U.S. patent application number 11/462729 was filed with the patent office on 2010-10-21 for synthesis of nickel nanopowders.
This patent application is currently assigned to Ferro Corporation. Invention is credited to Xiangdong Feng, Yang Xiang, Yi Yang.
Application Number | 20100263486 11/462729 |
Document ID | / |
Family ID | 39402314 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100263486 |
Kind Code |
A1 |
Yang; Yi ; et al. |
October 21, 2010 |
SYNTHESIS OF NICKEL NANOPOWDERS
Abstract
The invention relates to a method of making a nickel powder
having an average particle size of less than about 100 nanometers,
comprising contacting, at a temperature of about 50.degree. C. to
about 95.degree. C., a reduction solution with a nickel solution to
form a reaction mixture. The reduction solution comprises a base
and a reducing agent. The nickel solution comprises a nickel
compound water, a nucleation agent, a surfactant or dispersant, and
combinations thereof. The yield of nickel nanoparticles is greater
than about 90% relative to starting moles of nickel compound. The
nickel powder is suitable for use in electronics applications and
sintered metal applications.
Inventors: |
Yang; Yi; (Broadview
Heights, OH) ; Feng; Xiangdong; (Upland, CA) ;
Xiang; Yang; (Garfield Heights, OH) |
Correspondence
Address: |
RANKIN, HILL & CLARK LLP
23755 Lorain Road - Suite 200
North Olmsted
OH
44070-2224
US
|
Assignee: |
Ferro Corporation
Cleveland
OH
|
Family ID: |
39402314 |
Appl. No.: |
11/462729 |
Filed: |
August 7, 2006 |
Current U.S.
Class: |
75/374 |
Current CPC
Class: |
B22F 2998/00 20130101;
C22B 23/0461 20130101; C22B 5/00 20130101; B22F 9/24 20130101; B22F
1/0018 20130101; B22F 2998/00 20130101 |
Class at
Publication: |
75/374 |
International
Class: |
B22F 9/24 20060101
B22F009/24 |
Claims
1. A method of making a nickel powder having an average particle
size of less than 100 nanometers, comprising contacting, at a
temperature of about 50.degree. C. to about 95.degree. C., a
reduction solution with a nickel solution to form a reaction
mixture and initiate a reaction, a. wherein the reduction solution
comprises i. a base providing OH ions, and ii. a reducing agent
selected from the group consisting of hydrazine, sodium
borohydride, potassium borohydride, lithium aluminum hydride, b.
wherein the nickel solution excludes alcohol and glycol and
comprises i. water, ii. a nucleation agent, iii. a surfactant
selected from the group consisting of PAAm (polyacrylamide),
C.sub.16H.sub.33(OCH.sub.2CH.sub.2).sub.10OH (Brij 56), and gum
arabic, iv. a nickel compound selected from the group consisting of
nickel acetate, nickel chloride, nickel sulfate, and nickel
acetylacetonate said nickel compound providing nickel ions to the
nickel solution at a concentration of from 0.5 to 1.5 M, c. wherein
the mole ratio of OH ions to nickel ions is 1:1 to 2.5:1, d.
wherein the mole ratio of reducing agent to nickel ions is from
1.5:1 to 8:1, and e. wherein the reaction runs to completion in no
greater than 30 minutes.
2-8. (canceled)
9. The method of claim 1 wherein the base is selected from the
group consisting of KOH, NaOH, Na.sub.2CO.sub.3, NaHCO.sub.3, and
NH.sub.4OH, and combinations thereof.
10. The method of claim 1 wherein the nickel solution further
comprises a nucleation agent selected from the group consisting of
PdCl.sub.2, AgNO.sub.3, and K.sub.2PtCl.sub.4 such that the mole
ratio of nucleation agent to nickel is about 1:10000 to about
1:100.
11. The method of claim 1 wherein the average particle size does
not exceed about 70 nm, wherein the temperature is about 60.degree.
