U.S. patent application number 12/081274 was filed with the patent office on 2009-01-29 for method for manufacturing nickel nanoparticles.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Joon-Rak Choi, Jae-Woo Joung, Kwi-Jong Lee, Young-Il Lee.
Application Number | 20090025510 12/081274 |
Document ID | / |
Family ID | 40294077 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090025510 |
Kind Code |
A1 |
Lee; Young-Il ; et
al. |
January 29, 2009 |
Method for manufacturing nickel nanoparticles
Abstract
The present invention relates to a method for manufacturing
nickel nanoparticles and more particularly to a method including
preparing a mixture solution by adding a reducing agent, a
dispersing agent and a nickel salt to a polyol; stirring and
heating the mixture solution; and producing nickel nanoparticles by
reacting the mixture solution, so that it allows mass production of
nickel nanoparticles having uniformity of size 30 to 50 nm and high
dispersibility.
Inventors: |
Lee; Young-Il; (Anyang-si,
KR) ; Joung; Jae-Woo; (Suwon-si, KR) ; Choi;
Joon-Rak; (Gyeyang-gu, KR) ; Lee; Kwi-Jong;
(Hwaseong-si, KR) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
|
Family ID: |
40294077 |
Appl. No.: |
12/081274 |
Filed: |
April 14, 2008 |
Current U.S.
Class: |
75/374 |
Current CPC
Class: |
B22F 9/24 20130101 |
Class at
Publication: |
75/374 |
International
Class: |
B22F 9/16 20060101
B22F009/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 23, 2007 |
KR |
10-2007-0073598 |
Claims
1. A method for manufacturing nickel nanoparticles, comprising:
preparing a mixture solution by adding a reducing agent, a
dispersing agent and a nickel salt to a polyol; stirring and
heating the mixture solution; and producing nickel nanoparticles by
reacting the mixture solution.
2. The method of claim 1, wherein the reducing agent is at least
one selected from the group consisting of sodium hypophosphite
(NaH.sub.2PO.sub.2), hydrazine (N.sub.2H.sub.4), hydrochloride,
sodium borohydride (NaBH.sub.4), and sodium
hydroxymethylsulfoxylate
(NaHSO.sub.2.largecircle.CH.sub.2O.largecircle.H.sub.2O).
3. The method of claim 1, wherein the dispersing agent is at least
one selected from the group consisting of a cationic surfactant, an
anionic surfactant, an analogue of cellulose, a polymer, a
copolymer and a terpolymer.
4. The method of claim 1, wherein the dispersing agent is at least
one selected from the group consisting of cetyltrimethylammonium
bromide (CTAB), sodium dodecyl sulfate (SDS), sodium carboxymethyl
cellulose (Na-CMC), polyvinylpyrrolidone (PVP),
vinylpyrrolidone/vinylacetate (PVP/VA), and
vinylcaprolactam/vinylpyrrolidone/propylmethacylamide.
5. The method of claim 1, wherein the nickel salt is added in a
concentration of 0.001 to 1M with respect to the mixture
solution.
6. The method of claim 1, wherein the reducing agent is added in a
mole ratio of 2 to 10 with respect to the nickel salt.
7. The method of claim 1, wherein the dispersing agent is added in
a mole ratio of 1 to 20 with respect to the nickel salt.
8. The method of claim 1, wherein the nickel salt is at least one
selected from the group consisting of NiCl.sub.2,
Ni(NO.sub.3).sub.2, NiSO.sub.4 and (CH.sub.3COO).sub.2Ni.
9. The method of claim 1, wherein the polyol is at least one
selected from the group consisting of ethylene glycol, diethylene
glycol, triethylene glycol, and polyethylene glycol.
10. The method of claim 1, wherein the mixture solution is heated
to 80 to 160.degree. C.
11. The method of claim 1, further comprising washing, isolating,
and drying the produced nickel nanoparticles.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 10-2007-0073598 filed on Jul. 23, 2007, with the
Korea Intellectual Property Office, the contents of which are
incorporated here by reference in their entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention related to a method for manufacturing
nickel nanoparticles and more particularly, to a method for
manufacturing nickel nanoparticles having uniform size and high
dispersibility.
[0004] 2. Description of the Related Art
[0005] In response to demands for much smaller electronic
components, the multi layer ceramic capacitor has been widely used
as a capacitor having a miniaturized size and high capacity. Highly
expensive materials such as Pd, Pt, etc. have been used for the
internal electrode of the multi layer ceramic capacitor but they
are recently replaced with nickel particles for a cost matter.
Particularly, researches using nickel as a material of the internal
electrode of the multi layer ceramic capacitor having high capacity
has been greatly increased.
