U.S. patent application number 10/780671 was filed with the patent office on 2005-06-16 for zinc comprising nanoparticles and related nanotechnology.
This patent application is currently assigned to NanoProducts Corporation. Invention is credited to Yadav, Tapesh.
Application Number | 20050126338 10/780671 |
Document ID | / |
Family ID | 34656848 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050126338 |
Kind Code |
A1 |
Yadav, Tapesh |
June 16, 2005 |
Zinc comprising nanoparticles and related nanotechnology
Abstract
Nanoparticles comprising zinc, methods of manufacturing
nanoparticles comprising zinc, and applications of nanoparticles
comprising zinc, such as electrically conducting formulations,
reagents for fine chemical synthesis, pigments and catalysts are
provided.
Inventors: |
Yadav, Tapesh; (Longmont,
CO) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
NanoProducts Corporation
|
Family ID: |
34656848 |
Appl. No.: |
10/780671 |
Filed: |
February 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60449626 |
Feb 24, 2003 |
|
|
|
Current U.S.
Class: |
75/255 ; 75/332;
75/343 |
Current CPC
Class: |
C01G 9/02 20130101; C01P
2006/80 20130101; B82Y 30/00 20130101; C01P 2002/52 20130101; C01P
2004/64 20130101; C22C 18/00 20130101; C09C 1/04 20130101; C01P
2004/54 20130101; C01G 53/006 20130101; C01G 9/00 20130101; C01P
2002/60 20130101; C01P 2006/40 20130101; C01P 2002/72 20130101;
C01P 2006/12 20130101 |
Class at
Publication: |
075/255 ;
075/332; 075/343 |
International
Class: |
C22C 001/04; C22C
018/00 |
Claims
What is claimed is:
1. A nanomaterial composition of matter comprising zinc; and at
least one metal other than zinc wherein the composition of matter
has an electrical conductivity greater than 0.0001 mhos.cm.
2. The nanomaterial composition of matter of claim 1, wherein the
composition comprises aluminum.
3. The nanomaterial composition of matter of claim 1, wherein the
electrical conductivity is greater than 0.01 mhos.cm.
4. The nanomaterial composition of matter of claim 1, wherein the
nanomaterial comprises particles with an aspect ratio greater than
1.
5. The nanomaterial composition of matter of claim 1, wherein the
nanomaterial comprises non-spherical particles.
6. A coating comprising the nanomaterial composition of matter of
claim 1.
7. A transparent conductive layer comprising the nanomaterial
composition of matter of claim 1.
8. An electrode comprising the nanomaterial composition of matter
of claim 1.
9. A product comprising the nanomaterial composition of matter of
claim 1.
10. A device comprising the nanomaterial composition of matter of
claim 1.
11. A method for preparing a composition of matter comprising
providing nanoparticles of a first composition comprising zinc; and
reacting the nanoparticles with a reagent wherein the reacting
creates a second composition that is different from the first
composition.
12. The method of claim 11, wherein the first composition comprises
particles with an aspect ratio greater than 1.
13. The method of claim 11, wherein the first composition further
comprises oxygen.
14. The method of claim 11, wherein the reagent comprises
nitrogen.
15. The method of claim 11, wherein the reagent comprises a
halogen.
16. The method of claim 11, wherein the reagent comprises an acid
or an alkali.
17. The method of claim 11, wherein the reagent comprises
hydrogen.
18. The method of claim 11, wherein the reagent comprises
oxygen.
19. The method of claim 11, wherein the reagent comprises
carbon.
20. A product comprising the composition of matter prepared using
the method of claim 11.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application is a An application claiming the benefit
under 35 USC 119(e) U.S. Application 60/449,626, filed Feb. 24,
2003, incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to methods of manufacturing
submicron and nanoscale powders comprising zinc and applications of
such powders.
RELEVANT BACKGROUND
[0003] 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 U.S. Pat. No. 6,344,271 and in co-pending and commonly assigned
U.S. patent application Ser. Nos. 09/638,977, 10/004,387,
10/071,027, 10/113,315, and 10/292,263 all of which along with the
references contained therein are hereby incorporated by reference
in their entirety, teach some applications of sub-micron and
nanoscale powders.
SUMMARY OF THE INVENTION
[0004] Briefly stated, the present invention involves methods for
manufacturing nanoscale powders comprising zinc and applications
thereof.
[0005] In some embodiments, the present invention is nanoparticles
of doped or undoped zinc oxides
[0006] In some embodiments, the present invention is methods for
manufacturing doped or undoped metal oxides comprising zinc.
[0007] In some embodiments, the present invention is oxide
composites and coatings that comprise doped or undoped zinc.
[0008] In some embodiments, the present invention is applications
of powders comprising doped or undoped zinc oxides.
[0009] In some embodiments, the present invention is superior
ultraviolet absorbing pigment for a variety of applications.
[0010] In some embodiments, the present invention is superior
catalysts for a variety of applications.
[0011] In some embodiments, the present invention is superior
additives for a variety of applications.
[0012] In some embodiments, the present invention is materials and
devices for optical, sensing, thermal, biomedical, structural,
superconductive, energy, security and other uses.
[0013] In some embodiments, the present invention is methods for
producing novel nanoscale powders comprising zinc in high volume,
low-cost, and reproducible quality.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows an exemplary overall approach for producing
submicron and nanoscale powders in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] This invention is generally directed to very fine powders
comprising zinc (Zn). 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
outlined.
[0016] Definitions
[0017] For purposes of clarity the following definitions are
provided to aid the understanding of the description and specific
examples provided herein:
[0018] "Fine powders" as used herein, refers to powders that
simultaneously satisfy the following criteria:
[0019] (1) particles with mean size less than 10 microns; and
[0020] (2) particles with aspect ratio between 1 and 1,000,000.
[0021] 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.
[0022] "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.
[0023] 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.
[0024] 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%.
[0025] Nanomaterials, as the term used herein, are materials in any
dimensional form and domain size less than 100 nanometers.
[0026] "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.
[0027] The terms "powder," "particle," and "grain" are used
interchangeably and encompass 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.).
[0028] "Aspect ratio," as the term is used herein, refers to the
ratio of the maximum to the minimum dimension of a particle.
[0029] "Precursor," as the term is used herein, encompasses any raw
substance that can be transformed into a powder of 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.
[0030] "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.
[0031] "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 or
surface or deposition or a combination 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.
[0032] "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.
[0033] This invention is directed to submicron and nanoscale
powders comprising doped or undoped zinc oxides in certain
embodiments. Given the relative abundance of zinc in the earth's
crust and current limitations on purification technologies, it is
expected that many commercially produced materials would have
naturally occurring zinc impurities. These impurities are expected
to be below 100 parts per million and in most cases in
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 zinc impurities wherein zinc is present in a
concentration similar to other elemental impurities are excluded
from the scope of this invention. However, it is emphasized that in
one or more doped or undoped compositions of matter, zinc 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 patent.