C. to about 90.degree. C., wherein the nickel compound is nickel
acetate or nickel sulfate or nickel chloride, and wherein the mole
ratio of nucleation agent to nickel is about 1:2000 to about
1:100.
12-21. (canceled)
22. The method of claim 1, wherein the mole ratio of OH ions to
nickel ions is from 1.5:1 to 2:1.
23. The method of claim 1, wherein the mole ratio of reducing agent
to nickel ions is from 2:1 to 7:1.
24. The method of claim 1, wherein the mole ratio of reducing agent
to nickel ions is from 3:1 to 6:1.
25. The method of claim 23, wherein the mole ratio of OH ions to
nickel ions is from 1.5:1 to 2:1.
26. The method of claim 24, wherein the mole ratio of OH ions to
nickel ions is from 1.5:1 to 2:1.
27. The method of claim 1, wherein the yield of nickel powder is
greater than 95% relative to starting moles of nickel.
28. The method of claim 1, wherein the nickel powder having an
average particle size of less than 70 nanometers
29. The method of claim 1, wherein the nickel compound provides
nickel ions to the nickel solution at a concentration of from 0.606
to 1.5 M.
30. The method of claim 1, wherein the nickel compound provides
nickel ions to the nickel solution at a concentration of from 0.67
to 1.5 M.
31. The method of claim 1, wherein the nickel compound provides
nickel ions to the nickel solution at a concentration of from 1 to
1.5 M.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention relates to a process of producing nanoscale
nickel powders.
[0003] 2. Description of Related Art
[0004] In order to achieve high yields, prior art methods of making
nanometer scale ("nanoscale") nickel powders involved starting
reagents in extremely low concentrations (0.1 M or less). Prior art
methods beginning with reactants in higher concentrations often
resulted in low yields. Given that high yields of relatively
uniform particles was the goal, reaction of starting materials in
low concentrations required long reaction times and/or large
reaction volumes, which in turn resulted in large waste streams of
solvents such as water, alcohols, or other organic solvents, all of
which added expense and complexity to the production process.
[0005] Accordingly, it would be advantageous to produce nanoscale
nickel particles (averaging less than about 100 nm in diameter) in
relatively high concentration (initial nickel concentration up to 3
M) and in high yield (over 90% relative to starting moles of nickel
source.)
BRIEF SUMMARY OF THE INVENTION
[0006] The invention relates to a method of making a nickel powder
having an average panicle size of less than about 100 nanometers,
comprising contacting, at a temperature of about 50.degree. C. to
about 95.degree. C., a reduction solution with a nickel solution to
form a reaction mixture. The reduction solution comprises a base
providing OH ions, and a reducing agent such as hydrazine, sodium
borohydride, potassium borohydride, and lithium aluminum hydride.
The nickel solution comprises water, a nucleation agent, a
surfactant or dispersant, or combinations thereof, and a nickel
compound selected from the group consisting of nickel acetate,
nickel chloride, nickel sulfate, and nickel acetylacetonate. In
certain embodiments, the solvent in the nickel solution may be
water alone, devoid of other solvents. The nickel solution may
alternatively comprise absolute alcohol as a solvent, and be devoid
of water. Blends of water and one or more alcohols are also
suitable as solvents.
