U.S. patent application number 11/113320 was filed with the patent office on 2006-11-09 for nanomaterials manufacturing methods and products thereof.
This patent application is currently assigned to NANOPRODUCTS CORP.. Invention is credited to Tapesh Yadav.
Application Number | 20060248982 11/113320 |
Document ID | / |
Family ID | 37215355 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060248982 |
Kind Code |
A1 |
Yadav; Tapesh |
November 9, 2006 |
Nanomaterials manufacturing methods and products thereof
Abstract
Methods for manufacturing nanomaterials and related
nanotechnology are provided.
Inventors: |
Yadav; Tapesh; (Longmont,
CO) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
NANOPRODUCTS CORP.
|
Family ID: |
37215355 |
Appl. No.: |
11/113320 |
Filed: |
April 25, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09790036 |
Feb 20, 2001 |
6933331 |
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11113320 |
Apr 25, 2005 |
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10755024 |
Jan 9, 2004 |
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11113320 |
Apr 25, 2005 |
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60568132 |
May 4, 2004 |
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Current U.S.
Class: |
423/1 |
Current CPC
Class: |
A01N 25/12 20130101;
B82Y 30/00 20130101; C04B 2235/3217 20130101; C01B 13/20 20130101;
C01P 2002/54 20130101; C01P 2006/60 20130101; C01B 21/0826
20130101; C04B 2235/3281 20130101; C04B 2235/3418 20130101; A01N
2300/00 20130101; A01N 59/16 20130101; C01G 1/02 20130101; C01P
2006/12 20130101; C04B 2235/483 20130101; C01P 2004/64 20130101;
C01P 2004/62 20130101; C04B 2235/3291 20130101; C01P 2002/02
20130101; A01N 25/12 20130101; A01N 25/12 20130101; C04B 35/62665
20130101; C01B 33/18 20130101; C04B 2235/3463 20130101; C04B
2235/5409 20130101 |
Class at
Publication: |
075/369 ;
423/001 |
International
Class: |
B22F 1/00 20060101
B22F001/00; C22C 1/04 20060101 C22C001/04 |
Claims
1. A method of manufacturing a nanomaterial composition of matter
comprising providing a precursor comprising one or more metals;
feeding the precursor in a reactor such that the cavitation index
of the fed precursor is less than 15; processing, in the reactor,
the precursor at a temperature greater than 1500 K to create a high
temperature stream comprising the one or more metals from the
precursor; nucleating a nanomaterial from the high temperature
stream; and quenching the nucleated nanomaterial.
2. The method of claim 1, wherein the cavitation index is
negative.
3. The method of claim 1, wherein the processing temperature is
greater than 2500 K.
4. The method of claim 1, wherein the precursor is combined with an
oxidant prior to processing.
5. The method of claim 4, wherein the oxidant comprises oxygen.
6. A method of claim 4, wherein the molar ratio of the precursor to
oxidant is between 0.005 and 0.65.
7. The method of claim 1, wherein the precursor is a fluid.
8. The method of claim 1, wherein the reactor is operated at a
pressure of less than 1000 Torr.
9. The method of claim 1, wherein the processing temperature is
greater than 1000 K.
10. The method of claim 1, wherein the quenched nucleated
nanomaterial comprises particles having an aspect ratio greater
than 1.
11. The method of claim 1, wherein the quenched nucleated
nanomaterial comprises amorphous particles.
12. The method of claim 1, further comprising functionalizing the
surface of the nanomaterial.
13. The method of claim 12, further comprising doping the
nanomaterial with a metal ion.
14. The method of claim 13, wherein the metal ion is a silver or
copper ion.
15. A product comprising the nanomaterial composition of matter
produced using the method of claim 1.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/790,036, filed on Feb. 20, 2001, and is a
continuation-in-part of U.S. patent application Ser. No.
10/755,024, filed on Jan. 09, 2004. The present application claims
the benefit of provisional application number 60/568,132, filed May
4, 2004. Each of these three applications is hereby incorporated by
reference in its entirety.
[0002] The present invention generally relates to methods of
manufacturing submicron and nanoscale powders.
[0003] Powders are used in numerous applications. They are the
building blocks of electronic, telecommunication, electrical,
magnetic, structural, optical, biomedical, chemical, thermal, and
consumer goods. On-going market demands for smaller, faster,
superior and more portable products have demanded miniaturization
of numerous devices. This, in turn, demands miniaturization of the
building blocks, i.e. the powders. Sub-micron and nano-engineered
(or nanoscale, nanosize, ultrafine) powders, with a size 10 to 100
times smaller than conventional micron size powders, enable quality
improvement and differentiation of product characteristics at
scales currently unachievable by commercially available
micron-sized powders.
[0004] Nanopowders in particular and sub-micron powders in general
are a novel family of materials whose distinguishing feature is
that their domain size is so small that size confinement effects
become a significant determinant of the materials' performance.
Such confinement effects can, therefore, lead to a wide range of
commercially important properties. Nanopowders, therefore, are an
extraordinary opportunity for design, development and
commercialization of a wide range of devices and products for
various applications. Furthermore, since they represent a whole new
family of material precursors where conventional coarse-grain
physiochemical mechanisms are not applicable, these materials offer
unique combinations of properties that can enable novel and
multifunctional components of unmatched performance. Yadav et al.
in a co-pending and commonly assigned U.S. patent application Ser.
No. 09/638,977, which along with the references contained therein
is hereby incorporated by reference in its entirety, teach some
applications of sub-micron and nanoscale powders.
