WO2004094700A1

WO2004094700A1 - Metal particles and method for producing same

Info

Publication number: WO2004094700A1
Application number: PCT/JP2004/001599
Authority: WO
Inventors: Susumu Arai; Morinobu Endo; Kouichi Ichiki; Masashi Okubo
Original assignee: Shinshu University; Shinano Kenshi Kabushiki Kaisha
Priority date: 2003-02-18
Filing date: 2004-02-13
Publication date: 2004-11-04
Also published as: JP4421556B2; DE112004000296T5; US20060065543A1; JPWO2004094700A1

Abstract

Metal particles in which microfine carbon fibers are uniformly dispersed and a method for producing such metal particles are disclosed. The method is characterized by comprising a step wherein metal particles including microfine carbon fibers mixed therein are deposited on a cathode by electrolyzing an electrolytic solution in which the microfine carbon fibers are dispersed, and a step wherein the deposited metal particles are separated from the cathode. The separated metal particles are collected, cleaned and dried.

Description

Specification

Metal particles and method for producing the same

The present invention relates to a metal material that can be suitably used as a material for powder metallurgy, electric contacts, batteries, electromagnetic wave shields, conductive materials, friction material contacts, sliding materials, and the like, and a method for producing the same. Background art

Composite materials in which carbon nanotubes or carbon nanofibers (hereinafter referred to as fine carbon fibers) are dispersed in a metal are known. The composite material disclosed in Japanese Patent Application Laid-Open No. 2000-224304 is obtained by mixing fine carbon fibers and metal powder and sintering them to form a block.

By the way, fine carbon fibers are extremely fine with a diameter of about 5 to 50 nm, while metal powders generally have a diameter in the range of 200 to 100 nm. However, the diameter of the fine carbon fiber is an order of magnitude larger. If these two materials are simply mixed, uniform mixing is difficult.

Then, in the above-mentioned conventional one, the metal powder is first dissolved in an acid solution. For example, copper powder is dissolved in hydrochloric acid, sulfuric acid, or nitric acid. Then, fine carbon fibers are dispersed in this solution, and then dried and sintered to obtain a composite material.

However, in the above-mentioned conventional method for producing a composite material, the step of dissolving the metal powder and further drying and sintering the acid solution in which the fine carbon fibers are dispersed is extremely troublesome and requires a long time. In addition, there is a problem that costs are high. In addition, when the amount is large, there is a problem that it is difficult to uniformly disperse the fine carbon fibers. Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide metal particles in which fine carbon fibers are uniformly dispersed, and a method for producing the same. Disclosure of the invention

The method for producing metal particles according to the present invention comprises the steps of: electrolyzing an electrolytic solution in which fine carbon fibers are dispersed, and depositing metal particles mixed with fine carbon fibers on a force source electrode; Separating the power source electrode from the force source electrode.

In addition, the method includes a step of collecting, washing, and drying the separated metal particles.

Further, the present invention is characterized in that the metal particles are precipitated in the range of several hundred nm to several tens of m in average particle diameter by adjusting the electrolysis conditions.

The metal particles can be copper metal particles.

Further, the force source electrode on which the metal particles are deposited is immersed in acetone, and the metal particles are separated by irradiating ultrasonic waves. Alternatively, compressed air may be blown to the cathode electrode on which the metal particles are deposited, or impact or vibration may be applied to the force electrode electrode during electrolysis to separate the metal particles from the cathode electrode.

Further, it is preferable to add a dispersant comprising an organic compound to disperse the fine carbon fibers in the electrolytic solution.

Polyacrylic acid having a molecular weight of 500 or more can be suitably used as the dispersant.

Further, an electrode having a roughened surface can be used as the force sword electrode. Further, the metal particles according to the present invention are produced by any one of the production methods described above.

In addition, various composite materials can be obtained by melting the aggregate of the metal particles.

An aqueous solution, a molten salt, or an ionic liquid can be used as the electrolyte. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a scanning electron micrograph of metal particles deposited on a force source electrode in Example 1, FIG. 2 is an enlarged view of FIG. 1, and FIG. 4 is an enlarged view of FIG. 3, and FIG. 5 is a scanning electron microscope photograph of the metal particles deposited on the force source electrode in Example 3. FIG. 6 is an electron micrograph, FIG. 6 is a scanning electron micrograph of metal particles deposited on the force source electrode in Example 4, and FIG. 7 is a scanning electron micrograph of metal particles deposited on the force source electrode in Example 5. FIG. 8 is a scanning electron micrograph of the metal particles deposited on the force sword electrode in Example 6, and FIG. 9 is a scanning electron micrograph of the metal particles deposited on the force sword electrode in Example 7. 5 is a scanning electron micrograph of metal particles. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail.

