U.S. patent application number 10/591941 was filed with the patent office on 2007-08-16 for composite metal article and production method thereof.
Invention is credited to Kouichi Ichiki.
Application Number | 20070190348 10/591941 |
Document ID | / |
Family ID | 36202849 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070190348 |
Kind Code |
A1 |
Ichiki; Kouichi |
August 16, 2007 |
Composite metal article and production method thereof
Abstract
There is provided a production method of a composite metal
article with carbon nanotubes dispersed in the composite metal
article containing a metal which is difficult to provide modified
metal particles by an electrolytic process. It is characterized in
that when there is produced a composite metal article in which a
first metal portion comprising a metal 12 and a second metal
portion comprising a metal 12 are formed at random, carbon
nanotubes are mixed in the above-mentioned second metal portion,
using modified metal particles which are metal particles comprising
the metal 12 and modified with the carbon nanotubes which partially
protrude outward from the above-mentioned metal particles.
Inventors: |
Ichiki; Kouichi; (Ueda-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
36202849 |
Appl. No.: |
10/591941 |
Filed: |
October 7, 2005 |
PCT Filed: |
October 7, 2005 |
PCT NO: |
PCT/JP05/18606 |
371 Date: |
September 8, 2006 |
Current U.S.
Class: |
428/567 ; 419/66;
428/568 |
Current CPC
Class: |
B22F 2998/10 20130101;
B22F 2998/10 20130101; Y10T 428/1216 20150115; B22F 2998/10
20130101; B22F 2998/00 20130101; C22C 1/1036 20130101; B22F 1/02
20130101; B22F 2998/00 20130101; C22C 2026/002 20130101; B22F 1/02
20130101; B22F 3/14 20130101; B22F 3/14 20130101; B22F 1/02
20130101; C25D 15/00 20130101; B22F 1/0003 20130101; C25D 15/00
20130101; B22F 3/26 20130101; C22C 49/14 20130101; Y10T 428/12167
20150115; B22F 1/02 20130101; B22F 1/02 20130101; C22C 47/14
20130101; B22F 9/20 20130101; B22F 2998/00 20130101 |
Class at
Publication: |
428/567 ;
428/568; 419/066 |
International
Class: |
B22F 3/02 20060101
B22F003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 21, 2004 |
JP |
2004-307078 |
Claims
1. A composite metal article characterized in that the composite
metal article is formed by at least two kinds of metals, a first
metal portion comprising one side of said two kinds of metals and a
second metal portion comprising the other side of said two kinds of
metals are formed at random, and carbon nanotubes are dispersed and
incorporated in at least one side of said first metal portion and
second metal portion.
2. The composite metal article according to claim 1, wherein the
carbon nanotubes are mixed through modified metal particles
modified with the carbon nanotubes which partially protrude outward
from metal particles comprising at least a metal of the one side of
the metals which form the modified metal article.
3. The composite metal article according to claim 2, wherein the
modified metal particles are modified metal particles obtained by
an electrolytic process of passing an electric current between a
cathode and an anode immersed in an electrolytic solution in which
the carbon nanotubes are dispersed.
4. The composite metal article according to claim 2, wherein the
modified metal particles are modified metal particles obtained by
an oxidation-reduction process of forming composite particles which
contain the carbon nanotubes and comprise a metal salt or metal
oxide slightly soluble in water, and then performing reduction
treatment with a reducing agent which reduces the metal salt or
metal oxide of said composite particles.
5. A production method of a composite metal article characterized
in that when there is produced the composite metal article formed
by at least two kinds of metals, wherein a first metal portion
comprising one side of said two kinds of metals and a second metal
portion comprising the other side of said two kinds of metals are
formed at random, carbon nanotubes are mixed in at least one side
of said first metal portion and second metal portion, using
modified metal particles modified with the carbon nanotubes which
partially protrude outward from said metal particles.
6. The production method of a composite metal article according to
claim 5, wherein the modified metal particles are compression
molded to form the first metal portion comprising a porous body,
and then, a molten metal obtained by melting the metal which forms
the second metal portion is impregnated in said porous body.
7. The production method of a composite metal article according to
claim 6, wherein a molten metal obtained by melting a metal which
is difficult to provide modified metal particles by an electrolytic
process is used as the molten metal.