[0005] Some of the challenges in the cost-effective production of
powders involve controlling the size of the powders as well as
controlling other characteristics, such as the shape, distribution,
and composition of the powder. Thus, innovations are desired in the
production of sub-micron powders in general and nanoscale powders
in particular, which allow the control of the characteristics of
the powders produced.
[0006] Briefly stated, the present invention provides methods for
manufacturing nanoscale powders comprising a desired metal. The
present invention also provides applications of nanoscale
powders.
[0007] In some embodiments, the present invention provides
nanoparticles comprising doped or undoped metal oxides.
[0008] In some embodiments, the present invention provides
composites and coatings comprising doped or undoped metal
oxides.
[0009] In some embodiments, the present invention provides
applications of powders comprising doped or undoped metal
oxides.
[0010] In some embodiments, the present invention provides methods
for producing novel nanoscale powders comprising metals in high
volume, low-cost, and reproducible quality with control of various
powder characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows an exemplary overall approach for producing
submicron and nanoscale powders in accordance with the present
invention.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0012] The present invention is generally directed to very fine
inorganic powders. The scope of the teachings includes high purity
powders. Powders discussed herein are of mean crystallite size less
than 1 micron, and in certain embodiments less than 100 nanometers.
Methods for producing and utilizing such powders in high volume,
low-cost, and reproducible quality are also provided.
DEFINITIONS
[0013] For purposes of clarity the following definitions are
provided to aid the understanding of the description and specific
examples provided herein. Whenever a range of values are provided
for a specific variable, both the upper and lower limit of the
range are included within the definition.
[0014] "Fine powders" as used herein, refers to powders that
simultaneously satisfy the following criteria: [0015] (1) particles
with mean size less than 10 microns; and [0016] (2) particles with
aspect ratio between 1 and 1,000,000.
[0017] For example, in some embodiments, the fine powders are
powders that have particles with a mean domain size less than 5
microns and with an aspect ratio ranging from 1 to 1,000,000.
[0018] "Submicron powders" as used herein, refers to fine powders
with a mean size less than 1 micron. For example, in some
embodiments, the submicron powders are powders that have particles
with a mean domain size less than 500 nanometers and with an aspect
ratio ranging from 1 to 1,000,000.
[0019] The terms "nanopowders," "nanosize powders,"
"nanoparticles," and "nanoscale powders" are used interchangeably
and refer to fine powders that have a mean size less than 250
nanometers. For example, in some embodiments, the nanopowders are
powders that have particles with a mean domain size less than 100
nanometers and with an aspect ratio ranging from 1 to
1,000,000.
[0020] Pure powders, as the term used herein, are powders that have
composition purity of at least 99.9% by metal basis. For example,
in some embodiments the purity is 99.99%.
[0021] Nanomaterials, as the term used herein, are materials in any
dimensional form (zero, one, two, three) and domain size less than
100 nanometers.
[0022] "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.
[0023] The terms "powder," "particle," and "grain" are used
interchangeably and encompass, for example, oxides, carbides,
nitrides, borides, chalcogenides, halides, metals, intermetallics,
ceramics, polymers, alloys, and combinations thereof. These terms
include single metal, multi-metal, and complex compositions. These
terms further include hollow, dense, porous, semi-porous, coated,
uncoated, layered, laminated, simple, complex, dendritic,
inorganic, organic, elemental, non-elemental, composite, doped,
undoped, spherical, non-spherical, surface functionalized, surface
non-functionalized, stoichiometric, and non-stoichiometric forms or
substances. Further, the term powder in its generic sense includes
one-dimensional materials (fibers, tubes, etc.), two-dimensional
materials (platelets, films, laminates, planar, etc.), and
three-dimensional materials (spheres, cones, ovals, cylindrical,
cubes, monoclinic, parallelolipids, dumbbells, hexagonal, truncated
dodecahedron, irregular shaped structures, etc.). The term metal
used above includes any alkali metal, alkaline earth metal, rare
earth metal, transition metal, semi-metal (metalloids), precious
metal, heavy metal, radioactive metal, isotopes, amphoteric
element, electropositive element, cation forming element, and
includes any current or future discovered element from the periodic
table excluding non-metals.
[0024] "Aspect ratio," as the term is used herein, refers to the
ratio of the maximum to the minimum dimension of a particle.
[0025] "Precursor," as the term is used herein, encompasses any raw
substance that can be transformed into a powder of the same or
different composition. In certain embodiments, the precursor is a
liquid. The term precursor includes, but is not limited to,
organometallics, organics, inorganics, solutions, dispersions,
melts, sols, gels, emulsions, or mixtures.
[0026] "Powder," as the term is used herein, encompasses oxides,
carbides, nitrides, chalcogenides, metals, alloys, and combinations
thereof. The term includes hollow, dense, porous, semi-porous,
coated, uncoated, layered, laminated, simple, complex, dendritic,
inorganic, organic, elemental, non-elemental, dispersed, composite,
doped, undoped, spherical, non-spherical, surface functionalized,
surface non-functionalized, stoichiometric, and non-stoichiometric
forms or substances.
[0027] "Coating" (or "film" or "laminate" or "layer"), as the term
is used herein, encompasses any deposition comprising submicron and
nanoscale powders. The term includes in its scope a substrate,
surface, deposition, or a combination thereof that is hollow,
dense, porous, semi-porous, coated, uncoated, simple, complex,
dendritic, inorganic, organic, composite, doped, undoped, uniform,
non-uniform, surface functionalized, surface non-functionalized,
thin, thick, pretreated, post-treated, stoichiometric, or
non-stoichiometric form or morphology.