[0034] In generic sense, the invention teaches nanoscale powders,
and in more generic sense, submicron powders comprising at least
100 ppm by weight, in some embodiments greater than 1 weight % by
metal basis, and in other embodiments greater than 10 weight % by
metal basis of zinc (Zn).
[0035] While several embodiments for manufacturing nanoscale and
submicron powders comprising zinc are disclosed, for the purposes
herein, the nanoscale or submicron powders may be produced by any
method or may result as a byproduct from any process.
[0036] 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 zinc
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.
[0037] The process shown in FIG. 1 begins at 100 with a zinc
metal-containing precursor such as an emulsion, fluid,
particle-containing fluid suspension, or water-soluble salt. The
precursor may be evaporated zinc metal vapor, evaporated alloy
vapor, a gas, a single-phase liquid, a multi-phase liquid, a melt,
a sol, a solution, fluid mixtures, 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 more uniform.
[0038] In one embodiment of this invention, the precursors are
environmentally benign, safe, readily available, high-metal
loading, lower-cost fluid materials. Examples of zinc
metal-containing precursors suitable for 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, and metal-containing
emulsions.
[0039] In another embodiment, multiple metal precursors may be
mixed if complex nano-nanoscale and submicron powders are desired.
For example, a zinc precursor and praseodymium precursor may be
mixed to prepare praseodymium doped zinc oxide powders for pigment
applications. As another example, a zinc precursor and copper
precursor may be mixed in correct proportions to yield a high
purity, high surface area, mixed oxide powder for catalyst
applications. In yet another example, a cobalt precursor and a zinc
precursor may be mixed to yield powders for electroceramic varistor
device applications. Such complex nanoscale and submicron powders
can help 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.
[0040] 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.
[0041] 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.
[0042] While the above examples specifically 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. 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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, pyrolysis, electrical arcing in an appropriate reactor,
and combinations thereof. The plasma may provide reaction gases or
may provide a clean source of heat.
[0047] A high temperature thermal process at 106 results in a vapor
comprising fine powders. After the thermal processing, this vapor
is cooled at step 110 to nucleate submicron powders, in certain
embodiments nanopowders. In certain embodiments, the cooling
temperature at step 110 is maintained high enough to prevent
moisture condensation. The dispersed particles form because of the
thermokinetic conditions in the process. By engineering the process
conditions, such as pressure, 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
excels in satisfying the end application requirements and customer
needs.
[0048] In certain embodiments, the nanopowder 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 quenching may be used.
In other embodiments, coolant gases, water, solvents, cold
surfaces, or cryogenic fluids might 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.
[0049] 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.
[0050] The product nanoscale and submicron powders 120 may be
collected 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.
[0051] 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.
[0052] 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.
[0053] 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 include,
but 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 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.
[0054] In summary, one embodiment for manufacturing powders
consistent with teachings herein, comprises (a) preparing a
precursor comprising at least 100 ppm by weight of zinc element;
(b) feeding the precursor 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 rare earth metal in a process stream with a velocity above 0.25
mach in an inert or reactive atmosphere; (d) the vapor is cooled to
nucleate submicron or nanoscale powders; (e) the powders are then
quenched at high gas velocities to prevent agglomeration and
growth; and (f) the quenched powders are filtered from the
gases.
[0055] Another embodiment for manufacturing nanoscale powders
comprising zinc consistent with teachings herein, comprises (a)
preparing a fluid precursor comprising two or more metals, at least
one of which is zinc in a concentration greater than 100 ppm by
weight; (b) feeding the said precursor 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 said high temperature
reactor, the said precursor converts into vapor comprising zinc;
(d) the vapor is cooled to nucleate submicron or nanoscale powders;
(e) the powders are then quenched at gas velocities exceeding 0.1
Mach to prevent agglomeration and growth; and (f) the quenched
powders are separated 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.
[0056] One embodiment for manufacturing coatings comprises (a)
preparing a fluid precursor comprising one or more metals, one of
which is zinc; (b) feeding the said precursor 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 zinc; (d) the vapor is cooled to nucleate submicron or
nanoscale powders; (e) the powders are then quenched onto a
substrate to form a coating on the substrate comprising zinc.
[0057] The powders produced by teachings herein may be modified by
post-processing as 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
[0058] 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.
[0059] 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 zinc 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 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 zinc 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 zinc 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.
[0060] One embodiment for incorporating nanoscale or submicron
powders into plastics comprises (a) preparing nanoscale or
submicron powders comprising zinc 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.
[0061] The submicron and nanoscale powders taught herein may be
incorporated into glass by any method. In one embodiment,
nanoparticles of zinc are incorporated into glass by (a) preparing
nanoscale or submicron powders comprising zinc 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.
[0062] 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 zinc; (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 zinc 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.
[0063] 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 zinc 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 zinc 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.
[0064] 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 zinc by any method, such as a method 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 zinc 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.
[0065] Nanoparticles comprising zinc can be difficult to disperse
in water, solvents, plastics, rubber, glass, paper, etc. The
dispersability of the nanoparticles can be enhanced by treating the
surface of the zinc oxide powders or other zinc comprising
nanoparticles. For example, fatty acids (e.g. propionic acid,
stearic acid and oils) 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 cases, the
powder may be thermally treated to improve the dispersability of
the powder.
Applications of Nanoprarticles and Submicron Powders Comprising
Zinc
[0066] Pigments
[0067] Nanoparticles of zinc containing multi-metal oxides offer
some surprising and unusual benefits as pigments. Nanoparticles are
smaller than the visible wavelengths of light which leads to
visible wavelengths interacting in unusual ways with nanoparticles
compared to particles with grain sizes much bigger than the visible
wavelengths (400-700 nm). The small size of nanoparticles can also
lead to more uniform dispersion. In certain embodiments, it is
important that the nanoparticles be non-agglomerated (i.e. do not
have sintered neck formation or hard agglomeration). In some
embodiments, the nanoparticles have non-functionalized, i.e. clean
surface; in other embodiments, the surface is modified or
functionalized to enable bonding with the matrix in which they need
to be dispersed.
[0068] One of the outstanding process challenges for manufacturing
inorganic pigments is the ability to ensure homogeneous lattice
level mixing of elements in a complex multi-metal formulation. One
of the features of the process described herein is its ability to
prepare complex compositions with the necessary homogeneity.
Therefore, the teachings herein are ideally suited for creating
color and making superior performing pigments with nanoparticles
comprising zinc.
[0069] Some non-limiting illustrations of pigments containing zinc
are cobalt zinc-silicate, ceria nanolayer coated cobalt
zinc-silicate, zinc chromate, zinc ferrite, zinc dust, and
non-stoichiometric substances comprising zinc.
