, gadolinium, europium, terbium,
cerium, chromium, aluminum, indium, magnesium, praseodymium,
erbium, thulium, praisadinium, manganese, silver, copper, zinc,
sodium and dysprosium. Boric acid may be used with precursors for
phosphors as a coreactant and/or a fluxing agent. Other inorganic
salts may be included in the precursor medium, such as NaCl, KCl,
KF, NaF, KI and Nal and may be used as coreactants and/or as
fluxing agents.
[0134] The process can further be extended to cover inorganic
nanoparticle precursors that are sensitive to oxidation or
decomposition reaction pathways through reactions with H.sub.2O
and/or O.sub.2. In the preparation of these inorganic nanoparticle
precursors, air/moisture sensitive techniques will be utilized,
which techniques are referred to herein as "Schlenk techniques."
Further, the inorganic nanoparticle precursors will then be
dissolved in a liquid solution which has been purged of any
O.sub.2/H.sub.2O by an inert atmosphere gas of, for example,
N.sub.2 or Ar, or a reducing atmosphere H.sub.2 or ammonia. The
inorganic nanoparticle precursor in this embodiment optionally
comprises any metal on the periodic table in combination with one
or more of the following ligands: a halide, an amide (e.g.,
--N(SiMe.sub.3).sub.2, --N(isopropyl).sub.2), an alkyl, aryls,
alkoxides, thiolates, carboxylates, phosphines, phosphine oxides,
nitrites, isonitriles, ethers or amines.
[0135] In one particular implementation of the invention, the
inorganic nanoparticle precursor is accompanied by a surface
modifying or encapsulating agent. The surface modifying or
encapsulating agent can exist either as a separate moiety in the
precursor medium (dissolved or undissolved therein) or as a part of
the actual precursor material. An example of this is the synthesis
of iron and iron oxide nanoparticles from an Fe(oleate).sub.2-3
nanoparticle precursor molecule. By adjusting the conditions,
nanoparticles comprising Fe, Fe.sub.3O.sub.4, or Fe.sub.2O.sub.3
can be generated. Additionally, in this embodiment, the
encapsulating moiety is a part of the original precursor material
where the surface of the nanoparticle is coated with oleate.
[0136] The step of converting the inorganic nanoparticle precursor
to the inorganic nanoparticles may occur in any of a number of
steps according to the present invention. For example, the
inorganic nanoparticles may be formed during the step of generating
the aerosol, and/or during one or more subsequent processing steps.
It is also contemplated that the inorganic nanoparticles may be
formed from the inorganic nanoparticle precursor, at least in part,
prior to the step of generating the aerosol. For example, the
nanoparticles optionally are formed as the precursor medium is
prepared. In this embodiment, the nanoparticles are formed from a
nanoparticle precursor in situ within the precursor medium, at
least in part, prior to the step of generating the aerosol from the
precursor medium, as discussed in more detail below.
[0137] As previously noted, by nanoparticles it is meant particles
having a number average particle diameter of less than about 500
nm, and typically in a range of from 1 nm to 500 nm, based on
electron microscopy, although a particular diameter or diameter
range might be more preferred for some applications. One particular
advantage of the process of the present invention is the ability to
make nanoparticles having a number average particle diameter of
from about 50 nm to about 500 nm. Nonparticulates within this
diameter range are difficult to make using other processes for
making nanoparticles, which other processes often tend toward
production of smaller, and often much smaller, nanoparticles.
[0138] Current processes (other than those of the present
invention) often do not permit growth of the nanoparticles to these
larger nanoparticulate sizes. With the present invention, however,
there is a significant ability to control nanoparticulate growth
through use of the matrix structure and process conditions. For
example, smaller nanoparticles are generally favored for production
in the gas phase during particle formation through the use of
smaller proportions of nanoparticulate precursors to matrix
precursors in the liquid medium and shorter residence times of the
aerosol in a thermal zone during processing. Also, because of the
retention of the nanoparticles in a distributed state by the matrix
structure, with the present invention the nanoparticles may be
subjected to additional processing steps, either during or after
the the step of forming the nanoparticles to promote growth of the
nanoparticles to a desired size, such as for example by thermal
treatment to permit controlled agglomeration or coalescence of
smaller nanoparticulate domains to form larger nanoparticulate
domains of a desired size.
[0139] For many applications, it is preferred to use nanoparticles
having a number average particle diameter of generally larger than
about 50 nm. One reason that nanoparticles of this size are
preferred for many applications is because it is easier to handle
the larger nanoparticles than the smaller nanoparticles that are
smaller than about 50 nm. One advantage of the process of the
present invention is that it is often controllable to make
nanoparticles within a desired range. In one embodiment, the
nanoparticles in the multi-component particles manufacturable using
the process of the present invention have a number average particle
diameter in a range having in any combination a lower limit
selected from the group consisting of 50 nm, 55 nm, 60 nm, 65 nm,
70 nm and 75 nm and an upper limit selected from the group
consisting of 500 nm, 450 nm, 400 nm, 350 nm, 300 nm, 250 nm and
200 nm. In one particularly preferred embodiment, the nanoparticles
have a number average particle diameter of from 70 nm to 300
nm.
[0140] The processes of the present invention can also be used to
make smaller-size nanoparticles, which may be preferred for some
applications. In one embodiment, the nanoparticles in the
multi-component particles manufacturable using the processes of the
invention have a number average particle diameter in a range having
in any combination a lower limit selected from the group consisting
of 1 nm, 10 nm, 20 nm and 30 nm and an upper limit selected from
the group consisting of 150 nm, 100 nm, 75 nm and 50 nm.
[0141] In like manner to the description above concerning
manufacture of larger-size nanoparticles, the final size and other
properties of these smaller-size nanoparticles may result from the
step of generating the aerosol or from subsequent processing
performed after the formation of the aerosol and/or optionally
after the formation of the particles.
[0142] 4. Preformed Inorganic Nanoparticles
[0143] Additionally or alternatively, the precursor medium further
comprises inorganic nanoparticles. In this embodiment, the
precursor medium comprises fine inorganic nanoparticles that are
suspended therein, e.g., in the liquid vehicle. Optionally, the
inorganic nanoparticles are formed prior to the step of preparing
the precursor medium. In other words, the inorganic nanoparticles
are first formed (preformed) and then are added to the liquid
vehicle to form the precursor medium.
[0144] In this embodiment, the inorganic nanoparticles are
suspended in the liquid vehicle. For example, the nanoparticle
could be in the form of colloidal-size nanoparticles in the
precursor medium, which colloidal nanoparticles become part of the
multi-component particles made during formation of the
multi-component particles. In this embodiment, colloidal inorganic
nanoparticles may form all or part a part of the nanoparticles in
the final multi-component particles. In one embodiment, the
nanoparticles in the colloidal dispersion agglomerate and/or fuse
together to form larger inorganic nanoparticles in the final
multi-component particles. In one embodiment, the nanoparticles in
the colloidal dispersion seed the growth of other inorganic
nanoparticles in the final multi-component particles. In this case
the composition of the seeding nanoparticles may be different than
the inorganic nanoparticles in the final multi-compont particles.
Additionally, if useful for subsequent processing or for use in a
final application, the colloidal nanoparticles in the precursor
medium could be surface modified or functionalized. By
"functionalized," it is meant that chemical functional groups have
been attached to the surface of the colloidal nanoparticle to
provide some specific chemical functionality. Such chemical
functionality may be designed to aid in the processing of the
nanoparticle precursor, to aid in subsequent processing of the
multi-component particles, or for some purpose related to the
application for which the multi-component particles are
intended.
[0145] In another embodiment, as mentioned above, the inorganic
nanoparticles are formed in situ within the precursor medium prior
to the step of generating the aerosol from the precursor medium. In
this embodiment, an inorganic nanoparticle precursor is added to
the precursor medium. Once in the precursor medium, the inorganic
nanoparticle precursor is converted to the inorganic nanoparticles
prior to aerosol generation. In this embodiment, the conversion of
the inorganic nanoparticle precursor to the inorganic nanoparticles
may occur, for example, by contacting the inorganic nanoparticle
precursor with a reducing agent under conditions effective to form
the inorganic nanoparticles in the precursor medium. Optionally,
the precursor medium is heated to facilitate the conversion of the
inorganic nanoparticle precursor to the inorganic nanoparticles.
Many processes are known for forming inorganic nanoparticles. See,
for example, U.S. Patent Publications Nos. US 2003/0148024 A1,
filed Oct. 4, 2002; US 2003/0180451 A1, filed Oct. 4, 2002; US
2003/0175411 A1, filed Oct. 4, 2002; US 2003/0124259, filed Oct. 4,
2002, US 2003/0108664 A1, filed Oct. 4, 2002, and US 2003/0161959
A1, filed Nov. 1, 2002, the entireties of which are incorporated
herein by reference.
[0146] 5. Other Additives
[0147] In addition to the above-described components, the precursor
medium optionally includes one or more additives or reagents. In
one embodiment, the additive ultimately will become distributed
within (or become a part of) the organic matrix. In this aspect,
the addive optionally comprises one or more of a surfactant, a
reducing agent, a fluxing agent, an adhesion promoter or a
hardening agent.
[0148] In one aspect of the invention, the precursor medium
comprises one or more reagent additives, in addition to the liquid
vehicle and precursor(s). As used herein, a "reagent additive" or a
"reagent" in the precursor medium is a material, other than the
liquid vehicle, that is included in the precursor medium for a
reason other than to provide a component for inclusion in the
particles made during the formation of the multi-component
particles. Rather, the reagent additive serves another purpose that
is beneficial to the formulation of the precursor medium or aids
during processing to make the multi-component particles. An example
of a reagent additive would be, for example, a base or acid
material added to adjust solution pH of the liquid vehicle.
[0149] One important example of a reagent additive for some
implementations of the invention is a reducing agent. The optional
reducing agent may be in the form of a particulate suspended in the
liquid vehicle or, more likely, will be dissolved in the liquid
vehicle. The purpose of the reducing agent is to assist creation of
an environment during formation of the multi-component particles
that promotes formation of a material in a chemically reduced form
that is desired for inclusion in the multi-component particles as
the multi-component particles are formed. For example, the reducing
agent may facilitate the conversion of the inorganic nanoparticle
precursor to the inorganic nanoparticles and/or in the conversion
of the matrix precursor to the matrix. In the former embodiment,
the reducing agent is included to promote reduction of a metal
oxide, salt or other inorganic nanoparticle precursor compound to
the desired metallic form. A reducing agent does not necessarily
reduce an oxidized material to form a desired reduced form of the
material, but may simply change the chemistry of the precursor
medium to favor the formation of the reduced form of the material,
such as by scavenging or otherwise tying up oxidizing materials
present in the environment. In some implementations, the reduced
form of the material could be made without the use of the reducing
agent by processing the aerosol at a higher temperature as the
multi-component particles are formed, but use of the reducing agent
permits the desired reduced form of the material to be made at a
lower temperature. An important application is when making
particles that include metallic nanoparticles and matrix including
a material that cannot be effectively processed at high
temperatures that may be required to prepare the metallic
nanoparticles absent the use of a reducing agent. For example, use
of a reducing agent may permit the processing temperature to be
maintained below the melting temperature of the matrix precursor,
e.g., an organic salt or organic compound, or below the
decomposition temperature of the matrix material itself, whereas
the processing temperature would exceed those limits without use of
the reducing agent.
[0150] As an alternative to including a reducing agent in the
precursor medium, a reducing agent could instead be included in the
gas phase of the aerosol, such as for example using a nitrogen gas
phase or other oxygen-free gas composition with addition of some
hydrogen gas as a reducing agent. In other situations, the reduced
form of the material could be formed even at the desired lower
temperature using a nonoxidizing gas phase in the aerosol, such as
pure nitrogen gas or some other oxygen-free gas composition.
However, by including a reducing agent in the precursor medium, the
use of a nonoxidizing gas phase or a reducing agent in the gas
phase may often be avoided, and air may instead be used as the gas
phase. This is desirable because it is usually much easier and less
expensive to generate and process the aerosol using air. The
reducing agent preferably donates electrons (is oxidized) and/or is
a material that either reacts to bind oxygen or that produces
decomposition products that bind with oxygen. The bound oxygen
often exits in the gas phase in the form of one or more components
such as water vapor, carbon dioxide, carbon monoxide, nitrogen
oxides and sulfur oxides. Reducing agents included in the precursor
medium optionally are carbon-containing materials, with carbon from
the reducing agent reacting with oxygen to form carbon dioxide
and/or carbon monoxide. The reducing agent may also contain
hydrogen, which reacts with oxygen to form water. Table 7 shows
some non-limiting examples of reducing agents that may be included
in the precursor medium, typically dissolved in the liquid vehicle.
TABLE-US-00007 TABLE 7 EXEMPLARY REDUCING AGENTS MATERIALS SPECIFIC
EXAMPLES Amines Triethyl amine; Amino propanol Boranes Borane-
tetrahydrofuran Borane adducts Trimethylamineborane Borohydrides
Sodium borohydride, lithium borohydride Hydrides Tin hydride,
lithium hydride, lithium aluminum hydride Alcohols Methanol,
ethanol, isopropanol, terpineol, t-butanol, ethylene glycols,
citrates, other polyols Silanes Dichlorosilane Carboxylic acid
Formic acid Aldehyde Formaldehyde; octanal, decanal, dodecanal,
glucose Hydrazines Hydrazine, hydrazine sulfate Phosphorous
Hypophosphoric Acid compounds
[0151] Table 8 shows non-limiting examples of some preferred
combinations of reducing agents and inorganic nanoparticle
precursors that may be included in the precursor medium for
manufacture of a variety of metal nanoparticles. TABLE-US-00008
TABLE 8 EXEMPLARY NANOPARTICLE PRECURSOR/ REDUCING AGENT
COMBINATIONS NANOPARTICLE PRECURSOR REDUCING AGENT Most Metal
Nitrates Amines (e.g. triethylamine), ethylene glycols, alcohols
(terpineol), aminopropanol Copper Nitrate Long chain alcohols;
citrates, carboxylates Most Metal Amines (e.g. Carboxylates
triethylamine), ethylene glycols, alcohols (terpineol),
aminopropanol
[0152] Another important reagent additive that may be included in
the precursor medium in some implementations of the invention is an
oxidizing agent. The purpose of an oxidizing agent is to help
create an environment during formation of the multi-component
particles that is conducive to making a desired oxidized form of a
material for inclusion in particles made during the forming
particles. The oxidizing agent may provide oxygen in addition to
the oxygen that might be present when air is used as the gas phase
to make the aerosol. Alternatively, the oxidizing agent may be used
in combination with a nonoxidizing carrier gas, such as pure
nitrogen gas, to provide a controlled amount of oxygen to form the
desired oxidized form of the material. One application for such
control of the oxidation is when making one oxide of a metal that
may form into multiple different oxide forms. For example, a
controlled amount of oxygen may be used during the manufacture of
magnetite to inhibit formation of the more oxidized iron oxide form
of hematite.