[0028] "Dispersion," as the term is used herein, encompasses inks,
pastes, creams, lotions, Newtonian, non-Newtonian, uniform,
non-uniform, transparent, translucent, opaque, white, black,
colored, emulsified, with additives, without additives,
water-based, polar solvent-based, or non-polar solvent-based
mixture of powder in any fluid or fluid-like state of
substance.
[0029] In some embodiments, the present invention is directed to
submicron and nanoscale powders comprising doped or undoped metal
oxides. Given the relative abundance of metal in the earth's crust
and current limitations on purification technologies, it is
expected that many commercially produced materials would have
naturally occurring metal impurities. These impurities are expected
to be below 100 parts per million and in most cases in a
concentration similar to other elemental impurities. Removal of
such impurities does not materially affect the properties of
interest to an application. For the purposes herein, powders
comprising metal impurities wherein the impure metal is present in
a concentration similar to other elemental impurities are not
considered powders comprising metals for the purposes this
invention. However, it is emphasized that in one or more doped or
undoped compositions of matter, certain metal may be intentionally
engineered as a dopant into a powder at concentrations of 100 ppm
or less, and these are included in the scope of this invention.
[0030] In a generic sense, the present invention teaches nanoscale
powders, and in a more generic sense, submicron powders comprising
at least 100 ppm by weight of a metal, in some embodiments greater
than 1 weight % by metal basis, and in other embodiments greater
than 10 weight % by metal basis.
[0031] FIG. 1 shows an exemplary overall approach for the
production of submicron powders in general and nanopowders in
particular. The process shown in FIG. 1 begins with a metal
containing raw material (for example, but not limited to, coarse
oxide powders, metal powders, salts, slurries, waste products,
organic compounds, or inorganic compounds). FIG. 1 shows one
embodiment of a system for producing nanoscale and submicron
powders in accordance with the present invention.
[0032] The process shown in FIG. 1 begins at 100 with a
metal-containing precursor such as an emulsion, fluid,
particle-containing fluid suspension, or water-soluble salt. The
precursor may be evaporated metal vapor, evaporated alloy vapor, a
gas, a single-phase liquid, a multi-phase liquid, a melt, a sol, a
solution, a fluid mixture, a solid suspension, or combinations
thereof. The metal-containing precursor comprises a stoichiometric
or a non-stoichiometric metal composition with at least some part
in a fluid phase. Fluid precursors are utilized in certain
embodiments of this invention. Typically, fluids are easier to
convey, evaporate, and thermally process, and the resulting product
is typically more uniform.
[0033] In one embodiment of this invention, the precursors are
environmentally benign, safe, readily available, high-metal
loading, lower-cost fluid materials. Examples of metal-containing
precursors suitable for the purposes of this invention include, but
are not limited to, metal acetates, metal carboxylates, metal
ethanoates, metal alkoxides, metal octoates, metal chelates,
metallo-organic compounds, metal halides, metal azides, metal
nitrates, metal sulfates, metal hydroxides, metal salts soluble in
organics or water, ammonium comprising compounds of the metal, and
metal-containing emulsions.
[0034] In another embodiment, multiple metal precursors may be
mixed. Mixtures of precursors can be useful, if complex nanoscale
and submicron powders are desired. For example, a calcium precursor
and a titanium precursor may be mixed to prepare calcium titanium
oxide powders for electroceramic applications. As another example,
a cerium precursor, a zirconium precursor, and gadolinium precursor
may be mixed in correct proportions to yield a high purity, high
surface area, mixed oxide powder for ionic device applications. In
yet another example, a barium precursor (and/or zinc precursor) and
a tungsten precursor may be mixed to yield powders for pigment
applications. Such complex nanoscale and submicron powders can be
used to create materials with surprising and unusual properties not
available through the respective single metal oxides or a simple
nanocomposite formed by physically blending powders of different
compositions. An illustration of such an unusual property is the
refractive index of nanoscale aluminum silicate powder which can be
varied by changing the aluminum and silicon ratio of the
composition. The refractive index so achievable is not available
through either aluminum oxide or silicon oxide or a simple
nanocomposite formed by physically blending powders of aluminum
oxide and silicon oxide.
[0035] It is desirable to use precursors of a higher purity to
produce a nanoscale or submicron powder of a desired purity. For
example, if a purity greater than x % (by metal weight basis) is
desired, one or more precursors that are mixed and used may have
purities greater than or equal to x % (by metal weight basis) to
practice the teachings herein.
[0036] With continued reference to FIG. 1, the metal-containing
precursor 100 (containing one or a mixture of metal-containing
precursors) is fed into a high temperature process 106, which may
be implemented using a high temperature reactor, for example. In
some embodiments, a synthetic aid such as a reactive fluid 108 may
be added along with the precursor 100 as it is being fed into the
reactor 106. Examples of such reactive fluids include, but are not
limited to, hydrogen, ammonia, halides, carbon oxides, methane,
oxygen gas, and air.
[0037] While the discussion herein teach methods of preparing
nanoscale and submicron powders of oxides, the teachings may be
readily extended in an analogous manner to other compositions such
as carbides, nitrides, borides, carbonitrides, and chalcogenides.
These compositions can be prepared from micron-sized powder
precursors of these compositions or by utilizing reactive fluids
that provide the elements desired in these metal comprising
compositions. In some embodiments, high temperature processing may
be used. However, a moderate temperature processing or a
low/cryogenic temperature processing may also be employed to
produce nanoscale and submicron powders using the methods of the
present invention.