[0070] In one embodiment, a method for manufacturing a pigmented
product comprises (a) preparing nanoscale or submicron powders
comprising zinc; (b) providing powders of one or more plastics; (c)
mixing the nanoscale or submicron powders with the powders of
plastics; and (d) processing the mixed powders into the product. In
yet another embodiment, the zinc containing nanoscale or submicron
powders are pretreated to coat the powder surface for ease in
dispersability and to ensure homogeneity. In a further embodiment,
extrusion or injection molding of the mixed powders comprising
nanoscale powders and plastic powders can be employed to prepare
useful products.
[0071] Additives
[0072] Ultraviolet radiation in the 280-400 nm range causes most
damage to consumer products exposed to sun light. Furthermore,
ultraviolet radiation is also known to be harmful to human skin.
Methods for protecting consumer products and ultraviolet filters
are commercially needed. Organic pigments and additives are
currently utilized to provide such protection. However, such
organic pigments have a limited life as they provide the protection
by sacrificially absorbing ultraviolet radiation while undergoing
degradation. More permanent, long lasting protection is
desired.
[0073] Nanoparticles of metal oxides comprising zinc elements,
particularly those that contain two or more metals at least one of
which is zinc, offer a unique and surprising way to provide such
long lasting superior protection. It is important to tailor the
particle size distribution such that it is less than the wavelength
of visible light (that is, the d.sub.99 of particle size
distribution should be less than 200 nm, in certain embodiments
less than 100 nm). Once such oxide nanoscale powder comprising Zn
is available, it can be utilized to shield ultraviolet radiation
and consequent damage. The presence of one or more additional
metals in the zinc oxide lattice reduces the photocatalytic
behavior of zinc oxide such as is known to those in the art (e.g.
see Eggins et al., Journal of Photochemistry and Photobiology A:
Chemistry 118 (1998) pages 31-40). It is desirable to reduce this
inherent photoactivity of zinc oxide which can cause secondary and
undesired photocatalytic damage. Oxides comprising two or more
metals one of which being zinc, in certain embodiments with zinc
greater than 75% by metal weight, can reduce or eliminate this
photocatalytic effect. The metals combined with zinc at lattice
level to form a multi-metal oxide can be any metal. Suitable metals
include, but are not limited to, aluminum, copper, titanium,
silicon, magnesium, calcium, barium, iron, nickel, cobalt,
chromium, tantalum, niobium, silver, gold, tin, antimony, indium,
zirconium, tungsten, molybdenum, vanadium, sodium, potassium,
lithium, bismuth, hafnium, and rare earth metals.
[0074] Ultraviolet blocking submicron and nanoscale powders taught
herein may be incorporated into plastics, wood, fabric, paints,
furniture, glass, paper, food packaging materials, housing
products, flooring products, car interiors, cosmetics, and other
consumer products by techniques discussed herein or any other
suitable method.
[0075] In one embodiment, a method for protecting products from the
damaging effects of ultraviolet radiation comprises (a) preparing
nanoscale or submicron powders comprising zinc by any process, in
certain embodiments wherein one or more additional metals are
present in combination with zinc at the lattice level; (b)
providing powders of one or more constituents of the product (e.g.
plastics); (c) mixing the nanoscale or submicron powders with the
one or more constituents of the product; and (d) processing the
mixed powders into a desired shape. In another embodiment, the zinc
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, extrusion or injection
molding of the mixed powders comprising nanoscale powders and
plastic powders can be employed to prepare useful products.
[0076] In another embodiment, a method for protecting ultraviolet
radiation comprises (a) preparing nanoscale or submicron powders
comprising zinc; (b) providing a film of one or more plastics,
wherein the film may be laminated, extruded, blown, cast, or
molded; (c) coating the nanoscale or submicron powders on the film
of plastic by techniques such as, but not limited to, spin coating,
dip coating, spray coating, ion beam coating, vapor deposition, and
sputtering.
[0077] In other embodiments of a method for protecting goods from
ultraviolet radiation, glass may be used instead of plastics. In a
similar way, ultraviolet protective capability can be added to
composites, wood, adhesives, fabric, paints, inks, furniture,
leather, paper, food packaging materials, housing products,
flooring products, car interiors, biomedical storage products,
blood storage containers, bio-fluid containers, road signs, and
indicators.
[0078] In yet other embodiments, human and pet skin may be
protected from ultraviolet radiation using the following method:
(a) prepare nanoscale or submicron powders comprising zinc in a
process such as those described herein; (b) provide a medium, such
as cream, base, wax, spray, or solution; (c) disperse the nanoscale
or submicron powders into the medium; and (d) apply the medium over
the surface that needs protection. An embodiment is to use this
method with existing cosmetics or personal care product.
[0079] The teachings above are also useful in protecting
vegetables, fruits, meats and packaged food. It is well known that
foods that contain fats or oils (potato chips, snacks, meat, soups,
etc.) degrade when exposed to light, in particular when exposed to
ultraviolet radiation. In one embodiment, a method for enhancing
the storage life of food and of protecting food comprises (a)
preparing nanoscale or submicron powders comprising zinc and/or
additional metals by any method, such as the method taught herein;
(b) providing powders or films of one or more plastics; (c) mixing
or coating the nanoscale or submicron powders onto the plastic film
(laminates) or with the powders of plastics; (d) processing the
film or mixed powders into a desired package or shape. Current
techniques for protecting fat containing food is to package them in
metal or paper cans or in laminated plastic bags that include a
metal layer such as aluminum. These traditional techniques prevent
the consumer from viewing the quality of the product and thereby
limit the ability for marketing premium products. A surprising
advantage of the approach taught herein for protecting food is the
ability to maintain visual transparency of the packaging material
while eliminating over 95%, and in other embodiments 99% or more,
of the ultraviolet radiation reaching the product. In another
embodiment, this technique is used to protect biomedical products,
device components, and pharma products sensitive to ultraviolet
radiation. For example, this technique can be utilized to protect
medicines, bioactive liquid droplets, tracers, markers, biomedical
reagents, blood, biological samples, device tubing, catheters,
angioplasty kits, components, etc. In a further embodiment, instead
of plastics, glass is used as the packaging materials in
combination with nanoscale and submicron powders to provide
protection from UV radiation. One advantage of zinc-based UV
absorbing powder is that they are environmentally benign when the
product is disposed or destroyed by techniques such as
incineration. While the teachings herein specifically discuss the
use of zinc metal comprising nanoscale and submicron powders, other
compositions of powders that absorb UV radiation can also be
employed in the same way to deliver similar benefits to
consumers.
