U.S. patent application number 10/679611 was filed with the patent office on 2004-07-22 for printing inks and reagents for nanoelectronics and consumer products.
Invention is credited to Kostelecky, Clayton, Yadav, Tapesh.
Application Number | 20040139888 10/679611 |
Document ID | / |
Family ID | 22181337 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040139888 |
Kind Code |
A1 |
Yadav, Tapesh ; et
al. |
July 22, 2004 |
Printing inks and reagents for nanoelectronics and consumer
products
Abstract
Printing inks and pastes are disclosed that comprise of
nanofillers with domain size less than 100 nanometers thereby
exhibiting quantum confinement effects. The printing formulations
comprise of nanowhiskers, nanorods, fibers, plates and powders.
These printing formulations are useful for preparing
nanoelectronics, electrodes and nanotechnology-enabled devices and
products. The nanofillers composition taught include inorganic,
metallic, organic, oxides, borides, nitrides, carbides, halides,
sulfides, alloys and chalcogenides.
Inventors: |
Yadav, Tapesh; (Longmont,
CO) ; Kostelecky, Clayton; (Longmont, CO) |
Correspondence
Address: |
HOGAN & HARTSON LLP
ONE TABOR CENTER, SUITE 1500
1200 SEVENTEENTH ST
DENVER
CO
80202
US
|
Family ID: |
22181337 |
Appl. No.: |
10/679611 |
Filed: |
October 6, 2003 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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10679611 |
Oct 6, 2003 |
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10441683 |
May 20, 2003 |
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10441683 |
May 20, 2003 |
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09790036 |
Feb 20, 2001 |
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09790036 |
Feb 20, 2001 |
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09083893 |
May 22, 1998 |
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6228904 |
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09790036 |
Feb 20, 2001 |
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08739257 |
Oct 30, 1996 |
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5905000 |
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08739257 |
Oct 30, 1996 |
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08730661 |
Oct 11, 1996 |
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5952040 |
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08730661 |
Oct 11, 1996 |
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08706819 |
Sep 3, 1996 |
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5851507 |
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08730661 |
Oct 11, 1996 |
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08707341 |
Sep 3, 1996 |
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5788738 |
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10679611 |
Oct 6, 2003 |
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09753806 |
Jan 3, 2001 |
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6513362 |
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09753806 |
Jan 3, 2001 |
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09074534 |
May 7, 1998 |
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6202471 |
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60049077 |
Jun 9, 1997 |
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60069936 |
Dec 17, 1997 |
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60079225 |
Mar 24, 1998 |
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Current U.S.
Class: |
106/403 ;
106/31.65; 106/401; 106/404; 106/415; 106/455; 106/481;
106/499 |
Current CPC
Class: |
B01J 12/005 20130101;
C01P 2004/16 20130101; C04B 2235/3206 20130101; C04B 2235/3284
20130101; C04B 2235/5409 20130101; Y02P 70/50 20151101; B01J
2219/00135 20130101; B01J 2219/0894 20130101; B82B 1/00 20130101;
C01B 13/145 20130101; C04B 2235/3298 20130101; H01M 6/36 20130101;
C01B 13/363 20130101; C01P 2004/04 20130101; C04B 20/1018 20130101;
C04B 2235/549 20130101; C08K 3/08 20130101; H01G 4/12 20130101;
B22F 2999/00 20130101; C01G 49/0063 20130101; C04B 20/1029
20130101; C04B 2235/3286 20130101; C04B 2235/5454 20130101; Y02E
60/50 20130101; C04B 41/52 20130101; C04B 2235/6565 20130101; H01M
8/1213 20130101; B22F 1/16 20220101; B82Y 30/00 20130101; C01P
2004/38 20130101; C04B 35/01 20130101; C04B 35/547 20130101; C09C
3/10 20130101; B01J 19/24 20130101; C01B 35/04 20130101; C01P
2004/10 20130101; C01P 2004/86 20130101; C04B 2235/3201 20130101;
C01B 32/914 20170801; C01F 5/06 20130101; C01P 2002/54 20130101;
C04B 2111/00482 20130101; C09C 1/627 20130101; B05B 1/12 20130101;
B82Y 20/00 20130101; C01G 23/006 20130101; C04B 2235/3262 20130101;
C01P 2004/03 20130101; C04B 2/10 20130101; C04B 20/0004 20130101;
C04B 35/453 20130101; C04B 35/457 20130101; C04B 41/89 20130101;
C01F 11/06 20130101; C01G 19/02 20130101; C01P 2004/64 20130101;
C04B 35/653 20130101; H01C 7/112 20130101; C01G 41/02 20130101;
B01J 12/02 20130101; C01P 2002/34 20130101; C01P 2002/60 20130101;
C01P 2004/20 20130101; H01F 1/36 20130101; Y10T 428/31663 20150401;
C04B 35/6265 20130101; C09C 1/0081 20130101; Y02P 40/40 20151101;
Y10T 428/2998 20150115; C01P 2004/62 20130101; C04B 26/06 20130101;
B01J 2219/00155 20130101; C01B 21/062 20130101; C01G 49/0018
20130101; C01P 2004/51 20130101; C01P 2006/10 20130101; C04B
2111/00844 20130101; C04B 2235/3241 20130101; C09C 1/22 20130101;
H01M 6/20 20130101; C01P 2002/02 20130101; C01P 2004/54 20130101;
C08K 3/013 20180101; H01M 8/1246 20130101; H01M 2004/021 20130101;
B82Y 25/00 20130101; C08K 2201/011 20130101; C01G 53/006 20130101;
C04B 35/62222 20130101; H01M 4/9066 20130101; H01M 8/1253 20130101;
C08K 9/02 20130101; B22F 9/12 20130101; C01B 32/90 20170801; C04B
2235/6562 20130101; H01B 1/22 20130101; C04B 41/009 20130101; C01P
2006/42 20130101; C04B 35/63456 20130101; B22F 1/0003 20130101;
C04B 26/02 20130101; C04B 35/628 20130101; C04B 2235/3279 20130101;
C01G 19/006 20130101; C01P 2002/52 20130101; C01B 19/007 20130101;
C04B 2235/444 20130101; Y10S 977/70 20130101; C01P 2002/01
20130101; C04B 2111/00008 20130101; B22F 1/07 20220101; C01G 15/00
20130101; C09C 3/08 20130101; H01C 7/105 20130101; H01F 1/0063
20130101; C09C 1/00 20130101; B01J 2219/00094 20130101; B22F 1/054
20220101; C01B 25/08 20130101; C01G 19/00 20130101; C01P 2004/84
20130101; C01P 2006/12 20130101; C04B 2235/3418 20130101; H01M
4/5815 20130101; B01J 2219/00177 20130101; B29C 70/58 20130101;
C04B 35/265 20130101; C04B 2235/3275 20130101; H01F 1/344 20130101;
B01J 2219/0018 20130101; C01P 2004/52 20130101; C04B 41/90
20130101; C08K 3/01 20180101; C01P 2002/72 20130101; H01G 4/33
20130101; C01P 2004/61 20130101; B22F 2999/00 20130101; B22F 1/0003
20130101; B22F 1/054 20220101; B22F 2999/00 20130101; B22F 9/12
20130101; B22F 2202/13 20130101; C04B 26/02 20130101; C04B 20/1029
20130101; C04B 41/009 20130101; C04B 26/02 20130101; B22F 2999/00
20130101; B22F 1/10 20220101; B22F 1/054 20220101; C04B 26/06
20130101; C04B 14/30 20130101; C04B 20/008 20130101; C04B 24/2623
20130101; C04B 26/06 20130101; C04B 14/322 20130101; C04B 20/008
20130101; C04B 26/02 20130101; C04B 14/30 20130101; C04B 14/325
20130101; C04B 14/38 20130101; C04B 20/008 20130101; C04B 2103/40
20130101; C04B 2103/408 20130101; C04B 20/1018 20130101; C04B 14/30
20130101; C04B 41/009 20130101; C04B 35/10 20130101; C04B 41/52
20130101; C04B 41/4539 20130101; C04B 41/5116 20130101; C04B
41/5122 20130101; C04B 41/52 20130101; C04B 41/4539 20130101; C04B
41/4549 20130101; C04B 41/5027 20130101; C04B 41/5049 20130101;
B22F 2999/00 20130101; B22F 1/0003 20130101; B22F 1/054 20220101;
B22F 2999/00 20130101; B22F 1/10 20220101; B22F 1/054 20220101 |
Class at
Publication: |
106/403 ;
106/415; 106/499; 106/401; 106/404; 106/455; 106/481;
106/031.65 |
International
Class: |
C09D 011/00 |
Claims
We claim:
1. A printable formulation comprising fillers with domain size less
than 100 nanometers.
2. The printable formulation of claim 1 wherein the fillers are
nanowhiskers.
3. The printable formulation of claim 1 wherein the fillers are
fibers.
4. The printable formulation of claim 1 wherein the fillers are
plates.
5. The printable formulation of claim 1 wherein the fillers are
inorganic.
6. The printable formulation of claim 2 wherein the fillers are
organic.
7. The printable formulation of claim 2 wherein the fillers are
metallic.
8. The printable formulation of claim 1 wherein the printable
formulation is an ink.
9. The printable formulation of claim 1 wherein the printable
formulation is a paste.