[0038] The precursor 100 may be pre-processed in a number of other
ways before any thermal treatment. For example, the pH may be
adjusted to ensure precursor stability. Alternatively, selective
solution chemistry, such as precipitation with or without the
presence of surfactants or other synthesis aids, may be employed to
form a sol or other state of matter. The precursor 100 may be
pre-heated or partially combusted before the thermal treatment.
[0039] The precursor 100 may be injected axially, radially,
tangentially, or at any other angle into the high temperature
region 106. As stated above, the precursor 100 may be pre-mixed or
diffusionally mixed with other reactants. The precursor 100 may be
fed into the thermal processing reactor by a laminar, parabolic,
turbulent, pulsating, sheared, or cyclonic flow pattern, or by any
other flow pattern. In addition, one or more metal-containing
precursors 100 can be injected from one or more ports in the
reactor 106. The feed spray system may yield a feed pattern that
envelops the heat source or, alternatively, the heat sources may
envelop the feed, or alternatively, various combinations of this
may be employed. In some embodiments, the spray is atomized and
sprayed in a manner that enhances heat transfer efficiency, mass
transfer efficiency, momentum transfer efficiency, and reaction
efficiency. The reactor shape may be cylindrical, spherical,
conical, or any other shape. Methods and equipment such as those
taught in U.S. Pat. Nos. 5,788,738, 5,851,507, and 5,984,997 (each
of which is specifically incorporated herein by reference) can be
employed in practicing the methods of this invention.
[0040] In certain embodiments, the precursor feed conditions and
feed equipment are engineered to favor flash boiling. Precursor may
be fed utilizing any shape or size and device. Illustrative spray
device include spray nozzle, tubular feed orifice, flat or bent
nozzles, hollow pattern nozzle, flat or triangular or square
pattern nozzle and such. In certain embodiments, a feed system that
yields cavitation enhanced flash boiling is utilized for improved
performance. In this regard, a useful guideline is to utilize a
dimensionless number, commonly referred to as cavitation index
(C.I.), which is defined, for purposes herein, as
C.I.=(P.sub.o-P.sub.v)/.rho.V.sup.2
[0041] where, Po is the process pressure, P.sub.v is the vapor
pressure of the precursor in the feed nozzle, .rho. is the density
of the precursor, V is the average velocity of the precursor at the
exit of the feed nozzle (volumetric feed rate divided by cross
sectional area of the feed nozzle). In certain embodiments, a
negative value of cavitation index defined above is favorable. In
other embodiments, a value less than 15 for cavitation index is
favorable. In yet other embodiments, a value less than 125 for
cavitation index is favorable. In certain embodiments, the process
pressure is maintained between 1 Torr and 10,000 Torr. In other
embodiments, the process pressure is maintained between 5 Torr and
1,000 Torr. In certain embodiments, the process pressure is
maintained between 10 Torr and 500 Torr. The process pressure can
be maintained using any method such as, but not limited to,
compressors, pressurized fluids, vacuum pumps, venturi-principle
driven devices, such as eductors and the like.
[0042] If the density or the vapor pressure data for the precursor
are unknown, it is recommended that they be measured by methods
known in the art. Alternatively, as a useful guideline, higher feed
velocities are favorable in certain embodiments. In certain
embodiments, higher precursor feed temperatures are favorable.
Higher feed temperature precursors are useful in certain
embodiments wherein the precursor is viscous or becomes viscous due
to flow (viscosity is greater than that of water). In certain
embodiments, it is useful to select achieve flash evaporation or
cavitations of one or more components of the precursor stream upon
spraying in the process reactor 106 (FIG. 1). This result may be
achieved for example, by selecting suitable combinations of
precursor formulations, solvents, feed spray equipment design
(e.g., spray tip length, diameter, shape, surface roughness, etc.),
and precursor feed parameters. In some embodiments, flash
evaporation or cavitation can be achieved by engineering the fluid
dynamics of the feed stream such that the vapor pressure P.sub.v of
the feed is a value close to or higher than process pressure. In
some embodiments, solvents may be added that increase vapor
pressure of the feed. In other embodiments, the viscosity and wall
friction may be used to increase the vapor pressure of the feed. In
some embodiments, the temperature of the feed may be raised to
increase the vapor pressure of the feed. In some embodiments, the
process pressure may be reduced to achieve the C.I. index of less
than zero.
[0043] With continued reference to FIG. 1, after the precursor 100
has been fed into reactor 106, it may be processed at high
temperatures to form the product powder. In other embodiments, the
thermal processing may be performed at lower temperatures to form
the powder product. The thermal treatment may be done in a gas
environment with the aim to produce products, such as powders, that
have the desired porosity, density, morphology, dispersion, surface
area, and composition. This step produces by-products such as
gases. To reduce costs, these gases may be recycled, mass/heat
integrated, or used to prepare the pure gas stream desired by the
process.
[0044] In embodiments using high temperature thermal processing,
the high temperature processing may be conducted at step 106 (FIG.
1) at temperatures greater than 1500 K, in some embodiments greater
than 2500 K, in some embodiments greater than 3000 K, and in some
embodiments greater than 4000 K. Such temperatures may be achieved
by various methods including, but not limited to, plasma processes,
combustion in air, combustion in purified oxygen or oxygen rich
gases, combustion with oxidants, pyrolysis, electrical arcing in an
appropriate reactor, and combinations thereof. Plasma can be used
to provide reaction gases, or it can be used to provide a clean
source of heat.