8. The production method of a composite metal article according to
claim 5, wherein the metal which forms the first metal portion and
metal particles comprising the metal which forms the second metal
portion are hot compression molded.
9. The production method of a composite metal article according to
claim 5, wherein as the modified metal particles, there are used
modified metal particles obtained by an electrolytic process of
passing an electric current between a cathode and an anode immersed
in an electrolytic solution in which the carbon nanotubes are
dispersed.
10. The production method of a composite metal article according to
claim 5, wherein as the modified metal particles, there are used
modified metal particles obtained by an oxidation-reduction process
of forming composite particles which contain the carbon nanotubes
and comprise a metal salt or metal oxide slightly soluble in water,
and then performing reduction treatment with a reducing agent which
reduces the metal salt or metal oxide of said composite particles.
Description
TECHNICAL FIELD
[0001] The present invention relates to a composite metal article
and a production method thereof, and more particularly to a
composite metal article in which carbon nanotubes are dispersed and
a production method thereof.
BACKGROUND ART
[0002] A composite metal article with carbon nanotubes dispersed in
a metal has been proposed in JP-A-2000-223004.
[0003] In the case of producing this composite metal article, when
metal particles having a diameter of 200 to 1000 nm are merely
mixed with carbon nanotubes having a diameter of 5 to 20 nm, it is
difficult to obtain a mixture in which both are uniformly mixed,
because of a large difference of diameter therebetween.
[0004] For this reason, in the same patent document, the carbon
nanotubes are added to and dispersed in an acid solution in which
the metal particles have been dissolved, followed by drying and
sintering, thereby obtaining the composite metal article.
[0005] The production method of the composite metal article
proposed in this patent document has the disadvantages that a
process thereof is extremely troublesome, that a long period of
time is required, and that the production cost of the composite
metal article becomes expensive.
[0006] In contrast with the production method of the composite
metal article of such a patent document, the present applicant has
proposed in the Shinano Mainichi Shimbun published on September 2,
Heisei 15 (2003) that a modified metal particle comprising carbon
nanotubes and a metal such as copper with ends of the carbon
nanotubes protruding in echinoid form, which is shown in FIG. 11,
can be obtained by an electrolytic process using a metal
ion-containing electrolytic solution in which the carbon nanotubes
are dispersed with a special dispersing agent, and that a composite
metal article excellent in heat radiation properties can be formed
by thermopressing such modified metal particles.
DISCLOSURE OF THE INVENTION
[0007] According to the technique proposed in the above-mentioned
newspaper article by the present applicant, a composite metal
article with carbon nanotubes dispersed in a metal can be easily
obtained.
[0008] By the way, it is known that there are some metal particles
(for example, copper particles) from which modified metal particles
can be easily obtained by an electrolytic process and other metal
particles (for example, aluminum particles and alloy particles)
which are difficult to provide modified metal particles by an
electrolytic process.
[0009] However, in the metals which are difficult to provide
modified metal particles by an electrolytic process, there is a
metal necessary in the case of intending weight saving of a
structure and the like, such as aluminum.
[0010] Like this, even the composite metal article containing the
metal which is difficult to provide modified metal particles by an
electrolytic process can provide a composite metal article having
various physical properties as well as excellent heat radiation
properties, as long as carbon nanotubes can be dispersed in the
composite metal article.
[0011] Then, an object of the invention is to provide a composite
metal article with carbon nanotubes dispersed in the composite
metal article containing a metal which is difficult to provide
modified metal particles by an electrolytic process, and a
production method thereof.
[0012] The present inventors have made a series of studies for
achieving the above-mentioned object. As a result, it has been
found that carbon nanotubes can be dispersed in a metal such as
aluminum which is difficult to provide modified metal particles by
an electrolytic process, by using modified metal particles obtained
by an electrolytic process and modified with the carbon nanotubes
which partially protrude outward from metal particles comprising
copper or the like (hereinafter occasionally simply referred to as
modified metal particles), thus completing the present
invention.
[0013] That is to say, the present invention is a composite metal
article characterized in that the composite metal article is formed
by at least two kinds of metals, a first metal portion comprising
one side of the above-mentioned two kinds of metals and a second
metal portion comprising the other side of the above-mentioned two
kinds of metals are formed at random, and carbon nanotubes are
dispersed and incorporated in at least one side of the
above-mentioned first metal portion and second metal portion.