[0080] The teachings herein are also useful in protecting wood,
construction products, and adhesives. Wood, construction products,
and numerous commercial adhesives degrade when exposed to light, in
particular when exposed to ultraviolet radiation. In one
embodiment, a method for enhancing the useful life of wood products
comprises (a) preparing nanoscale or submicron powders comprising
zinc and/or other metals by any method, such as the method taught
herein; (b) providing a wood product; (c) permeating or coating the
nanoscale or submicron powders on the wood product; and (d) thereby
reducing the UV exposure to the wood and reducing the degradation
of the wood product by UV light. A surprising advantage of the
approach taught herein for protecting wood is (a) the ability of
nanoparticles to infiltrate the pores of the wood product and
adhere to the wood fibers; and (b) the ability to maintain visual
appeal of the wood product while eliminating over 95%, in other
embodiments 99% or more, of the ultraviolet radiation reaching the
product. In another embodiment, this technique is used through
incorporating the nanoparticles in wood polishes, wood protective
sprays and other such protective varnishes and creams. One
advantage of zinc-based UV absorbing powder is that they are
environmentally benign when the product is disposed or destroyed by
techniques such as incineration. While the teachings herein discuss
the use of zinc metal comprising nanoscale and submicron powders,
other compositions of powders that absorb UV radiation can also be
employed in the same way to deliver similar benefits to
consumers.
[0081] The teachings herein can be used to enhance the life of and
protect paper, archival materials, prints, photographs, currency,
valuable documents, such as passports, art work, fabric, and other
products. These products degrade when exposed to light, in
particular when exposed to ultraviolet radiation. In one
embodiment, a method for enhancing the useful life of paper,
archival materials, prints, photos, currency, valuable documents
such as passports, fabric, art work, and other products, comprises
(a) preparing nanoscale or submicron powders comprising zinc by any
method, such as the method taught herein; (b) providing paper,
archival materials, prints, photos, currency, valuable documents
such as passports, fabric, art work, and other products; (c)
infiltrating or coating the nanoscale or submicron powders onto the
paper, archival materials, prints, photos, currency, valuable
documents such as passports, fabric, art work and, other products;
and (d) thereby reducing the UV radiation experienced by and
consequent damage by UV to the paper, archival materials, prints,
photos, currency, valuable documents such as passports, fabric, art
work, and other products. A surprising advantage of the approach
taught herein for protecting paper, archival materials, prints,
photos, currency, valuable documents such as passports, fabric, art
work, and other products is (a) the ability of nanoparticles to
infiltrate or nanolayer coat the pores or ink of the product and
adhere to the fibers constituting the product; and (b) the ability
to maintain visual integrity and appeal of the product while
eliminating over 95%, in other embodiments 99% or more, of the
ultraviolet radiation reaching the product. In another embodiment,
this technique is used through incorporating the nanoparticles in
preservative polishes, protective sprays, and other such protective
varnishes and creams. While the teachings herein discuss the use of
zinc metal comprising nanoscale and submicron powders, other
compositions of powders that absorb UV radiation can also be
employed in the same way to deliver similar benefits to consumers
or can be used in combination with zinc comprising nanoparticles to
deliver value to consumers. Similarly, while UV pigments are
discussed in detail, with composition optimization, zinc containing
nanoparticles (such as Zinc Sulfide) can be made to reflect or
absorb infrared (IR) wavelengths. Such IR pigments can be used with
glass or plastics to improve thermal management of environment
inside a package or inside a room.
[0082] Sulfur Limiting Agent
[0083] The unusually high affinity of zinc oxide for sulfur when
combined with nanoparticle technology enables novel applications.
It can be used to capture or reduce the undesirable activity of
sulfur in any process or product such as plastics, rubber, fuels,
and acid rain causing exhaust gases. The high surface area of zinc
oxide nanoparticles, particularly when the mean particle size is
less than 100 nanometers, make them useful in these
applications.
[0084] In one embodiment, a method for employing zinc comprising
nanoparticles as sulfur limiting agent comprises (a) preparing
nanoscale or submicron powders comprising zinc; (b) providing a
powder or film of one or more plastics, wherein the plastics may be
laminated or extruded or blown or cast or molded; and (c)
integrating the nanoscale or submicron powders in or on the plastic
by techniques such as spin coating, dip coating, spray coating, ion
beam coating, vapor deposition, mixing, laminating, extruding,
casting, molding, and sputtering.
[0085] Electroceramics, Batteries and Fuel Cells
[0086] Nanoparticles comprising zinc offer several unusual benefits
to electroceramic applications. These benefits are a consequence of
(a) the small size of nanoparticles which can enable very thin film
devices, (b) high surface area which can lower the sintering
temperatures and sintering times, and (c) unusual grain boundary
effects. These properties can be used to prepare electroceramic
devices such as voltage-surge protection and current-surge
protection components. Other nanodevices that can be prepared from
nanoscale powders comprising zinc include chemical sensors,
biomedical sensors, phosphors, and anti-static coatings.
[0087] Nanoparticles comprising zinc offer several benefits to
zinc-air battery and fuel cell applications. These benefits are a
consequence of (a) the small size of nanoparticles which can enable
very thin film devices, (b) high surface area which can lower the
forming temperatures and forming times, (c) unusual grain boundary
effects, and (d) higher surface area for superior electrochemical
kinetics. For these applications, nanoparticulate zinc dust can be
prepared by processes as described herein or oxides comprising zinc
can be reduced to prepare metallic nanoparticles comprising zinc.
In certain embodiments for battery and fuel cell applications, the
nanoparticles comprising zinc have a surface area greater than 1
m.sup.2/gm, in some embodiments greater than 5 m.sup.2/gm, and in
other embodiments greater than 20 m.sup.2/gm. These nanoparticles
can be used generally to prepare superior zinc-based batteries
and/or fuel cells. Of particular relevance to zinc comprising
nanoparticles are button type or miniature batteries used in
applications such as, but not limited to, hearing aids, special
effect glasses, etc.
[0088] Any method can be employed to utilize nanoparticles
comprising zinc in electroceramic devices taught herein. In one
embodiment, a method for employing zinc comprising nanoparticles in
miniature batteries comprises (a) preparing nanoscale or submicron
powders comprising zinc; (b) preparing an electrode from the
powders; and (c) integrating the electrode prepared from the
powders into a miniature battery.
[0089] Electrically Conductive Materials and Coatings
[0090] Electrical, television communication, and wireless products
create and emit electromagnetic radiation. These radiations can
affect the proper and safe operation of other devices. In some
circumstances, these electromagnetic radiation have been suggested
to cause adverse reactions to physiology. Technologies that can
provide shielding and protection from electromagnetic radiation are
sought.
[0091] It is known to those in the electromagnetic radiation
shielding art that conductive materials and coatings can provide
such a shielding and protection function. Novel conductive
materials and coatings are therefore desired by industry.
[0092] Similarly thin film heating elements such as those used in
car wind shields and side and rear windows/glass seek novel
conductive materials and coatings that are both transparent and
conductive.
[0093] Displays in products such as flat panel displays,
interactive kiosks, cellular phones, etc. use conductive films. The
applications seek novel conductive materials and coatings that are
both transparent and conductive.