[0045] In certain embodiments, the high temperature is achieved by
utilizing enriched oxygen, pure oxygen, or other oxidants.
Adiabatic temperatures greater than 3000 K, 4000 K, or 5000 K can
be achieved by utilizing purified oxygen. In certain embodiments, a
low cavitation index in combination with purified oxidant stream
favors useful peak temperatures. In certain embodiments, a gas
stream with greater than 25% oxygen is useful. In other
embodiments, a gas stream with greater than 50% oxygen is useful.
In other embodiments, a gas stream with greater than 75% oxygen is
useful. In yet other embodiments, a gas stream with greater than
95% oxygen is useful. In other embodiments, a gas stream with
greater than 99.5% oxygen is useful. In certain embodiments, the
reactor is operated at pressures greater than 500 Torr, greater
than 1000 Torr, greater than 1500 Torr, or greater than 2000
Torr.
[0046] In some embodiments, the precursor and feed gas stream feed
conditions are mixed in a ratio that favors complete evaporation of
the precursor. In certain embodiments, molar ratios of precursor to
gas stream between 0.001 and 0.72 are useful. In certain
embodiments, molar ratios of precursor to gas stream between 0.01
and 0.3 are useful. In certain embodiments, molar ratios of
precursor and gas stream between 0.05 and 0.2 are useful for high
temperature thermal processing. In certain embodiments, the oxygen
may be added in stages thereby controlling the thermokinetic ratio
of fuel to oxidant. In other embodiments, the fuel to oxidant ratio
may be maintained between the upper and lower flame limits for the
precursor.
[0047] The combusted precursor and oxidant stream may be further
heated utilizing various thermal sources such as, but not limited
to, plasma processes (DC, RF, microwave, transferred arc,
non-transferred arc, etc.), radiation, nuclear energy, etc.
[0048] In certain embodiments, a plug flow system can be used. A
plug flow eliminates axial mixing and thereby can yield narrow size
distribution nanopowders. In certain embodiments, the design
principle for the design of plug flow reactor system is given by
UL/D>.beta. Where, [0049] U: axial velocity [0050] L: axial
length of the reactor [0051] D: axial dispersion coefficient [0052]
.beta.: plug flow index In some embodiments, the plug flow index
(.beta.) can be 5 or more, in some embodiments 50 or more, and in
some embodiments 500 or more. In some embodiments, the axial
velocity of the process stream may be increased to achieve a high
plug flow index. In other embodiments, the axial dispersion
coefficient may be reduced. In some embodiments, the axial length
of the reactor may be increased to achieve a high plug flow
index.
[0053] A high temperature thermal process at 106 results in a vapor
comprising elements, ionized species, and/or elemental clusters.
After the thermal processing, this vapor is cooled at step 110 to
nucleate nanopowders. The nanoscale particles form because of the
thermokinetic conditions in the process. By engineering the process
conditions, such as pressure, temperature, residence time,
supersaturation and nucleation rates, gas velocity, flow rates,
species concentrations, diluent addition, degree of mixing,
momentum transfer, mass transfer, and heat transfer, the morphology
of the nanoscale and submicron powders can be tailored. It is
important to note that the focus of the process should be on
producing a powder product that satisfies the end application
specifics and customer needs.
[0054] The surface and bulk composition of the nanopowders can be
modified by controlling the process temperature, pressure,
diluents, reactant compositions, flow rate, addition of synthetic
aids upstream or downstream of the nucleation zone, process
equipment design and such. In certain embodiments, the nucleation
temperature is adjusted to a temperature range wherein the
condensed species is in liquid form at the process pressure. In
these cases, the nanomaterial product tends to take a spherical
shape; thereafter the spherical nanomaterial is then cooled further
to solidify. In certain embodiments, the nucleation temperature is
adjusted to a temperature range wherein the condensed species is in
solid form at the process pressure. In these embodiments, the
nanomaterial product tends to take faceted shapes, platelet shapes,
or a shape wherein the particles' aspect ratios are greater than
one. By adjusting the nucleation temperature in accordance with
other process parameters, the shape, size and other characteristics
of the nanomaterial can be varied.
[0055] In certain embodiments, the nanopowder comprising stream is
quenched after cooling to lower temperatures at step 116 to
minimize and prevent agglomeration or grain growth. Suitable
quenching methods include, but are not limited to, methods taught
in U.S. Pat. No. 5,788,738. In certain embodiments, sonic to
supersonic processing before quenching and during quenching are
useful. In certain embodiments, process stream velocities and
quench velocities greater than 0.1 mach are useful (determined at
298 K and 760 Torr or any other combination of temperature and
pressure). In other embodiments, velocities greater than 0.5 mach
can be used. In still other embodiments, velocities greater than 1
mach can be used. Joule-Thompson expansion based quenching can be
used in certain embodiments. In other embodiments, coolant gases,
water, solvents, cold surfaces, radiative cooling, convective
cooling, conductive cooling, cryogenic fluids and the like, either
alone or a combination of such methods may be employed. In certain
embodiments, quenching methods are employed which can prevent
deposition of the powders on the conveying walls. These methods may
include, but are not limited to, electrostatic means, blanketing
with gases, the use of higher flow rates, mechanical means,
chemical means, electrochemical means, or sonication /vibration of
the walls.