10. The printable formulation of claim 2 wherein the filler
comprises at least one element from the group consisting of
aluminum, antimony, boron, bromine, carbon, chlorine, fluorine,
germanium, hydrogen, indium, iodine, nickel, nitrogen, oxygen,
phosphorus, selenium, silicon, sulfur, or tellurium.
11. The printable formulation of claim 3 wherein the filler
comprises at least one element from the group consisting of
aluminum, antimony, boron, bromine, carbon, chlorine, fluorine,
germanium, hydrogen, indium, iodine, nickel, nitrogen, oxygen,
phosphorus, selenium, silicon, sulfur, or tellurium.
12. The printable formulation of claim 4 wherein the filler
comprises at least one element from the group consisting of
aluminum, antimony, boron, bromine, carbon, chlorine, fluorine,
germanium, hydrogen, indium, iodine, nickel, nitrogen, oxygen,
phosphorus, selenium, silicon, sulfur, or tellurium.
13. The printable formulation of claim 2 wherein the nanowhiskers
are nanorods.
14. The printable formulation of claim 2 wherein the nanowhiskers
have an aspect ratio greater than 2.
15. A product manufactured using the printable formulation of claim
1.
16. A device manufactured using the printable formulation of claim
14.
Description
1. RELATED APPLICATIONS
[0001] This application is a divisional of co-pending U.S. patent
application Ser. No. 10/441,683 titled "INK NANOTECHNOLOGY" filed
on May 20, 2003 which is a division of co-pending Ser. No.
09/790,036 titled "NANOTECHNOLOGY FOR DRUG DELIVERY, CONTRAST
AGENTS AND BIOMEDICAL IMPLANTS" filed on Feb. 20, 2001, which is a
divisional of U.S. Pat. No. 6,228,904 filed on May 22, 1998, which
is incorporated herein by reference and which claims the benefit of
U.S. Provisional applications 60/049,077 filed on Jun. 9, 1997,
60/069,936 filed on Dec. 17, 1997, and 60/079,225 filed on Mar. 24,
1998. U.S. Pat. No. 6,228,904 is a continuation-in-part of U.S.
patent application Ser. No. 08/739,257, filed Oct. 30, 1996, now
U.S. Pat. No. 5,905,000, titled NANOSTRUCTURED ION CONDUCTING SOLID
ELECTROLYTES, which is a continuation-in-part of U.S. Ser. No.
08/730,661, filed Oct. 11, 1996, now U.S. Pat. No. 5,952,040 titled
"PASSIVE ELECTRONIC COMPONENTS FROM NANO-PRECISION ENGINEERED
MATERIALS" which is a continuation-in-part of U.S. Ser. No.
08/706,819, filed Sep. 3, 1996, now U.S. Pat. No. 5,851,507 titled
"INTEGRATED THERMAL PROCESS FOR THE CONTINUOUS SYNTHESIS OF
NANOSCALE POWDERS" and U.S. Ser. No. 08/707,341, filed Sep. 3,
1996, now U.S. Pat. No. 5,788,738 titled "METHOD OF PRODUCING
NANOSCALE POWDERS BY QUENCHING OF VAPORS". This application is also
a continuation-in-part of co-pending U.S. patent application Ser.
No. 09/753,806 titled "LOW-COST MULTILAMINATE SENSORS" which is a
divisional of U.S. Pat. No. 6,202,471 filed on May 7, 1998 titled
"LOW-COST MULTILAMINATE SENSORS". All of the patents and patent
applications referenced in this paragraph are incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 2. Field of the Invention
[0003] In one aspect, the invention comprises a nanostructured
filler, intimately mixed with a matrix to form a nanostructured
composite. At least one of the nanostructured filler and the
nanostructured composite has a desired material property which
differs by at least 20% from the same material property for a
micron-scale filler or a micron-scale composite, respectively. The
desired material property is selected from the group consisting of
refractive index, transparency to light, reflection
characteristics, resistivity, permittivity, permeability,
coercivity, B-H product, magnetic hysteresis, breakdown voltage,
skin depth, curie temperature, dissipation factor, work function,
band gap, electromagnetic shielding effectiveness, radiation
hardness, chemical reactivity, thermal conductivity, temperature
coefficient of an electrical property, voltage coefficient of an
electrical property, thermal shock resistance, biocompatibility and
wear rate.
[0004] The nanostructured filler may comprise one or more elements
selected from the s, p, d, and f groups of the periodic table, or
it may comprise a compound of one or more such elements with one or
more suitable anions, such as aluminum, antimony, boron, bromine,
carbon, chlorine, fluorine, germanium, hydrogen, indium, iodine,
nickel, nitrogen, oxygen, phosphorus, selenium, silicon, sulfur, or
tellurium. The matrix may be a polymer (e.g., poly(methyl
methacrylate), poly(vinyl alcohol), polycarbonate, polyalkene, or
polyaryl), a ceramic (e.g., zinc oxide, indium-tin oxide, hafnium
carbide, or ferrite), or a metal (e.g., copper, tin, zinc, or
iron). Loadings of the nanofiller may be as high as 95%, although
loadings of 80% or less are preferred. The invention also comprises
devices which incorporate the nanofiller (e.g., electrical,
magnetic, optical, biomedical, and electrochemical devices).
[0005] Another aspect of the invention comprises a method of
producing a composite, comprising blending a nanoscale filler with
a matrix to form a nanostructured composite. Either the
nanostructured filler or the composite itself differs substantially
in a desired material property from a micron-scale filler or
composite, respectively. The desired material property is selected
from the group consisting of refractive index, transparency to
light, reflection characteristics, resistivity, permittivity,
permeability, coercivity, B-H product, magnetic hysteresis,
breakdown voltage, skin depth, curie temperature, dissipation
factor, work function, band gap, electromagnetic shielding
effectiveness, radiation hardness, chemical reactivity, thermal
conductivity, temperature coefficient of an electrical property,
voltage coefficient of an electrical property, thermal shock
resistance, biocompatibility, and wear rate. The loading of the
filler does not exceed 95 volume percent, and loadings of 80 volume
percent or less are preferred.
[0006] The composite may be formed by mixing a precursor of the
matrix material with the nanofiller, and then processing the
precursor to form a desired matrix material. For example, the
nanofiller may be mixed with a monomer, which is then polymerized
to form a polymer matrix composite. In another embodiment, the
nanofiller may be mixed with a matrix powder composition and
compacted to form a solid composite. In yet another embodiment, the
matrix composition may be dissolved in a solvent and mixed with the
nanofiller, and then the solvent may be removed to form a solid
composite. In still another embodiment, the matrix may be a liquid
or have liquid like properties.
[0007] Many nanofiller compositions are encompassed within the
scope of the invention, including nanofillers comprising one or
more elements selected from the group consisting of actinium,
aluminum, arsenic, barium, beryllium, bismuth, cadmium, calcium,
cerium, cesium, cobalt, copper, dysprosium, erbium, europium,
gadolinium, gallium, gold, hafnium, hydrogen, indium, iridium,
iron, lanthanum, lithium, magnesium, manganese, mendelevium,
mercury, molybdenum, neodymium, neptunium, nickel, niobium, osmium,
palladium, platinum, potassium, praseodymium, promethium,
protactinium, rhenium, rubidium, scandium, silver, sodium,
strontium, tantalum, terbium, thallium, thorium, tin, titanium,
tungsten, vanadium, ytterbium, yttrium, zinc, and zirconium.
[0008] "Domain size" as that term is used herein, refers to the
minimum dimension of a particular material morphology. In the case
of powders, the domain size is the grain size. In the case of
whiskers and fibers, the domain size is the diameter. In the case
of plates and films, the domain size is the thickness.
[0009] As used herein, a "nanostructured powder" is one having a
domain size of less than 100 nm, or alternatively, having a domain
size sufficiently small that a selected material property is
substantially different from that of a micron-scale powder, due to
size confinement effects (e.g., the property may differ by 20% or
more from the analogous property of the micron-scale material).
Nanostructured powders often advantageously have sizes as small as
50 nm, 30 nm, or even smaller. Nanostructured powders may also be
referred to as "nanopowders" or "nanofillers." A nanostructured
composite is a composite comprising a nanostructured phase
dispersed in a matrix.
[0010] As it is used herein, the term "agglomerated" describes a
powder in which at least some individual particles of the powder
adhere to neighboring particles, primarily by electrostatic forces,
and "aggregated" describes a powder in which at least some
individual particles are chemically bonded to neighboring
particles.
[0011] 3. Relevant Background
[0012] A very wide variety of pure phase materials such as polymers
are now readily available at low cost. However, low cost pure phase
materials are somewhat limited in the achievable ranges of a number
of properties, including, for example, electrical conductivity,
magnetic permeability, dielectric constant, and thermal
conductivity. In order to circumvent these limitations, it has
become common to form composites, in which a matrix is blended with
a filler material with desirable properties. Examples of these
types of composites include the carbon black and ferrite mixed
polymers that are used in toners, tires, electrical devices, and
magnetic tapes.
[0013] The number of suitable filler materials for composites is
large, but still limited. In particular, difficulties in
fabrication of such composites often arise due to issues of
interface stability between the filler and the matrix, and because
of the difficulty of orienting and homogenizing filler material in
the matrix. Some desirable properties of the matrix (e.g.,
rheology) may also be lost when certain fillers are added,
particularly at the high loads required by many applications. The
availability of new filler materials, particularly materials with
novel properties, would significantly expand the scope of
manufacturable composites of this type.