[0014] In such a present invention, the carbon nanotubes are mixed
through modified metal particles modified with the carbon nanotubes
which partially protrude outward from metal particles comprising at
least a metal of the one side of the metals which form the
composite metal article, thereby being able to prevent separation
between the carbon nanotubes and the metal particles, even when
compression molding is performed.
[0015] As the modified metal particles, there can be suitably used
modified metal particles obtained by an electrolytic process or an
oxidation-reduction process.
[0016] Here, the modified metal particles by the electrolytic
process can be obtained by passing an electric current between a
cathode and an anode immersed in an electrolytic solution in which
the carbon nanotubes are dispersed.
[0017] On the other hand, the modified metal particles by the
oxidation-reduction process can be obtained by an
oxidation-reduction process of forming composite particles which
contain the carbon nanotubes and comprise a metal salt or metal
oxide slightly soluble in water, and then performing reduction
treatment with a reducing agent which reduces the metal salt or
metal oxide of the above-mentioned composite particles.
[0018] Further, the present invention is a production method of a
composite metal article characterized in that when there is
produced the composite metal article formed by at least two kinds
of metals, wherein a first metal portion comprising one side of the
above-mentioned two kinds of metals and a second metal portion
comprising the other side of the above-mentioned two kinds of
metals are formed at random, carbon nanotubes are mixed in at least
one side of the above-mentioned first metal portion and second
metal portion, using modified metal particles modified with the
carbon nanotubes which partially protrude outward from the
above-mentioned metal particles.
[0019] In such a present invention, the composite metal article in
which the carbon nanotubes are dispersed can be obtained by
compression molding the modified metal particles to form the first
metal portion comprising a porous body, and then impregnating a
molten metal obtained by melting the metal which forms the second
metal portion in the above-mentioned porous body.
[0020] Here, by using as the molten metal a molten metal obtained
by melting a metal which is difficult to provide modified metal
particles by an electrolytic process, even the metal which is
difficult to provide modified metal particles by an electrolytic
process can easily disperse the carbon nanotubes.
[0021] Alternatively, the carbon nanotubes can also be easily
dispersed in the metal by hot compression molding of modified metal
particles comprising the metal which forms the first metal portion
and metal particles comprising the metal which forms the second
metal portion.
[0022] As such modified metal particles, there can be suitably used
the modified metal particles obtained by the above-described
electrolytic process or oxidation-reduction process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic view for illustrating one example of a
composite metal article relating to the present invention.
[0024] FIG. 2 is a schematic view for illustrating one example of a
modified metal particle according used in the present
invention.
[0025] FIG. 3 is a schematic view for illustrating another example
of a modified metal particle used in the present invention.
[0026] FIG. 4 is a schematic view for illustrating a porous body
obtained by compression molding modified metal particles.
[0027] FIG. 5 is an electron micrograph showing one example of a
composite metal article relating to the present invention.
[0028] FIG. 6 is an electron micrograph showing one example of a
modified metal particle used in the present invention.
[0029] FIG. 7 is an electron micrograph with respect to a cross
section of a composite metal article obtained by using the modified
metal particle shown in FIG. 6.
[0030] FIG. 8 is an electron micrograph with respect to a fractured
surface of the composite metal article shown in FIG. 7.
[0031] FIG. 9 is an electron micrograph with respect to a cross
section of another metal article obtained by using the modified
metal particle shown in FIG. 6.
[0032] FIG. 10 is an electron micrograph with respect to a
fractured surface of the composite metal article shown in FIG.
9.
[0033] FIG. 11 shows an electron micrograph of conventional
modified metal particles.
BEST MODE FOR CARRYING OUT THE INVENTION
[0034] An outline of one example of a composite metal article
relating to the present invention is shown in FIG. 1. A composite
metal article 10 shown in FIG. 1 comprises a first metal portion
comprising a porous body formed by compression molding metal
particles comprising a metal 12 to a specified form, and a second
metal portion comprising a metal 14 which goes into pores of this
porous body.
[0035] In the composite metal article 10 shown in this FIG. 1,
carbon nanotubes 16, 16.cndot..cndot. are dispersed in the porous
body which forms the first metal portion comprising the metal 12.