[0153] Table 9 shows non-limiting examples of some oxidizing agents
that may be included in the precursor medium, typically dissolved
in the liquid vehicle, such as to assist in the making of oxide
materials. TABLE-US-00009 TABLE 9 OXIDIZING AGENTS CHEMICAL TYPES
EXAMPLES FORMULA Amine Oxides Trimethylamine-N- Me.sub.3NO Oxide
Mineral Acids nitric acid, sulfuric HNO.sub.3, H.sub.2SO.sub.4,
acid, aqua regia HNO.sub.3/HCl Organic Acids carboxylic acids
R--COOH Peroxides hydrogen peroxide HOOH Phosphine Oxides trioctyl
phosphine OP(C.sub.8H.sub.17).sub.3 oxide Ozone O.sub.3 Sulfur
Oxides sulfur dioxide SO.sub.2 Ammonia in NH.sub.3 & O.sub.2
combination with Oxygen
[0154] Another reagent additive that may be included in the
precursor medium in some situations is a fluxing agent to assist
crystal growth or recrystalization of material in the particles
made during formation of the multi-component particles. As
indicated above, one or more of NaCl, KCl, KF, NaF, KI, NaI, or any
of the salts listed in Table 6 may be included in the precursor
medium as fluxing agents. A particularly preferred fluxing agent
for particles containing phosphor materials is lithium nitrate.
[0155] The relative quantities of precursors, liquid vehicle and
additives in the precursor medium will vary, depending on, for
example, the desired composition and morphology of the
multi-component particles to be produced according to the present
invention and the particular feed materials used to prepare the
aerosol during the generation of the aerosol. In most situations,
however, the liquid vehicle will be present in the precursor medium
in the largest proportion, with the precursor medium typically
comprising at least 50 weight percent of the liquid vehicle and
often at least 70 weight percent of the precursor medium.
[0156] As indicated above, the precursor medium comprises at least
one precursor to a material for inclusion in the particles made
during formation of the multi-component particles, such as material
that forms all or part of the nanoparticles or a material that
forms all or part of the matrix. As generated during the generation
of the aerosol, the gas phase of the aerosol may also comprise one
or more than one precursor. For example, when making oxide
materials, air is often used as the carrier gas to generate the
aerosol, and the oxygen component of the air is often used as a
precursor to provide at least a portion of the oxygen component of
the oxide material. The precursor medium will typically comprise,
in solution and/or as particulate precursor, no more than about 50
weight percent precursor(s), and preferably no more than about 25
weight percent precursor(s). In most situations, however, the
precursor medium will comprise at least 5 weight percent
precursor(s). When the precursor medium comprises dissolved
precursors, the precursor medium will typically comprise no more
than 25 weight percent of such dissolved precursor(s).
[0157] In another embodiment, the precursor medium further
comprises a dispersing agent and/or a dispersing agent precursor.
As discussed in greater detail below, a dispersing agent in the
final multi-component particles minimizates nanoparticle
agglomeration as the nanoparticles in the multi-component particles
are dispersed from the multi-component particles, e.g., as the
matrix is dissolved in a liquid medium. For example, a polymer or
surfactant, as listed previously, for use as the dispersing agent
could be dissolved in the liquid vehicle, with the polymer
precipitating out and being included in the particles during
formation of the multi-component particles. Alternatively, the
dispersing agent may be a material that is formed during formation
of the multi-component particles from reaction of precursor(s)
included in the precursor medium and/or the carrier gas.
[0158] In another embodiment, the precursor medium further
comprises a adhesion agent and/or a hardening agent precursor.
These precursors may be incorporated into the nanoparticle phase or
the organic matrix phase of the final multi-component particles.
Depending on the application, adhesion promoters may be added to
the multi-component particles to improve adhesion of either the
nanoparticles or the multi-component particles themselves when
deposited on various substrates. For example, metal oxides may be
added to multi-component particles that contain silver. When the
silver nanoparticles are dispersed from the organic matrix and
applied in a thin film and sintered together, the adhesion
promoters will aid in improving adhesion of the film on glass or
ceramic type substrates. Likewise, hardening promoters may be added
to help the improve the hardness of similar nanoparticle thin
films.
C. Generation of the Aerosol
[0159] As indicated above, in various embodiments of the present
invention, a mist or aerosol is generated from the precursor
medium. As used herein, the term "aerosol" means a gas dispersion
comprising a disperse phase that includes a plurality of droplets
dispersed in and suspended by a gas phase. Thus, as generated, the
aerosol has a disperse phase of droplets of the precursor medium
dispersed in and suspended by the gas phase.
[0160] The aerosol may be prepared using any technique for
atomizing the precursor medium (e.g., converting the precursor
medium to an aerosol of finely divided form of droplets). During
the step of generating the aerosol, the atomized droplets of
precursor medium are dispersed and suspending in a gas phase.
[0161] As noted previously, in the step of generating the aerosol,
droplets of the precursor medium are formed, dispersed and
suspended in a carrier gas to form the aerosol. The droplets may be
generated using any appropriate apparatus for finely dividing
liquids to produce droplets. Apparatuses for generating such
droplets are referred to by a variety of names, including liquid
atomizers, mist generators, nebulizers and aerosol generators. The
technique and apparatus used to generate the aerosol may vary
depending upon the application.
[0162] One example of an apparatus for generating the droplets and
mixing the droplets with the carrier gas to form the aerosol is an
ultrasonic aerosol generator, in which ultrasonic energy is used to
form or assist formation of the droplets. One type of ultrasonic
aerosol generator is a nozzle-type apparatus, with the nozzle
ultrasonically energizable to aid formation of droplets of a fine
size and narrow size distribution. Another example of an ultrasonic
aerosol generator ultrasonically energizes a reservoir of precursor
medium, causing atomization cones to develop, from which droplets
of the precursor medium form, and the droplets are swept away by a
flowing carrier gas. The reservoir-type ultrasonic aerosol
generators can produce very small droplets of a relatively narrow
size distribution and are preferred for use in applications when
the final multi-component particles are desired to be in a range of
from about 0.2 to about 5 microns (weight average particle size),
and especially when a narrow size distribution of the particles is
desired. An example of a reservoir-type ultrasonic aerosol
generator is described, for example, in U.S. Pat. No. 6,338,809,
the entire contents of which are incorporated by reference herein
as if set forth herein in full. Although both the nozzle-type
ultrasonic aerosol generator and the reservoir-type ultrasonic
aerosol generator produce small droplets of a relatively narrow
size distribution, the reservoir-type generally produces finer
droplets of a more uniform size.
[0163] Another example of an apparatus for generating droplets is a
spray nozzle (not ultrasonically energized). Several different
types of spray nozzles exist for producing droplets in aerosols,
and new spray nozzles continue to be developed. Some examples of
spray nozzles include 2-fluid nozzles, gas nozzles and liquid
nozzles. Spray nozzle generators have an advantage of very high
throughput compared to ultrasonic generators. Droplets produced
using spray nozzles, however, tend to be much larger and to have a
much wider size distribution than droplets produced by ultrasonic
generators. Therefore, spray nozzles are preferred for making
relatively large multi-component particles. Other types of droplet
generators that may be used include rotary atomizers, and droplet
generators that use expansion of a supercritical fluid or high
pressure dissolved gas to provide the energy for droplet formation.
Still another process for generating droplets is disclosed in U.S.
Pat. No. 6,601,776, the entire contents of which are incorporated
herein by reference in as if set forth herein in full.
[0164] It will be appreciated that no matter what type of droplet
generator is used, the size of the multi-component particles
ultimately produced will depend not only upon the size of the
droplets produced by the generator, but also on the composition of
the precursor medium (such as the concentration and types of
precursor(s) in the precursor medium).
[0165] As initially generated, the aerosol will have a gas phase
that is wholly, partially or primarily composed of the carrier gas
used to generate the aerosol. The gas phase may have some minor
components provided by the precursor medium during the generation
of the aerosol, such as some liquid vehicle vapor from vaporization
of some liquid vehicle during the generation of the aerosol. The
carrier gas may be any convenient gas composition and may be, for
example, a single component gas composition (such as for example
pure nitrogen gas) or a mixture of multiple gas components (such as
for example air, or a mixture of nitrogen and hydrogen). As the
aerosol is processed, however, the composition of the gas phase
will change. For example, during the formation of the particles,
the liquid vehicle is removed from the droplets to the gas phase,
typically by evaporation caused by heating. Also, if the precursor
medium contains reactive precursors or reagents, as the precursors
or reagents react, the composition of the gas phase will contain
decomposition products and reaction byproducts. At the conclusion
of the forming of the multi-component particles, the aerosol will
typically comprise an altered gas phase composition and a
dispersion of the multi-component particles.
[0166] In some implementations, the carrier gas used to generate
the aerosol will be substantially non-reactive. For example, the
gas phase may contain only one or more inert gases, such as
nitrogen and/or argon, depending upon the situation. Air can be
used as a non-reactive carrier gas, when the oxygen component of
the air is not reactive during processing. In other cases the
carrier gas will include one or more reactive components that react
during processing, and often during the formation of the
multi-component particles. For example, the carrier gas, and
therefore the gas phase of the aerosol as generated, may contain a
reactive precursor to a material for inclusion in the particles
(such as for example reactive oxygen gas when making some oxide
materials) or a reactive reagent (such as hydrogen gas useful as a
reducing agent when making some metallic materials).
D. Processing of the Droplets
[0167] After the aerosol is generated, the aerosol preferably is
processed to remove at least a portion of the liquid vehicle in the
droplets and form the multi-component particles. During this
processing step, the nanoparticles are maintained in a distributed
state within the multi-component particles by the matrix.
[0168] During the processing step, the liquid vehicle is removed
from the droplets and particles are formed, which particles are
dispersed in the aerosol. Removal of the liquid vehicle from the
droplets may be accomplished, for example, by vaporizing the liquid
vehicle to form a vaporized vehicle, which is yielded into and
mixed with the gas phase. Such vaporization is preferably aided by
heating of the aerosol. Also during the processing step, precursors
(e.g., the inorganic nanoparticle precursor and/or the matrix
precursor) in the aerosol may undergo one or more reactions or
other transformations or modifications required to make the
multi-component particles.
[0169] Thus, the processing step may include, for example, reaction
of precursors, material phase redistribution, crystal growth or
regrowth, nanoparticulate phase formation, growth of
nanoparticulate sizes (such as through nanoparticulate
agglomeration or coalescence), compositional modification, particle
coating, etc. The nanoparticles may agglomerate and coalese during
formation of the multi-component particles to form larger diameter
nanoparticles. For example, particles formed in the aerosol may not
have undergone all necessary chemical reactions or morphological
modifications necessary to form the desired final particles. In
this case, the particles may be collected from the aerosol and
subjected to a subsequent heat treatment during which precursor
reactions or other particle transformations or modifications may
occur that are required to make the desired final particles. Also,
all precursors and reagents required to form the desired final
particles may be included in the aerosol, or one or more precursor
or reagent may be introduced separately during subsequent
processing steps.
[0170] The formation of the multi-component particles may be
performed in any apparatus suitable for removing liquid vehicle
from the droplets to the gas phase of the aerosol and reacting or
otherwise processing the precursors to make the particles
comprising the desired nanoparticles and matrix. Reactions to be
accommodated during formation of the multi-component particles may
include for example thermal decomposition of precursor(s), reaction
of precursor(s) with other materials and reaction of reagents.
Other processing of the precursors that may occur during formation
of the multi-component particles may include for example,
precipitating dissolved precursor(s) from the liquid vehicle and
fusing particulate precursor(s).
[0171] Removing liquid from the droplets and reaction of
precursor(s) may occur in the same or different equipment. The
removing liquid is typically accomplished by vaporizing liquid
vehicle, with the liquid vehicle vapor then mixing into the gas
phase of the aerosol. Vaporization of the liquid vehicle is
preferably accomplished by heating the aerosol to a temperature at
which most, and preferably substantially all, of the liquid vehicle
in the droplets vaporizes. In one embodiment, the step of removing
the liquid vehicle comprises heating the droplets to a maximum
temperature of from about 50.degree. C. to about 800.degree. C.
(e.g., from about 100.degree. C. to about 500.degree. C. or from
about 200.degree. C. to about 400.degree. C.) for a period of time
of at least about 0.5 seconds, e.g., at least 1 second, at least
about 5 seconds or at least about 10 seconds. In a preferred
embodiment, reactions or other processing of precursors to form the
desired particles are accomplished in a reactor or reactors. By a
reactor, it is meant an apparatus in which a chemical reaction or
structural change to a material is effected. The removing of the
liquid vehicle from the droplets may occur in the reactor or may
occur in separate process equipment upstream of the reactor, or in
both.
[0172] During formation of the multi-component particles, at least
a portion and preferably substantially all, of the liquid vehicle
is removed from the droplets to the gas phase of the aerosol. Also
during formation of the multi-component particles, the
matrix/nanoparticulate structure of the multi-component particles
is formed, with the nanoparticles being maintained in a distributed
state throughout the multi-component particles by the matrix.
Removing at least a portion of the liquid vehicle from the droplets
during formation of the multi-component particles occurs in the
aerosol, and often the nanoparticulate/matrix structure is also
formed in the aerosol, so that the multi-component particles that
result from the forming of the particles are formed in a dispersed
state in the aerosol. The removing of the liquid vehicle from the
droplets and the formation of the nanoparticulate/matrix structure
of the multi-component particles may occur in the aerosol in a
single apparatus or processing stage (e.g., both may occur while
the aerosol passes through a thermal reactor). Alternatively,
removing at least a portion of the liquid vehicle may be performed
in a separate apparatus or step from the termination of the
nanoparticulate/matrix structure (e.g., aerosol first dried in a
dryer to form precursor particles without the
nanoparticulate/matrix structure, followed by processing of the
aerosol through a separate thermal reactor in which the
nanoparticulate/matrix structure is formed). In yet another
alternative, at least part of the liquid vehicle is removed from
the droplets in the aerosol to form such precursor particles, the
precursor particles are then separated from the aerosol, and the
separated precursor particles are then processed to form the
nanoparticulate/matrix structure (e.g., by controlled thermal
treatment such as in a belt furnace, rotary furnace or tray
furnace, with or without the introduction into the furnace of
additional reactant(s) or control of the furnace atmosphere).