[0006] Since a nickel electrode layer of the multi layer ceramic
capacitor has a lower packing density than that of a nickel molding
obtained by the powder metallurgy and much larger shrinkage than a
dielectric substance during the sintering process, the defect rate
is high with shorten-turn and broken phenomena. In order to avoid
such defects nickel particles should not contain large size
particles but have narrow and uniform particle distribution and
good dispersibility without coagulation.
[0007] Various methods for manufacturing nickel powders to be used
as a material of the internal electrode of the multi layer ceramic
capacitors have been introduced but any method until now has not
satisfied to manufacture nickel powders having uniform size of less
than 100 nm which is suitable for multi-layered and high capacity
capacitors.
[0008] Particularly, conventionally nickel chloride is carried for
the gas phase reduction with hydrogen at a high temperature of
about 1000.degree. C. However, even if the surface of particles is
smooth due to thermal history of the reaction at a high
temperature, the particle distribution is wide and the size of
particles is large, larger than 1.0 .mu.m, since nucleation and
growth are occurred at the same time. Thus, these particles are
insufficient for thinning layers of the internal electrode.
[0009] Further, a wet reduction for manufacturing nickel powders is
introduced which reduces a solution of nickel chloride and nickel
sulfate with a reducing agent of hydrazine and hydrazine hydrate in
the presence of a strong alkali. Even if this method provides a
narrower particle distribution compared to the gas phase reduction,
the surface of particles is not smooth and thus it is not suitable
for the internal electrode.
[0010] Further, after adding ethylene glycol, a capping molecule
and a reducing agent, a metal precursor and an alcohol compound are
added and then acetone and ethylene glycol are added to produce
metal nanoparticles. In this method, the reaction temperature is
increased before the metal precursor is added. This method is not
simple.
[0011] In addition, various methods for manufacturing metal
nanoparticles have been introduced and among these methods the wet
reduction is relatively easy to control shape and size of particles
and provides fine particles having a sub-micron size. However,
since there are several reaction variables during the reaction
process, the reaction can be ununiform and it is difficult to
manufacture fine particles having uniformity of a size of 200 nm to
1 .mu.m which is less than 100 nm. Further, it requires an
additional reduction step, so that it is not suitable for mass
production of uniform nickel nanoparticles.
SUMMARY
[0012] An aspect of the present invention is to provide a method
for manufacturing nickel nanoparticles which have uniform particle
distribution and high dispersibility and allows mass production
with a simple process.
[0013] In order to resolve the aforementioned problems associated
with the conventional methods, is a method for manufacturing nickel
nanoparticles provided, the method including: preparing a mixture
solution by adding a reducing agent, a dispersing agent and a
nickel salt to a polyol; stirring and heating the mixture solution;
and producing nickel nanoparticles by reacting the mixture
solution.
[0014] According to an embodiment of the present invention, the
reducing agent may be at least one chosen from sodium hypophosphite
(NaH.sub.2PO.sub.2), hydrazine (N.sub.2H.sub.4), hydrochloride,
sodium borohydride (NaBH.sub.4), and sodium
hydroxymethylsulfoxylate
(NaHSO.sub.2.largecircle.CH.sub.2O.largecircle.2H.sub.2O).
[0015] According to an embodiment of the present invention, the
dispersing agent may be at least one chosen from a cationic
surfactant, an anionic surfactant, an analogue of cellulose, a
polymer, a copolymer and a terpolymer.
[0016] According to an embodiment of the present invention, the
dispersing agent may be at least one chosen from
cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate
(SDS), sodium carboxymethyl cellulose (Na-CMC),
polyvinylpyrrolidone (PVP), vinylpyrrolidone/vinylacetate (PVP/VA),
and vinylcaprolactam/vinylpyrrolidone/propylmethacylamide.
[0017] According to an embodiment of the present invention, the
nickel salt may be added in a concentration of 0.001 to 1M with
respect to the mixture solution.
[0018] According to an embodiment of the present invention, the
reducing agent may be added in a mole ratio of 2 to 10 with respect
to the nickel salt.
[0019] According to an embodiment of the present invention, the
dispersing agent may be added in a mole ratio of 1 to 20 with
respect to the nickel salt.
[0020] According to an embodiment of the present invention, the
nickel salt may be at least one chosen from NiCl.sub.2,
Ni(NO.sub.3).sub.2, NiSO.sub.4 and (CH.sub.3COO).sub.2Ni.
[0021] According to an embodiment of the present invention, the
polyol may be at least one chosen from ethylene glycol, diethylene
glycol, triethylene glycol, and polyethylene glycol.