When the carbon nanotubes 16, 16.cndot..cndot. coagulate and are
unevenly distributed in the composite metal article 10, the
physical properties such as the electric conductivity and thermal
conductivity of the composite metal article 10 can not be
sufficiently improved by mixing of the carbon nanotubes 16,
16.cndot..cndot..
[0036] By the way, even when a mixture in which the metal particles
comprising the metal 12, the metal particles comprising the metal
14 and the carbon nanotubes 16, 16.cndot..cndot. are merely mixed
is compression molded to a specified form, the carbon nanotubes 16,
16.cndot..cndot. are easily separated from the metal particles
during that process. This is because the particle size difference
and the specific gravity difference between both are extremely
large.
[0037] For this reason, when the composite metal article 10 shown
in FIG. 1 is produced, at least one of a modified metal particle 18
shown in FIG. 2 and a modified metal particle 20 shown in FIG. 3 is
used. The modified metal particle 18 shown in FIG. 2 is one in
which an outer peripheral surface of a granular metal particle 22
is modified with the carbon nanotubes 16, 16.cndot..cndot.
partially protruding outward.
[0038] Further, The modified metal particle 20 shown in FIG. 3 is
one in which an outer peripheral surface of a fibrous metal
particle 24 is modified with the carbon nanotubes 16,
16.cndot..cndot. partially protruding outward.
[0039] Such modified metal particles 18 and 20 shown in FIGS. 2 and
3 can each be used alone, or both may be used together.
[0040] In such modified metal particles 18 and 20 shown in FIGS. 2
and 3, each of the carbon nanotubes 16, 16.cndot..cndot. are
partially embedded in the metal particle 22 or the metal fiber 24,
and the remainder protrudes outward from the metal particle 22 or
the metal fiber 24.
[0041] Specifically, they are in a state where each base side is
embedded in the metal particle 22 or the metal fiber 24 and a tip
side protrudes, or in a state where both end sides thereof are
embedded in the metal particle 22 or the metal fiber 24 and an
intermediate portion is exposed, or in a state where both states
coexist.
[0042] The carbon nanotube 16 used in such modified metal particles
18 and 20 may be either a monolayer or a multilayer, and one end or
both ends thereof may be closed with a fullerene-like cap or
cups.
[0043] Further, the carbon nanotube 16 has a tubular form in which
the length thereof is 100 times or more the diameter.
[0044] As this carbon nanotube 16, it is preferred to use one
having a diameter of several nanometers to several hundred
nanometers (for example, 300 nm) or less.
[0045] In the case of the carbon nanotube 16 having a diameter of
less than 15 nm, the electric conductivity decreases in some cases.
In the carbon nanotube 16 having a diameter of less than 15 nm,
when two integers which determine the chiral vector for specifying
a spiral direction of a crystal structure thereof, n and m (chiral
index), are multiples of n-m=3 or n=m, the electric conductivity
occurs.
[0046] On the other hand, the carbon nanotube 16 having a diameter
of 15 nm or more shows the electric conductivity, even when the
chiral index is other than the above-mentioned conditions.
[0047] Such a carbon nanotube 16 has no anisotropy in electric
conductivity like graphite, and the current flows in all directions
on a surface.
[0048] For this reason, in the modified metal particles 18 and 20
whose outer peripheral surfaces are modified with the carbon
nanotubes 16, the carbon nanotubes 16 come into contact with each
other or with other metal particles at surface layer planes
thereof. Accordingly, what is necessary is just to be one in which
at least an outermost layer (contact layer) of the metal particle
22 or metal fiber 24 is modified with the carbon nanotubes 16.
[0049] Further, the metal particle 22 or metal fiber 24 modified
with the carbon nanotubes 16 may be one comprising a metal easily
modified with the carbon nanotubes 16, for example, copper.
[0050] The shape of the metal particle 22 may be aspherical or
flaky, as well as spherical, and is not limited.
[0051] In order to obtain the composite metal article 10 having an
internal structure shown in FIG. 1, at least one of the modified
metal particles 18 and 20 shown in FIG. 2 and FIG. 3 is first
produced.
[0052] Each of the modified metal particles 18 and 20 shown in FIG.
2 and FIG. 3 can be obtained by applying the current between a
cathode and an anode inserted in an electrolytic solution in which
the carbon nanotubes 16, 16.cndot..cndot. have been dispersed,
thereby conduct electrolysis, and electrolytically depositing metal
particles (metal powder) containing the modified metal particles 18
and 20, on a surface of the cathode.