[0173] In one embodiment of the present invention, removing at
least a portion of the liquid vehicle (and perhaps substantially
all of the liquid vehicle) from the droplets of precursor medium in
the aerosol and reacting precursors to form the desired materials
for inclusion in the multi-component particles are performed in
separate steps. The removing of the liquid vehicle from the
droplets may be performed in a reactor, furnace or using spray
drying equipment, to produce a precursor particulate product that
is collected for further processing. In some cases, the precursor
particulate product made by removing the liquid vehicle from the
droplets may not have distinct matrix and nanoparticulate phases,
but may contain a single phase of mixed precursor(s) that have not
yet reacted to form the matrix and nanoparticles. However, in other
cases the precursor(s) to the matrix and the precursor(s) to the
nanoparticles may already be in separate phases. The precursor
particulate product made by removing the liquid vehicle from the
droplets may then be subjected to a heat treatment in a separate
reactor or furnace (e.g. belt furnace, tray furnace or rotary
furnace) to react the precursors to form the desired matrix and
nanoparticles and to impart the nanoparticulate/matrix structure.
It should be noted that in some cases during the heat treatment the
matrix material of several multi-component particles may fuse
together to form a continuous structure of matrix material with
distributed nanoparticles and no longer be in the form of
individual multi-component particles. If it is desirable to have
discrete multi-component particles, the continuous structure of
matrix with distributed nanoparticles may be jet milled or hammer
milled to form separate multi-component particles.
[0174] Another example of a reactor for possible use during
formation of the multi-component particles is a plasma reactor. In
a plasma reactor, the aerosol is passed through an ionized plasma
zone, which provides the energy for effecting reactions and/or
other modifications in the aerosol. Another example of a reactor
for possible use during formation of the multi-component particles
is a laser reactor. In a laser reactor, the aerosol is passed
through a laser beam (e.g., a CO.sub.2 laser), which provides the
energy for effecting reactions and/other modifications in the
aerosol. Plasma reactors and laser reactors have an advantage of
being able to reach very high temperatures, but both require
relatively complicated peripheral systems and provide little
ability for control of conditions within the reactor during
particle formation.
[0175] Another example of a reactor for possible use during the
forming particles is a hot-wall furnace reactor. In a hot-wall
furnace reactor, heating elements heat zones of the inside wall of
the reactor to provide the necessary energy to the aerosol as it
flows through the reactor. Hot-wall furnace reactors have
relatively long residence times relative to flame, plasma and laser
reactors. Also, by varying the temperature and location of heat
input from heating elements in the different heating zones in the
reactor, there is significant ability to control and vary the
environment within the reactor during particle formation.
[0176] A spray drier is another example of a reactor that may be
used during the forming particles. Spray driers have the advantage
of having high throughput, allowing large amounts of particles to
be produced. However, because of their larger size they provide
less of an ability to control the reactor conditions during
particle formation.
[0177] In one embodiment of present invention, during the forming
of the particles, the average stream temperature of the aerosol
does not exceed a melting temperature of the matrix material for
longer than a specific period of time. The length of the specific
period of time will depend on the particular reactor used during
the forming of the particle. As a non-limiting example, in those
cases in which a spray dryer is being used in the forming
particles, the period of time may be as much as about 10 seconds,
as much as about 20 seconds, as much as about 30 second or even as
much as about 40 seconds. However, if a different reactor system is
being used in the forming particles step, the period of time may be
as short as about 8 seconds, as short as about 5 seconds or even as
short as about 1 second. In other situations, the period of time
may be less than about 1 second, such as from about 0.01 seconds to
about 0.5 seconds.
E. Collection and Quenching of the Multi-Component Particles
[0178] In one embodiment, the process of the present invention
includes a step of collecting the multi-component particles after
the formation of the particles. The collecting of the particles may
be performed, for example, immediately following formation of the
multi-component particles or after further processing of the
particles in aerosol. During the collecting of the particles, at
least a portion and preferably substantially all of the particles
are separated from the aerosol. The separation may be effected by
any solid/gas separation technique, for example by using a filter,
a cyclone, bag house, or electrostatic precipitator.
[0179] In one preferred embodiment, during the collection of the
particles the multi-component particles are separated from the gas
phase of the aerosol directly into a liquid medium. The particles
may be collected directly into the liquid medium by spraying the
liquid medium into the aerosol, such as by using venturi scrubbers,
to capture the particles in the droplets of liquid medium, and then
collecting the liquid medium containing the particles. The
particles may be collected directly into a liquid medium by
impinging the particles into a "wall" of liquid medium, such as by
using a wetted wall electrostatic precipitator. The wall of liquid
medium may be, for example, a flowing film or sheet of the liquid
medium. The gas phase of the aerosol may pass through the wall of
liquid medium, or a flow of the aerosol may be subjected to a
sudden change indirection, with momentum carrying the particles
into the wall of liquid medium. The liquid substance containing the
particles is then collected.
[0180] One advantage of collecting the particles directly into a
liquid medium is inhibition, and preferably prevention, of
agglomeration of the particles, which may occur with other
collection techniques. More importantly, many implementations of
the present invention include processing the particles in a liquid
medium, and collecting the particles directly into a liquid medium
can significantly simplify the processing. For example, if the
particles are collected directly into a liquid medium of a type to
be used for processing, this eliminates the need to collect and
then disperse the collected particles in the liquid medium. The
dispersion in the liquid medium has been accomplished as part of
the collection. After the particles have been collected into the
desired liquid medium, then reagents/reactants may be added to the
liquid medium for desired processing (e.g., for modification of
nanoparticles or matrix). Alternatively, at the time of particle
collection, the liquid medium may already have one or more reagents
and/or reactants for such processing.
[0181] In one embodiment, the liquid medium into which the
particles are collected is a solvent for one or more materials
included in the matrix of the particles. Consequently, removal of
at least a portion, or even substantially all, of the matrix is
automatically effected in the liquid medium as it is being used to
collect the particles. In one embodiment, the liquid medium may
dissolve a sufficient portion of material of the matrix to
automatically release the nanoparticles from the particles. In
another embodiment, the liquid vehicle may dissolve only a portion
of the matrix material that is not sufficient to release the
nanoparticles, so that the nanoparticles continue to be held in a
distributed state by the remaining matrix material. In this case,
the matrix may be comprised of multiple materials, with the liquid
medium being a selective solvent for one of the matrix materials
relative to another of the matrix materials, so that there is
selective removal of one of the matrix materials relative to
another of the matrix materials.
[0182] In another variation of collecting particles directly into a
liquid medium during the collecting of the particles, the liquid
medium as used during the collecting of the particles may be a
solvent for one or more materials of the matrix and also contain
one or more reactants and/or reagents for performing a modification
of the nanoparticles. Such a modification could involve, for
example, a surface modification, compositional modification and/or
structural modification of the nanoparticles or the matrix, in a
manner as previously discussed. For example, the liquid medium may
contain a surface-modifying material, such as a dispersing agent,
that surface modifies the nanoparticles in the liquid medium of the
collection. As another example, liquid medium used for collection
may include reactants for use in attaching functional groups to the
surface of the nanoparticles, or reactants for use to
compositionally modify the nanoparticles.
[0183] In one aspect the process of the invention includes a step
of quenching particles performed prior to the collecting of the
particles. The quenching of the particles may be performed to
quickly reduce the temperature of the particles after formation of
the particles. Preferably, the quenching of the multi-component
particles occurs within about 1 second, e.g., within about 0.1
seconds, within about 0.01 seconds or within about 0.001 seconds,
of the step of collecting the multi-component particles in the
liquid medium. This might be necessary, for example, to maintain a
crystalline structure of the nanoparticles or matrix and avoid or
limit crystal growth. Additionally, if it is undesirable to have
the particles agglomerate after the forming of the particles, the
quenching of the particles may be performed to quickly reduce the
temperature of the particles to prevent them from or minimize
agglomeration.
[0184] In one embodiment, the multi-component particles are formed
in the aerosol, and a quench gas that is at a lower temperature
than the aerosol is used during the quenching of the particles to
reduce the temperature of the particles. In this embodiment, the
quench gas is mixed into the aerosol after the particles have been
formed, such as by injecting a stream of the quench gas cocurrent
with or counter current to the flow of the aerosol. In most cases,
the quench gas will contain non-reactive gases that merely reduce
the temperature of the particles and do not react with any
materials in the particles. However, in some cases, the quench gas
may contain oxidizing agents, reducing agents or precursors that
react with materials in the particles to form a new material or
modify existing materials in the particles.
[0185] In another embodiment of the process the quenching of the
particles may be performed using a liquid medium. In this case, the
quenching of the particles and the collecting of the particles may
be accomplished in a single step using a single liquid medium. The
liquid medium used for collection of the particles may also quench
the particles as they are collected in the liquid medium. The
liquid medium used to collect and quench the particles may contain
a variety of materials for modifying the matrix and/or the
nanoparticles.
F. Applications for the Multi-Component Particles
[0186] The multi-component particles according to the present
invention have a variety of applications.
[0187] One particularly useful application for use of the
nanoparticles made using the present invention is in ink and paste
formulations. Nanoparticles provide a variety of advantages over
larger particulates in ink and paste formulations such as higher
solid loading, better flowability, an ability to deposit smaller
features and ink stability (e.g., reduced tendency for particle
settling). A variety of techniques are available for depositing,
patterning and/or printing inks and pastes that contain
nanoparticles made using the present invention, some non-limiting
examples of which include ink jet printing, lithographic printing,
flexographic printing, roll printing, intaglio, spraying, dip
coating, spin coating, stenciling, stamping, liquid embossing,
gravure printing and screen printing.
[0188] The advantages achieved by using nanoparticles in inks and
pastes are particularly important in printing circuit features for
display and electronic applications, manufacturing membrane
electrode assemblies for use in fuel cells and manufacturing of
batteries. Many circuit features, or components, of displays and
electronics, such as conductors, dielectrics, light emitters and
resistors are deposited onto substrates (organic and inorganic)
using inks and pastes, which are applied to the substrates using a
variety of techniques, such as those previously listed. Typically,
after an ink or paste is deposited onto a substrate, the deposited
paste or ink is subjected to heat treatment to convert the ink or
paste into the desired circuit component. For example, one
technique for making electrically conductive lines on circuit
boards is by depositing an ink containing particles of electrically
conductive material (such as particles of an electrically
conductive metal, e.g., gold, silver, copper, nickel, conductive
alloys) onto the circuit board substrate, such as by ink-jetting,
and then heat treating the deposited ink to form a solid
electrically conductive line. These inks typically contain metallic
particles. Because of the smaller size, using nanoparticles in the
inks will allow the deposition of thinner conducting lines on
substrates, and consequently, will allow a greater number of
circuit features to be deposited per unit area of substrate (e.g.,
electrically conductive lines can be formed with a smaller pitch,
or center-to-center spacing between the lines). Similarly, use of
the nanoparticles made using the present invention in inks for
display applications will allow a greater number of features to be
deposited per area of substrate. Similarly, use of nanoparticles
made using the present invention in inks for resistor, inductor,
capacitior, transitor, or other electrical applications will allow
for a wide of electronic circuits to be directly printed. Examples
of resistor materials for use in the present invention include
RuO.sub.2, OSO.sub.4, TaN, Bi.sub.2Ru.sub.2O.sub.7,
Pb.sub.2Ru.sub.2O.sub.6, Ni--Cr, SnO.sub.2, SrRuO.sub.3,
BaRuO.sub.3, TiSi.sub.2 and Pd--Ag--Pd--O.
[0189] The multi-component particles also have applications in the
catalysis field. For example, fabrication of membrane electrode
assemblies (MEAs) for use in fuel cells can also benefit from the
use of inks containing the nanoparticles made using the present
invention. For example, an ink containing carbon and/or catalyst
nanoparticles can be printed on a substrate of ion exchange
membrane to form an electrocatalyst layer. Catalysts used in MEAs
can be very expensive (e.g., platinum catalystic metal), and the
ability to fabricate MEAs using nanoparticulate-sized catalyst
particles can greatly reduce the cost of manufacturing MEAs.
Additionally, increased surface area that may be provided by
nanoparticles can also contribute to improved performance of the
MEAs.
IV. POST PROCESSING OF MULTI-COMPONENT PARTICLES
A. Processes for Dispersing the Nanoparticles From the
Multi-Component Particles
[0190] In one implementation of the invention, the multi-component
particles comprise a matrix that is designed to be wholly or
partially removable. As the matrix is removed, in one aspect, the
nanoparticles within the multi-component particles are dispersed
from the matrix to form a nanoparticle dispersion. The formation of
a nanoparticle dispersion may be highly desirable in various
applications, as discussed above. For example, the nanoparticle
dispersion may be ideally suited to serve as an ink in ink jet
applications.
[0191] As indicated above, in a preferred embodiment, the
nanoparticles are dispersable in a liquid medium to form dispersed
nanoparticles having from about 1 to about 10 monolayers (e.g.,
from about 2 to about 8 or from about 3 to about 6 monolayers)
disposed thereon, wherein the monolayers are formed from the
organic matrix. Additionally or alternatively, the dispersion of
nanoparticles has a surface tension greater than about 5 dynes/cm,
more preferably greater than about 10 dynes/cm, more preferably
from about 20 to about 80 dynes/cm or from about 25 to about 50
dynes/cm, and a viscosity of greater than 1 centipoise, more
preferably greater than about 3 centipoise, and optionally from
about 3 to about 10,000 centipoise or from about 5 to about 100
centipoise.
[0192] In one variation, the removability of the matrix material is
an aid to further processing of the nanoparticles to prepare the
nanoparticles for final use in an application. For example, the
matrix may be wholly removable, thereby effecting decomposition of
the particles and releasing the nanoparticles. This may be
desirable, for example, when the nanoparticles need to be modified
prior to use (such as for example surface modification for enhanced
dispersability), or need to be in a free state for use (for
example, for incorporation of the nanoparticles into a paste or
slurry, such as in an ink formulation for ink jet printing). In
another variation, a portion of the matrix is removable to leave
enough matrix to retain the structure of a particle that maintains
the nanoparticles in a distributed state in the particle. In a
preferred embodiment of this variation, the matrix comprises at
least two different materials, with one matrix material being
selectively removable relative to another matrix material.