SUMMARY OF THE INVENTION
[0014] Briefly stated, the present invention is directed to inks
based on novel nanofillers that enhance a wide range of properties.
In another aspect, the present invention is directed to methods for
preparing nanocomposites that enable nanotechnology applications
offering superior functional performance. In an example method,
nanofillers and a substance having a polymer are mixed. Both
low-loaded and highly-loaded nanocomposites are contemplated.
Nanoscale coated and un-coated fillers may be used. Nanocomposite
films may be coated on substrates.
[0015] In one aspect, the invention comprises a nanostructured
filler, intimately mixed with a matrix to form a nanostructured
composite. At least one of the nanostructured filler and the
nanostructured composite has a desired material property which
differs by at least 20% from the same material property for a
micron-scale filler or a micron-scale composite, respectively. The
desired material property is selected from the group consisting of
refractive index, transparency to light, reflection
characteristics, resistivity, permittivity, permeability,
coercivity, B-H product, magnetic hysteresis, breakdown voltage,
skin depth, curie temperature, dissipation factor, work function,
band gap, electromagnetic shielding effectiveness, radiation
hardness, chemical reactivity, thermal conductivity, temperature
coefficient of an electrical property, voltage coefficient of an
electrical property, thermal shock resistance, biocompatibility and
wear rate.
[0016] The nanostructured filler may comprise one or more elements
selected from the s, p, d, and f groups of the periodic table, or
it may comprise a compound of one or more such elements with one or
more suitable anions, such as aluminum, antimony, boron, bromine,
carbon, chlorine, fluorine, germanium, hydrogen, indium, iodine,
nickel, nitrogen, oxygen, phosphorus, selenium, silicon, sulfur, or
tellurium. The matrix may be a polymer (e.g., poly(methyl
methacrylate), poly(vinyl alcohol), polycarbonate, polyalkene, or
polyaryl), a ceramic (e.g., zinc oxide, indium-tin oxide, hafnium
carbide, or ferrite), or a metal (e.g., copper, tin, zinc, or
iron). Loadings of the nanofiller may be as high as 95%, although
loadings of 80% or less are preferred. The invention also comprises
devices which incorporate the nanofiller (e.g., electrical,
magnetic, optical, biomedical, and electrochemical devices).
[0017] Another aspect of the invention comprises a method of
producing a composite, comprising blending a nanoscale filler with
a matrix to form a nanostructured composite. Either the
nanostructured filler or the composite itself differs substantially
in a desired material property from a micron-scale filler or
composite, respectively. The desired material property is selected
from the group consisting of refractive index, transparency to
light, reflection characteristics, resistivity, permittivity,
permeability, coercivity, B-H product, magnetic hysteresis,
breakdown voltage, skin depth, curie temperature, dissipation
factor, work function, band gap, electromagnetic shielding
effectiveness, radiation hardness, chemical reactivity, thermal
conductivity, temperature coefficient of an electrical property,
voltage coefficient of an electrical property, thermal shock
resistance, biocompatibility, and wear rate. The loading of the
filler does not exceed 95 volume percent, and loadings of 80 volume
percent or less are preferred.
[0018] The composite may be formed by mixing a precursor of the
matrix material with the nanofiller, and then processing the
precursor to form a desired matrix material. For example, the
nanofiller may be mixed with a monomer, which is then polymerized
to form a polymer matrix composite. In another embodiment, the
nanofiller may be mixed with a matrix powder composition and
compacted to form a solid composite. In yet another embodiment, the
matrix composition may be dissolved in a solvent and mixed with the
nanofiller, and then the solvent may be removed to form a solid
composite. In still another embodiment, the matrix may be a liquid
or have liquid like properties.
[0019] Many nanofiller compositions are encompassed within the
scope of the invention, including nanofillers comprising one or
more elements selected from the group consisting of actinium,
aluminum, arsenic, barium, beryllium, bismuth, cadmium, calcium,
cerium, cesium, cobalt, copper, dysprosium, erbium, europium,
gadolinium, gallium, gold, hafnium, hydrogen, indium, iridium,
iron, lanthanum, lithium, magnesium, manganese, mendelevium,
mercury, molybdenum, neodymium, neptunium, nickel, niobium, osmium,
palladium, platinum, potassium, praseodymium, promethium,
protactinium, rhenium, rubidium, scandium, silver, sodium,
strontium, tantalum, terbium, thallium, thorium, tin, titanium,
tungsten, vanadium, ytterbium, yttrium, zinc, and zirconium.
[0020] "Domain size" as that term is used herein, refers to the
minimum dimension of a particular material morphology. In the case
of powders, the domain size is the grain size. In the case of
whiskers and fibers, the domain size is the diameter. In the case
of plates and films, the domain size is the thickness.
[0021] As used herein, a "nanostructured powder" is one having a
domain size of less than 100 nm, or alternatively, having a domain
size sufficiently small that a selected material property is
substantially different from that of a micron-scale powder, due to
size confinement effects (e.g., the property may differ by 20% or
more from the analogous property of the micron-scale material).
Nanostructured powders often advantageously have sizes as small as
50 nm, 30 nm, or even smaller. Nanostructured powders may also be
referred to as "nanopowders" or "nanofillers." A nanostructured
composite is a composite comprising a nanostructured phase
dispersed in a matrix.
[0022] As it is used herein, the term "agglomerated" describes a
powder in which at least some individual particles of the powder
adhere to neighboring particles, primarily by electrostatic forces,
and "aggregated" describes a powder in which at least some
individual particles are chemically bonded to neighboring
particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The invention is described with reference to the several
figures of the drawing, in which,
[0024] FIG. 1 is a diagram of a nanostructured filler coated with a
polymer;
[0025] FIG. 2 portrays an X-ray diffraction (XRD) spectrum for the
stoichiometric indium tin oxide powder of Example 1;
[0026] FIG. 3 is a scanning electron microscope (SEM) micrograph of
the stoichiometric indium tin oxide powder of Example 1; and
[0027] FIG. 4 is a diagram of the nanostructured varistor of
Example 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Prior art filler materials for polymeric composites are
usually powders with an average dimension in the range of 10-100
.mu.m. Thus, each filler particle typically has on the order of
10.sup.15-10.sup.18 atoms. In contrast the typical polymer chain
has on the order of 10.sup.3-10.sup.9 atoms. While the art of
precision manufacturing of polymers at molecular levels is
well-developed, the knowledge of precision manufacturing of filler
materials at molecular levels has remained largely unexplored.
[0029] The number of atoms in the filler particles of the invention
(hereinafter called "nanostructured filler" or "nanofiller") is on
the order of or significantly less than the number of atoms in the
polymer molecules, e.g., 10.sup.2-10.sup.10. Thus, the filler
particles are comparable in size or smaller than the polymer
molecules, and therefore can be dispersed with orders of magnitude
higher number density. Further, the fillers may have a dimension
less than or equal to the critical domain sizes that determine the
characteristic properties of the bulk composition; thus, the
fillers may have significantly different physical properties from
larger particles of the same composition. This in turn may yield
markedly different properties in composites using nanofillers as
compared to the typical properties of conventional polymer
composites.
[0030] These nanostructured filler materials may also have utility
in the manufacture of other types of composites, such as ceramic-
or metal-matrix composites. Again, the changes in the physical
properties of the filler particles due to their increased surface
area and constrained domain sizes can yield changes in the
achievable properties of composites.
[0031] The nanofillers of the invention can be inorganic, organic,
or metallic, and may be in the form of powders, whiskers, fibers,
plates or films. The fillers represent an additive to the overall
composite composition, and may be used at loadings of up to 95% by
volume. The fillers may have connectivity in 0, 1, 2, or 3
dimensions. Fillers may be produced by a variety of methods, such
as those described in U.S. Pat. Nos. 5,486,675; 5,447,708;
5,407,458; 5,219,804; 5,194,128; and U.S. Pat. No. 5,064,464.
Particularly preferred methods of making nanostructured fillers are
described in U.S. patent application Ser. No. 09/046,465, by
Bickmore, et al., filed Mar. 23, 1998, now U.S. Pat. No. 5,987,997
and Ser. No. 08/706,819, by Pirzada, et al., filed Sep. 3, 1996,
now U.S. Pat. No. 5,851,507 both of which are incorporated herein
by reference.
[0032] A method of making nanostructured fillers is described in
commonly owned U.S. patent application Ser. No. 09/046,465, by
Bickmore, et al., filed Mar. 23, 1998, now U.S. Pat. No. 5,987,997
which is herewith recited. For example, if a doped complex of
composition:
d.sub.1-M.sub.1M.sub.2 X
[0033] is desired, then according to the invention, one should
prepare solutions or suspensions of dopant d.sub.1, metals M.sub.1
and M.sub.2, and anion X, where M.sub.1 and M.sub.2 are selected
from the s, p, f, and d groups of the periodic table, and X is
selected from the p group of the periodic table. Solutions or
suspensions may be prepared, for example, by mixing solutions
containing each of the constituent elements of the desired powder.
Elements dopant d.sub.1, metals M.sub.1 and M.sub.2 are selected
from the group consisting of the s group, p group, d group, or f
group of the periodic table, and X is selected from the group
consisting of carbon, nitrogen, oxygen, boron, phosphorus, sulfur,
chalcogens, and halogens.