[0053] Such modified metal particles 18 and 20 can be easily
obtained, when there are used the modified metal particles 18 and
20 comprising a metal which is easily deposited by an electrolytic
method, for example, copper.
[0054] In contrast, compared to the modified metal particles 18 and
20 comprising copper, it is difficult to obtain the modified metal
particles 18 and 20 comprising aluminum by electrolysis under
ordinary conditions. Further, it is also difficult to obtain the
modified metal particles 18 and 20 comprising an alloy by
electrolysis under ordinary conditions, as a rule.
[0055] In this manner, at least one of the granular modified metal
particle 18, 18.cndot..cndot. and the fibrous modified metal
particle 20, 20.cndot..cndot. obtained by the electrolytic method
are compression molded to obtain the porous body. This porous body
may be further baked as needed.
[0056] In such a compression molding process, the carbon nanotubes
16, 16.cndot..cndot. are also partially embedded in the metal
particle 22 or the metal fiber 24. Accordingly, even when the force
of compression molding or the like is applied, separation between
the metal particle 22 or the metal fiber 24 and the carbon
nanotubes 16, 16.cndot..cndot. can be prevented.
[0057] An outline of the porous body 30 obtained by compression
molding the modified metal particles 18, 18.cndot..cndot. shown in
FIG. 2 is shown in FIG. 4. In the resulting porous body 30, the
modified metal particles 18, 18.cndot..cndot. come into contact
with one another, and pores 32, 32.cndot..cndot. are formed among
the modified metal particles 18, 18.cndot..cndot.. The carbon
nanotubes 16, 16.cndot..cndot. are entangled with one another, and
go into this pore 32.
[0058] Then, the porous body 30 having an internal structure shown
in FIG. 4 is immersed in a molten metal obtained by melting a metal
different from the metal which forms the granular modified metal
particle 18, and the molten metal is impregnated in the pores 32,
32.cndot..cndot. in the porous body 30. In this case, it is
preferred that the porous body 30 is immersed in the molten metal
while aspirating under vacuum or pressurizing, thereby forcedly
impregnating the molten metal in the porous body 30.
[0059] After that, the porous body 30 impregnated with the molten
metal is taken out of the molten metal and cooled, thereby being
able to obtain the composite metal article 10 shown in FIG. 1.
[0060] The second metal portion comprising the metal 14 of the
composite metal article 10 shown in FIG. 1 is one formed by cooling
the molten metal filled in each of the pores 32, 32.cndot..cndot.
of the porous body 30, the first metal portion.
[0061] The carbon nanotubes 16, 16.cndot..cndot. are entangled with
one another, and go into each of such pores 32, 32.cndot..cndot.,
and the carbon nanotubes 16, 16.cndot..cndot. are also dispersed in
the second metal portion comprising the metal 14.
[0062] For this reason, for example, the porous body 30 which is
the first metal portion is formed, using the metal particles 22
comprising copper which easily forms the modified metal particles
18, by the modified metal particles 18 in which the outer
peripheral surfaces of the metal particles 22 are modified with the
carbon nanotubes 16, 16.cndot..cndot., and then molten aluminum is
impregnated in the porous body 30, thereby being able to obtain the
composite metal article 10 in which the first metal portion
comprising copper as the metal 12 and the second metal portion
comprising aluminum as the metal 14 are formed at random, and the
carbon nanotubes 16, 16.cndot..cndot. are dispersed in the first
metal portion.
[0063] The porous body 30 as the first metal portion shown in FIG.
4 is one obtained by compression molding the granular modified
metal particles 18, 18. However, it can also be obtained by
compression molding the fibrous modified metal particles 20,
20.cndot..cndot..
[0064] As the production method of the composite metal article 10
shown in FIG. 1, there has hitherto been described the production
method of impregnating the porous body 30 which forms the first
metal portion obtained by compression molding the granular or
fibrous modified metal particles 18 or 20 in which the metal
particles 22 or metal fibers 24 comprising the metal 12 are
modified with the carbon nanotubes 16, 16.cndot..cndot., with the
molten metal obtained by melting the metal 14 which forms the
second metal portion. However, it can also be obtained by adding at
least one of the granular modified metal particle 18 and fibrous
modified metal particle 20 which form the first metal portion to
the molten metal obtained by melting the metal 14 which forms the
second metal portion, followed by kneading.