[0094] Nanoparticles comprising two or more metals one of which is
zinc can be made conductive. Zinc oxide by itself is a
semiconducting substance. However, by doping zinc with an element
with a different oxidation state, in some embodiments a higher
oxidation state, conductive formulations can be achieved. Such a
doping creates lattice defects and associated free electrons for
electrical conductivity. The conductivity of the nanoparticles,
measured at 100 kgf compressive pressure, can be higher than
0.000001 mhos.cm, in certain embodiments greater than 0.0001
mhos.com, in other embodiments greater than 0.01 mhos.com, in some
embodiments greater than 1 mhos.cm, and in some embodiments greater
than 100 mhos.com. The conductivity can be improved by reduction
and by surface treatment.
[0095] In one embodiment, aluminum with oxidation state of 3 can be
doped into the lattice of zinc oxide nanoparticles (with zinc
oxidation state of 2) in concentrations between 0.1 atomic percent
to 7.5 atomic percent (other ranges can be employed in different
embodiments) to achieve conductivity that is over 10 times the
conductivity of 99.99 atomic percent pure zinc oxide nanoparticles,
in some embodiments over 1000 times the conductivity of 99.99
atomic percent pure zinc oxide nanoparticles, and in other
embodiments over 100,000 times the conductivity of 99.99 atomic
percent pure zinc oxide nanoparticles. Other non-limiting
illustrations of dopants that can be used to enhance electrical
conductivity in zinc oxide nanoparticles include B, Ga, In, Sn, Ti,
Zr, Hf, V, Nb, Ta, Cr, W, Mo, Mn, and rare earth elements.
[0096] In certain embodiments, a particle size distribution such
that the d.sub.95 of particle size distribution is less than 500 nm
is used, in other embodiments this is less than 100 nm. Once such
multi-metal oxide nanoscale powder comprising Zn is available, it
can be utilized to shield electromagnetic radiation. This powder
can be mixed into products or applied as coatings by techniques
such as spin coating, dip coating, casting, screen printing, and
other known deposition techniques. If desired, the coatings can
then be dried and/or calcined and/or sintered to achieve the best
combination of structural, optical, thermal, electrical, magnetic,
electrochemical, and other properties. It is recommended that such
post processing be optimized to achieve or limit grain growth of
the nanoparticles.
[0097] One of the unusual and surprising properties of doped zinc
oxide nanoparticles, particularly with d.sub.99 g of 400 nm, and in
other embodiments 200 nm, is that they offer conductivity and
optical transparency with minimal haze. Furthermore, these
formulations do not create an undesirable blue tinge that distorts
color. This makes these materials suitable for preparing conductive
and transparent coatings and films. Such a combination of
conductive and transparent characteristics can be applied in
heating films in automobile wind shields, defogging systems and/or
deicing windows and mirrors, micro-displays, displays, device
electrodes, solar cells and energy conversion devices,
electrochromic systems, consumer advertising, product display
cases, sensors, aircraft instruments and glasses, telescopes,
microscopes, surgical visualization products, etc. Similarly, these
conductive and transparent compositions can be applied to enhance
electromagnetic shielding from products such as cathode ray tubes,
electron beam activated or phosphor comprising products, to meet
electromagnetic radiation emission requirements, and to meet
electromagnetic radiation robustness requirements in consumer,
scientific, or military products.
[0098] While the above discussion is presented in context of
nanoparticles comprising two or more metals one of which is zinc, a
more broader concept may be utilized to prepare conductive
materials. Generally, any semiconducting nanoparticle can be doped
to enhance electrical conductivity. More specifically, by doping a
metal oxide, wherein the metal has a given oxidation state, with an
element with different oxidation state, in certain embodiments
higher oxidation state, conductive formulations can be achieved.
Such a doping creates lattice defects and associated free electrons
for electrical conductivity. For example, a metal with oxidation
state of 3 can be doped into the lattice of metal oxide
nanoparticles wherein the metal has an oxidation state of 2, where
the doped metal is in concentrations between 0.1 atomic percent to
20 atomic percent thereby enhancing the conductivity over the
conductivity of pure metal oxide. As another example, a metal with
oxidation state of 4 can be doped into the lattice of a metal oxide
nanoparticles wherein the metal has an oxidation state of 3, where
the doped metal is in concentrations between 0.1 atomic percent to
20 atomic percent thereby enhancing the conductivity over the
conductivity of pure metal oxide. In yet another example, a metal
with oxidation state of 3 can be doped into the lattice of a metal
oxide nanoparticles wherein the metal has an oxidation state of 1,
where the doped metal is in concentrations between 0.1 atomic
percent to 20 atomic percent thereby enhancing the conductivity
over the conductivity of pure metal oxide. In another example, a
metal with oxidation state of 1 can be doped into the lattice of a
metal oxide nanoparticles wherein the metal has an oxidation state
of 2, where the doped metal is in concentrations between 0.1 atomic
percent to 20 atomic percent thereby modifying the conductivity
over the conductivity of pure metal oxide. More than one dopant
where the said dopants either have the same or different oxidation
states between each other may be employed and the concentrations of
the dopant can be different than the ranges suggested above.
Additionally, the nanoparticles may be reduced (with hydrogen or
carbon monoxide or ammonia etc) to modify the electrical properties
of the nanoparticles. The applications taught herein for zinc
containing conductive materials can be used for these materials as
well.
[0099] In one embodiment, a method for shielding electromagetic
radiation comprises (a) preparing nanoscale powders comprising two
or more metals one of which is zinc by any process, such as a
process taught herein; (b) providing a surface; (c) applying the
nanoscale powders over the surface by techniques such as spin
coating, dip coating, spraying, screen printing, casting and/or
other deposition methods; and (d) processing the nanoscale powders
by techniques such as drying, setting, calcining and/or sintering.
In yet another embodiment, the zinc 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, glasses or polymers may be mixed with nanoscale powders
before preparing a useful shielding product.
[0100] In one embodiment, a method for preparing transparent
electrically conductive coatings or layers comprises (a) preparing
nanoscale powders comprising two or more metals one of which is
zinc by any process, such as a process taught herein; (b) providing
a surface or substrate; (c) applying the nanoscale powders over the
surface by techniques such as spin coating, dip coating, spraying,
screen printing, casting, and/or other deposition methods; and (d)
processing the nanoscale powders by techniques such as drying,
setting, calcining, and/or sintering. In yet another embodiment,
the zinc containing nanoscale or submicron powders are pretreated
to coat the powder surface for ease in dispersability and to ensure
homogeneity. In a further embodiment, glass or polymers may be
mixed with nanoscale powders before preparing useful coatings or
products.