[0193] In another implementation of the present invention, the
matrix may comprise two or more different materials, with at least
one material being selectively removable to produce a controlled
pore characteristic (e.g., percent porosity, pore size,
permeability) in the remaining particle. In one variation, the
matrix may comprise uniformly sized regions of one matrix material
that serve as a template to provide a length scale for porosity.
The uniformly sized regions of material are then selectively
removed to form relatively uniformly sized pores throughout the
particle. In one particular implementation of this variation, the
matrix is initially composed of two different matrix materials, an
organic salt and a polymer, with the polymer being in the form of
substantially uniformly sized particles or beads. When the polymer
is selectively removed by being dissolved with a solvent or
vaporized in a heater or reactor, leaving the organic salt matrix
material remains with pores of substantially uniform size. The
uniformly sized regions of matrix material that aid in forming
controlled porosity in the multi-component particles may, however,
be made of any convenient material. Some non-limiting examples of
materials that may be used in the matrix to create a template for
generating controlled porosity in the multi-component particles
include: long carbon chain organic salts, polymers (e.g., shaped as
spheres, such as latex spheres; beads; or other shapes), surfactant
salts, and biomolecules or bio-materials, (proteins, enzymes,
viruses, etc.). Additionally, surfactants can be added to the
precursor medium to form micelles (or reverse micelles) that
control the size of a matrix material by isolating a matrix
precursor within the micelles and constraining the size of the
domains of the matrix material that is formed during formation of
the multi-component particles.
[0194] In yet another implementation of the invention, the matrix
is designed to be wholly removable and merely serves as an aid for
delivering the nanoparticles into a final application or product.
For example, in catalytic applications it might be useful to have a
porous network of nanoparticles of a catalyst material deposited on
a catalytic support surface. However, such a network of
nanoparticles might be difficult to form directly on the surface.
Using one embodiment of the present invention, multi-component
particles containing a matrix and an interconnected network of
nanoparticles, such as shown and described below with respect to
FIG. 5, may be used to deposit the desired network on the catalytic
support surface. The multi-component particles containing matrix
and the network of nanoparticles may be deposited onto the desired
catalytic support surface as a dry powder, an ink or a paste, and
then washed with a solvent for the matrix to dissolve the matrix
and leave the interconnected network of nanoparticles on the
catalytic support surface.
[0195] A generalized process for one implementation of the
invention involves the decomposition of multi-component particles
to free the nanoparticles. During the decomposing of the
multi-component particles, sufficient matrix material is removed
from the multi-component particles to effectively decompose the
structure of the multi-component particles, thereby releasing the
nanoparticles.
[0196] Removal of matrix material may be effected in any convenient
way that effectively destroys the structure of the multi-component
particles to release the nanoparticles. As one example, matrix
material may be removed by chemical reaction of, or reacting away
the matrix material. The particles are subjected to reactant(s)
that react with one or more materials of the matrix, thereby
removing matrix material from and decomposing the particles. Table
10 shows some non-limiting examples of combinations of matrix
materials and reactants or stimuli resulting in reaction of a
matrix material to effect removal of the matrix material.
TABLE-US-00010 TABLE 10 EXEMPLARY MATRIX MATERIAL/REACTANT
COMBINATIONS REACTANT/ MATRIX MATERIAL STIMULUS Oxygen sensitive
polymers Oxygen Acid sensitive materials Acids Base sensistive
materials Bases Heat sensitive materials Heat Light sensitive
materials Light
[0197] In another example, matrix material may be removed by
sublimation of the matrix material. In this embodiment, the
multi-component particles are subjected to conditions of
temperature and pressure, which may be a vacuum pressure, at which
the matrix material sublimes. Some non-limiting examples of
sublimable matrix materials include lower molecular weight organic
materials, such as: naphthalene and anthracene.
[0198] In one preferred embodiment, during the decomposition of the
multi-component particles, sufficient matrix material is dissolved
into a liquid medium to effect the decomposition of the
multi-component particles. For example, organic salt matrix
materials, such as salts of carboxylic acids and alkyl ammonium
salts. As another example, a polymer matrix could be dissolved into
an organic liquid, or aqueous liquid, depending upon the polymer.
In any event, it is important that the liquid medium be selective
for dissolving the matrix material relative to the nanoparticles,
so that material from the nanoparticles is substantially not
dissolved into the liquid medium. The dissolution of the matrix
material in a liquid medium may be performed using any adequate
process or apparatus such as for example a stirred tank or other
equipment that agitates the liquid medium to promote contact of the
liquid medium with the multi-component particles.
[0199] Another aspect of the invention involves removing
nanoparticles from a matrix structure and re-dispersing the
nanoparticles in a new medium. The re-dispersion may be in a new
matrix. In one embodiment, at least a portion of the matrix, and
preferably substantially all of the matrix, is removed using a
liquid medium, with corresponding release of the nanoparticles into
the liquid medium, followed by separation of the nanoparticles from
the liquid medium and then re-dispersion of the nanoparticles in a
new liquid medium or in a new matrix.
[0200] In one aspect of the invention, the re-dispersing of the
nanoparticles is aided by the matrix. For example, at least a
portion of the matrix optionally is dissolved and acts as a surface
adsorbed substance (e.g., surfactants and/or polymers) and helps
disperse the nanoparticles through steric or electrostatic forces.
For example, the organic matrix may comprise PVP and the inorganic
nanoparticles may comprise silver. Upon placing this particular
multi-component particle in water or a protic solvent, the PVP
absorbs or adsorbs on the surface of the silver nanoparticles and
helps prevent (or minimize) agglomeration of the silver
nanoparticles and keeps the silver nanoparticles dispersed.
[0201] In another embodiment, the multi-component particles are
decomposed followed by the steps of separating the nanoparticles
and dispersing the nanoparticles. During the decomposing of the
multi-component particles, at least a portion of the matrix is
removed from the particles sufficient to release the nanoparticles
into a first liquid medium. The nanoparticles are then separated
from at least a portion, and preferably substantially all, of the
first liquid medium. The separated nanoparticles are then mixed
with and dispersed in a new (second) liquid medium. The dispersing
of the nanoparticles is often aided by a surface modification
performed on the nanoparticles prior to the step of separating the
nanoparticles. The surface modification may include coating the
nanoparticles with a dispersing agent that is compatible with the
new liquid medium.
[0202] The step of separating the nanoparticles from the first
liquid medium may be performed using any suitable liquid/solid
separation technique. Some examples of liquid/solid separation
techniques that may be used include ultrafiltration,
centrifugation, sedimentation/decantation, diafiltration and froth
flotation, using any separation aids as appropriate, such as filter
aids, flocculants and frothing reagents. In one embodiment, the
separating of the nanoparticles is performed by partitioning the
nanoparticles from one liquid medium to another immiscible liquid
medium. For example, decomposing the particles may be performed
using an aqueous liquid medium and the separating of the
nanoparticles may be performed by contacting the aqueous medium
with an organic liquid medium into which the nanoparticles
preferentially partition. For example, metal nanoparticles may be
partitioned from an aqueous liquid into an organic liquid
containing a metal complexing agent, such as for example an amine
or phosphorus-containing extractant such as are used in solvent
extraction operations. As another example, metal nanoparticles may
be surface modified with a hydrophobic modifying agent that aids in
partitioning the metal nanoparticles from an aqueous liquid into an
organic liquid. In one embodiment, a first liquid medium is a
process liquid used to remove the matrix and a second liquid medium
is formulated for a particular final application. For example, the
second liquid medium into which the nanoparticles are re-dispersed
could be an organic liquid for preparation of a paste or slurry
composition, such as an ink composition comprising the
nanoparticles, for example for ink jet printing or offset
lithographic printing. Alternatively, the second liquid medium may
be formulated so that the nanoparticles are stable during storage,
transportation or to facilitate further processing of the
nanoparticles.
[0203] Regarding the ultrafiltration/diafiltration of nanoparticles
reference may be made, for example, to U.S. Pat. Nos. 6,328,894;
5,879,715; 6,245,494 and 6,811,885, the entire disclosures of which
are incorporated by reference herein. Briefly, ultrafiltration and
diafiltration use a filtration under pressure through a membrane
which allows only components of a certain maximum size to pass
therethrough. In the present case, the inorganic nanoparticles will
be retained by the membrane while the first liquid medium and
preferably a major part or substantially all of the contaminants
(e.g., dissolved inorganic matter, excess adsorptive substance,
etc.) and the like will be able to pass through the membrane. Any
size of membrane as well as any channel (pore) size thereof can be
used as long as the process permits a preferably substantial
separation of the inorganic nanoparticles from the first liquid
medium and optionally separation of contaminants and the like. In a
preferred aspect, the membrane may vibrate to substantially reduce
clogging and/or to permit a higher permeate flow rate. Also, the
ultrafiltration/diafiltration may be pressure-driven (e.g.,
involving pressing through the membrane) or vacuum-driven (e.g.,
involving sucking through the membrane). Membrane configurations
include, but are not limited to, flat sheet membranes, cross flow
membranes, spiral wound tubes, or hollow fiber tubes. For example,
a three compartment through-flow cell comprising two membranes may
be used. Non-limiting examples of membrane materials include
polymeric and ceramic materials such as, e.g., polysulfone,
polyethersulfone, sulfonated polysulfone, polyamide, cellulose
acetate, zirconium oxide and alumina. By way of non-limiting
example, the membrane may have a molecular weight cutoff (MWCO) in
the range of from about 10,000 to about 1,000,000, e.g., about
50,000, about 100,000, about 200,000 or about 500,000, and/or a
pore size of from about 0.01 .mu.m to about 1 .mu.m (preferably at
least about 0.02 .mu.m and not higher than about 0.5 .mu.m) and/or
a lumen of from about 0.1 mm to about 5 mm (preferably at least
about 2 mm and not more than about 3 mm).
[0204] The nanoparticles that are separated from the first liquid
phase optionally are subjected to a washing operation to remove at
least a substantial portion of the impurities that may still be
associated therewith, e.g., materials that are not adsorbed on the
surface of the nanoparticles to any significant extent. For
example, these impurities may include inorganic salts formed during
the reduction of the metal compound, residual solvent(s) from the
precipitation step and surfactants and/or polymers, e.g.,
surfactants and/or polymers that are merely present as an impurity
without being adsorbed on the nanoparticles. The washing liquid
used for the washing operation preferably is, or comprises, a
solvent that is capable of dissolving the impurities associated
with the nanoparticles, in particular, excess surfactants and/or
polymers. By way of non-limiting example, the washing liquid may
comprise a protic organic solvent such as, e.g., a
hydroxyl-containing compound, preferably, an alcohol and/or a
polyol and/or water. Illustrative and non-limiting examples of
alcohols and polyols that may be used for the washing operation
include aliphatic alcohols having from 1 to about 12 carbon atoms
such as, e.g., methanol, ethanol, propanol, isopropanol, butanol,
pentanol, cyclopentanol, hexanol, cyclohexanol, octanol, decanol,
dodecanoland the like, and polyols having from 1 to about 4
hydroxyl groups and from 2 to about 12 carbon atoms such as, e.g.,
ethylene glycol, propylene glycol, glycerol and the like. A
preferred solvent for use in the washing operation includes
ethanol, which may be used alone or in combination with other
solvents (e.g., water).
[0205] The washing operation may, for example, be carried out by
dispersing the separated inorganic nanoparticles in the washing
liquid, followed by another separation step (e.g., diafiltration,
ultrafiltration and/or centrifugation). This process may optionally
be repeated one or more times. The washed (purified) nanoparticles
may thereafter be dried (e.g., under reduced pressure and/or at a
temperature that does not adversely affect the surface adsorbed
substance to any significant extent) and thereafter stored and/or
shipped. Even after storage for extended periods the dry particles
can be redispersed in a desired liquid to form a dispersion (e.g.,
a printing ink) that is substantially stable over several days or
even weeks.
[0206] In a further embodiment, the last liquid medium that is
added to the nanoparticles before the ultrafiltration/diafiltration
thereof is completed may be selected to be the vehicle of a desired
dispersion of the nanoparticles (for example of a printing ink) or
a component thereof, thereby making it possible to convert the
separated nanoparticles into the desired nanoparticle containing
product in a single unit/operation. Also, one or more additives may
be incorporated in the washing liquid and/or the liquid that is
intended to be the vehicle of the desired dispersion or a component
thereof. For example, in order to keep the dissolution of surface
adsorbed substance at a minimum, it may be advantageous to add some
adsorptive substance (e.g., surfactants and/or polymers) to, e.g.,
the washing liquid. In addition additives may also be incorporated
into the washing, liquid (adhesion promoters, humectants,
etc.).
[0207] By way of non-limiting example, the
diafiltration/ultrafiltration may be carried out by placing the
dispersed nanoparticles (in the first liquid medium) in a
diafiltration unit and concentrating the reaction mixture therein
to a predetermined fraction of the original volume by pressing
(application of pressure) or drawing (application of vacuum) the
reaction mixture through one or more ultrafiltration membranes of
suitable MWCO/pore size. Thereafter, a first extraction medium that
is capable of dissolving impurities and contaminants present in the
reaction mixture (in particular, excess surfactant and/or polymer)
may be added to the concentrated reaction mixture (e.g., in an
amount sufficient to restore the originally employed volume of the
reaction mixture) and the resulting mixture may be concentrated in
the same way as the originally employed dispersed nanoparticles. A
second extraction medium which is capable of dissolving impurities
and contaminants and which may be the same as or different from the
first extraction medium may be added to the resulting concentrate
and the resulting mixture may be concentrated again. This process
may be repeated as often as necessary with a third, fourth, etc.
extraction mixture. Alternatively, before concentrating the
original dispersed nanoparticles a predetermined amount of the
first extraction medium may be added thereto and the resulting
mixture may be concentrated, e.g., until the original volume of the
dispersed nanoparticles is reached again. Then the second
extraction medium may be added and a second concentration operation
may be carried out, etc. Of course, any combination of the two
alternatives described above may be used as well. For example, the
original dispersed nanoparticles may be concentrated first and then
the first extraction mixture may be added in an amount which
results in a volume of the resultant mixture which exceeds the
volume of the original dispersed nanoparticles, whereafter the
resultant mixture may be concentrated to the volume of the original
dispersed nanoparticles, whereafter a second extraction medium may
be added, etc. At the end of each of these alternative ways of
isolating/purifying the inorganic nanoparticles by
ultrafiltration/diafiltration the extraction medium(s) may be
removed partially or completely by ultrafiltration/diafiltration,
leaving behind the purified substantially non-agglomerated
inorganic nanoparticles with the surface absorbed substance
thereon, or a concentrated and stable dispersion thereof. The
nanoparticles may then optionally be dried to form a powder batch
of dry nanoparticles. Alternatively, the extraction mediums that
are used for the diafiltration operation may be selected such that
at least at the end of the diafiltration operation the purified
nanoparticles are combined with a second liquid medium which is the
vehicle or at least a part of the vehicle of a desired
re-dispersion of the inorganic nanoparticles (e.g., a printing
ink). The extraction mediums that may be used for carrying out the
diafiltration/ultrafiltration include those which have been
mentioned above in the context of the separation of the
nanoparticles from the liquid phase and the washing of the
separated nanoparticles.