[0065] Further, at least one of the granular modified metal
particle 18 and the fibrous modified metal particle 20 comprising
the metal 12 which forms the first metal portion are mixed with the
metal particle comprising the metal 14 which forms the second metal
portion, and then, compression molded to a formed article of a
specified form, which is heated to melt the metal particles
comprising the metal 14, thereby also being able to obtain the
composite metal article 10 shown in FIG. 1. In this case, the
melting point of the metal 14 is preferably lower than that of the
metal 12 which forms the modified metal particles 18 and 20.
[0066] Further, as production methods of the granular modified
metal particles 18 or the fibrous modified metal particles 20,
various production methods can be employed in addition to the
electrolytic method.
[0067] For example, they can be obtained by scattering the carbon
nanotubes 16, 16.cndot..cndot. in a nonoxidative atmosphere, and
granulating or fibrillating and injecting the molten metal into
this nonoxidative atmosphere with a piezoelectric pump, thereby
adhering and fixing the carbon nanotubes 16 to the surfaces of the
metal particles 22 or the metal fibers 24.
[0068] Furthermore, they can also be formed by crushing,
granulating or fibrillating the molten metal in which the carbon
nanotubes 16, 16.cndot..cndot. are dispersed by kneading.
[0069] Alternatively, the granular modified metal particles 18 or
the fibrous modified metal particles 20 can also be obtained by an
oxidation-reduction process of forming composite particles which
contain the carbon nanotubes 16, 16 and comprise a metal salt or
metal oxide slightly soluble in water, and then, reducing deposited
composite particles with a reducing agent which reduces the
above-mentioned metal salt or metal oxide.
[0070] Specifically, the granular modified metal particles 18 or
the fibrous modified metal particles 20 can be obtained by
dissolving a water-soluble metal salt in an aqueous solution in
which the carbon nanotubes 16, 16.cndot..cndot. have been
dispersed, thereafter, adding to the aqueous solution an alkali
which reacts with a metal ion dissolved in this aqueous solution to
produce a metal salt or metal oxide slightly soluble in water,
while dispersing the carbon nanotubes 16, 16, thereby depositing
composite particles which contain the carbon nanotubes 16,
16.cndot..cndot. and comprise the metal salt or metal oxide
slightly soluble in water, and then, reducing the deposited
composite particles with a reducing agent which reduces the metal
salt or metal oxide.
[0071] In this oxidation-reduction process, dispersion of the
carbon nanotubes 16, 16 can also be performed by giving a shock to
the aqueous solution by an ultrasonic wave, or by adding a
dispersing agent with stirring the aqueous solution by mechanical
stirring according to a stirrer or the like. This dispersing agent
may be any, as long as it is a surfactant which can disperse the
carbon nanotubes 16, 16.cndot..cndot.. The surfactants include
octylphenoxypolyethoxyethanol, sodium dodecylsulfate and
polyacrylic acid.
[0072] In order to perform more easily such dispersion of the
carbon nanotubes 16, 16.cndot..cndot., it is preferred to give a
shock by an ultrasonic wave to the aqueous solution to which the
above-mentioned dispersing agent has been added.
[0073] Further, as the water-soluble metal salt, there can be
suitably used a water-soluble metal salt comprising copper, nickel
or silver, and more preferably, there can be used a sulfate, a
nitrate, or an acetate comprising copper, nickel or silver.
[0074] The fine composite particles comprising the metal salt or
metal oxide slightly soluble in water, which has been thus
obtained, are substantially spherical, and composite particles
containing the carbon nanotubes 16, 16.cndot..cndot. having a
particle size of 1 .mu.m or less.
[0075] Further, such composite particles are formed in the aqueous
solution in which the carbon nanotubes 16, 16.cndot..cndot. are
dispersed, the carbon nanotubes 16, 16.cndot..cndot. dispersed in
the aqueous solution can be taken in the composite particles in the
course of forming the composite particles, and the carbon nanotubes
16, 16.cndot..cndot. are contained in the formed composite
particles in a uniformly dispersed state.