[0034] It will be understood by those skilled in the art that
powders comprising larger numbers of dopants, metals, and anions
can also be produced by the same methods. In particular,
polymetallic materials comprising at least three metals and at
least one anion can be produced. These materials are useful in the
manufacture of capacitors, inductors, varistors, resistors,
piezo-devices, thermistors, thermoelectric devices, filters,
connectors, magnets, ion-conducting devices, sensors, fuel cells,
catalysts, optics, photonic devices, lasers, tooling bits, armor,
superconductors, inks, and pigments, for example. Prior art
polymetallic powders are limited to sizes in excess of 300 nm, and
mostly to sizes in excess of 1 micrometer. By the methods of the
invention, solid or porous polymetallic nanopowders can be made,
with sizes less than 250 nm, and preferably less than 100 nm.
Furthermore, by the methods of the invention, nano-whiskers and
nano-rods can be produced with aspect ratios of 25 or less, having
a minimum dimension of less than 250 nm, and preferably less than
100 nm. At this scale, size confinement effects can come into play
for many polymetallic powders.
[0035] While this invention does not limit itself to a specific
cation or anion, it is desirable to use anions and cations that are
either part of the final product or completely volatile. The final
products are not limited to ionic materials, and include covalent
and mixed ionic-covalent materials such as carbides, borides,
nitrides, sulfides, oxycarbides, oxynitrides, oxyborides and
oxysulfides. Illustrative formulations, but not exhaustive, then
are nitrate, nitrites, nitriles, nitrides, carbonates,
bicarbonates, hydroxides, cyanos, organometallics, carboxylates,
amines, and amides.
[0036] In one aspect of commonly owned U.S. patent application Ser.
No. 09/046,465, by Bickmore, et al., filed Mar. 23, 1998, now U.S.
Pat. No. 5,987,997 which is herewith recited, the invention
comprises a method of continuously producing fine powders of
complex inorganic compositions, including, but not limited to,
carbides, nitrides, oxides, chalcogenides, halides, phosphides,
borides, and combinations thereof by combustion of emulsions. By
varying the characteristics of the initial emulsion, the size,
shape, surface area, morphology, surface characteristics, surface
composition, distribution, and degree of agglomeration of the final
powder may be controlled. And, in conjunction with varying
combustion conditions, the product chemistry may be varied to
obtain non-stoichiometric, reduced oxide, or mixed anion materials.
Examples of this embodiment include the use of non-stoichiometric
flames or reducing gases such as hydrogen, forming gas, or ammonia.
It is an advantage of these aspects of the invention that the
method can use low cost, safe, readily available and
environmentally benign precursors to produce fine powders. In a
preferred embodiment, the method ensures high yield and high
selectivity, including harvesting 95% or more of the fine powder
produced. In another embodiment, the method prevents the damage of
the fine powders during and after their synthesis.
[0037] In another aspect, the invention includes multimetallic
powders having a median particle size of less than 5 micrometers
and a standard deviation of particle size of less than 100 nm. In
preferred embodiments, the median particle size is less than 100 nm
and the standard deviation of particle size is less than 25 nm, and
in further preferred embodiments, the median particle size is less
than 30 nm and the standard deviation of particle size is less than
10 nm. The multimetallic powders include at least two elements
selected from the s group, p group, d group, and f group of the
periodic table (e.g., aluminum, antimony, barium, bismuth, boron,
bromine, cadmium, calcium, carbon, cerium, cesium, chlorine,
chromium, cobalt, copper, dysprosium, erbium, europium, gadolinium,
gallium, germanium, gold, hafnium, holmium, indium, iodine,
iridium, iron, lanthanum, lead, lithium, lutetium, magnesium,
manganese, molybdenum, neodymium, nickel, niobium, nitrogen,
osmium, oxygen, palladium, phosphorus, platinum, praseodymium,
potassium, rhenium, rhodium, rubidium, samarium, scandium, silicon,
silver, sodium, strontium, sulfur, tantalum, terbium, thulium, tin,
titanium, tungsten, vanadium, ytterbium, yttrium, zinc, and
zirconium), and may include three or more such elements. The
powders may be unagglomerated and/or unaggregated. The
multimetallic powders may also comprise nanowhiskers and/or
nanorods, with aspect ratios in a range of 1-25.
[0038] The term "nanopowder" describes a powder whose mean diameter
is so small that its physical properties are substantially affected
by size related confinement effects. Nanopowders usually have a
mean diameter less than or equal to 250 nm, and preferably have a
mean diameter less than or equal to 100 nm. More preferably,
nanopowders may have a mean diameter less than 50 nm.
[0039] The term "agglomerated" describes a powder in which at least
some individual particles of the powder adhere to neighboring
particles, primarily by electrostatic forces, and "aggregated"
describes a powder in which at least some individual particles are
chemically bonded to neighboring particles.
[0040] The term "aspect ratio" refers to the ratio of the maximum
to the minimum dimension of a particle. The term "whisker" refers
to any elongated particle (e.g., a particle having an aspect ratio
greater than one, and preferably at least two). Whiskers may be
round or faceted, and may have varying diameters. "Rods" are
substantially cylindrical whiskers. "Nanowhiskers" and "nanorods"
refer to rods and whiskers whose smallest dimension is so small
that their physical properties are substantially affected by size
related confinement effects. Nanowhiskers and nanorods usually have
a minimum dimension less than or equal to 250 nm, and preferably
have a minimum dimension less than or equal to 100 nm. More
preferably, these particles may have a minimum dimension less than
50 nm.
[0041] A distinctive feature of the invention described in commonly
owned U.S. patent application Ser. No. 09/046,465, by Bickmore, et
al., filed Mar. 23, 1998, now U.S. Pat. No. 5,987,997 which is
herewith recited, is the use of emulsion as the vehicle for
carrying fuels and metals. Once an emulsion formulation has been
established, dopants and other metals can be readily added to the
said emulsion to prepare and vary complex compositions. The
emulsion is combusted using designs such as, but not limited to,
those taught by Khavkin (Combustion System Design, PennWell Books,
Tulsa Okla., 1996) and Fischer (Combustion Engineer's Handbook, G.
Newnes Publisher, London, 1961), which are incorporated herein by
reference. The combustion can be accomplished using a laminar or
turbulent flame, a premixed or diffusion flame, a co-axial or
impinging flame, a low-pressure or high-pressure flame, a sub-sonic
or sonic or super-sonic flame, a pulsating or continuous flame, an
externally applied electromagnetic field free or externally applied
electromagnetic field influenced flame, a reducing or oxidizing
flame, a lean or rich flame, a secondary gas doped or undoped
flame, a secondary liquid doped or undoped flame, a secondary
particulate doped or undoped flame, an adiabatic or non-adiabatic
flame, a one-dimensional or two-dimensional or three-dimensional
flame, an obstruction-free or obstructed flame, a closed or open
flame, an externally heated or externally cooled flame, a
pre-cooled or pre-heated flame, a one burner or multiple burner
flame, or a combination of one or more of the above. Usually,
combustion temperatures will be in excess of 600.degree. C., a
temperature at which diffusion kinetics will be sufficiently fast
that a compositionally uniform powder will be produced. The
emulsion can also be a feed to other processes of producing
nanoscale powders. Examples include the powder-formation processes
described in copending and commonly assigned U.S. patent
application Ser. No. 08/707,341, "Boundary Layer Joule--Thompson
Nozzle for Thermal Quenching of High Temperature Vapors," now U.S.
Pat. No. 5,788,738 and Ser. No. 08/706,819, "Integrated Thermal
Process and Apparatus for the Continuous Synthesis of Nanoscale
Powders," now U.S. Pat. No. 5,851,507, both of which are
incorporated herein.
[0042] A wide variety of nanofiller compositions are possible. Some
exemplary compositions include metals (e.g., Cu, Ag, Ni, Fe, Al,
Pd, and Ti), oxide ceramics (e.g., TiO.sub.2, TiO.sub.2-x,
BaFe.sub.2 O4, dielectric compositions, ferrites, and manganites),
carbide ceramics (e.g., SiC, BC, TiC, WC, WCsub.1-x), nitride
ceramics (e.g., Si.sub.3 N.sub.4, TiN, VN, AlN, and Mo.sub.2 N),
hydroxides (e.g., aluminum hydroxide, calcium hydroxide, and barium
hydroxide), borides (e.g., AlB.sub.2 and TiB.sub.2), phosphides
(e.g., NiP and VP), sulfides (e.g., molybdenum sulfide, titanium
sulfide, and tungsten sulfide), silicides (e.g., MoSi.sub.2),
chalcogenides (e.g., Bi.sub.2 Te.sub.3, Bi.sub.2 Se.sub.3), and
combinations of these.
[0043] The fillers are immediately mixed with a matrix material,
which is preferably polymeric, buy may also be ceramic, metallic,
or a combination of the above. The matrix may be chosen for
properties such as ease of processibility, low cost, environmental
benignity, commercial availability, and compatibility with the
desired filler. The fillers are preferably mixed homogeneously into
the matrix, but may also be mixed heterogeneously if desired, for
example to obtain a composite having a gradient of some property.
Mixing techniques for incorporating powders into fluids and for
mixing different powders are well known in the art, and include
mechanical, thermal, electrical, magnetic, and chemical momentum
transfer techniques, as well as combinations of the above.
[0044] The viscosity, surface tension, and density of a liquid
matrix material can be varied for mixing purposes, the preferred
values being those that favor ease of mixing and that reduce energy
needed to mix without introducing any undesirable contamination.