[0208] In one aspect of the invention, the nanoparticles are
released from the multi-component particles through mechnical
agitaion or a process that aids in breaking apart the organic
matrix. For example, milling, ultrsonification, and/or shear mixing
may be used in order to aid the release of the inorganic
nanoparticles from the matrix.
B. Processes for Modifying the Nanoparticles
[0209] During and after the decomposing of the multi-component
particles, it is generally preferred to significantly inhibit or
substantially prevent the dispersed nanoparticles from
agglomerating, because of the difficulty in subsequently
redispersing the nanoparticles for further processing or use. One
way of significantly inhibiting agglomeration of the nanoparticles
is to make the multi-component particles during the formation of
the particles to include a surface-modifying material that inhibits
agglomeration and promotes dispersion of the nanoparticles in the
liquid medium. The surface-modifying material optionally comprises
one or more surfactants or polymer compounds, as discussed above,
which covalently bond, coordinate and/or adsorb to the surface of
the nanoparticles to decrease the surface energy thereof and
inhibit agglomeration. Such surface-modifying materials are
generically referred to herein as dispersants or dispersing agents.
The dispersing agent may rely on physical or chemical interactions
with the nanoparticles to promote dispersion. Typically, when a
dispersing agent is included in the multi-component particles, it
will be part of the matrix of the particles. In that regard, the
matrix may comprise substantially only the dispersing agent or may
comprise multiple matrix materials, of which the dispersing agent
is only one. In any event, the dispersing agent is of such a nature
that when the particles are decomposed, at least a portion of the
dispersing agent associates with a surface of the nanoparticles in
a way to inhibit agglomeration in the liquid medium of released
nanoparticles. As one example, the dispersant may be an amphiphile,
with a polar portion that interacts with one of the nanoparticles
and the liquid medium and a nonpolar portion that interacts with
the other of the nanoparticles and the liquid medium, to promote
maintenance of the nanoparticles in the liquid medium in a
dispersed state. The dispersing agent may be an ionic, nonionic or
zwitterionic surfactant, or a polymer, that interact with the
surface of the nanoparticles. Some non-limiting examples of
possible dispersing agents for use in polar and nonpolar liquid
media include: ammonium salt of polyacrylic acid; ammonium salt of
a polymeric carboxylic acid; sodium salt of a polymeric carboxylic
acid; anionic macromolecular surfactant, condensed naphthalene
sulfonic acid; methyl hydroxyethyl cellulose; monono-calcium salt
of polymerized alkyl-aryl sulfonic acid; anionic and nonionic
surfactants; polycarboxylic acid surfactant;
polyoxyethylenesorbitan fatty acid ester; polyoxyethylene sorbitan
monooleate; polyoxyethylene sorbitan monostearat; salts of
polyfunctional oligomer; sodium dodecyl benzene sulfonate; sodium
or ammonium salt of a sulfate ester an
alkylphenoxypoly(ethyleneoxy)ethanol; sodium salt of a carboxylated
polyelectrolyte; sodium salt of condensed naphthalene sulfonate;
sodium salt of disulohonic acids; sodium salt of polyacrylic acids
Polyacrylic acids; sodium salt of polymerized alkyl naphthalene
sulfonic acid; sodium salt of polymerized alkyl-aryl sulfonic acid;
sodium salts of polymerized substituted alkyl-aryl sulfonic acids;
sodium salts of polymerized substituted benzoid alkyl sulfonic
acids; sodium tetraborate; ammonium salt of carboxylated
polyelectrolyteAlkylphenol ethoxylates; condensation product of
naphthalene sulfonic acid formaldehyde; condensation product
sulfo-succini acid ester of an alkoxylated novolak; nonylphenol
novolak ethoxylate; condensation product of
cresol-formaldehyde-schaffer salt; sodium salt of a
cresol-formaldehyde condensation product; fatty acid methyl tauride
sodium salt; phosphate of EO-PO-EO blockpolymer;
2,4,6-Tri-(1-phenylethyl)-phenol polyglycol ether phosphoric acid
ester; 2,4,6-Tri-1(1-phenylethyl)-phenol polyglycol ether
monophosphate triethanolamine salt; tri-sec,-butylphenol polyglycol
ether phosphoric acid ester with 4 EO; alkyl polyglycol ether
phosphoric acid ester with 6 EO; alkyl polyglycol ether phosphoric
acid ester with 8 EO; 2,4,6-Tri-(1-phenylethyl)-phenol polyglycol
ether sulfate ammonium salt; sulfosuccinic ester of ethoxylated
castor oil; mannitol; sodium lauryl sulfate; and mono &
disaccharides.
[0210] When the multi-component particles include a dispersing
agent, a precursor for the dispersing agent will typically be
included in the precursor medium from which droplets are formed
during the generation of the aerosol. For example, a polymer for
use as the dispersing agent could be dissolved in the liquid
vehicle, with the polymer precipitating out and being included in
the particles during formation of the multi-component particles.
Alternatively, the dispersing agent may be a material that is
formed during formation of the multi-component particles from
reaction of precursor(s) included in the precursor medium and/or
the carrier gas. For example, a monomer or monomers for a polymer
(which may be a homopolymer, copolymer, terpolymer, etc.) to be
used as a dispersing agent may be included in the precursor medium,
which monomer(s) polymerize to form the dispersing agent during the
formation of the multi-component particles.
[0211] In one embodiment of the present invention, the dispersed
nanoparticles are modified in one or more post manufacture
modification steps. An alternative to including the dispersing
agent in the multi-component particles is for the dispersing agent
to be present in the liquid medium, which contacts the
multi-component particles and causes the multi-component particles
to decompose. Contacting the nanoparticles with a dispersing agent
in a liquid medium during or following the decomposition of the
particles is one example of post manufacture modification of the
nanoparticles, in that the dispersing agent effects a surface
modification of the nanoparticles to inhibit agglomeration and
promote dispersibility. Alternatively, the dispersing agent
optionally is added to the liquid medium after it initially
contacts the multi-component particles, but preferably prior to
completion of the decomposition of the particles. In a preferred
variation of this alternative, the dispersing agent is predissolved
into the liquid medium prior to contacting the liquid medium with
the particles during the decomposing of the particles, so that the
dispersing agent is immediately available to intimately contact and
associate with the nanoparticles as they are exposed during the
decomposing of the particles. During the decomposition of the
particles, the mixture of liquid medium and particles is preferably
agitated, such as with a mixer, to promote effective decomposition
of the particles and intimate contact between the nanoparticles and
the dispersing agent.
[0212] Another example of post manufacture modification of the
nanoparticles is contacting the nanoparticles with a dispersing
agent or other surface-modifying agent in a fluidized bed following
the decomposing of the particles. The present invention, however,
provides significant flexibility to effect a variety of
post-manufacture modifications to one or both of the nanoparticles
and the matrix.
[0213] A generalized process for modifying nanoparticles following
particle formation involves nanoparticle surface modification by
contacting the nanoparticles with a dispersing agent as described
above. The modifying of the nanoparticles may be performed while
the nanoparticles are in the multi-component particles; after
removal of a portion of the matrix from the multi-component
particles, but while the nanoparticles are still held in a
distributed state by the matrix; or after decomposition of the
multi-component particles to release the nanoparticles.
Non-limiting examples of some types of modifications of the
nanoparticles that may be performed include surface modification of
a surface of the nanoparticles, compositional modification of the
nanoparticles and structural modification of the nanoparticles
(e.g., modifications of morphology, crystallinity and/or
composition).
[0214] One type of surface modification that may be performed on
the nanoparticles is coating or covering a surface of the
nanoparticles with a material that masks, or otherwise modifies,
the surface properties of the nanoparticles. By coating a surface
it is meant covering a portion or all of the surface with
surface-modifying material(s), also referred to herein as
surface-modifying agents. A surface-modifying material may be held
in association with the surface by any mechanism, including
physical absorption, chemisorption or attachment through chemical
bonding to the surface of the nanoparticles (e.g., through covalent
or ionic bonding).
[0215] The surface-modifying material may perform one or a number
of functions at the surface of the nanoparticles. The
surface-modifying material may function as a surfactant to modify
the surface properties. The surface-modifying material may function
as a dispersing agent to promote uniform separation and dispersion
of the nanoparticles in a liquid medium. The surface modifying
material may function as a stabilizer to inhibit chemical
degradation of the nanoparticles.
[0216] Surface modification of the nanoparticles can be completed
before (nanoparticles in the precursor solution), during the
formation of the nanoparticles, or afterward, e.g., when being
redispersed.
[0217] Table 11 shows some non-limiting examples of polymers that
may be used as surface-modifying materials to coat the surface of
metal oxide, metal and/or semiconductor nanoparticles.
TABLE-US-00011 TABLE 11 EXEMPLARY POLYMERS FOR SURFACE MODIFYING
NANOPARTICULATE METAL OXIDES, METALS AND SEMICONDUCTORS SURFACE
MODIFYING MATERIALS Reactive Polysiloxanes Crown Ethers Dendrimers
Amphiphilic Polymers Polyanilines Starches Gelatins
Polyelectrolytes Polypyrroles Polythiophenes Thiol Polymers
[0218] Additional exemplary surface modifying materials
(surfactants and/or polymers) that may be implemented during the
step of surface modification include: Tyloxapols such as
4-(1,1,3,3-tetramethylbutyl)-phenol polymer with ethylene oxide and
formaldehyde; polyvinylpyrrolidone (PVP); poloxamers (copolymers of
ethylene oxide and propylene oxide) such as Pluronics.TM. F68,
F108, F127; poloxamines (copolymers of propylene oxide, ethylene
oxide and ethylenediamine) such as Tetronic.TM. 908; gelatin;
sulfated poloxamers; sulfated poloxamines; casein; lecithin
(phosphatides) such as Chocotop.TM. (Lucas Meyer GMBH & Co.);
glycerol; gum acacia; cholesterol; tragacanth; stearic acid;
benzalkonium chloride; calcium stearate; glycerol monostearate;
cetostearyl alcohol; cetomacrogol emulsifying wax; sorbitan esters;
polyoxyethylene; polyoxyethylene alkyl ethers such as macrogol
ethers (e.g., cetomacrogol 1000); polyoxyethylene alkyl esters;
polyoxyethylene castor oil derivatives; polyoxyethylene sorbitan
fatty acid esters such as Tweens.TM. and Tween.TM. 80; polyethylene
glycols (PEG) such as Carbowax.TM. 3350, 1450 and Carbopol 934;
polyoxyethylene stearates; phosphates; sodium dodecylsulfate;
ethylene oxide and butylene oxide copolymers; cellulose ethers such
as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose,
hydroxypropylmethylcellulose phthalate, carboxymethylcellulose,
carboxymethylcellulose calcium and carboxymethylcellulose sodium;
polysaccharides such as dextrin, guar gum and starch; vinyl acetate
and vinyl pyrrolidone copolymers such as Plasdone.RTM. S630;
Kollidone.RTM. VA 64; vinylacetate and vinylalcohol copolymers;
noncrystalline cellulose; magnesium aluminum silicate;
triethanolamine; polyvinyl alcohol (PVA); dextran; dialkylesters of
sodium sulfosuccinic acid such as aerosol OT.TM. (dioctyl ester of
sodium sulfosuccinic acid); sodium lauryl sulfate (e.g.,
Duponol.TM.); alkyl aryl polyether sulfonate (e.g., Triton.TM.