[0056] In some embodiments, the high temperature processing system
includes instrumentation and software that can assist in the
quality control of the process. Furthermore, in certain
embodiments, the high temperature processing zone 106 is operated
to produce fine powders 120, in certain embodiments submicron
powders, and in certain embodiments nanopowders. The gaseous
products from the process may be monitored for composition,
temperature, and other variables to ensure quality at step 112
(FIG. 1). The gaseous products may be recycled to be used in
process 108 or used as a valuable raw material when nanoscale and
submicron powders 120 have been formed, or they may be treated to
remove environmental pollutants if any. Following quenching step
116, the nanoscale and submicron powders may be cooled further at
step 118 and then harvested at step 120. The product nanoscale and
submicron powders 120 may be harvested by any method. Suitable
collection means include, but are not limited to, bag filtration,
electrostatic separation, membrane filtration, cyclones, impact
filtration, centrifugation, hydrocyclones, thermophoresis, magnetic
separation, and combinations thereof.
[0057] The quenching at step 116 may be modified to enable
preparation of coatings. In such embodiments, a substrate may be
provided (in batch or continuous mode) in the path of the quenching
powder containing gas flow. By engineering the substrate
temperature and the powder temperature, a coating comprising the
submicron powders and nanoscale powders can be formed.
[0058] In some embodiments, a coating, film, or component may also
be prepared by dispersing the fine nanopowder and then applying
various known methods, such as, but not limited to, electrophoretic
deposition, magnetophorectic deposition, spin coating, dip coating,
spraying, brushing, screen printing, ink-jet printing, toner
printing, and sintering. The nanopowders may be thermally treated
or reacted to enhance their electrical, optical, photonic,
catalytic, thermal, magnetic, structural, electronic, emission,
processing, or forming properties before such a step.
[0059] It should be noted that the intermediate or product at any
stage of the process described herein, or similar process based on
modifications by those skilled in the art, may be used directly as
a feed precursor to produce nanoscale or fine powders by methods
taught herein and other methods. Other suitable methods for
producing nanoscale or fine powders include, but are not limited
to, those taught in commonly owned U.S. Pat. Nos. 5,788,738,
5,851,507, and 5,984,997, and co-pending U.S. patent application
Ser. Nos. 09/638,977 and 60/310,967, which are all incorporated
herein by reference in their entirety. For example, a sol may be
blended with a fuel and then utilized as the feed precursor mixture
for thermal processing above 2500 K to produce nanoscale simple or
complex powders.
[0060] In summary, one embodiment for manufacturing powders
consistent with teachings herein comprises (a) preparing a
precursor comprising at least one metal; (b) feeding the precursor
under conditions wherein the cavitation index is less than 1.0 and
wherein the precursor is fed into a high temperature reactor
operating at temperatures greater than 1500 K, in certain
embodiments greater than 2500 K, in certain embodiments greater
than 3000 K, and in certain embodiments greater than 4000 K; (c)
wherein, in the high temperature reactor, the precursor converts
into vapor comprising the metal in a process stream with a velocity
above 0.1 mach in an inert or reactive atmosphere; (d) cooling the
vapor to nucleate submicron or nanoscale powders; (e) quenching the
nucleated powders at high gas velocities to prevent agglomeration
and growth; and (f) filtering the quenched powders from the gas
suspension.
[0061] Another embodiment for manufacturing inorganic nanoscale
powders comprises (a) preparing a fluid precursor comprising two or
more metals, at least one of which is in a concentration greater
than 100 ppm by weight; (b) feeding the said precursor into a high
temperature reactor with a negative cavitation index (c) providing
an oxidant such that the molar ratio of the precursor and oxidant
is between 0.005 and 0.65 (d) wherein the precursor and oxidant
heat to a temperatures greater than 1500 K, in some embodiments
greater than 2500 K, in some embodiments greater than 3000 K, and
in some embodiments greater than 4000 K in an inert or reactive
atmosphere; (e) wherein, in the said high temperature reactor, the
said precursor converts into vapor comprising the metals; (f)
cooling the vapor to nucleate submicron or nanoscale powders (in
some embodiments, at a temperature where the condensing species is
a liquid; in other embodiments, at a temperature where the
condensing species is a solid); (g) in some embodiments, providing
additional time to let the nucleated particles grow to a desired
size, shape and other characteristics; (h) quenching the nucleated
powders by any technique to prevent agglomeration and growth; and
(i) processing the stream comprising quenched powder to separate
solids from the gases. In certain embodiments, the fluid precursor
may include synthesis aids such as surfactants (also known as
dispersants, capping agents, emulsifying agents, etc.) to control
the morphology or to optimize the process economics and/or product
performance.
[0062] One embodiment for manufacturing coatings comprises (a)
preparing a fluid precursor comprising one or more metals; (b)
feeding the said precursor at negative cavitation index into a high
temperature reactor operating at temperatures greater than 1500 K,
in some embodiments greater than 2500 K, in some embodiments
greater than 3000 K, and in some embodiments greater than 4000 K in
an inert or reactive atmosphere; (c) wherein, in the high
temperature reactor, the precursor converts into vapor comprising
the metals; (d) cooling the vapor to nucleate submicron or
nanoscale powders; (e) quenching the powders onto a substrate to
form a coating on a surface to be coated.
[0063] The powders produced by teachings herein may be modified by
post-processing, such as the processing taught by commonly owned
U.S. patent application Ser. No. 10/113,315, which is hereby
incorporated by reference in its entirety.
Methods for Incorporating Nanoparticles into Products
[0064] The submicron and nanoscale powders taught herein may be
incorporated into a composite structure by any method. Some
non-limiting exemplary methods are taught in commonly owned U.S.
Pat. No. 6,228,904, which is hereby incorporated by reference in
its entirety.