[0007] Another embodiment of the invention involves a method of
making a nickel powder having an average particle size of less than
about 100 nanometers, comprising contacting, at a temperature of
about 50.degree. C. to about 95.degree. C., a reduction solution
with a nickel solution to form a reaction mixture. The reduction
solution comprises a base providing OH ions, and a reducing agent
such as hydrazine, sodium borohydride, potassium borohydride, and
lithium aluminum hydride. The nickel solution excludes water and
comprises absolute alcohol, a surfactant or dispersant, a
nucleation agent, and a nickel compound such as nickel acetate,
nickel chloride, nickel sulfate, and nickel acetylacetonate, and
combinations thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0008] The invention involves a method of making a nickel powder
having an average particle size of less than about 100 nanometers,
comprising contacting, at a temperature of about 50.degree. C. to
about 95.degree. C., a reduction solution with a nickel solution to
form a reaction mixture, wherein the reduction solution comprises a
base providing OH ions, and a reducing agent selected from the
group consisting of hydrazine, sodium borohydride, potassium
borohydride, lithium aluminum hydride, and wherein the nickel
solution comprises water, a nucleation agent, a surfactant or
dispersant, or combinations thereof, and a nickel compound selected
from the group consisting of nickel acetate, nickel chloride,
nickel sulfate, and nickel acetylacetonate. The nickel solution may
alternatively comprise absolute alcohol as a solvent, and be devoid
of water.
[0009] Based on the reaction methods disclosed herein, the
resultant yield of nickel nanoparticles can exceed about 90%
relative to starting moles of nickel salt. Preferably the nickel
nanoparticle yield is greater than about 95% and more preferably
greater than about 99%. As stated, the inventive method involves a
reduction solution and a nickel solution. The details of each, as
well as reaction conditions, are set forth hereinbelow.
[0010] Reduction Solution: The reduction solution includes a
reducing agent and a base. The reducing agent donates electrons to
reduce Ni(II) to Ni(0). Useful reducing agents include hydrazine,
sodium borohydride, potassium borohydride, and lithium aluminum
hydride. When developing the reactions disclosed herein, the
inventors have discovered that a molar excess of reducing agent
relative to nickel is desirable. The reaction mixture
advantageously contains reducing agent and Ni ions in a molar ratio
of about 1.5:1 to about 8:1, preferably about 2:1 to about 7:1, and
more preferably about 3:1 to about 6:1.
[0011] The base may be any strong Bronsted base that provides OH
ions to the reaction mixture and may include one or more of the
following: KOH, NaOH, Na.sub.2CO.sub.3, NaHCO.sub.3, and
NH.sub.4OH. Combinations of such bases may also be used, and other
Bronsted bases known in the art may be used. The concentration of
the base in the reduction solution is typically in the range of
about 4 M to about 10 M, preferably about 4 M to about 8 M. The
concentration of base is provided such that the reaction mixture
contains OH ions and Ni ions in a molar ratio of about 1 to about
3, preferably about 1.5 to about 2.
[0012] Nickel solution. The nickel solution comprises a nickel
compound in a concentration of about 0.1 to about 3 M, preferably
about 0.4 to about 2 M, and more preferably about 0.5 to about 1.5
M. The nickel solution is typically aqueous, in order to solvate
Ni(II) ions from the nickel compound, which is usually an ionic
salt. The nickel compound may be selected from nickel acetate,
nickel chloride, nickel sulfate, and nickel acetylacetonate.
Preferably, the nickel compound is selected from nickel acetate,
nickel sulfate, or nickel chloride. More preferably, the nickel
compound is nickel acetate or nickel sulfate. The solvent may
alternatively comprise at least one alcohol or glycol in addition
to water. Finally, the solvent may comprise absolute alcohol, and
be devoid of water.
[0013] The nickel solution may alternatively comprise a slightly
soluble or insoluble nickel compound. In such case, the nickel
solution is more aptly termed a slurry. However, for the purposes
of the specification and claims herein, in the broadest sense, the
phrase "nickel solution" contemplates both a solution as
traditionally defined and a slurry.