[0101] In another embodiment, a method for preparing an electrode
film comprises (a) preparing nanoscale powders comprising two or
more metals one of which is zinc by any process, such as a process
taught herein; (b) providing a surface or substrate; (c) applying
the nanoscale powders over the surface by techniques such as spin
coating, dip coating, spraying, screen printing, casting, and/or
other deposition methods; and (d) processing the nanoscale powders
by techniques such as drying, setting, calcining, and/or sintering.
In yet another embodiment, the zinc 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, glass or polymers or additives or metals or
combinations may be mixed with nanoscale powders before preparing
the electrodes.
[0102] Conductive nanoparticles can also be utilized to provide
conductive surfaces that resist dust collection. Many surfaces
become unclean because they develop static charge over time for
reasons such as natural air flow, dust collision, electron
radiation, rubbing, etc. The static on the surface attracts dust of
opposite charge thereby causing the dust to stick to the surface.
By providing a conductive surface, in certain embodiments a
transparent conductive surface, the surface charge can be
dissipated and therefore the attractive forces between the surface
and the dust in air can be reduced. If the attractive forces become
too low, gravity and natural Brownian motion can help achieve a
surface that reduces dust build up over time and thereby keeping
surfaces clean longer. Such self clean preserving surfaces are
desirable in product display cases in retails, for automotive
windows and wind shields, aircraft parts, electronic and telecom
displays, computer displays, micro-displays, watches, plastic
products, glass products, ceramic products, bottles, jewelry,
mirrors, glass windows, instruments, biomedical devices, clean
rooms, etc.
[0103] In additional embodiments, conductive nanoparticles that are
also UV absorbent could be used to provide multi-functional
pigments--i.e., pigments that provide UV protection, that are
transparent, and that are conductive enough to reduce dust build
up. In one embodiment, such a nanoparticle pigment is aluminum
doped zinc oxide, wherein aluminum concentration is less than 10
atomic percent by metal basis.
[0104] In other embodiments, nanoparticles comprising zinc
compounds when incorporated in coatings can provide sustained
deodorant, sanitizer, disinfectant, fungicide, virucide, and
mildewstat functions. These functions can be particularly useful in
ceilings, walls, floors, windows, carpets, furnitures, sanitary
products, and other similar consumer products.
[0105] Catalysts
[0106] Zinc containing nanoparticles can serve as excellent
catalysts for a number of chemical reactions. For example, they can
be used in methanol synthesis or in processes aiming to convert
alcohols to hydrogen at low temperatures using nanoparticles
comprising zinc. In one embodiment, a method for producing more
desirable or valuable substances from less desirable or valuable
substances comprises (a) preparing nanoscale multi-metal powders
comprising zinc by any method, such as the method taught herein,
such that the surface area of the said powder is greater than 25
square meter per gram, in some embodiments greater than 75 square
meter per gram, and in some embodiments greater than 150 square
meter per gram; and (b) reducing the powder in a reducing
environment (or activating the powder in any other way) and then
conducting a chemical reaction over the said nanoscale powders
comprising doped or undoped zinc metals. In some embodiments, a
further step of dispersing the nanoscale powders in a solvent and
then depositing these powders onto a substrate from the dispersion
may be employed before chemical reactions are conducted.
[0107] The catalyst powders described above can be combined with
zeolites and other well defined porous materials to enhance the
selectivity and yields of useful chemical reactions.
[0108] Optics and Phosphors
[0109] Non-stoichiometric nanoparticles comprising zinc offer
several unusual benefits as phosphors and for detector
applications. These benefits are a consequence of one or more of
the following characteristics (a) small size, (b) high surface
area, (c) dispersability in various media, inks, and solid
matrices, (e) unusual and complex combinations of density, vapor
pressures, work functions, and band gaps. The advantages of
phosphors and detectors comprising zinc-containing nanoparticles
are (a) high dots per inch density, (b) ability to form homogeneous
products, and (c) the ability to prepare very thin films thereby
reducing the raw material required for same or superior
performance. Nanoparticles can also be post-processed (calcination,
sintering) to grow the grain to the optimal size in order to
provide the brightness level, decay time and other characteristics
as desired.
[0110] Multi-metal compositions (two, three, four, or more metals)
comprising zinc are used in certain embodiments. These phosphor
nanopowders can be used for display applications, lamps,
fluorescent bulbs, light emitting devices, markers, security
pigments, fabric pigments, paints, toys, special effects, etc.
[0111] Biomedical Applications and Dental Cements
[0112] Nanoparticles comprising zinc offer several benefits in
health care and biomedical applications. Zinc is one of the
essential elements for plants and animals. In humans, zinc is the
most prevalent micronutrient next to iron. Zinc oxide nanoparticles
of pharmaceutical purity when used in current formulations can
enable faster assimilation and improved assimilation. This benefit
is a consequence of one or more of the following characteristics
(a) small size, (b) high surface area, and (c) dispersability in
various media. Similarly, zinc comprising nanoparticles can serve
as nutrients for plants, agriculture, flowers, and pets. Other uses
of zinc oxide nanoparticles include dental cement wherein the
nanoscale can enhance the functionality of zinc oxide in the
cement.
[0113] Quality wound healing formulations, creams, lotions, and
sprays can be prepared from nanoscale powders of zinc oxides and
zinc compounds. The role of zinc oxide has been described by Argen
et al. (EWMA Journal, vol 1, number 1, pages 15-17 (2001)) which
along with references cited therein is hereby incorporated by
reference in full. The Argen et al. study and current commercial
products, such as diaper rash soothing creams and anti-itch creams,
incorporate coarse zinc oxide powders. The benefit of nanoscale
powders taught herein and produced by methods, such as the methods
taught herein, can yield superior wound management, diaper rash
soothing creams, anti-itch creams, and other such products. The
superior performance of nanoscale powders comprising zinc is a
consequence of one or more of the following characteristics (a)
small size that can better reach finer and deeper into
pores/cuts/rash and thereby provide a reservoir of zinc, (b) high
surface area that can enhance the dissolution rate and
pharmokinetic processes, (c) homogeneous distribution of the
particles per unit amount applied which means more effective
application and superior Fick's diffusion, (d) the mild
anti-bacterial, anti-inflammatory, anti-microbials and
cytoprotective activity, and (e) dispersability in various media
for more uniform and sustained release.
[0114] In one embodiment, an anti-inflammatory cream, lotion,
stick, spray, bandage, product is prepared and used as follows: (a)
prepare nanoscale or submicron oxide powders comprising zinc in a
process, such as a process taught herein; (b) provide a medium,
such as a cream, base, wax, spray, or solution; (c) disperse the
nanoscale or submicron powders into the medium; and (d) apply the
medium over the surface that can benefit from inflammatory
protection. In one embodiment, this method can be used in existing
anti-inflammatory products or personal care products. Like
anti-inflammatory products in the embodiment above, superior
products incorporating nanoparticles comprising zinc oxide can be
prepared for the care of burns, blisters, gum disease, sunburn, and
insect bites. Similarly, superior products incorporating
nanoparticles comprising zinc oxide can be prepared for healing of
wounds, such as cuts, skin irritations, abrasions, burns, sores,
and the healing of wounds that result from surgical incisions.