[0022] According to an embodiment of the present invention, the
mixture solution may be heated to 80 to 160.degree. C.
[0023] According to an embodiment of the present invention, the
method may further include washing, isolating, and drying the
produced nickel nanoparticles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a SEM image of nickel nanoparticles produced in
Example 1 of the present invention.
[0025] FIG. 2 is a XRD graph of nickel nanoparticles produced in
Example 1 of the present invention.
[0026] FIG. 3 is a SEM image of nickel nanoparticles produced in
Comparison Example 1.
[0027] FIG. 4 is a XRD graph of nickel nanoparticles produced in
Comparison Example 1
DETAILED DESCRIPTION
[0028] Hereinafter, the method for manufacturing nickel
nanoparticles according to the invention will be described in more
detail.
[0029] Nickel nanoparticles are produced by preparing a mixture
solution by adding a reducing agent, a dispersing agent, a nickel
salt to a polyol, stirring and heating the mixture solution,
producing nickel particles through a reducing reaction under
control of a reaction temperature and a reaction time, and washing,
isolating, and drying.
[0030] The nickel salt may be a water soluble salt such as
NiCl.sub.2, Ni(NO.sub.3).sub.2, NiSO.sub.4, and
(CH.sub.3COO).sub.2Ni and it may be used alone or a combination of
at least two. The nickel salt may be NiCl.sub.2. The nickel salt
may be added in a concentration of 0.001 to 1M. When the
concentrating of the nickel salt is less than 0.001M, the
efficiency is not preferable due to low concentration of nickel
ions, while when it exceeds more than 1M, it causes overgrowth
coagulation of particles. Here, the less amount of a nickel
precursor is used the smaller the nickel nanoparticles are
produced.
[0031] The polyol such as ethylene glycol, diethylene glycol,
triethylene glycol, and polyethylene glycol may be used alone or as
a combination of at least two, preferably ethylene glycol
alone.
[0032] Ethylene glycol reduces the metal precursor along with the
reducing agent by preventing remaining of unreacted compounds, so
that it increases the yield of manufacturing. Further, ethylene
glycol may not only be used as a solvent to dissolve the metal
precursor but also removes unreacted PVP with addition of excess
amount of acetone and completes the reaction.
[0033] Examples of the reducing agent include dimethylformamide
(DMF), glucose, ascorbic acid, tannic acid, tetrabutyl ammonium
borohydride, sodium hypophosphite (NaH.sub.2PO.sub.2), hydrazine
(N.sub.2H.sub.4), hydrochloride, sodium borohydride (NaBH.sub.4),
sodium hydroxymethylsulfoxylate
(NaHSO.sub.2.largecircle.CH.sub.2O.largecircle.2H.sub.2O), etc.,
preferably sodium hypophosphite (NaH.sub.2PO.sub.2).
[0034] The may be added in a mole ratio of 2 to 10 with respect to
the nickel salt. When it is added less than 2 mole ratio, the
nickel ions cannot be sufficiently reduced, while when it is added
more than 10 mole ratio, excess amount of byproducts are produced
and thus it is not economical since the reducing agent is used much
more than the amount to reduce 100% of the nickel ions.
[0035] The dispersing agent may be a cationic or anionic surfactant
such as cetyltrimethylammonium bromide (CTAB) or sodium dodecyl
sulfate (SDS), an analogue of cellulose such as sodium
carboxymethyl cellulose (Na-CMC), a polymer such as
polyvinylpyrrolidone (PVP), a copolymer such as
vinylpyrrolidone/vinylacetate (PVP/VA), a terpolymer such as
vinylcaprolactam/vinylpyrrolidone/propylmethacrylamide, etc., and
it can be used alone or a combination of at least two, preferably
PVP alone, and more preferably PVP having a molecular weight of
40,000 alone.
[0036] Further, the dispersing agent may be used in a mole ratio of
1 to 20 with respect to the nickel salt. When it is less than 1
mole ratio, it can be difficult to control the shape and size of
particles and thus cannot provide sufficient dispersibility of the
produced particles, while when it is more than 20 mole ratio, the
viscosity of the precursor solution is rapidly increased, it may be
difficult to mix uniformly, the reaction cannot be performed
uniformly, it produces excess amount of unreacted compounds or
byproducts, and it requires large amount of a solvent to wash and
isolate which is then uneconomical.
[0037] The polyol mixture solution, in which the reducing agent,
the dispersing agent and the nickel salt are dissolved, may be
heated to 80 to 160.degree. C. When the temperature is higher than
160.degree. C., the reaction may proceed rapidly and thus the
stability gets decreased and the produced particles are not
uniform, while it is lower than 80.degree. C., the reduction is not
sufficiently performed.