One method of mixing is to dissolve the matrix in a solvent which
does not adversely affect the properties of the matrix or the
filler and which can be easily removed and recovered. Another
method is to melt the matrix, incorporate the filler, and cool the
mixture to yield a solid composite with the desired properties. Yet
another method is to synthesize the matrix in-situ with the filler
present. For example, the nanofiller can be mixed with a liquid
monomer, which can then be polymerized to form the composite. In
this method, the filler may be used as a catalyst or co-catalyst
for polymerization. The mixing may also be accomplished in the
solid state, for example by mixing a powdered matrix composition
with the filler, and then compacting the mixture to form a solid
composite.
[0045] Mixing can be assisted using various secondary species such
as dispersants, binders, modifiers, detergents, and additives.
Secondary species may also be added to enhance one to more of the
properties of the filler-matrix composite.
[0046] Mixing can also be assisted by pre-coating the nanofiller
with a thin layer of the matrix composition or with a phase that is
compatible with the matrix composition. Such a coated nanoparticle
is illustrated in FIG. 1, which shows a spherical nanoparticle 6
and a coating 8. In one embodiment, when embedding nanofillers in a
polymer matrix, it may be desirable to coat the filler particles
with a related monomer. When mixing nanofillers into a ceramic
matrix, pre-coating can be done by forming a ceramic layer around
the nanoscale filler particle during or after the synthesis of the
nanoscale filler, by methods such as partial oxidation,
nitridation, carborization, or boronation. In these methods, the
nanostructured filler is exposed to a small concentration of a
precursor that reacts with the surface of the filler to form a
ceramic coating. For example, a particle may be exposed to oxygen
in order to create an oxide coating, to ammonia in order to create
a nitride coating, to borane to create a boride coating, or to
methane to create a carbide coating. It is important that the
amount of precursor be small, to prevent thermal runaway and
consequent conversion of the nanostructured filler into a ceramic
particle.
[0047] In case of polymer matrix, the filler can be coated with a
polymer or a monomer by numerous methods, for example, surface
coating in-situ, spray drying a dispersion of filler and polymer
solution, co-polymerization on the filler surface, and melt
spinning followed by milling. A preferred method is surface coating
in-situ. In this process, the filler is first suspended in
demineralized water (or another solvent) and the suspension's pH is
measured. The pH is then adjusted and stabilized with small
addition of acid (e.g., acetic acid or dilute nitric acid) or base
(e.g., ammonium hydroxide or dilute sodium hydroxide). The pH
adjustment produces a charged state on the surface of the filler.
Once a desired pH has been achieved, a coating material (for
example, a polymer or other appropriate precursor) with opposite
charge is introduced into the solvent. This step results in
coupling of the coating material around the nanoscale filler and
formation of a coating layer around the nanoscale filler. Once the
layer has formed, the filler is removed from the solvent by drying,
filtration, centrifugation, or any other method appropriate for
solid-liquid separation. This technique of coating a filler with
another material using surface charge can be used for a variety of
organic and inorganic compositions.
[0048] When a solvent is used to apply a coating as in the in-situ
surface coating method described above, the matrix may also be
dissolved in the solvent before or during coating, and the final
composite formed by removing the solvent.
[0049] A very wide range of material properties can be engineered
by the practice of the invention. For example, electrical,
magnetic, optical, electrochemical, chemical, thermal, biomedical,
and tribological properties can be varied over a wider range than
is possible using prior art micron-scale composites.
[0050] Nanostructured fillers can be used to lower or raise the
effective resistivity, effective permittivity, and effective
permeability of a polymer or ceramic matrix. While these effects
are present at lower loadings, they are expected to be most
pronounced for filler loadings at or above the percolation limit of
the filler in the matrix (i.e., at loadings sufficiently high that
electrical continuity exists between the filler particles). Other
electrical properties which may be engineered include breakdown
voltage, skin depth, curie temperature, temperature coefficient of
electrical property, voltage coefficient of electrical property,
dissipation factor, work function, band gap, electromagnetic
shielding effectiveness and degree of radiation hardness.
Nanostructured fillers can also be used to engineer magnetic
properties such as the coercivity, B-H product, hysteresis, and
shape of the B-H curve of a matrix.
[0051] An important characteristic of optical material is its
refractive index and its transmission and reflective
characteristics. Nanostructured fillers may be used to produce
composites with refractive index engineered for a particular
application. Gradient lenses may be produced using nanostructured
materials. Gradient lenses produced from nanostructured composites
may reduce or eliminate the need for polishing lenses. The use of
nanostructured fillers may also help filter specific wavelengths.
Furthermore, a key advantage of nanostructured fillers in optical
applications is expected to be their enhanced transparency because
the domain size of nanostructured fillers ranges from about the
same as to more than an order of magnitude less than visible
wavelengths of light.
[0052] The high surface area and small grain size of nanofilled
composites make them excellent candidates for chemical and
electrochemical applications. When used to form electrodes for
electrochemical devices, these materials are expected to
significantly improve performance, for example by increasing power
density in batteries and reducing minimum operating temperatures
for sensors. (An example of the latter effect can be found in
copending and commonly assigned U.S. application Ser. No.
08/739,257, "Nanostructured Ion Conducting Solid Electrolytes," by
Yadav, et al. now U.S. Pat. No. 5,905,000). Nanostructured fillers
are also expected to modify the chemical properties of composites.
These fillers are catalytically more active, and provide more
interface area for interacting with diffusive species. Such fillers
may, for example, modify chemical stability and mobility of
diffusing gases. Furthermore, nanostructured fillers may enhance
the chemical properties of propellants and fuels.
[0053] Many nanostructured fillers have a domain size comparable to
the typical mean free path of phonons at moderate temperatures. It
is thus anticipated that these fillers may have dramatic effects on
the thermal conductivity and thermal shock resistance of matrices
into which they are incorporated.
[0054] Nanostructured fillers--in coated and uncoated form--and
nanofilled composites are also expected to have significant value
in biomedical applications for both humans and animals. For
example, the small size of nanostructured fillers may make them
readily transportable through pores and capillaries. This suggests
that the fillers may be of use in developing novel time-release
drugs and methods of administration and delivery of drugs, markers,
and medical materials. A polymer coating can be utilized either to
make water-insoluble fillers into a form that is water soluble, or
to make water-soluble fillers into a form that is water insoluble.
A polymer coating on the filler may also be utilized as a means to
time drug-release from a nanoparticle. A polymer coating may
further be used to enable selective filtering, transfer, capture,
and removal of species and molecules from blood into the
nanoparticle.
[0055] A nanoparticulate filler for biomedical operations might be
a carrier or support for a drug of interest, participate in the
drug's functioning, or might even be the drug itself. Possible
administration routes include oral, topical, and injection routes.
Nanoparticulates and nanocomposites may also have utility as
markers or as carriers for markers. Their unique properties,
including high mobility and unusual physical properties, make them
particularly well-adapted for such tasks.
[0056] In some examples of biomedical functions, magnetic
nanoparticles such as ferrites may be utilized to carry drugs to a
region of interest, where the particles may then be concentrated
using a magnetic field. Photocatalytic nanoparticles can be
utilized to carry drugs to region of interest and then
photoactivated. Thermally sensitive nanoparticles can similarly be
utilized to transport drugs or markers or species of interest and
then thermally activated in the region of interest. Radioactive
nanoparticulate fillers may have utility for chemotherapy.
Nanoparticles suitably doped with genetic and culture material may
be utilized in similar way to deliver therapy in target areas.
Nanocomposites may be used to assist in concentrating the particle
and then providing the therapeutic action. To illustrate, magnetic
and photocatalytic nanoparticles may be formed into a composite,
administered to a patient, concentrated in area of interest using
magnetic field, and finally activated using photons in the
concentrated area. As markers, nanoparticulate fillers--coated or
uncoated--may be used for diagnosis of medical conditions. For
example, fillers may be concentrated in a region of the body where
they may be viewed by magnetic resonance imaging or other
techniques. In all of these applications, the possibility exists
that nanoparticulates can be released into the body in a controlled
fashion over a long time period, by implanting a nanocomposite
material having a bioabsorbable matrix, which slowly dissolves in
the body and releases its embedded filler.
[0057] As implants, nanostructured fillers and composites are
expected to lower wear rate and thereby enhance patient acceptance
of surgical procedures. Nanostructured fillers may also be more
desirable than micron-scale fillers, because the possibility exists
that their domain size may be reduced to low enough levels that
they can easily be removed by normal kidney action without the
development of stones or other adverse side effects. While
nanoparticulates may be removed naturally through kidney and other
organs, they may also be filtered or removed externally through
membranes or otherwise removed directly from blood or tissue.
Carrier nanoparticulates may be reactivated externally through
membranes and reused; for example, nutrient carriers may be removed
from the bloodstream, reloaded with more nutrients, and returned to
carry the nutrients to tissue. The reverse process may also be
feasible, wherein carriers accumulate waste products in the body,
which are removed externally, returning the carriers to the
bloodstream to accumulate more waste products.
EXAMPLES
Example 1
Indium Tin Oxide Fillers in PMMA
[0058] A stoichiometric (90 wt % ln203 in SnO.sub.2) indium tin
oxide (ITO) nanopowder was produced using the methods of copending
patent application Ser. No. 09/046,465. 50 g of indium shot was
placed in 300 ml of glacial acetic acid and 10 ml of nitric acid.