X-200); PEG-phospholipids; dimyristoyl phosphatidyl glycerol;
Na-dioctylsulfosuccinate (DOSS) (e.g., Ablusol.TM. C-78 and
Ablusol.TM. M-75); PEG-cholesterol; PEG-vitamin A; PEG-vitamin E;
PEG-liposomes such as DPP-PEG-OH
a-(dipalmitoylphosphatidyl)-.omega.-hydroxypolyoxyethylene),
DSPE-PEG-COOH
(distearoylphosphatidyl-N-(3-carboxypropionylpolyoxyethylene
succinyl)ethanolamine), PEG-5000.TM. and PEG-2000.TM.; sodium
dodecylbenzene sulfonate; sodium stearate;
decanoyl-N-methylglucamide; N-decyl .beta.-D-glucopyranoside;
N-decyl .beta.-D-maltopyranoside; N-dodecyl
.beta.-D-glucopyranoside; N-dodecyl .beta.-D-maltoside;
heptanoyl-N-methylglucamide; N-heptyl .beta.-D-glucopyranoside;
N-heptyl .beta.-D-thioglucoside; N-hexyl .beta.-D-glucopyranoside;
nonanoyl-N-methylglucamide; N-nonyl .beta.-D-glucopyranoside;
Octanoyl-N-methylglucamide; N-octyl .beta.-D-glucopyranoside; Octyl
.beta.-D-thioglucopyranoside; Zwitterionic stabilizers such as Abil
9950-polysiloxane polyorgano betaine copolymers, Betadet
DM-24-alkyldimethylaminobetaine, Betadet
5-20-laurylhydroxysultaine; poly-n-methylpyridinium; anthryul
pyridinium chloride; cationic phospholipids; chitosan; polylysine;
polyvinylimidazole; polybrene; polymethylmethacrylate
trimethylammoniumbromide bromide (PMMTMABr);
pexyldesyltrimethylammonium bromide (HDMAB); quaternary ammonium
compounds such as stearyltrimethylammonium chloride,
benzyl-di(2-chloroethyl)ethylammonium bromide, coconut trimethyl
ammonium chloride or bromide, coconut methyl dihydroxyethyl
ammonium chloride or bromide, decyl triethyl ammonium chloride,
decyl dimethyl hydroxyethyl ammonium chloride or bromide,
C.sub.12-15 dimethyl hydroxyethyl ammonium chloride or bromide,
coconut dimethyl hydroxyethyl ammonium chloride or bromide,
myristyl trimethyl ammonium methyl sulphate, lauryl dimethyl benzyl
ammonium chloride or bromide, lauryl dimethyl (ethenoxy).sub.4
ammonium chloride or bromide, N-alkyl (C.sub.12-18)dimethylbenzyl
ammonium chloride, N-alkyl (C.sub.14-18)dimethyl-benzyl ammonium
chloride, N-tetradecylidmethylbenzyl ammonium chloride monohydrate,
dimethyl didecyl ammonium chloride, N-alkyl and (C.sub.12-14)
dimethyl 1-napthylmethyl ammonium chloride, trimethylammonium
halide, alkyl-trimethylammonium salts, dialkyl-dimethylammonium
salts, lauryl trimethyl ammonium chloride, ethoxylated
alkyamidoalkyldialkylammonium salt, ethoxylated trialkyl ammonium
salt, dialkylbenzene dialkylammonium chloride, N-didecyldimethyl
ammonium chloride, N-tetradecyldimethylbenzyl ammonium, chloride
monohydrate, N-alkyl(C.sub.12-14) dimethyl 1-naphthylmethyl
ammonium chloride, dodecyldimethylbenzyl ammonium chloride, dialkyl
benzenealkyl ammonium chloride, lauryl trimethyl ammonium chloride,
alkylbenzyl methyl ammonium chloride, alkyl benzyl dimethyl
ammonium bromide, C.sub.12, C.sub.15, C.sub.17 trimethyl ammonium
bromides, dodecylbenzyl triethyl ammonium chloride,
poly-diallyldimethylammonium chloride (DADMAC), dimethyl ammonium
chlorides, alkyldimethylammonium halogenides, tricetyl methyl
ammonium chloride, decyltrimethylammonium bromide,
dodecyltriethylammonium bromide, tetradecyltrimethylammonium
bromide, methyl trioctylammonium chloride (ALIQUAT 336.TM.),
POLYQUAT 10.TM., tetrabutylammonium bromide, and benzyl
trimethylammonium bromide; choline esters such as choline esters of
fatty acids; benzalkonium chloride; stearalkonium chloride
compounds such as stearyltrimonium chloride and di-stearyldimonium
chloride; cetyl pyridinium bromide or chloride; halide salts of
quaternized polyoxyethylalkylamines; MIRAPOL.TM.; ALKAQUA.TM.;
amines such as alkylamines, dialkylamines, alkanolamines,
polyethylenepolyamines, N,N-dialkylaminoalkyl acrylates and vinyl
pyridine; amine salts such as lauryl amine acetate, stearyl amine
acetate, alkylpyridinium salt and alkylimidazolium salt; amine
oxides; imide azolinium salts; protonated quaternary acrylamides;
methylated quaternary polymers such as poly[diallyl
dimethylammonium chloride] and poly-[N-methyl vinyl pyridinium
chloride]; cationic guar; carboxylates; citrates; thiols and di
thiols.
[0219] In one embodiment of the implementation of the invention,
the surface modification of the nanoparticles comprises
functionalizing a surface of the nanoparticles. By functionalizing,
it is meant that chemical functional groups of a desired type are
attached to the surface of the nanoparticles through chemical
bonding (e.g., covalent bonding or ionic bonding). The functional
group could be bonded directly to the nanoparticles, or could be
bonded to the nanoparticles through some intermediate group or
groups. Preferably, the functionalizing group and/or the
intermediate group is derived from a component in the matrix. At
least a portion of the matrix optionally acts as a surface adsorbed
substance (e.g., surfactants and/or polymers). In one embodiment
the matrix contains PVP that can interact (through nitrogen lone
pairs of the pyrrolidone nitrogen) with the surface of a metal
nanoparticle. Often, the functional group will be a part of a
longer constituent group that is bonded to the nanoparticles. The
bonding to the nanoparticles may in some cases be effected through
a coupling agent that acts as a couplant intermediate between a
nanoparticulate and the functional group. As used herein, a
coupling agent refers to each of the following: a molecule or ionic
group that is reactable with the nanoparticles to form a chemical
bond with the nanoparticles, the residual portion of that molecule
or ionic group bonded to the nanoparticles following reaction with
the nanoparticles, and any further residual linking group bonded to
a functional group following further reaction to attach a
functional group. One common group of coupling agents useful in
many situations are silane coupling agents. Non-limiting examples
of some silane coupling agents that may be used with the invention
include: aminopropyltriethoxysilane; aminopropyltrimethoxysilane;
aminopropylmethyldiethoxysilane; aminopropylmethyldimethoxysilane;
aminoethylaminopropyltrimethoxysilane;
aminoethylaminopropyltriethoxysilane;
aminoethylaminopropylmethyldimethoxysilane;
diethylenetriaminopropyltrimethoxysilane;
diethylenetriaminopropyltriethoxysilane;
diethylenetriaminopropylmethyldimethoxysilane;
diethylenetriaminopropylmethyldiethoxysilane;
cyclohexylaminopropyltrimethoxysilane;
hexanediaminomethyltriethoxysilane; anilinomethyltrimethoxysilane;
anilinomethyltriethoxysilane; diethylaminomethyltriethoxysilane;
(diethylaminomethyl) methyldiethoxysilane;
methylaminopropyltrimethoxysilane; bis(triethoxysilylpropyl)
tetrasulfide; bis(triethoxysilylpropyl)disulfide;
mercaptopropyltrimethoxysilane; mercaptopropyltriethoxysilane;
mercaptopropylmethyldimethoxysilane;
3-thiocyantopropyltriethoxysilane; glycidoxypropyltrimethoxysilane;
glycidoxypropyltriethoxysilane;
glycidoxypropylmethyldimethoxysilane;
glycidoxypropylmethyldiethoxysilane;
methacryloxypropyltrimethoxysilane;
methacryloxypropyltriethoxysilane;
methacryloxypropylmethyldimethoxysilane;
chloropropyltrimethoxysilane; chloropropyltriethoxysilane;
chloromethyltrimethoxysilane; chloromethyltriethoxysilane;
dichloromethyltriethoxysilane; vinyltrimethoxysilane;
vinyltriethoxysilane; vinyltris(2-methoxyethoxy)silane;
hexamethyldisilazane; dimethylchlorosilane; hexamethyldisiloxane;
hexamethyldisilane; dimethyltrichlorosilane; methyltrichlorosilane;
and silicon oils.
[0220] Non-limiting examples of some chemical functional groups
that may be used to functionalize the nanoparticles include
hydroxyl, carboxyl, sulfo, oxo, amine, amide, acyl, alkyl, vinyl,
carbonate, ammonium, sulfate, sulfhydryl, carbonyl, silyl, siloxy,
acetyl, and any substituted form of any of the foregoing. In some
embodiments of the present invention, functional groups may be
attached to the surface of the nanopaticulates for the purpose of
forming a precursor to a material on the surface of the
nanoparticles. This may be useful for example in an ink composition
used in forming conductive features on a substrate. Ink
compositions used in forming conductive features on a substrate may
contain conductive particles that once deposited on a substrate in
a desired pattern, are heated to fuse the particles together to
form an electrically conductive feature. In one embodiment of the
present invention, a nanoparticulate made of a conductive material
may be functionalized with a chemical functional group that is then
reacted to form a precursor to a conductive material on the surface
of the nanoparticles. When the nanoparticles, with such a precursor
on their surface, are used in an ink that is deposited on a
substrate and heated, the precursor material on the surface of the
nanoparticles reacts to form the conductive material, which aids in
fusing the nanoparticles together and forming a conductive
feature.
[0221] Non-limiting examples of some types of functionality that
may be imparted to the nanoparticles by the functional group
include metal addition, hydrophilicity, hydroprobicity,
lipophilicity, dispersibility in or compatibility with any desired
material with which the nanoparticles may be subsequently contacted
or combined during subsequent processing or use. Also, the
functional group may be selected to provide a reactive site for
further modification at a later time. For example, the functional
group may provide a reaction site for later grafting a polymer
segment or a site for initiation of a polymerization reaction to
form a polymer segment at the reactive site.
[0222] One preferred example of functionalizing nanoparticles is
attaching hydrophobic groups to metal or metal oxide nanoparticles
for enhanced compatibility with, and/or dispersibility in, an
organic medium such as dispersion in an organic liquid or a polymer
composition. For example, the hydrophobic groups may be attached by
substitution at hydroxyl sites on the surface of the nanoparticles
such as through use of a silane coupling agent or some other
coupling agent. As another example, polymer segments may be grafted
to the surface of the nanoparticles directly, or through the use of
a coupling agent, in order to make the nanoparticles more
compatible with and dispersible in a particular polymer, aiding the
preparation of a homogeneous blend of the nanoparticles in a
composition of the particular polymer. In the first example, the
modified nanoparticles may be more easily dispersible in an organic
liquid to form a homogeneous composition, such as for preparation
of an ink composition for ink jet printing.
[0223] As noted, the nanoparticles may be modified by attaching
directly, or through the use of some intermediate linking group, a
group containing a reactive site for subsequent modification. The
reactive site may be a site, for example, for polymerization, for
grafting polymer segments, for cross-linking in a cross-linked
polymer network or an ionic site for ionic bonding with other
materials or for ion exchange.
[0224] Another type of surface modification that may be performed
during the modifying of the nanoparticles is removal of surface
groups or characteristics from the nanoparticles. One example of
this is dehydroxylating the surface of metal or metal oxide
nanoparticles to remove hydroxyl functionalization that may have
formed on the nanoparticles.
[0225] A compositional modification that may be performed during
the modifying of the nanoparticles involves changing the
composition in the interior of the nanoparticles. For example, a
metal oxide material contained in the nanoparticles may be
compositionally modified by reduction to form a metallic material
(e.g., silver oxide to silver, nickel oxide to nickel). Conversely,
a metallic material contained in the nanoparticles may be oxidized
to form a metal oxide material. As another example, when the
nanoparticles contain a monomer, the monomer may be polymerized to
form a polymer. As another example, pre-polymer blocks in
nanoparticles could be linked together or cross-linkable polymers
in the nanoparticles could be cross-linked.
[0226] Structural modification that may be performed during the
modifying of the nanoparticles involves a non-compositional,
physical change to the nanoparticulate crystallinity or particle
morphology. Such structural modification often involves subjecting
the nanoparticles to a thermal treatment at elevated temperature.
As one example, structural modification may involve annealing the
nanoparticles, such as for crystal growth, to change the
crystallinity or to redistribute materials within the
nanoparticles. Another example of a structural modification is
changing the size of the nanoparticles, which may involve a heat
treatment to grow the size of the nanoparticles.
[0227] It should be appreciated, that the modifying of the
nanoparticles may involve one or more than one of any number of
surface modifications and/or compositional modifications and/or
structural modifications. As an example, the nanoparticles could be
annealed in the presence of a reactive component to effect both a
compositional change and a physical change.
[0228] The modifying of the nanoparticles may be performed while
the nanoparticles are maintained in a distributed state in the
multi-component particles made during formation of the
multi-component particles, after modifying the matrix of the
multi-component particles, or after decomposing the multi-component
particles to release the nanoparticles. Also, the modifying of the
nanoparticles may involve multiple modifications to the
nanoparticles. For example, one or more modifications may be
performed to the nanoparticles while the nanoparticles are
maintained in a distributed state within the particles made during
formation of the multi-component particles; one or more additional
modifications may be performed on the nanoparticles during
decomposition of the multi-component particles and one or more
modifications may be performed on the nanoparticles after
decomposition of the multi-component particles to release the
nanoparticles (such as for example surface modifying the
nanoparticles by contacting the nanoparticles with an appropriate
surface modifying material in a fluidized bed after release of the
nanoparticles from the matrix).
[0229] In one embodiment, the nanoparticles are modified after the
formation of the multi-component particles and prior to the
decomposing of the particles. The modification of the nanoparticles
involves a surface, composition and/or structural modification, as
discussed above, while the nanoparticles are maintained in a
distributed state within the particles made during the formation of
the particles. Modifying the nanoparticles while they are in a
distributed state within the multi-component particles provides the
advantage of making modifications to the nanoparticles in a
controlled way while avoiding the problem of nanoparticulate
agglomeration. As previously stated, the matrix may be temporary or
permanent. In the case where the matrix is permanent, the
nanoparticles may be modified to impart a characteristic that is
desired in a final product. In the case where the matrix is
temporary, the matrix will continue to act as a
handling/storage/processing aid for the nanoparticles prior to use
of the nanoparticles in a final application.
[0230] The modification of the nanoparticles may be performed while
the particles are still in the aerosol. Thus, the modifying of the
nanoparticles may be performed in series after the forming of the
particles without intermediate collection of the particles. One
example of this is annealing or calcining the particles on-the-fly
in the aerosol. Alternatively, the modifying of the nanoparticles
could be performed after removal of the particles from the aerosol.
One example of this is annealing or calcining the particles in a
kiln, rotary calciner, fluidized bed, belt furnace or tray furnace
after collection of the particles. In some cases during the
annealing or calcining, the matrix material from several
multi-component particles may fuse together to form a continuous
structure of matrix with distributed nanoparticles. If it is
desirable to have discrete multi-component particles, the
continuous structure of matrix with distributed nanoparticles may
be jet milled or hammer milled to form separated multi-component
particles.
[0231] In another embodiment, the modification of the nanoparticles
is performed after the decomposition of the particles, rather than
modifying the nanoparticles and then decomposing the particles.
Alternatively, the modifying of the nanoparticles could instead be
performed completely, or partially, during the decomposing of the
particles.
[0232] In another embodiment, the process of the invention includes
two nanoparticle modification steps, the first of which occurs
prior to the decomposing of the multi-component particles and the
second of which occurs after the decomposing of the multi-component
particles. As one example, modifying the nanoparticles prior to
decomposition may involve a compositional modification to the
nanoparticles and modifying the nanoparticles after may involve a
surface modification to the nanoparticles to enhance the
dispersability of the nanoparticles and/or to inhibit agglomeration
of the nanoparticles.