[0038] When the mixture solution is heated as described above, the
reduction is performed at a temperature of 100 to 140.degree. C.
according the mole ratio of the nickel salt and the reducing agent.
The reaction time is in a range of 1 minute to 1 hour. When the
reaction time is within 1 minute, the reduction is not performed
sufficiently and the yield thus becomes lowered. On the other hand,
when the reaction time is more than 1 hour, it causes overgrowth of
particles and ununiformity.
[0039] When the reduction completes to produce nickel
nanoparticles, the reaction is quickly cooled by using ice-water to
prevent overgrowth of particles and the nickel nanoparticles
produced are isolated by centrifuge, etc. The isolated nickel
nanoparticles are washed with water and acetone to remove
byproducts and any remained compound. The washed nickel
nanoparticles are then dried in a vacuum oven at a temperature of
30 to 80.degree. C. for 2 to 8 hours.
[0040] While the present invention has been described with
reference to particular embodiments, it is to be appreciated that
various changes and modifications may be made by those skilled in
the art without departing from the spirit and scope of the present
invention, as defined by the appended claims and their equivalents.
Throughout the description of the present invention, when
describing a certain technology is determined to evade the point of
the present invention, the pertinent detailed description will be
omitted.
EXAMPLE 1
Preparation of Nickel Nanoparticles
[0041] Nickel chloride 95.04 g (0.4M), sodium hypophosphite 106 g
(1.2M), PVP 444 g (1.2M), ethylene glycol 500 ml were mixed in a
beaker. The mixture solution was dissolved while stirring and the
temperature was slowly increased up to 120.degree. C. at a rate of
2.degree. C./min. The reaction mixture was turned to black due to
the reduction at a temperature of 120.degree. C. and preceded for
30 min. The reaction mixture was then cooled down quickly by using
ice-water and black nickel nanoparticles were recovered from the
reaction mixture by centrifuge. The produced nickel nanoparticles
were washed with acetone and distilled water 3 times and dried in a
vacuum oven at a temperature of 50.degree. C. for 3 hours to
provide target nickel nanoparticles 12 g.
[0042] A SEM image of the nickel nanoparticles produced in Example
1 is shown in FIG. 1. According to FIG. 1, it is noted that the
nickel nanoparticles have a size of 30 to 50 nm and are
uniform.
[0043] A XRD graph of the nickel nanoparticles produced in Example
1 is shown in FIG. 2. According to FIG. 2, it is noted that pure
nickel crystalline having face-centered cubic lattice structure
(FCC structure) is formed without any impurity and oxidized
compound. When pure nickel particles having FCC structure are
formed, 3 distinctive peaks are appeared at 111, 200, and 220
corresponding to each FCC structure as shown in FIG. 2.
COMPARISON EXAMPLE 1
[0044] In order to compare with the result of Example 1, a reaction
in which a metal salt was added after increasing the reaction
temperature was performed as follows.
[0045] Sodium hypophosphite 106 g, PVP 444 g, ethylene glycol 400 g
were mixed in a beaker and the mixture solution was dissolved while
stirring and increasing the temperature up to 120.degree. C. at a
rate of 2.degree. C./min. Nickel chloride 95.04 g was dissolved in
ethylene glycol 150 g and the mixture solution was then heated to
120.degree. C. The mixture solution of nickel chloride was added at
once to the mixture solution of sodium hypophosphite, PVP, ethylene
glycol and then thoroughly mixed using a stirrer while keeping the
temperature at 120.degree. C. The reaction mixture was turned
slowly to black and further preceded for 60 minutes. The reaction
mixture was then cooled down quickly by using ice-water and black
nickel nanoparticles were recovered from the reaction mixture by
centrifuge. The produced nickel nanoparticles were washed with
acetone and distilled water 3 times and dried at a vacuum oven at a
temperature of 50.degree. C. for 3 hours to provide target nickel
nanoparticles 8 g.
[0046] A SEM image of the nickel nanoparticles produced in
Comparison Example 1 is shown in FIG. 3. According to FIG. 3, it is
noted that the nickel nanoparticles are ununiform with heavy
coagulation.
[0047] A XRD graph of the nickel nanoparticles produced in
Comparison Example 1 is shown in FIG. 4. According to FIG. 4, it is
noted that the nickel crystalline is not a face-centered cubic
lattice structure (FCC structure). It is also noted that nickel
crystalline is not formed smoothly according to the conventional
method which adds a metal salt after the temperature is increased
as shown in Comparison Example 1.
* * * * *