[0065] The submicron and nanoscale powders taught herein may be
incorporated into plastics by any method. In one embodiment, the
method comprises (a) preparing nanoscale or submicron powders
comprising metal(s) by any method, such as a method that employs
fluid precursors and a peak processing temperature exceeding 1500
K; (b) providing powders of one or more plastics; (c) mixing the
nanoscale or submicron powders with the powders of plastics; and
(d) co-extruding or injection molding the mixed powders into a
desired shape at temperatures greater than the softening
temperature of the powders of plastics but less than the
degradation temperature of the powders of plastics. In another
embodiment, a masterbatch of the plastic powder comprising
nanoscale or submicron powders comprising metal(s) is prepared.
These masterbatches can later be processed into useful products by
techniques well known to those skilled in the art. In yet another
embodiment, the metal containing nanoscale or submicron powders are
pretreated to coat the powder surface for ease in dispersability
and to ensure homogeneity. In a further embodiment, injection
molding of the mixed powders comprising nanoscale powders and
plastic powders is employed to prepare useful products.
[0066] One embodiment for incorporating nanoscale or submicron
powders into plastics comprises (a) preparing nanoscale or
submicron powders comprising metal(s) by any method, such as a
method that employs fluid precursors and peak processing
temperature exceeding 1500 K; (b) providing a film of one or more
plastics, wherein the film may be laminated, extruded, blown, cast,
or molded; and (c) coating the nanoscale or submicron powders on
the film of plastic by techniques such as spin coating, dip
coating, spray coating, ion beam coating, sputtering. In another
embodiment, a nanostructured coating is formed directly on the film
by techniques such as those taught in herein. In some embodiments,
the grain size of the coating is less than 200 nm, in some
embodiments less than 75 nm, and in some embodiments less than 25
nm.
[0067] The submicron and nanoscale powders taught herein may be
incorporated into glass by any method. In one embodiment,
nanoparticles of metal(s) are incorporated into glass by (a)
preparing nanoscale or submicron powders comprising metal(s) by any
method, such as a method that employs fluid precursors and
temperature exceeding 1500 K in an inert or reactive atmosphere;
(b) providing glass powder or melt; (c) mixing the nanoscale or
submicron powders with the glass powder or melt; and (d) processing
the glass comprising nanoparticles into articles of desired shape
and size.
[0068] The submicron and nanoscale powders taught herein may be
incorporated into paper by any method. In one embodiment, the
method comprises (a) preparing nanoscale or submicron powders
comprising metal(s); (b) providing paper pulp; (c) mixing the
nanoscale or submicron powders with the paper pulp; and (d)
processing the mixed powders into paper by steps such as molding,
couching, and calendering. In another embodiment, the metal
containing nanoscale or submicron powders are pretreated to coat
the powder surface for ease in dispersability and to ensure
homogeneity. In a further embodiment, nanoparticles are applied
directly on the manufactured paper or paper-based product; the
small size of nanoparticles enables them to permeate through the
paper fabric or reside on the surface of the paper and thereby
functionalize the paper.
[0069] The submicron and nanoscale powders taught herein may be
incorporated into leather, fibers, or fabric by any method. In one
embodiment, the method comprises (a) preparing nanoscale or
submicron powders comprising metal(s) by any method, such as a
process that includes a step that operates above 1000 K; (b)
providing leather, fibers, or fabric; (c) bonding the nanoscale or
submicron powders with the leather, fibers, or fabric; and (d)
processing the bonded leather, fibers, or fabric into a product. In
yet another embodiment, the metal containing nanoscale or submicron
powders are pretreated to coat or functionalize the powder surface
for ease in bonding or dispersability or to ensure homogeneity. In
a further embodiment, nanoparticles are applied directly on a
manufactured product based on leather, fibers, or fabric; the small
size of nanoparticles enables them to adhere to or permeate through
the leather, fibers (polymer, wool, cotton, flax, animal-derived,
agri-derived), or fabric and thereby functionalize the leather,
fibers, or fabric.
[0070] The submicron and nanoscale powders taught herein may be
incorporated into creams or inks by any method. In one embodiment,
the method comprises (a) preparing nanoscale or submicron powders
comprising metal(s), such as by the methods described herein that
employs fluid precursors and peak processing temperature exceeding
1500 K; (b) providing a formulation of cream or ink; and (c) mixing
the nanoscale or submicron powders with the cream or ink. In yet
another embodiment, the metal(s) comprising nanoscale or submicron
powders are pretreated to coat or functionalize the powder surface
for ease in dispersability and to ensure homogeneity. In a further
embodiment, pre-existing formulation of a cream or ink is mixed
with nanoscale or submicron powders to functionalize the cream or
ink.
[0071] Nanoparticles comprising metal(s) may be difficult to
disperse in water, solvents, plastics, rubber, glass, paper, etc.
in certain cases. The dispersability of the nanoparticles can be
enhanced in certain embodiments by treating the surface of the
metal oxide powders or other metal comprising nanoparticles. For
example, fatty acids (e.g. propionic acid, stearic acid and oils)
or reactive organometallic compounds of silicon, titanium, or
zirconium can be applied to or with the nanoparticles to enhance
the surface compatibility. If the powder has an acidic surface,
ammonia, quaternary salts, or ammonium salts can be applied to the
surface to achieve desired surface pH. In other cases, acetic acid
wash can be used to achieve the desired surface state. Trialkyl
phosphates and phosphoric acid can be applied to reduce dusting and
chemical activity. In yet other embodiments, the powder may be
thermally treated to improve the dispersability of the powder.