The combination, in a 1000 ml Erlenmeyer flask, was heated to
reflux while stirring for 24 hours. At this point, 50 ml of
HNO.sub.3 was added, and the mixture was heated and stirred
overnight. The solution so produced was clear, with all of the
indium metal dissolved into the solution, and had a total final
volume of 318 ml. An equal volume (318 mL) of 1-octanol was added
to the solution along with 600 mL ethyl alcohol in a 1000 mL HDPE
bottle, and the resulting mixture was vigorously shaken. 11.25 ml
of tetrabutyltin was then stirred into the solution to produce a
clear indium/tin emulsion. When the resulting emulsion was burned
in air, it produced a brilliant violet flame. A yellow nanopowder
residue was collected from the flamed emulsion. The nanopowder
surface area was 13.5 m.sup.2/gm, and x-ray diffractometer mean
grain size was 60 nm.
[0059] FIG. 2 shows the measured X-ray diffraction (XRD) spectrum
for the powder, and FIG. 3 shows a scanning electron microscope
(SEM image of the powder. These data show that the powder was of
nanometer scale.
[0060] The nanostructured powder was then mixed with poly(methyl
methacrylate) (PMMA) in a ratio of 20 vol % powder to 80 vol %
PMMA. The powder and the polymer were mixed using a mortar and
pestle, and then separated into three parts, each of which was
pressed into a pellet. The pellets were pressed by using a Carver
hydraulic press, pressing the mixture into a 1/4 inch diameter die
using a 1500 pound load for one minute.
[0061] After removal from the die, the physical dimensions of the
pellets were measured, and the pellets were electroded with silver
screen printing paste (Electro Sciences Laboratory 9912-F).
[0062] Pellet resistances were measured at 1 volt using a
Megohmmeter/IR tester 1865 from QuadTech with a QuadTech component
test fixture. The volume resistivity was calculated for each pellet
using the standard relation, 1 = R ( A t ) ( 1 )
[0063] where .rho. represents volume resistivity in ohm-cm, R
represents the measured resistance in ohms, A represents the area
of the electroded surface of the pellet in cm.sup.2, and t
represents the thickness of the pellet in cm. The average volume
resistivity of the stoichiometric ITO composite pellets was found
to be 1.75.times.10.sup.4 ohm-cm.
[0064] Another quantity of ITO nanopowder was produced as described
above, and was reduced by passing 2 SCFM of forming gas (5%
hydrogen in nitrogen) over the powder while ramping temperature
from 25.degree. C. to 250.degree. C. at 5.degree. C./min. The
powder was held at 250.degree. C. for 3 hours, and then cooled back
to room temperature. The XRD spectrum of the resulting powder
indicated that the stoichiometry of the reduced powder was
In.sub.18SnO.sub.29-x, with x greater than 0 and less than 29.
[0065] The reduced ITO nanopowder was combined with PMMA in a 20:80
volume ratio and formed into pellets as described above. The
pellets were electroded as described, and their resistivity was
measured. The average resistivity for the reduced ITO composite
pellets was found to be 1.09.times.10.sup.4 ohm-cm.
[0066] For comparison, micron scale ITO was purchased from Alfa
Aesar (catalog number 36348), and was formed into pellets with PMMA
and electroded as described above. Again, the volume fraction of
ITO was 20%. The average measured resistivity of the micron scale
ITO composite pellets was found to be 8.26.times.10.sup.8 ohm-cm,
representing a difference of more than four orders of magnitude
from the nanoscale composite pellets. It was thus established that
composites incorporating nanoscale fillers can have unique
properties not achievable by prior art techniques.
Example 2
[0067] Hafnium Carbide Fillers in PMMA
[0068] Nanoscale hafnium carbide fillers were prepared as described
in copending U.S. patent application Ser. No. 08/706,819 and Ser.
No. 08/707,341. The nanopowder surface area was 53.5 m.sup.2/gm,
and mean grain size was 16 nm. Micron scale hafnium carbide powder
was purchased from Cerac (catalog number H-1004) for
comparison.
[0069] Composite pellets were produced as described in Example 1,
by mixing filler and polymer with a mortar and pestle and pressing
in a hydraulic press. Pellets were produced containing either
nanoscale or micron scale powder at three loadings: 20 vol %
powder, 50 vol % powder, and 80 vol % powder. The pellets were
electroded as described above, and their resistivities were
measured. (Because of the high resistances at the 20% loading,
these pellets' resistivities were measured at 100V. The other
pellets were measured at IV, as described in Example 1).
[0070] Results of these resistivity measurements are summarized in
Table 1. As can be seen, the resistivity of the pellets differed
substantially between the nanoscale and micron scale powders. The
composites incorporating nanoscale powder had a somewhat decreased
resistivity compared to the micron scale powder at 20% loading, but
had a dramatically increased resistivity compared to the micron
scale powder at 50% and 80% loading.
1TABLE 1 Resistivity of Resistivity of Volume nanoscale powder
micron scale powder % filler composite (ohm-cm) composite (ohm-cm)
20 .sup. 5.54 .times. 10.sup.12 .sup. 7.33 .times. 10.sup.13 50
7.54 .times. 10.sup.9 2.13 .times. 10.sup.4 80 3.44 .times.
10.sup.9 1.14 .times. 10.sup.4
Example 3
Copper Fillers in PMA and PVA
[0071] Nanoscale copper powders were produced as described in U.S.
patent application Ser. Nos. 08/706,819 and 08/707,341. The
nanopower surface area was 28.1 m2/gm, and mean grain size was 22
nm. Micron scale copper powder was purchased from Aldrich (catalog
number 32645-3) for comparison.
[0072] The nanoscale and micron scale copper powders were each
mixed at a loading of 20 vol % copper to 80 vol % PMMA and formed
into pellets as described above. In addition, pellets having a
loading of 15 vol % copper in poly(vinyl alcohol) (PVA) were
produced by the same method. The pellets were electroded and
resistivities measured at 1 volt as described in Example 1. Results
are shown in Table 2.
2TABLE 2 Volume Resistivity Additive Polymer Volume % filler
(ohm-cm) nanoscale copper PMMA 20 5.68 .times. 10.sup.10 nanoscale
copper PVA 15 4.59 .times. 10.sup.5 micron scale copper PMMA 20
4.19 .times. 10.sup.12
[0073] It can be seen from Table 2 that the resistivity of the
nanoscale copper powder/PMMA composite was substantially reduced
compared to the micron scale copper powder/PMMA composite at the
same loading, and that the resistivity of the nanoscale copper
powder/PVA composite was lower still by five orders of
magnitude.
Example 4
[0074] Preparation of Polymer-Coated Nanostructured Filler
[0075] The stoichiometric (90 wt % In.sub.2O.sub.3 in SnO.sub.2)
indium tin oxide (ITO) nanopowder of Example 1 was coated with a
polymer as follows.
[0076] 200 milligrams of ITO nanopowders with specific surface area
of 53 m.sup.2/gm were added to 200 ml of demineralized water. The
pH of the suspension was adjusted to 8.45 using ammonium hydroxide.
In another container, 200 milligrams of poly(methyl methacrylate)
(PMMA) was dissolved in 200 ml of ethanol. The PMMA solution was
warmed to 100.degree. C. while being stirred. The ITO suspension
was added to the PMMA solution and the stirring and temperature of
100.degree. C. was maintained till the solution reduced to a volume
of 200 ml. The solution was then cooled to room temperature to a
very homogenous solution with very light clear-milky color. The
optical clarity confirmed that the powders are still
nanostructured. The powder was dried in oven at 120.degree. C. and
its weight was measured to be 400 milligrams. The increase in
weight, uniformity of morphology and the optical clarity confirmed
that the nanopowders were coated with PMMA polymer.
[0077] The electrochemical properties of polymer coated nanopowders
were different than the as-produced nanopowders. The as-produced
nanopowder when suspended in demineralized water yielded a pH of
3.4, while the polymer coated nanopowders had a pH of 7.51.
Example 5
Preparation of Electrical Device Using Nanostructured Fillers
[0078] A complex oxide nanoscale filler having the following
composition was prepared: Bi.sub.2 O.sub.3 (48.8 wt %), NiO (24.4
wt %), CoO (12.2 wt %), Cr.sub.2 O.sub.3 (2.4 wt %), MnO (12.2 wt
%), and Al.sub.2 O.sub.3 (<0.02 wt %). The complex oxide filler
was prepared from the corresponding nitrates of the same cation.
The nitrates of each constituent were added to 200 mL of deionized
water while constantly stirring. Hydroxides were precipitated with
the addition of 50 drops of 28-30% NH.sub.4OH. The solution was
filtered in a large buchner funnel and washed with deionized water
and then with ethyl alcohol. The powder was dried in an oven at
80.degree. C. for 30 minutes. The dried powder was ground using a
mortar and pestle. A heat treatment schedule consisting of a
15.degree. C./min ramp to 350.degree. C. with a 30 minute dwell was
used to calcine the ground powder.
[0079] The nanofiller was then incorporated at a loading of 4% into
a zinc oxide ceramic matrix. The composite was prepared by
mechanically mixing the doped oxide nanofiller powder with zinc
oxide powder, incorporating the mixture into a slurry, and screen
printing the slurry (further described below). For comparison,
devices were made using both a nanoscale matrix powder produced by
the methods of copending and commonly assigned U.S. application
Ser. No. 08/706,819, and using a micron scale matrix powder
purchased from Chemcorp. The fillers and the matrix powders were
mixed mechanically using a mortar and pestle.