[0076] Then, the resulting composite particles are reduced with the
reducing agent which reduces the metal salt or metal oxide slightly
soluble in water, thereby being able to obtain the granular
modified metal particles 18 or the fibrous modified metal particles
20.
[0077] As such a reducing agent, there can be used one or two or
more kinds of the group consisting of hydrazine, a hydrazine
compound, formalin, acetaldehyde, formic acid, rochelle salt,
hydroxylamine, glucose and hydrogen peroxide. This reducing agent
may be added to the aqueous solution in which the composite
particles comprising the metal salt or the metal oxide are
precipitated, or may be brought into direct contact with the
composite particles comprising the metal salt or the metal oxide,
which has been separated from the aqueous solution, thereby
reducing the metal salt or the metal oxide When foaming occurs by
the reduction reaction due to the reducing agent added to the
aqueous solution or by the surfactant added to the aqueous
solution, an antifoaming agent such as an alcohol may be added.
[0078] According to these production methods of the modified metal
particles 18 and 20, even the metal 14 which is difficult to obtain
the metal particles 18 and 20 by an electrolytic process can
provide the metal particles 18 and 20.
[0079] For this reason, at least one of the granular modified metal
particle 18 and the fibrous modified metal particle 20 comprising
the metal 12 which forms the first metal portion is mixed with the
metal particle comprising the metal 14 which forms the second metal
portion, and then, compression molded, thereby being able to obtain
the composite metal article 10 shown in FIG. 1. Also in this case,
baking may be performed after the compression molding as
needed.
[0080] Using the composite metal article 10 shown in FIG. 1, which
has hitherto been described, only the metal 12 which forms the
modified metal particles 18 and 20 may be removed by chemically
dissolving or melting it to form the composite metal article with
the carbon nanotubes 16, 16.cndot..cndot. dispersed in the metal
14
[0081] Further, the composite metal article from which the metal 12
has been removed may be impregnated with a molten metal comprising
the metal 14, or may be impregnated with a molten metal comprising
another kind of metal.
[0082] Furthermore, in place of the composite metal article 10
shown in FIG. 1, the composite metal article of the invention may
be a composite metal article in which spaces among the second metal
portions comprising the metal 14 are filled with the first metal
portions comprising the metal 12 with the carbon nanotubes 16, 16
dispersed.
[0083] Such a composite metal article can be obtained by mixing the
metal particle comprising the metal 14 with at least one of the
granular modified metal particle 18 and the fibrous modified metal
particle 20, and performing hot compression molding.
[0084] After the metal particle comprising the metal 14 are mixed
with at least one of the granular modified metal particle 18 and
the fibrous modified metal particle 20, compression molding is
performed, and baking may be further performed.
EXAMPLE 1
[0085] An electric current is passed between a cathode and an anode
inserted in an electrolytic solution in which carbon nanotubes 16,
16.cndot..cndot. having a diameter of 200 nm are dispersed to
conduct electrolysis, thereby electrolytically depositing copper
particles on a surface of the cathode. According to an electron
micrograph for the copper particles, there were obtained modified
metal particles 18 modified with the carbon nanotubes 16,
16.cndot..cndot. which partially protrude outward from the copper
particles 22, as shown in FIG. 2.
[0086] The metal particles comprising the modified metal particles
18 are compression molded to obtain a formed article of a specified
form. When a cross section of this formed article was observed
under a microscope, it was a porous body in which a number of pores
were formed, as shown in FIG. 4.
[0087] The resulting formed article was immersed in molten aluminum
maintained at 750.degree. C. for about 1 hour while aspirating
under vacuum, thereby forcedly impregnating the molten metal in the
formed article.
[0088] Then, the formed article taken out of molten aluminum was
cooled to obtain a composite metal article comprising copper,
aluminum and the carbon nanotubes. When a cross section of this
composite metal article was observed under a microscope, second
metal portions comprising aluminum were randomly formed in a first
metal portion comprising the porous body formed by copper, as shown
in FIG. 1.
[0089] According to an electron micrograph shown in FIG. 5 for a
cross section of this composite metal article, the carbon nanotubes
(indicated by arrows) were dispersed in copper and aluminum.