EXAMPLE 1
Aluminum Silicon Oxide Nanomaterials
[0072] OAO.RTM. aluminum precursor from Chattem Chemicals was mixed
with Octamethylcyclotetrasiloxane silicon precursor from Gelest
Chemicals in a ratio that provided 44 atomic % A1 and 56 atomic %
Si. This mix was sprayed into a thermal plasma reactor described
above at a rate of about 65 ml/min using about 180 standard liters
per minute oxygen. The cavitation index for the feed was less than
125. The peak vapor temperature in the thermal plasma reactor,
processed at velocities greater than 0.25 mach, was above 3000 K.
The vapor was cooled and then quenched by Joule-Thompson expansion.
The powders collected were analyzed using X-ray diffraction
(Warren-Averbach analysis) and BET Surface Area Analyzer
(Quantachrome). It was discovered that the powders were mostly
amorphous (partly crystalline) and had a specific surface area of
greater than 20 m.sup.2/gm. The refractive index of the powder was
between 1.5 and 1.55.
EXAMPLE 2
Aluminum Silicon Oxide Nanomaterials
[0073] OAO.RTM. aluminum precursor from Chattem Chemicals was mixed
with Octamethylcyclotetrasiloxane silicon precursor from Gelest
Chemicals in a ratio that provided 23 atomic % A1 and 77 atomic %
Si. This mix was sprayed into a thermal plasma reactor described
above at a rate of about 65 ml/min using about 180 standard liters
per minute oxygen. The cavitation index for the feed was less than
15. The peak vapor temperature in the thermal plasma reactor,
processed at velocities greater than 0.5 mach, was above 3000 K.
The vapor was cooled and then quenched by Joule-Thompson expansion.
The powders collected were analyzed using X-ray diffraction
(Warren-Averbach analysis) and BET Surface Area Analyzer
(Quantachrome). It was discovered that the particles were mostly
amorphous (partly crystalline) and had a specific surface area of
greater than 40 m.sup.2/gm. The refractive index of the powder was
between 1.47 and 1.51.
EXAMPLE 3
Aluminum Silicon Oxide Nanomaterials
[0074] OAO.RTM. aluminum precursor from Chattem Chemicals was mixed
with Octamethylcyclotetrasiloxane silicon precursor from Gelest
Chemicals in a ratio that provided 70 atomic % A1 and 30 atomic %
Si. This mix was sprayed into a thermal plasma reactor described
above at a rate of about 65 ml/min using about 220 standard liters
per minute oxygen. The cavitation index for the feed was less than
15. The peak vapor temperature in the thermal DC plasma reactor,
processed at velocities greater than 0.5 mach, was above 3000 K.
The vapor was cooled and then quenched by radiative cooling
combined with expansion. The powders collected were analyzed using
X-ray diffraction (Warren-Averbach analysis) and BET Surface Area
Analyzer (Quantachrome). It was discovered that the powders were
mostly amorphous (partly crystalline) and a specific surface area
of greater than 30 m.sup.2/gm. The refractive index of the powder
was between 1.57 and 1.64.
EXAMPLE 4
Functionalized Aluminum Silicon Oxide Nanomaterials
[0075] 100 grams of aluminum silicon oxide nanopowders from Example
1 were mixed with 12 grams of deionized water. To the mix, about 4
grams of isobutyltriethoxysilane dissolved in 10 grams of methanol
was added. Next, the mix was heated to 110.degree. C. under dry
argon for 30 minutes. While the gas was flowing, the powders were
mixed. The powder was cooled and characterized. It was found that
the powders were hydrophobic and dispersed well in polymers and in
non-polar solvents. The powders had been functionalized with
isobutyl functional groups on the surface.
EXAMPLE 5-6
Silver doped Aluminum Silicon Oxide Nanomaterials
[0076] 10 grams of silane solution was prepared by mixing 5 grams
of deionized water and 5 grams of N-(2-Amino ethyl)-3-Amino propyl
trimethoxy silane. 25 grams of aluminum silicon oxide nanopowders
from Example 1 were mixed with 10 grams of silane solution. Next,
the mix was heated to 110.degree. C. under dry argon for 30
minutes. While the gas was flowing, the powders were mixed. The
powder was cooled and characterized. Next the functionalized
nanopowder was mixed into a solution consisting of 2 wt % silver
nitrate solution in water. The silver transferred from the solution
to the N-(2-Amino ethyl)-3-Amino propyl functional groups on the
surface of the powder thereby doping silver ions into the aluminum
silicate nanomaterial. The powder was filtered and dried at
65.degree. C. in an oven. A white aluminum silicate nanopowder
comprising silver was thus prepared. Such powders are useful in
anti-microbial and other biocidal applications in form of clear
coatings and plastic composites.
[0077] In another example, instead of silver, the functionalized
nanopowder was mixed into a solution consisting of 2 wt % copper
nitrate solution in water. The copper ions transferred from the
solution to the N-(2-Amino ethyl)-3-Amino propyl functional groups
on the surface of the powder thereby doping copper ions into the
aluminum silicon oxide nanomaterial. The powder was filtered and
dried at 65.degree. C. in an oven. A purplish blue aluminum
silicate nanopowder comprising of copper was thus prepared. Such
powders are useful in anti-microbial and other biocidal
applications in form of clear coatings and plastic composites.
These examples show that the nanopowders can be surface
functionalized and doped with positively charged species such as
metal ions.
[0078] 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.
* * * * *