C. Process for Modifying the Matrix
[0233] In another embodiment, the present invention provides a
process in which the matrix is modified after the formation of the
multi-component particles. During the modification of the matrix,
one or more than one surface modification and/or compositional
modification and/or structural modification is performed on the
matrix. The previous discussions concerning surface modification,
compositional modification and structural modification of
nanoparticles, and the exemplary materials for use during such
modifications apply equally to the modifying of the matrix, except
that the modifications are performed on the matrix or a component
thereof rather than on the nanoparticles or a component thereof.
When both the nanoparticles and the matrix are to be modified, the
modifying of the matrix may be performed partially or entirely
prior to, simultaneously with, or after a modification of the
nanoparticles.
[0234] One particularly preferred embodiment involving modifying
the matrix is to remove only a portion of the matrix to increase
porosity in the matrix and enhance access to the nanoparticles
through the increased porosity. The matrix with increased porosity
may be a permanent matrix, and the increase in porosity may be
useful for a final application. For example in catalytic
applications, a porous matrix is useful to provide access to
catalytic nanoparticles distributed in the porous matrix.
Alternatively, the matrix with increased porosity may be a
temporary, non-permanent matrix, and the enhanced porosity may be
useful to provide access to the nanoparticles to modify the
nanoparticles, (e.g., surface modification, compositional
modification and/or structural modification). The increased
porosity enhances infiltration of treating chemicals and reagents
that may be used to modify the nanoparticles.
[0235] The matrix could initially be composed of a single material
with the increase in porosity being effected by removal of a
portion of the matrix, (e.g., partial dissolution of the single
matrix material). In another, preferred implementation however, the
matrix initially comprises multiple materials with one matrix
material being selectively removable relative to another matrix
material to effect the increase in matrix porosity. The selective
removal may be performed, for example, by selective sublimation,
selective dissolution into a liquid medium, selective chemical
removal, selective thermal decomposition at elevated temperature or
selective melting of one matrix material relative to the other
matrix material. By selective chemical removal it is meant that the
matrix material is reacted with one or more reactants to form
reaction products that are removed from the matrix, while the other
matrix material is substantially not removed.
[0236] The selective removability of the matrix materials requires
that the materials be selected to have different properties in
relation to the removal technique to be used, with one material
being substantially removable by the technique and the other being
substantially not removable by the technique. For example, the
matrix could contain one material that dissolves into a particular
liquid medium and another material that does not dissolve into that
liquid medium. As one example, a first matrix material may be a
water soluble organic salt and a second matrix material may be a
water insoluble polymer, with the selective removal being effected
by dissolving at least a portion, and preferably substantially all,
of the first matrix material into an aqueous liquid. As another
example, the selective removal of the second matrix material could
be effected by dissolving the polymer into an organic solvent in
which the organic salt or organic compound is substantially
insoluble. As another example, the matrix could comprise two
different organic salts with different solubilities in an aqueous
liquid. As another example, the matrix could comprise two polymers
with different solubilities in an aqueous or organic liquid. As
another example, the matrix could comprise of two organic compounds
where one is soluble in aqueous liquid and the other is
insoluble.
[0237] The partial removal of the matrix may be performed in a
aerosol. For example, the partial removal of the matrix may be
performed in series following the forming of the particles while
the particles are in the same aerosol. Alternatively, the partial
removal of the matrix may occur after collection of the particles,
which particles may then be re-dispersed in a new carrier gas to
form a new gas phase in which the partial removal of the matrix is
performed. As another alternative, the partial removal of the
matrix may occur in an environment other than an aerosol. For
example, after collection of the particles from the aerosol, the
particles may be mixed with a liquid medium that is a selective
solvent for one of the matrix materials.
D. Processes for Modifying the Multi-Component Particles
[0238] Another aspect of the present invention involves modifying,
e.g., manipulating and/or treating, the multi-component particles.
Such modification may be, for example, as an aid to handling,
storage, transportation, further processing or use of the
nanoparticles. This aspect of the invention includes any and all of
the different operations discussed above performed following
manufacture of the multi-component particles during formation of
the multi-component particles.
[0239] In one aspect, a mixture is formed comprising
multi-component particles and liquid medium, the multi-component
particles comprising nanoparticles maintained in a distributed
state in the multi-component particles by matrix. The
multi-component particles are treated while in the mixture, and
solutes are removed from the liquid medium to thereby reduce the
concentration of the solutes in the mixture, and preferably to
reduce the molar concentration of the solutes by at least a factor
of 10. The treating of the multi-component particles may involve
any treatment that may be performed in a liquid medium, including
for example, decomposing the multiphase particles to release the
nanoparticles or any of the modification to the multiphase
particles discussed above (such as any of the modifications to the
matrix and/or nanoparticles as discussed above), or some other
treatment. The performing of such a treatment often results in
solutes in the liquid medium. The solutes may include, for example,
one or more of: residual treating material left over from the
treatment, matrix material or nanoparticle dissolved into the
liquid medium during the treatment, and reaction or decomposition
products produced during the treatment. The multi-component
particles subjected to the treatment are preferably made as
described herein, but may be made by another route.
[0240] In another aspect, the multi-component particles are
subjected to a treatment step. During the treating of the
particles, the multi-component particles in a mixture with a liquid
medium are subjected to some treatment in such a manner that during
or after the treating of the particles, the liquid medium contains
the solutes, at least a portion of which are removed from the
liquid medium. The treating of the particles may involve any of the
previous processes descriped. The solutes are substances dissolved
in the liquid medium for which partial or total removal is
desired
[0241] At least some, preferably a majority, and most preferably
substantially all, of one or more of the solutes are removed from
the liquid medium in the separation step. Removal of the solutes
reduces the concentration of dissolved components in the liquid
medium. This is often important to prepare the liquid
medium/nanoparticulate mixture for use as a product (such as an
ink, paste or other slurry formulation), or to permit further
processing of the liquid medium that would be interfered with by
the solutes if not removed. For example, after the solutes are
removed during the separation step, then one or more additives
could be added to the remaining mixture or a portion of the liquid
medium could be removed to thicken the mixture, in preparation for
formulating an ink, paste or other slurry composition. When
thickening the mixture by removing a portion of the liquid medium,
a mixture is prepared that is more concentrated in the
nanoparticles, regardless of whether the nanoparticles are still
retained in a matrix structure or not. Alternatively, reactants or
reagents could be added to the liquid medium for performance of a
different treatment, for which the presence of the solutes would be
detrimental. In this latter alternative, additional solutes may be
introduced into the liquid medium and another removing solutes step
could be performed after performing the different treatment to
remove at least a portion of one or more of the additional
solutes.
[0242] Also, although the treatment of the particles and the
removal of the solutes may be sequential, the steps may also be
performed partially or wholly simultaneously. For example, solutes
may be removed from the liquid medium while the multi-component
particles are being subjected to the treatment to immediately
commence removal of solutes as they begin to build up in the liquid
medium.
[0243] The removing of the solutes may be performed by any
technique. One preferred technique is membrane separation of the
solutes by preferentially passing the solutes through a
semipermeable membrane relative to particulates in mixture with the
liquid medium. The particulates may comprise, for example, modified
forms of the multi-component particles or nanoparticles that have
been released from the matrix structure through decomposition of
the multi-component particles. By semipermeable membrane, it is
meant that the membrane is significantly more permeable to passage
of the solutes to be removed than passage of the particulates.
Passage of the solutes across the membrane may be due to unaided
diffusion of the solutes through the membrane, or the membrane may
be functionalized or contain ion exchange activity to facilitate
transport of one or more solutes across the membrane. For example,
dissolved salt ions, from dissolution of a salt matrix may be
removed in a dialysis-type membrane separation. Likewise, special
molecule polymers may also be removed in such a dialysis-type
membrane separation. Alternatively, diafiltration techniques,
described in detail above, may be used to remove the solutes. For
larger polymers, or macromolecules, a diasolysis or other membrane
separation technique may be used. Examples of some membranes that
may be used for removing smaller molecule solutes include, for
example parchment membranes, collodion, cellophane, asbestos fiber
and perfluorosulfonic acid membrane (such as NAFION.TM. membranes
from DuPont). For removal of larger polymer molecules, some
examples of some membranes that may be used include gum, plastic or
rubber membranes. Another technique is to partition target solutes
into another liquid that is immiscible with the liquid medium. For
example, some polymer solutes could be partitioned into an organic
liquid that is immiscible with the liquid medium, such as for
example when the liquid medium is an aqueous liquid.
E. Processes for Forming Composite Structure from the
Multi-Component Particles
[0244] Another aspect of the present invention involves
re-dispersing nanoparticles in a composite structure with a new
matrix. The matrix of the multi-component particles may be useful
for subsequent processing, handling, transportation or storage of
the nanoparticles, but it may be desirable at same point to have a
different matrix for further processing, handling, storage or
transportation, or for a final application for use of the
nanoparticles. The new matrix may be a permanent matrix for a final
use or it may be a non-permanent temporary matrix for intermediate
handling, storage, transportation or further processing, or have
functionality in the final application. In this aspect of the
invention, the process includes a step of decomposing the particles
and forming a composite structure after the formation of the
particles. The composite structure formed includes nanoparticles
distributed in a new matrix. The nanoparticles in the composite
structure are fixedly distributed, meaning that the nanoparticles
are maintained in a distributed state by the new matrix. The
composite structure may be in a particulate form or a
non-particulate form (e.g., monolithic form, sheet, layer, film,
bar, etc.).
[0245] As with the matrix of the particles described previously,
the matrix of the composite structure may be comprised of a single
material or of multiple materials that function to maintain the
nanoparticles in a distributed state. The new matrix of the
composite structure may have the same composition or a different
composition than the matrix removed during the decomposing of the
particles. More often, the new matrix of the composite structure
will have a different composition than that of the matrix removed
during the decomposition of the particles, because the new matrix
in the composition structure will typically serve a different
purpose. The new matrix of the composite structure may include any
suitable materials for a desired purpose. Examples of materials
previously identified for the particles, made during formation of
the multi-component particles, are examples of materials that may
be used for the new matrix of the composite structure.
[0246] Any procedure useful for distributing the nanoparticles in a
matrix may be used during the formation of the composite structure.
As one example, the nanoparticles may be distributed in a melt of
matrix materials and then cooled to solidify the composite
structure (e.g., distributed in a polymer melt).
[0247] As another example, the nanoparticles may be dispersed and
the new matrix may then be formed around the dispersed
nanoparticles. As a specific example, nanoparticles may be
dispersed in a solution of reactable monomers or pre-polymer
segments that are then polymerized or otherwise reacted to form the
matrix around the dispersed nanoparticles. As a further example,
nanoparticles may be dispersed in a polymer solution that gels upon
inducing some change in the system. The polymer solution may change
from a liquid to gel form, for example, in response to a change in
temperature, pH or light. As another example, nanoparticles may be
dispersed in a solution of cross-linkable polymer that is then
cross-linked to form the matrix around the dispersed
nanoparticles.
[0248] In one implementation, the composite structure is made in
particulate form by aerosol processing during the forming of the
composite structure. Droplets comprising the nanoparticles, and
preferably also comprising one or more precursors for the new
matrix, are formed and dispersed in and suspended by a carrier gas
to form a new aerosol. The droplets are formed from a feed medium
comprising the nanoparticles dispersed in a liquid vehicle.
Precursor(s) for material(s) of the new matrix are preferably
dissolved or suspended in a liquid vehicle, but precursor(s) for
material(s) of the new matrix may also be included in the carrier
gas. In the aerosol, liquid is removed from the droplets and the
precursors for the new matrix are reacted or otherwise processed to
form the new matrix. The new aerosol may be made, for example as
previously discussed with respect to forming the initial aerosol.
Examples of liquid vehicles and matrix precursors that may be
included in the feed medium are similar to those described
previously with respect to the generation of the initial aerosol.
After particles of the composite structure have been made in the
new aerosol, the particles may be collected for further processing
or use. The collection of the particles involves separating the
particles of the composite structure from the gas phase of the new
aerosol, such as by cyclone, filter, electrostatic precipitation,
or in a bag house.
[0249] The composite structure made during the formation of the
composite structure may be designed as a permanent structure for a
final use or may be a temporary structure useful for intermediate
storage, transportation, handling or further processing of the
nanoparticles prior to final use. One example of a composite
structure designed for final use is a dispersion of thermally
conductive metal nanoparticles (such as copper or silver) in a
polymer matrix for use as a thermal interface material.
V. EXAMPLES
[0250] The present invention will be better understood in view of
the following non-limiting examples. In each example, the precursor
medium was processed using a lab scale system, which had a droplet
generator box having only one piezo transducer. The transducer was
separated from the solution by a polyimide (Kapton) membrane.
Although some of the experiments described here employed nitrogen
as carrier gas, there was no appreciable difference in the final
products when either nitrogen or air was used as the carrier
gas.
A. Process Examples
Example 1
Silver Nanoparticles and Polymer Matrix from AgNO.sub.3
[0251] A precursor medium containing silver nitrate, AgNO3 and PVP,
dissolved in deionized water is prepared. The precursor medium
contains: TABLE-US-00012 AgNO.sub.3 7.5 g PVP 0.5 g Deionized
H.sub.2O 92 g
This precursor medium is designed for 8 wt % loading of solids, and
to yield particles consisting of 46 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 400.degree. C. and a carrier
gas flow rate of 15 liter per minute (lpm). XRD analysis of the
resulting powder shows strong peaks of silver with the presence of
small amount of silver nitrate.
Example 2
Silver Nanoparticles and Polymer Matrix from AgNO.sub.3 With Use of
Ethanol
[0252] A precursor medium containing silver nitrate, AgNO.sub.3 and
PVP, dissolved in deionized water is prepared. The precursor medium
contains: TABLE-US-00013 AgNO.sub.3 15.0 g PVP 0.5 g Deionized
H.sub.2O 74.5 g Ethanol 10.0 g
This precursor medium is designed for 15.5 wt % loading of solids,
and to yield particles consisting of 64 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 400.degree. C. and a carrier
gas flow rate of 15 liter per minute (lpm). XRD analysis of the
resulting powder shows strong peaks of silver with the presence of
silver nitrate.