[0014] Surfactant or Dispersant. The nickel solution typically
includes a surfactant or dispersant, or both. Commercially
available dispersants and surfactants sold by Noveon Performance
Coatings of Cleveland, Ohio under the Solsperse.RTM. trademark as
well as those sold by Sigma Aldrich of St. Louis, Mo., under the
Brij.RTM. trademark (e.g., Brij.RTM. 56 and Brij.RTM. 58) are
suitable. Generally, suitable surfactants and dispersants include
polyacrylamide, polyvinylpyrrolidone, polyacrylic acid, sodium
polyacrylate, polyethylene glycol, polyethyleneimine, sodium
dodecyl sulfate, stearic acid, ethoxylated ethers, ethoxylated
alkyl phenols, ethoxylated aryl phenols, ethoxylated sorbitan fatty
acid esters, polyoxyethylene sorbitan monolaurate, polyoxyethylene
sorbitan monopalmitate, polyoxyethylene sorbitan monostearate,
polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan
monooleate, polyoxyethylene sorbitan trioleate, gum arabic and
polyoxyethylene alcohols having a formula represented by
C.sub.mH.sub.2m+1(OCH.sub.2CH.sub.2).sub.nOH, where m is 8 to 18
and n is 10 to 100. Examples of the latter include Brij.RTM. 56
(where m is 16 and n is about 10) and Brij.RTM. 58 (where m is 16
and n is about 20). Polyacrylamide is preferred.
[0015] Nucleation agent. The nickel solution may include a
nucleation agent selected from the group consisting of PdCl.sub.2,
AgNO.sub.3, and K.sub.2PtCl.sub.4 such that the mole ratio of
nucleation agent to nickel is about 1:10000 to about 1:100.
Preferably, the mole ratio of nucleation agent to nickel is about
1:2000 to about 1:100, more preferably, about 1:1000 to about
1:200, still more preferably, about 1:500 to about 1:200.
[0016] Optional alcohol or glycol. Although the reduction reaction
disclosed herein may be conducted in aqueous solution absent
alcohol, solvent blends of alcohol and water are also envisioned.
Suitable alcohols include C.sub.1-C.sub.15 aliphatic alcohols,
C.sub.6-C.sub.30 aromatic alcohols, C.sub.2-C.sub.30 glycols, and
combinations thereof. For example, methanol, ethanol, isopropanol,
ethylene glycol, and propylene glycol, and combinations thereof are
suitable. When both water and alcohol are present in the nickel
solution, their volume ratio may be about 1:20 to about 20:1,
preferably about 1:10 to about 10:1, more preferably about 1:5 to
about 5:1.
[0017] Reaction. The reaction temperature is typically moderate,
under about 100.degree. C., preferably about 50.degree. C. to about
95.degree. C., more preferably about 60.degree. C. to about
90.degree. C. The overall reaction mixture may be formed by pouring
the reduction solution into a container already containing the
nickel salt solution. Alternatively, the reduction solution and
nickel salt solution may be added simultaneously to a reaction
vessel, such as by double-injection. The goal of the invention is
to produce nanoscale nickel metal particles having an average size
of less than about 100 nanometers. In certain embodiments, the
reactions disclosed herein can produce nickel particles having an
average size of less than about 70 nanometers, less than about 50
nanometers, and even less than about 30 nanometers.
[0018] The nickel nanoparticles made by the procedures detailed
herein are suitable for use in a variety of applications,
including, without limitation, catalysts, fuel cells, sintered
metal applications, and conductive pastes and inks for use in
electronics applications including multilayer ceramic chip (MLCC)
capacitors, radio frequency identification (RFID) devices,
integrated circuits, electrodes, and storage batteries.
EXAMPLES
[0019] The following examples are intended only to illustrate the
invention and should not be construed as imposing limitations upon
the claims.
Example 1
[0020] A reduction solution was prepared by dissolving 10.03 g of
85% potassium hydroxide into 24.51 g of 98% hydrazine monohydrate.
The solution, having a volume of 34 mL, was stirred for 20
minutes.
[0021] A nickel salt solution was prepared by dissolving 20.32 g of
98% nickel acetate tetrahydrate (Aldrich) and 0.94 g of 50%
polyacrylamide (PAAm, MW=10000, Aldrich) solution into 66 mL of a
mixed solvent of ethanol and water at a ratio of 30:70 (volume).