[0080] Using the filler-added micron scale powder, a paste was
prepared by mixing 4.0 g of powder with 2.1 g of a commercial
screen printing vehicle purchased from Electro Science Laboratories
(ESL vehicle 400). The doped nanoscale powder paste was made using
3.5 g powder and 3.0 g ESL vehicle 400. Each paste was mixed using
a glass stir rod. Silver-palladium was used as a conducting
electrode material. A screen with a rectangular array pattern was
used to print each paste on an alumina substrate. First a layer of
silver-palladium powder (the lower electrode) was screen printed on
the substrate and dried on a hot plate. Then the ceramic filled
powder was deposited, also by screen printing. Four print-dry
cycles were used to minimize the possibility of pinhole defects in
the varistor. Finally, the upper electrode was deposited.
[0081] The electrode/composite/electrode varistor was formed as
three diagonally offset overlapping squares, as illustrated in FIG.
4. The effective nanostructured-filler based composite area in the
device due to the offset of the electrodes was 0.036 in.sup.2
(0.2315 cm.sup.2). The green thick films were co-fired at
900.degree. C. for 60 minutes. The screen printed specimen is shown
in FIG. 4, where light squares 10 represent the silver-palladium
electrodes, and dark square 12 represents the composite layer.
[0082] Silver leads were attached to the electrodes using silver
epoxy. The epoxy was cured by heating at a 50.degree. C./min ramp
rate to 600.degree. C. and then cooling to room temperature at a
rate of 50.degree. C./min. The TestPoint computer software, in
conjunction with a Keithley.RTM. current source, was used to obtain
a current-voltage curve for each of the varistors. Testpoint and
Keithley are trademarks or registered trademark of Keithley
Scientific Instruments, Inc.
[0083] The electrode/micron scale matrix composite/electrode based
varistor device had a total thickness of 29-33 microns and a
composite layer thickness of 19 microns. The electrode/nanoscale
matrix composite/electrode based varistor device had a total
thickness of 28-29 microns and a composite layer thickness of 16
microns. Examination of current-voltage response curves for both
varistors showed that the nanostructured matrix varistor had an
inflection voltage of about 2 volts, while the inflection voltage
of the micron scale matrix varistor had an inflection voltage of
about 36 volts. Fitting the current-voltage response curves to the
standard varistor power-law equation
I=nV.sup.a (2)
[0084] yielded values of voltage parameter a of 2.4 for the
micron-scale matrix device, and 37.7 for the nanoscale matrix
device. Thus, the nonlinearity of the device was shown to increase
dramatically when the nanoscale matrix powder was employed.
Example 6
Thermal Battery Electrode Using a Nanostructured Filler
[0085] Thermal batteries are primary batteries ideally suited for
military ordinance, projectiles, mines, decoys, torpedoes, and
space exploration systems, where they are used as highly reliable
energy sources with high power density and extremely long shelf
life. Thermal batteries have previously been manufactured using
techniques that place inherent limits on the minimum thickness
obtainable while ensuring adequate mechanical strength. This in
turn has slowed miniaturization efforts and has limited achievable
power densities, activation characteristics, safety, and other
important performance characteristics. Nanocomposites help overcome
this problem, as shown in the following example.
[0086] Three grams of raw FeS.sub.2 powder was mixed and milled
with a group of hard steel balls in a high energy ball mill for 30
hours. The grain size of produced powder was 25 nm. BET analysis
showed the surface area of the nanopowder to be 6.61 m.sup.2/gm.
The TEM images confirmed that the ball milled FeS.sub.2 powder
consists of the fine particles with the round shape, similar
thickness and homogenous size. The cathode comprised FeS.sub.2
nanopowders (68%), eutectic LiCl--KCl (30%) and SiO.sub.2 (2%)
(from Aldrich Chemical with 99% purity). The eutectic salts
enhanced the diffusion of Li ions and acted as a binder. Adding
silicon oxide particles was expected to immobilize the LiCl--KCl
salt during melting. For comparison, the cathode pellets were
prepared from nanostructured and micron scale FeS.sub.2 powders
separately.
[0087] To improve electrochemical efficiencies and increase the
melting point of anode, we chose micron scale Li 44%-Si 56% alloy
with 99.5% purity (acquired from Cyprus Foote Mineral) as the anode
material in this work. A eutectic salt, LiCl 45%-KCl 55% (from
Aldrich Chemical with 99% purity), was selected as electrolyte. The
salt was dried at 90.degree. C. and fused at 500.degree. C. To
strengthen the pellets and prevent flowing out of electrolyte when
it melted, 35% MgO (Aldrich Chemical, 99% purity) powder was added
and mixed homogeneously with the eutectic salt powder.
[0088] The pellets of anode electrodes were prepared by a cold
press process. A hard steel die with a 20 mm internal diameter was
used to make the thin disk pellets. 0.314 grams of Li 44%-Si 56%
alloy powder (with 76-422 mesh particle size) was pressed under
6000 psi static pressure to form a pellet. The thickness and
density of the pellets so obtained was determined to be 0.84 mm and
1.25 g/cm.sup.2, respectively. Electrolyte pellets were produced
using 0.55 grams of blended electrolyte powder under 4000 psi
static pressure. The thickness and density of the pellets obtained
were 0.84 mm and 2.08 g/cm.sup.2 respectively. The cathode pellet
was prepared using 0.91 grams of mixed micron scale
FeS.sub.2--LiCl--KCl--SiO.sub.2 powder pressed under 4000 psi
static pressure. The thickness and density of the pellets obtained
were 0.86 mm and 3.37 g/cm.sup.2, respectively.
[0089] A computerized SOLARTRON.RTM. 1287 electrochemical interface
and a 1260 Gain/Phase Analyzer were employed to provide constant
current and to monitor variation in potential between anode and
cathode of cells during the discharging. "Solartron" is a
registered trademark of the Solartron Electronic Group, Ltd. The
cutoff potential of discharge was set at 0.8 volt. The thermal
battery with the nanocomposite cathode provided 1A constant current
for 246 seconds, until the potential fell to 0.8 volt. It was
observed that the power density of the nanostructured single cell
thermal battery was 100% higher than that achievable with micron
sized materials. Thus, nanoscale fillers can help enhance the
electrochemical performance of such a device.
Example 7
A Magnetic Device Using Nanostructured Ferrite Fillers
[0090] Ferrite inductors were prepared using nanostructured and
micron-scale powders as follows. One-tenth of a mole (27.3 grams)
of iron chloride hexahydrate (FeCl.sub.3-6H.sub.2 O) was dissolved
in 500 ml of distilled water along with 0.025 moles (3.24 grams) of
nickel chloride (NiCl.sub.2) and 0.025 moles (3.41 grams) of zinc
chloride (ZnCl.sub.2). In another large beaker, 25 grams of NaOH
was dissolved in 500 ml of distilled water. While stirring the NaOH
solution rapidly, the metal chloride solution was slowly added,
forming a precipitate instantaneously. After 1 minute of stirring,
the precipitate solution was vacuum filtered while frequently
rinsing with distilled water. After the precipitate had dried
enough to cake and crack, it was transferred to a glass dish and
allowed to dry for 1 hour in an 80.degree. C. drying oven. At this
point, the precipitate was ground with a mortar and pestle and
calcined in air at 400.degree. C. for 1 hour to remove any
remaining moisture and organics.
[0091] BET analysis of the produced powder yielded a surface area
of 112 m.sup.2/g, confirming the presence of nanometer-sized
individual particles with an estimated BET particle size of 11 nm.
XRD analyses of all nanoscale powders showed the formation of a
single (Ni, Zn)Fe.sub.2O.sub.4 ferrite phase with peak shapes
characteristic of nanoscale powders. XRD peak broadening
calculations reported an average crystallite size of 20 nm of the
thermally quenched powders and 8 nm for the chemically derived
powders. SEM-EDX analyses of sintered nanopowder pellets showed an
average composition of 14.8% NiO, 15.8% ZnO, and 69.4%
Fe.sub.2O.sub.3, which corresponded to the targeted stoichiometric
composition of the N.sub.0.5Zn.sub.0.5Fe.sub.2O.sub.4.
[0092] Nanoscale ferrite filler powders were uniaxially pressed at
5000 pounds in a quarter-inch diameter die set into green pellets.
The powders were mixed with 2 weight percent Duramax.RTM. binder
for improved sinterability. The amount of powder used for pressing
varied from 1.5 to 1.7 grams, typically resulting in cylinders
having a post-sintered height of approximately 1.5 cm. To avoid
cracking and other thermal stress effects, a multi-level heating
profile was employed. The pellets were fired at a rate of 5.degree.
C./min to 300.degree. C., 10.degree. C./min to 600.degree. C., and
20.degree. C./min to the final sintering temperature, where it was
held for four hours. Pellets were cooled from the sintering
temperature at a rate of 10.degree. C./min to ensure the sintering
temperature ranged from 900.degree. C. to 1300.degree. C., but was
typically greater than 1200.degree. C. to ensure an acceptable
density. Sintered pellets were then wound with 25 turns of 36 gauge
enamel coated wire, the wire ends were stripped, and the completed
solenoids where used for electrical characterization. An air coil
was prepared for the purpose of calculating magnetic properties.
This coil was created by winding 25 turns of the enamel coated wire
around the die plunger used previously. This coil was taped with
masking tape, slid off the plunger slowly to maintain shape and
characteristics, and was characterized along with the ferrite
solenoids.