[0115] Nanoparticles of zinc oxide can also be included in the
liner of bandages, flexible cloths, and pads to enhance the
usefulness of these products. In one embodiment, a bandage or
personal care product is prepared and used to provide faster
healing as follows: (a) prepare nanoscale or submicron powders
comprising zinc in a process, such as a process taught herein; (b)
provide a bandage or personal care product; (c) disperse the
nanoscale or submicron powders onto or into the bandage or personal
care product; and (d) apply the bandage or personal care product
over the surface that needs to be healed. Alternatively,
nanoparticles comprising zinc can be coated, bonded, or trapped
into textiles or on the surface of textiles to provide sustained
protection or to prepare products for those with chronic tissue
damage. Combined with other nanoparticles such as those taught
herein (astringent, deodorant, etc.), multi-functional textiles and
wound care products can be prepared.
[0116] The above embodiments for various products can be applied
alone or in combination with other functional additives such as
deodorants, nutrients, lubricants, analgesics, anti-microbials,
pigments, perfumes, etc.
[0117] Reagent and Raw Material for Synthesis
[0118] Nanoparticles of zinc oxide and zinc containing multi-metal
oxide nanoparticles are useful reagents and precursors to prepare
other compositions of nanoparticles comprising zinc. In a generic
sense, nanoparticles comprising zinc are reacted with another
substance such as, but not limited to, an acid, alkali, organic,
monomer, ammonia, halogens, phosphorus compounds, chalcogenides,
biological materials, gas, vapor or solvent; the high surface area
of nanoparticles facilitates the reaction and the product resulting
from this reaction is also nanoparticles. These product
nanoparticles can then be suitably applied or utilized to catalyze
or as reagents to prepare other fine chemicals for a wide range of
applications. A few non-limiting illustrations utilizing zinc
comprising nanoparticles follow. These teachings can be extended to
multi-metal oxides and to other compositions such as zinc acetate
and organometallics based on zinc. In certain embodiments, the
nanoparticles may be treated or functionalized or activated under
various temperatures, pressure, charge or environment composition
before use.
[0119] Zinc Fluoride: Zinc oxide nanoparticles are reacted with
aqueous hydrofluoric acid to produce nanoparticles of
ZnF.sub.2.4H.sub.2O. If desired, the water of crystallization can
be driven off by heating the nanocrystals in a vacuum or ambient
pressures or higher pressures at temperatures such as 400 K, 800 K,
1200 K, etc. Zinc fluoride nanoparticles are commercially valuable
in glasses with high refractive index, glazes and enamels for
porcelain, as an additive to electrolytic galvanizing baths,
fluorinating agent in organic synthesis, and as a flux in welding
and soldering particularly in micro-welding or micro-soldering. In
some applications, such as conductive coating, nanoparticles of
partially fluorinated zinc oxide (e.g. ZnO.F) may be desirable.
These can be prepared by treating zinc oxide nanoparticles with
hydrofluoric vapors or through controlled reaction of zinc oxide
with HF in solution. In one embodiment, a method for producing
nanoparticles comprising zinc and fluorine comprises (a) preparing
nanoscale powders comprising zinc by any method, such as a method
herein; (b) reacting the nanoscale powders with a fluid comprising
hydrogen fluoride; and (c) collecting resultant nanoparticles
comprising zinc and fluorine. In another embodiment, a method for
applying nanoparticles comprising zinc and fluorine is a high
refractive index glass prepared from nanoparticles of zinc
fluoride; more specifically, a high refractive index glass
comprising (a) preparing nanoscale powders comprising zinc and
fluorine by any method, such as a method taught herein; and (b)
utilizing the nanoscale powders to prepare glass with high
refractive index.
[0120] Zinc Chloride: Zinc metal nanoparticles or zinc oxide
nanoparticles are reacted with fluid comprising hydrochloric acid
to produce nanoparticles of ZnCl.sub.2. It is important to note
that zinc chloride is strongly hygroscopic and results in very high
heat evolution when water vapor combines with zinc chloride.
Solvents such as alcohol, ether, acetone, glycerine, amines, and
acetates may be used to provide better reaction control given the
solubility of zinc chloride in these solvents. Zinc chloride
nanoparticles are commercially valuable as organic condensation
reaction catalysts, catalysts to prepare chloroalkanes,
chloroaromatics and thiocarbamates, hydrolysis catalysts, and other
catalysts. Zinc chloride nanoparticles can be used to prepare
superior emulsion breakers in petrochemical processes and waste
spills, deodorizing agent, zinc soaps, and filling materials for
batteries. Additionally, zinc chloride nanoparticles can be used as
reagents to prepare useful chemicals such as zinc cyanide and
aquoacids. A non-limiting synthesis embodiment for a method for
producing nanoparticles comprising zinc and chlorine comprises (a)
preparing nanoscale powders comprising zinc by any method, such a
method taught herein; (b) reacting the nanoscale powders with a
fluid comprising hydrogen chloride; and (c) collecting resultant
nanoparticles comprising zinc and chlorine. In one embodiment, a
method for applying nanoparticles comprising zinc and chlorine is a
battery filling material prepared from nanoparticles of zinc
chloride; more specifically, a battery comprising nanoparticles of
zinc chloride.
[0121] Zinc Bromide: Zinc metal nanoparticles or zinc oxide
nanoparticles are reacted with fluid comprising hydrobromic acid to
produce nanoparticles of ZnBr.sub.2. Zinc bromide nanoparticles are
also strongly hygroscopic like zinc chloride. Anhydrous zinc
bromide nanoparticles can be formed by thermal treatments in a
suitable environment such as dry CO.sub.2, at temperatures such as
between 500 K-1000 K. Zinc bromide nanoparticles can be used to
prepare superior electrolytes for zinc bromide batteries, as a mild
Lewis acid for alkylation reactions, a catalyst, production of
porous or activated materials such as carbon, and in photographic
materials. In one embodiment, a method for producing nanoparticles
comprising zinc and bromine comprises (a) preparing nanoscale
powders comprising zinc by any method, such as the method taught
herein; (b) reacting the nanoscale powders with a fluid comprising
hydrogen bromide; and (c) collecting resultant nanoparticles
comprising zinc and bromine. In one embodiment applying these
nanoparticles, a method for applying nanoparticles comprising zinc
and bromine is a battery electrolyte prepared from nanoparticles of
zinc bromide; more specifically, a battery comprising nanoparticles
of zinc bromide.