EXAMPLE 2
[0090] (1) Production of Modified Metal Particles 18 Carbon
nanotubes (VGCF manufactured by Showa Denko K.K.) (0.36 g), 100 g
of water and 0.4 g of octylphenoxypolyethoxyethanol [trade name:
TRITON X-100 (manufactured by ICN Biomedical, Inc.)] were subjected
to dispersion treatment by means of an ultrasonic homogenizer
(VC-750 manufactured by Ultra Sonic, Inc.), and then, 28 g of
nickel chloride (NiCl.sub.2) was put in, followed by heating up to
50.degree. C. while stirring with a stirrer to obtain a
dispersion.
[0091] Further, an alkali solution obtained by adding 13 g of
sodium hydroxide (NaOH) to 50 g of pure water was prepared.
[0092] Then, the alkali solution was added to the resulting
dispersion while stirring by giving an ultrasonic wave with an
ultrasonic washing machine [US-1 manufactured by As One Co., Ltd.]
and with a glass rod. The dispersion became a deposition solution
in which composite particles were deposited.
[0093] While heating this deposition solution up to 60.degree. C.
and stirring with a stirrer, 64 g of a hydrazine hydrate
(N.sub.2H.sub.4.H.sub.2O) as a reducing agent was added to conduct
a reduction reaction. In that case, 100 g of ethanol was added
depending on a state of foaming, and the reduction reaction was
terminated. After the reduction reaction was terminated, the
deposition solution was cooled to ordinary temperature, and a
precipitate was collected, followed by washing and drying under
vacuum.
[0094] The resulting composite particles were nickel colored,
nickel metal particles containing 5% by weight of the carbon
nanotubes, and granular modified metal particles in which one end
portion of the carbon nanotube protruded outward from the granular
metal particle, as indicated by arrows in FIG. 6.
(2) Production of Composite Metal Article
[0095] After the resulting granular modified metal particles were
mixed with an atomized copper powder, the mixture was kept at a
temperature of 500.degree. C. for 1 hour while pressurizing it, and
molded to a specified form. The amount of this atomized copper
powder mixed was adjusted so that the atomized copper powder in a
baked article became 60% by weight.
[0096] The resulting baked article was one in which a first metal
portion comprising nickel filled as a binder around a second metal
portion comprising the atomized copper powder, as shown in a
micrograph of a cross section of FIG. 7.
[0097] In a nickel portion of a fractured surface of such a baked
article, carbon nanotubes were dispersed, as indicated by arrows in
an electron micrograph of FIG. 8.
EXAMPLE 3
[0098] After the modified metal particles obtained in Example 2,
which comprise the carbon nanotubes and nickel, were mixed with a
tungsten powder, the mixture was kept at a temperature of
500.degree. C. for 2 hours while pressurizing it, thereby
performing baking. The amount of this tungsten powder mixed was
adjusted so that the tungsten powder in a baked article became 55%
by volume.
[0099] The resulting baked article was one in which a first metal
portion comprising nickel filled as a binder around a second metal
portion comprising the tungsten powder, as shown in a micrograph of
a cross section of FIG. 9.
[0100] In a nickel portion of a fractured surface of such a baked
article, carbon nanotubes were dispersed, as indicated by arrows in
an electron micrograph of FIG. 10.
INDUSTRIAL APPLICABILITY
[0101] Even when a mixture in which metal particles of plural
species are merely mixed with carbon nanotubes is compression
molded to a specified form, the carbon nanotubes coagulate to be
easily separated from the metal particles during that process. It
is therefore extremely difficult to obtain a composite metal
article with the carbon nanotubes dispersed in the metal article
comprising metals of plural species.
[0102] In this regard, according to the present invention, when
there is produced a composite metal article formed by at least two
kinds of metals, wherein a first metal portion comprising one side
of the above-mentioned two kinds of metals and a second metal
portion comprising the other side of the above-mentioned two kinds
of metals are formed at random, carbon nanotubes can be mixed in at
least one side of the first metal portion and second metal portion
without separation of the carbon nanotubes during the production
process of the composite metal, by using modified metal particles
which are metal particles comprising at least one metal of the two
kinds of metals and modified with the carbon nanotubes which
partially protrude outward from the metal particles.
[0103] These first metal portion and second metal portion are
formed at random in the composite metal article, so that according
to the present invention which can mix the carbon nanotubes in at
least one side of such first metal portion and second metal
portion, there can be obtained the composite metal article in which
the carbon nanotubes are dispersed.
* * * * *