[0093] Inductance characterization was performed with a
Hewlett-Packard 429A RF Impedance/Materials Analyzer. Impedance,
parallel inductance, q factor, and impedance resistance were
measured over a logarithmic frequency sweep starting at 1 MHz and
ending at 1.8 GHz. Values for permeability (.mu.) and loss factor
(LF) were calculated from inductance (L), air coil inductance
(L.sub.o), and impedance resistance (R) using the following
equations: 2 = L L 0 ( 3 ) LF = L 0 R L 2 ( 4 )
[0094] Resistivity measurements were made with a Keithley.RTM. 2400
SourceMeter using a four-wire probe attachment and TestPoint.TM.
data acquisition software. Voltage was ramped from 0.1 to 20 volts
while simultaneously measuring current. The results were plotted as
field (voltage divided by pellet thickness) versus current density
(current divided by electrode cross sectional area). The slope of
this graph gives material resistivity (p).
[0095] Table 3 summarizes electrical properties of inductors
prepared from micron-sized powder or from nanopowder. In most cases
there is an advantage to using nanoscale precursor powder instead
of micron-sized powder. It is important to keep in mind that all
measurements were taken from cylindrical devices, which have
inherently inefficient magnetic properties. Solenoids of this shape
were used in this study because of the ease of production and
excellent reproducibility. All measured properties would be
expected to improve with the use of higher magnetic efficiency
shapes such as cores or toroids, or by improving the aspect ratio
(length divided by diameter) of the cylindrical samples.
3TABLE 3 Micron Nano Micron Nano Loss Factor @ 1 MHz Critical
Frequency Average 0.0032 0.0025 Average 68.9 MHz 78.3 MHz Q Factor
@ 1 MHz Resistivity Average 37.2 52.2 Average 0.84 M.OMEGA. 33.1
M.OMEGA.
[0096] The inductors made from ferrite nanopowders exhibited
significantly higher Q-factor, critical resonance frequency, and
resistivity. They also exhibited more than 20% lower loss factor as
is desired in commercial applications.
[0097] The following examples are recited from U.S. Pat. No.
5,851,507 which was previously incorporated by reference.
Example 8
[0098] Zinc: Commercially available zinc powder (-325 mesh) was
used as the precursor to produce nanosize zinc powder. Feed zinc
powder was fed into the thermal reactor suspended in an argon
stream (argon was used as the plasma gas; the total argon flow rate
was 2.5 ft.sup.3/min). The reactor was inductively heated with 16
kW of RF plasma to over 5,000K in the plasma zone and about 3,000K
in the extended reactor zone adjacent the converging portion of the
nozzle. The vaporized stream was quenched through the
converging-diverging nozzle. The preferred pressure drop across the
nozzle was 250 Torr, but useful results were obtained at different
pressure drops, ranging from 100 to 550 Torr. After undergoing a
pressure drop of 100 to 550 Torr through the converging-diverging
nozzle, the powder produced was separated from the gas by means of
a cooled copper-coil-based impact filter followed by a screen
filter. The nanosize powder produced by the invention were in the
5-25 nanometer range. The size distribution was narrow, with a mean
size of approximately 15 nm and a standard deviation of about 7.5
nm.
Example 9
[0099] Iron-Titanium Intermetallic: 2-5 micron powders of iron and
10-25 micron powders of titanium were mixed in 1:1 molar ratio and
fed into the thermal reactor suspended in an argon stream (total
gas flow rate, including plasma gas, was 2.75 ft.sup.3/min). The
reactor was inductively heated with 18 kW of RF plasma to over
5,000K in the plasma zone and above 3,000K in the extended reactor
zone adjacent the converging portion of the nozzle. The vaporized
stream was quenched through the converging-diverging nozzle. The
preferred pressure drop across the nozzle was 250 Torr, but useful
results were obtained at different pressure drops, ranging from 100
to 550 Torr. After undergoing a pressure drop of 100 to 550 Torr
through the converging-diverging nozzle, the powder produced was
separated from the gas by means of a cooled copper-coil-based
impact filter followed by a screen filter. The nanopowders produced
by the invention were in the 10-45 nanometer range. The size
distribution was narrow, with a mean size of approximately 32 nm
and a standard deviation of about 13.3 nm.
Example 10
[0100] Tungsten Oxide: Commercially available tungsten oxide powder
(-325 mesh size) was used as the precursor to produce nanosize
WO.sub.3. The tungsten oxide powder was suspended in a mixture of
argon and oxygen as the feed stream (flow rates were 2.25
ft.sup.3/min for argon and 0.25 ft.sup.3/min for oxygen). The
reactor was inductively heated with 18 kW of RF plasma to over
5,000K in the plasma zone and about 3,000K in the extended reactor
zone adjacent the converging portion of the nozzle. The vaporized
stream was quenched through the converging-diverging nozzle. The
preferred pressure drop across the nozzle was 250 Torr, but useful
results were obtained at different pressure drops, ranging from 100
to 550 Torr. After undergoing a pressure drop of 100 to 550 Torr
through the converging-diverging nozzle, the powder produced was
separated from the gas by means of a cooled copper-coil-based
impact filter followed by a screen filter. The powder produced by
the invention were in the 10-25 nanometer range. The size
distribution was narrow, with a mean size of about 16.1 nm and a
standard deviation of about 6.3 nm.
Example 11
[0101] Cerium Oxide: Commercially available cerium oxide powder
(5-10 micron size) was used as the precursor to produce nanosize
CeO.sub.2. The cerium oxide powder was suspended in a mixture of
argon and oxygen as the feed stream (at total rates of 2.25
ft.sup.3/min for argon and 0.25 ft.sup.3/min for oxygen). The
reactor was inductively heated with 18 kW of RF plasma to over
5,000K in the plasma zone and about 3,000K in the extended reactor
zone adjacent the converging portion of the nozzle. The vaporized
stream was quenched through the converging-diverging nozzle. The
preferred pressure drop across the nozzle was 250 Torr, but useful
results were obtained at different pressure drops, ranging from 100
to 650 Torr. The powder produced was separated from the gas by
means of a cooled copper-coil-based impact filter followed by a
screen filter. The powder produced by the invention was in the 5-25
nanometer range. The size distribution was narrow, with a mean size
of about 18.6 nm and a standard deviation of about 5.8 nm.
Example 12
[0102] Silicon Carbide: Commercially available silicon carbide
powder (-325 mesh size) was used as the precursor to produce
nanosize SiC. The powder was suspended in argon as the feed stream
(total argon flow rate of 2.5 ft.sup.3/min). The reactor was
inductively heated with 18 kW of RF plasma to over 5,000K in the
plasma zone and about 3,000K in the extended reactor zone adjacent
the converging portion of the nozzle. The vaporized stream was
quenched through the converging-diverging nozzle. The preferred
pressure drop across the nozzle was 250 Torr, but useful results
were obtained at different pressure drops, ranging from 100 to 550
Torr. The powder produced was separated from the gas by means of a
cooled copper-coil-based impact filter followed by a screen filter.
The SiC powder produced by the invention were in the 10-40
nanometer range. The size distribution was narrow, with a mean size
of approximately 28 nm and a standard deviation of about 8.4
nm.
Example 13
[0103] Molybdenum Nitride: Commercially available molybdenum oxide
(MoO.sub.3) powder (-325 mesh size) was used as the precursor to
produce nanosize Mo.sub.2N. Argon was used as the plasma gas at a
feed rate of 2.5 ft.sup.3/min. A mixture of ammonia and hydrogen
was used as the reactant gases (NH.sub.3 at 0.1 ft.sup.3/min;
H.sub.2 at 0.1 ft.sup.3/min). The reactor was inductively heated
with 18 kW of RF plasma to over 5,000K in the plasma zone and about
3,000K in the extended reactor zone adjacent the converging portion
of the nozzle. The vaporized stream was quenched through the
converging-diverging nozzle. The preferred pressure drop across the
nozzle was 250 Torr, but useful results were obtained at different
pressure drops, ranging from 100 to 550 Torr. The powder produced
was separated from the gas by means of a cooled copper-coil-based
impact filter followed by a screen filter. The Mo.sub.2N powder
produced by the invention was in the 5-30 nanometer range. The size
distribution was narrow, with a mean size of about 14 nm and a
standard deviation of about 4.6 nm.
Example 14
[0104] Nickel Boride Ceramic: 10-50 micron powder of nickel boride
were fed into the thermal reactor with argon (fed at a total rate,
including plasma gas, of 2.75 ft.sup.3/min). Once again, the
reactor was inductively heated with 18 kW of RF plasma to over
5,000K in the plasma zone and about 3,000K in the extended reactor
zone adjacent the converging portion of the nozzle. The vaporized
stream was quenched through the converging-diverging nozzle. The
preferred pressure drop across the nozzle was 250 Torr, but useful
results were obtained at different pressure drops, ranging from 100
to 550 Torr. The powder produced was separated from the gas by
means of a cooled copper-coil-based impact filter followed by a
screen filter. The Ni.sub.3B powder produced by the invention was
in the 10 to 30 nanometer range. The size distribution was narrow,
with a mean size of about 12.8 nm and a standard deviation of about
4.2 nm.
[0105] Other embodiments of the invention will be apparent to those
skilled in the art from a consideration of the specification or
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with
the true scope and spirit of the invention being indicated by the
following claims.
* * * * *