Example 3
Silver Nanoparticles and Polymer Matrix from AgNO.sub.3 With Use of
Ethylene Glycol
[0253] A precursor medium containing silver nitrate, AgNO3 and PVP,
dissolved in deionized water is prepared. The precursor medium
contains: TABLE-US-00014 AgNO.sub.3 15.0 g PVP 0.5 g Deionized
H.sub.2O 74.5 g Ethylene glycol 15.0 g
This precursor medium is designed for 15.5 wt % loading of solids,
and to yield particles consisting of 64 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 15 liter per minute (lpm). Under these conditions,
the vapor quickly condensed onto the filter paper, as a result, the
pressure built up quickly in less than 5 min. XRD analysis of the
resulting powder shows strong peaks of silver with the presence of
silver nitrate.
[0254] The precursor medium is also processed on the lab scale
system at 400.degree. C. and a carrier gas flow rate of 15 lpm. XRD
pattern for this powder shows mainly silver peaks with very weak
peaks attributed to silver nitrate.
Example 4
Silver Nanoparticles and Polymer Matrix from AgNO.sub.3 With Use of
Reducing Agent
[0255] A precursor medium containing silver nitrate, AgNO.sub.3 and
PVP, dissolved in deionized water is prepared. The precursor medium
contains: TABLE-US-00015 AgNO.sub.3 7.5 g PVP 1.5 g Deionized
H.sub.2O 75.5 g Ethanol 15.0 g Glucose 0.5 g
This precursor medium is designed for 8.0 wt % loading of solids,
and to yield particles consisting of 25 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 300.degree. C. and a carrier
gas flow rate of 15 liter per minute (lpm). Under these conditions,
the vapor quickly condensed onto the filter paper, as a result, the
pressure built up quickly in less than 5 min. XRD analysis of the
resulting powder shows only strong peaks of silver without the
presence of silver nitrate.
[0256] The precursor medium is also processed on the lab scale
system at 300.degree. C. and at a carrier gas flow rate of 7, 20,
30 and 40 lpm, respectively. XRD patterns indicate that the
reactions are complete except for the case with a flow rate of 30
and 40 lpm. All the product silver particles are partially
dispersable in water. Example 5: Silver nanoparticles and Polymer
Matrix from AgNO.sub.3 with use of reducing agent.
[0257] A precursor medium containing silver nitrate, AgNO.sub.3 and
PVP, dissolved in deionized water is prepared. The precursor medium
contains: TABLE-US-00016 AgNO.sub.3 7.5 g PVP 1.5 g Deionized
H.sub.2O 75.5 g Ethanol 15.0 g Glucose 0.5 g
This precursor medium is designed for 8.0 wt % loading of solids,
and to yield particles consisting of 25 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 20 liter per minute (lpm). Under these conditions,
the vapor quickly condensed onto the filter paper, as a result, the
pressure built up quickly in less than 5 min. XRD analysis of the
resulting powder shows strong peaks of silver with the presence of
silver nitrate.
[0258] The precursor medium is also processed on the lab scale
system at 250.degree. C. and at a carrier gas flow rate of 10 and
30 lpm, respectively. XRD patterns indicate that the reactions are
incomplete with the products composed of both silver and silver
nitrate.
Example 6
Silver Nanoparticles and Polymer Matrix from AgTFA
[0259] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00017 AgTFA 6.75 g PVP 1.05 g
Deionized H.sub.2O 92.2 g
This precursor medium is designed for 7.8 wt % loading of solids,
and to yield particles consisting of 25 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 5 liter per minute (lpm) was used. XRD analysis of
the resulting powder shows only peaks of silver.
[0260] The precursor medium is also processed on the lab scale
system at 250.degree. C. and at a carrier gas flow rate of 15, and
30 lpm, respectively. XRD patterns indicate that the reactions are
complete with only silver peaks. All the product silver particles
are dispersable in water.
Example 7
Silver Nanoparticles and Polymer Matrix from AgTFA
[0261] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00018 AgTFA 6.75 g PVP 0.5 g
Deionized H.sub.2O 92.75 g
This precursor medium is designed for 7.25 wt % loading of solids,
and to yield particles consisting of 40 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 5 liter per minute (lpm) was used. XRD analysis of
the resulting powder shows peaks of silver with the presence of
silver precursor.
[0262] The precursor medium is also processed on the lab scale
system at 250.degree. C. and at a carrier gas flow rate of 15, and
30 lpm, respectively. XRD patterns indicate that the reaction with
a 30 lpm flow rate is incomplete with only silver peaks. All the
product silver particles are dispersable in water.
Example 8
Silver Nanoparticles and Polymer Matrix from AgTFA
[0263] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00019 AgTFA 6.75 g PVP 0.3 g
Deionized H.sub.2O 92.95 g
This precursor medium is designed for 7.05 wt % loading of solids,
and to yield particles consisting of 53 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 5 liter per minute (lpm) was used. XRD analysis of
the resulting powder shows peaks of silver with the presence of
small amount of silver precursor.
[0264] The precursor medium is also processed on the lab scale
system at 250.degree. C. and at a carrier gas flow rate of 15, and
30 lpm, respectively. XRD patterns indicate that the reactions are
incomplete with product as a mixture of silver and silver
precursor. All the product silver particles are partially
dispersable in water.
Example 9
Silver Nanoparticles and Polymer Matrix from AgTFA
[0265] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00020 AgTFA 6.75 g PVP 1.05 g
Deionized H.sub.2O 92.2 g
This precursor medium is designed for 7.8 wt % loading of solids,
and to yield particles consisting of 25 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 300.degree. C. and a carrier
gas flow rate of 5 liter per minute (lpm) was used. XRD analysis of
the resulting powder shows only peaks of silver.
[0266] The precursor medium is also processed on the lab scale
system at 250.degree. C. and at a carrier gas flow rate of 15, and
30 lpm, respectively. XRD patterns indicate that the reactions are
complete with only silver peaks. All the product silver particles
are only slightly or partially dispersable in water; product
produced with a lower flow rate has less dispersity in water
Example 10
Silver Nanoparticles and Polymer Matrix From AgTFA
[0267] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00021 AgTFA 6.75 g PVP 0.5 g
Deionized H.sub.2O 92.75 g
This precursor medium is designed for 7.25 wt % loading of solids,
and to yield particles consisting of 40 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 300.degree. C. and a carrier
gas flow rate of 5 liter per minute (lpm) was used. XRD analysis of
the resulting powder shows peaks of silver without the presence of
silver precursor.
[0268] The precursor medium is also processed on the lab scale
system at 300.degree. C. and at a carrier gas flow rate of 15, and
30 lpm, respectively. XRD patterns indicate that the reaction are
complete with only silver peaks. All the product silver particles
are not dispersable in water.
Example 11
Silver Nanoparticles and Polymer Matrix From AgTFA
[0269] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00022 AgTFA 6.75 g PVP 0.3 g
Deionized H.sub.2O 92.95 g
This precursor medium is designed for 7.05 wt % loading of solids,
and to yield particles consisting of 53 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 300.degree. C. and a carrier
gas flow rate of 5 liter per minute (lpm) was used. XRD analysis of
the resulting powder shows peaks of silver without the presence of
silver precursor.
[0270] The precursor medium is also processed on the lab scale
system at 300.degree. C. and at a carrier gas flow rate of 15, and
30 lpm, respectively. XRD patterns indicate that the reaction with
a flow rate 30 is incomplete with product as a mixture of silver
and AgTFA.
Example 12
Silver Nanoparticles and Polymer Matrix From AgTFA
[0271] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00023 AgTFA 6.75 g PVP 0.25 g
Deionized H.sub.2O 93.0 g
This precursor medium is designed for 7.0 wt % loading of solids,
and to yield particles consisting of 53 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 5 liter per minute (lpm) was used. Air pressure
was quickly built up and the reaction was stopped in less than 2
min as a result. There is no enough material to take the XRD
pattern. SEM images of the material indicates particles of 30-80 nm
in the matrix.
[0272] The precursor medium is also processed on the lab scale
system at 300.degree. C. and at a carrier gas flow rate 5 1.mu.m,
XRD patterns indicate that the reaction is complete. SEM images of
the material indicates particles of 60-100 nm in the matrix
Example 13
Silver Nanoparticles and Polymer Matrix From AgTFA
[0273] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00024 AgTFA 6.75 g PVP 0.20 g
Deionized H.sub.2O 93.5 g
This precursor medium is designed for 6.95 wt % loading of solids,
and to yield particles consisting of 57 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 5 liter per minute (lpm) was used. Air pressure
was quickly built up and the reaction was stopped in less than 2
min as a result. There is no enough material to take the XRD
pattern. SEM images of the material indicates particles of 70-100
nm in the matrix.
[0274] The precursor medium is also processed on the lab scale
system at 300.degree. C. and at a carrier gas flow rate 5 lpm, XRD
patterns indicate that the reaction is complete. SEM images of the
material indicates particles of ca. 120 nm in the matrix
Example 14
Silver Nanoparticles and Polymer Matrix From AgTFA--Effect of
Glucose
[0275] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00025 AgTFA 4.0 g PVP 0.25 g
Deionized H.sub.2O 95.0 g Glucose 0.75
This precursor medium is designed for 5.0 wt % loading of solids,
and to yield particles consisting of 45 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 20 liter per minute (lpm) was used. XRD pattern
shows peaks of only silver without starting material. SEM images of
the material indicate particles of 20 nm in the matrix.
[0276] The precursor medium is also processed on the lab scale
system at 250.degree. C. and at a carrier gas flow rate 20 lpm
without the addition of glucose, XRD patterns indicate that the
reaction is incomplete with product being a mixture of silver and
silver trifluoroacetate.
Example 15
Silver Nanoparticles and Polymer Matrix From AgTFA--Effect of
Glucose
[0277] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00026 AgTFA 6.0 g PVP 0.4 g
Deionized H.sub.2O 93.35 g Glucose 0.25
This precursor medium is designed for 6.65 wt % loading of solids,
and to yield particles consisting of 45 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 30 liter per minute (lpm) was used. XRD pattern
shows peaks of only silver without starting material. SEM images of
the material indicate particles of 20 nm in the matrix.
[0278] The precursor medium is also processed on the lab scale
system at 250.degree. C. and at a carrier gas flow rate 30 1.mu.m
without the addition of glucose, XRD patterns indicate that the
reaction is incomplete with product being a mixture of silver and
silver trifluoroacetate.
Example 16
Silver Nanoparticles and Polymer Matrix from AgTFA--Effect of
Sodium Dioctyl Sulfosuccinate (AOT)
[0279] A precursor medium containing silver trifluoroacetate
(AgTFA) and PVP, dissolved in deionized water is prepared. The
precursor medium contains: TABLE-US-00027 AgTFA 4.0 g PVP 0.35 g
Deionized H.sub.2O 95.4 g AOT 0.25
This precursor medium is designed for 4.6 wt % loading of solids,
and to yield particles consisting of 35 vol % silver metal in a PVP
matrix. The precursor medium is processed on the lab scale system
described above, at a temperature of 250.degree. C. and a carrier
gas flow rate of 30 liter per minute (lpm) was used. XRD pattern
shows the reaction in incomplete.
[0280] The precursor medium is also processed on the lab scale
system at a carrier gas flow rate 20 lpm, XRD patterns indicate
that the reaction is still incomplete. As a mixture of silver and
silver precursor, the product from both reactions disperses very
well in water.
Example 17
Silver Nanoparticles and Polymer Matrix
[0281] A precursor medium is prepared containing: TABLE-US-00028
AgNO.sub.3 30 g Polyvinylpyrrolidone 10,000 MW 12 g Deionized
H.sub.2O 235 g
[0282] The precursor medium has 15 wt % soluble components and is
designed to yield particles with 13.4 vol % silver nanoparticles
inside a PVP matrix. The precursor medium is formulated with the
idea of achieving similar results as have been achieved by liquid
batch routes in the polyol process, which produces silver
nanoparticles of approximately 50 nm in size.
[0283] The precursor medium is processed using the pilot scale
system at 550.degree. C. with a carrier gas flow rate of 60 lpm.
The resulting powder is very dark brown. XRD of the resulting
powder indicates contamination of strontium nitrate from a previous
precursor medium, but primarily shows the presence of silver. Some
silver nitrate appears to be present, but is difficult to identify.
SEM images of the powder show spherical particles on the order of 1
to 5 microns. The surface of the spherical particles appears to
contain nanoparticles. The larger particles contain features less
than 100 nm in diameter on their surfaces. Some of the larger
particles appear to be hollow and the nanoparticles can be seen in
pieces of crumbled micron size hollow particles.
[0284] The precursor medium is also processed using the pilot scale
system at 350.degree. C. with a carrier gas flow rate of 60 lpm.
XRD of this sample is also contaminated with strontium nitrate from
previously processed precursor mediums, but does clearly show the
presence of silver. The morphology of the powder is similar to the
powder produced at 550.degree. C., with sub-100 nm features visible
on the surface of micron size particles.
[0285] The foregoing discussion of the invention has been presented
for purposes of illustration and description. The foregoing is not
intended to limit the invention to only the form or forms
specifically disclosed herein. Although the description of the
invention has included description of one or more embodiments and
certain implementations, variations and modifications, other
implementations, variations and modifications are within the scope
of the invention, e.g., as may be within the skill and knowledge of
those in the art after understanding the present disclosure. It is
intended to obtain rights which include alternative embodiments to
the extent permitted, including alternate, interchangeable and/or
equivalent structures, functions, ranges or steps to those claimed,
whether or not such alternate, interchangeable and/or equivalent
structures, functions, ranges or steps are disclosed herein, and
without intending to publicly dedicate any patentable subject
matter. Furthermore, any feature described with respect to any
disclosed embodiment, implementation or variation of any aspect of
the invention may be combined in any combination with one or more
features of any other embodiment, implementation or variation of
the same or any other aspect of the invention. For example,
additional processing steps can be included at any point before,
during or after processing disclosed in any of the process
embodiments described herein or shown in any of the figures, so
long as the additional steps are not incompatible with the
disclosed processing according to the present invention. Moreover,
processing steps disclosed in any of the process embodiments
described herein can be combined with any other processing steps
described with any other process embodiment. The terms
"comprising," "containing," "including," and "having," and
variations thereof, are intended to be non-limiting in that the use
of such terms indicates the presence of some condition or feature,
but not to the exclusion of the presence of any other condition or
feature. Percentages stated herein are by weight unless otherwise
expressly stated.
* * * * *