[0122] Zinc Iodide: Zinc metal nanoparticles directly or zinc oxide
nanoparticles in presence of catalyst, such as precipitated silver,
are reacted with fluid comprising aqueous hydroiodic acid to
produce nanoparticles of ZnI.sub.2. Zinc iodide nanoparticles are
also hygroscopic like zinc chloride. Zinc iodide nanoparticles can
be used as a superior topical antiseptic astringent. The advantage
of nanoparticles is their small size (which is less than the skin
pores size and the pore size of undesirable and harmful
microorganisms) which means lesser quantities may provide
sufficient yet complete, faster, superior and homogeneous
application near target areas.
[0123] In one embodiment, the present invention provides an
antiseptic prepared with nanoparticles comprising a halide such as
iodine. More specifically, a method for applying nanoparticles
comprising zinc and iodine is an antiseptic astringent comprising
nanoparticles of zinc iodide.
[0124] Zinc Sulfate: Zinc metal nanoparticles directly or zinc
oxide nanoparticles are reacted with fluid comprising sulfuric acid
to produce nanoparticles of hydrated ZnSO.sub.4. Anhydrous zinc
sulfate nanoparticles can be prepared by heat treating hydrated
zinc sulfate usually below 400 K or with dehydrating the crystals
with alcohols. Zinc sulfate nanoparticles offer higher surface
areas, faster dissolution, and small size (which means that they
can reach smaller target areas). Zinc sulfate nanoparticles can be
used as a superior water treatment chemical, an electrolyte in
galvanizing baths, a zinc nutrient source for plants and animals, a
wood preservative, a flocculent, and as an additive in paper
bleaching. Zinc sulfate nanoparticles are also excellent raw
materials for the manufacture of nanoparticles or coarser forms of
zinc soaps, zinc phosphides, zinc cyanamide, lithopone pigment,
zinc sulfide pigment, antidandruff agents, such as zinc pyrithione,
and zinc-based fungicides.
[0125] Another application of zinc sulfate nanoparticles is as an
emetic, astringent, and disinfectant. The advantage of
nanoparticles is their small size (which is less than the skin pore
size and the pore size of undesirable and harmful microorganisms)
which means lesser quantities may provide sufficient yet complete,
faster, superior, and homogeneous application near target areas.
Zinc sulfate nanoparticles may be dispersed in glycerine or other
solvents for ease of application.
[0126] In one embodiment, a disinfectant prepared with
nanoparticles comprising a sulfur or halide is provided. More
specifically, a method for applying nanoparticles comprising zinc
sulfate is a disinfectant comprising nanoparticles of zinc
sulfate.
EXAMPLES 1-2
Zinc Oxide Powders
[0127] 99 weight % by metal pure zinc ethylhexanoate precursor was
diluted with hexane until the viscosity of the precursor was less
than 100 cP. This mix was sprayed into a thermal plasma reactor
described above at a rate of about 50 ml/min using about 50
standard liters per minute oxygen. The peak temperature in the
thermal plasma reactor was above 3000 K. The vapor was cooled to
nucleate nanoparticles and then quenched by Joule-Thompson
expansion. The powders collected were analyzed using X-ray
diffraction (Warren-Averbach analysis) and BET. It was discovered
that the powders had a crystallite size of less than 50 nm and a
specific surface area of about 10 m.sup.2/gm.
[0128] Next, in a separate run with the same process, the mix was
sprayed at a rate of about 50 ml/min using about 65 standard liters
per minute oxygen. The peak temperature in the thermal plasma
reactor 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. It was
discovered that the powders had a crystallite size of about 35 nm
and a specific surface area of about 14 m.sup.2/gm.
[0129] These examples show that nanoparticles comprising zinc can
be prepared and that the characteristics of zinc oxide powder can
be varied with process variations.
EXAMPLES 3
Nickel Zinc Ferrite Powders
[0130] A mixture of nickel, zinc, and iron organometallic
(octoates, 1:1:2::Ni:Zn:Fe ratios) precursor was prepared. Using
the process of Example 1, the mixture was processed at a peak
temperature exceeding 2000 K, and the powder was collected. The
powders were characterized using X-ray diffractometer and 10 point
BET surface area analyzer. The powders were found to be nickel zinc
ferrite nanoparticles. No independent peaks of zinc, nickel, or
iron oxide were observed suggesting lattice level mixing of atoms.
The powders were of a brown color, and had a mean crystallite size
less than 15 nanometers and a surface area greater than 40
m.sup.2/gm. The powders were found to be magnetic.
[0131] This example shows that color pigment nanoparticles can be
prepared from zinc and that complex three metal oxide nanoparticles
can be produced.
EXAMPLE 4
Aluminum doped Zinc Oxide Powders
[0132] A mixture of aluminum and zinc organometallic precursors
were prepared. The ratio was adjusted between the two metal
precursors to achieve 1.5 wt % aluminum oxide and 98.5 wt % zinc
oxide. Using the process of Example 1, the mixture was processed at
a peak temperature exceeding 2000 K, and the powder was collected.
The powders were characterized using X-ray diffractometer and 10
point BET surface area analyzer. The powders were found to be doped
zinc oxide nanoparticles. No independent peaks of zinc or aluminum
oxide were observed suggesting lattice level mixing of atoms. The
powders had a mean crystallite size of about 25 nanometers and a
surface area of about 20 m.sup.2/gm. Electrical conductivity of
zinc oxide from Example 1 and aluminum-doped zinc oxide from this
example were measured. It was discovered that the doped zinc oxide
was over 10 times more conductive than the pure zinc oxide
nanopowder.
[0133] This example shows that electrically conductive
nanoparticles can be prepared from zinc and that doped zinc oxides
offer unusual and surprising properties.
EXAMPLE 5
Bismuth and Cobalt Doped Zinc Oxide
[0134] A mixture of bismuth, cobalt and zinc, organometallic
precursors were prepared. Using the process of Example 1, the
mixture was processed at a peak temperature exceeding 2000 K, and
the powder was collected. The powders were characterized using
X-ray diffractometer and 10 point BET surface area analyzer. The
powders were found to be doped zinc oxide nanoparticles. The
powders had a mean crystallite size of less than 100 nanometers and
a surface area greater than 5 m.sup.2/gm.
EXAMPLES 6-7
Zinc Oxide Nanoparticles as Reagent
[0135] Zinc oxide nanoparticles from Example 2 were added to
2-ethyl hexanoic acid (2-EH) distributed by Ashland Chemicals in
1:2 molar ratio respectively. The mixture was stirred using a
magnetic stirrer and warmed to 70.degree. C. It was observed that
the zinc oxide nanoparticles vigorously reacted with 2-EH and
formed a composition different than either ZnO or 2-EH.
[0136] Zinc oxide nanoparticles prepared in Example 2 were reduced
in a mixture of 5% hydrogen in argon by passing the reducing gas in
a tubular reactor maintained at various temperatures. It was
observed that zinc oxide can be converted to zinc dust at
temperatures above 400.degree. C. These example illustrates the
beneficial aspects of zinc oxide nanoparticles as a reagent.
[0137] 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.
* * * * *