The nickel salt solution was stirred for 20 minutes.
[0022] The final reaction mixture (100 mL) was obtained by adding
the reduction solution quickly into the nickel salt solution in a
500 ml flask. The color of the solution turned from green into deep
blue immediately and the temperature rose from room temperature to
40.degree. C. The flask was immediately dipped into an 80.degree.
C. water bath. The solution finally turned to black, indicating
formation of nickel nanoparticles. After 30 minutes from the mixing
event of the two solutions, the reaction was stopped. Nickel
nanoparticles were subsequently filtered out, followed by washing
in turn with DI water, ethanol, and acetone. The product was dried
in nitrogen gas to obtain a powder. The average nickel particle
size was 92 nm as measured by transmission electron microscopy.
Examples 2-15
[0023] Further exemplary reaction mixtures were formulated
according to the ingredients and parameters set forth in Table 1
according to the procedures of Example 1 with a few exceptions.
While typically, the base was KOH and the surfactant was PAAm, in
Example 5, Brij 56 was used as the surfactant, and NaOH was the
base. In Example 8, NaOH was used as the base. In Example 13, the
surfactant was gum arabic. For those examples having a solution
volume other than 100 mL, the reduction solution and the nickel
salt solution were added to a 5 liter reaction vessel
simultaneously by double injection. In all examples where the mixed
EtOH/H.sub.2O solvent was used, the volume ratio was 3
EtOH:7H.sub.2O. EG is ethylene glycol. The particles were either
spherical or spiky as known in the art. The yield of nickel
relative to moles of starting nickel salt was calculated for two
examples: In Example 10, the yield was 99.75%; in Example 11, the
yield was 99.84%.
TABLE-US-00001 TABLE 1 Nickel Particle Formation Reaction
parameters are nickel particle properties. Surfactant
N.sub.2H.sub.4 Reaction Reaction Moles Pd/Ni (g) content KOH Temp
time TEM Solution ID Nickel Salt Nickel (mol %) (PAAm) (mol)
content (mol) Solvent (.degree. C.) (min) Shape (nm) volume (ml) 1
Ni(Ac).sub.2 0.08 0 0.94 0.48 0.152 EtOH + 80 30 spiky 92 100
H.sub.2O 2 Ni(Ac).sub.2 0.1 0.05 0.59 0.6 0.19 H.sub.2O 80 30 spiky
65 100 3 Ni(Ac).sub.2 0.1 0.2 3.17 0.6 0.19 H.sub.2O 80 30 spiky 42
100 4 Ni(Ac).sub.2 0.08 0.4 0.47 0.48 0.152 EtOH + 80 30 spiky 27
100 H.sub.2O 5 NiSO.sub.4 0.08 0.4 0.39 (Brij56) 0.24 0.16 (NaOH)
H.sub.2O 60 10 spherical 21 100 6 NiSO.sub.4 0.08 0.4 1.88 0.48
0.152 EtOH + 80 10 spherical 16 100 H2O 7 NiSO.sub.4 0.02 0 0 0.12
0.04 EG 60 28 spherical 9.9 100 8 NiSO.sub.4 0.8 0.4 18.79 1.6 1.6
(NaOH) H.sub.2O 80 10 spherical 16 950 9 NiSO.sub.4 0.8 0.4 46.97
2.4 1.2 H.sub.2O 60 12 spherical 23 930 10 NiSO.sub.4 0.8 0.4 46.98
2.4 1.52 H.sub.2O 60 7.5 spherical 19 950 11 NiSO.sub.4 0.8 0.4
46.98 1.6 1.52 H.sub.2O 60 7 spherical 27 950 12 NiSO.sub.4 0.8 0.1
46.97 2.4 1.52 H.sub.2O 60 9 spherical 36 950 13 NiSO.sub.4 0.8 0.3
4.7 (Gum Arabic) 4.8 1.52 H.sub.2O 80 11 spherical 25 1250
* * * * *