As described above, the method for producing metal particles according to the present invention includes the steps of: electrolyzing an electrolytic solution in which fine carbon fibers are dispersed, thereby precipitating metal particles mixed with fine carbon fibers on a force source electrode. Separating the deposited metal particles from above the cathode electrode.

The required metal particles can be obtained by collecting, washing, and drying the separated metal particles.

By adjusting electrolysis conditions such as current density and electrolysis time, metal particles having an average particle size of several hundred nm to several tens m can be precipitated.

The optimum value of the current density is selected in consideration of the particle size and productivity.

In the case of mass production, for example, in the case of a copper electrolytic solution, put an aqueous solution of copper sulfate aqueous solution and sulfuric acid as a main component in an electrolytic cell and disperse CNT or CNF in the electrolytic solution using an organic compound as a dispersant. Let it. Electrolytic copper is used as the anode electrode in the electrolytic cell to supply copper ions during electrolysis. For the supply of copper ions to the electrolyte, a metal other than copper, for example, lead may be used as the anode electrode, and copper ions may be supplied from the outside.

The electrolytic solution during the electrolysis is stirred by a pump, and at the same time, the electrolytic solution concentration and the component amount are controlled so as to have a predetermined ratio.

To separate the deposited metal particles from the force electrode, The metal particles can be separated by immersing the cathode electrode in acetone and irradiating it with ultrasonic waves.

Alternatively, the metal particles may be separated from the cathode electrode by blowing compressed air to the force source electrode on which the metal particles are deposited, or by applying an impact or vibration to the force source electrode during electrolysis.

An organic or inorganic compound such as thiourea, gelatin, tungsten, or chloride may be added to the electrolytic solution in order to adjust the particle size and strength of the precipitated particles and the separability from the cathode electrode.

It is preferable to use titanium for the force sword electrode, which has poor adhesion of the metal to be precipitated and easily separates the precipitated particles. Further, it is desirable that the surface of the force sword electrode be roughened in order to make the precipitated metal particles. For example, niobium, tantalum, or platinum fixed to the surface of titanium in the form of microprojections can be suitably used for the force source electrode.

In order to disperse the fine carbon fibers in the electrolytic solution, a dispersant composed of an organic compound may be added. For this dispersant, polyacrylic acid having a molecular weight of 500 or more can be suitably used.

The particle size of the CNT or CNF-modified metal particles produced depends on the metal ion concentration in the electrolyte, the electrolysis current density, the diameter of the CNT or CNF fiber and its length in correlation. The type of metal of the metal particles is not limited to copper.

Various composite materials can be obtained by melting the aggregate of the metal particles. In this case, various additives may be added to the metal particles to form a composite material. For example, a composite material in which the blending amount of the fine carbon fibers is controlled can be realized by appropriately controlling and mixing the mixing ratio of the metal particles mixed with the fine carbon fibers and the metal particles not containing the fine carbon fibers.

In addition, it can be used as a material for various composite materials, such as being mixed with a resin.

As means for producing these composite materials, means such as resin molding, sintering, metal injection molding and the like can be used. The metal particles obtained as described above are extremely fine particles of several hundred nm to several tens of m, and fine carbon fibers are mixed in each metal particle. Therefore, the composite material obtained by melting the aggregate of these metal particles contains fine carbon fibers uniformly mixed therein.

In addition, by changing the amount of fine carbon fibers dispersed in the electrolytic solution, the electrolysis conditions, and the like, various amounts of fine carbon fibers can be mixed and metal particles having a particle size can be obtained. Accordingly, the amount of fine carbon fibers in the obtained composite material can be arbitrarily controlled.

By utilizing the properties of CNT or CNF, such composite materials can be used in a variety of applications, such as bearings that require mobility, electrodes and electrical contacts that require high electrical conductivity, and heat dissipation mechanisms that require high thermal conductivity. Available to

00 1 6

Example 1

CuS0 ₄ · 5H ₂ 0 0.85M

II 2 SO 4 '0.55M

PA5000 2 X 10— ⁵ M

CNF 2 g / L

(Note that PA5000 is polyacrylic acid with a molecular weight of 5000, and CNF is carbon nanofiber: fine carbon fiber.)

Using the above electrolyte solution, stirring, 2 when 5 ° C, 5 was carried out for 5 minutes electrolysis at a current density of A / dm ^2, scanning electron micrographs of a film deposited on the surface of the cathode one cathode electrode Figures 1 and 2 show the results. As can be seen in Fig. 1 and Fig. 2, a Cu-CNF composite with a ゥ -like appearance was formed, in which a large amount of CNF was incorporated into extremely fine spherical copper particles with a particle size of about 2-3. I have. These composites could be easily separated from the cathode electrode and formed into particles by ultrasonic irradiation in compressed air blown acetone. Example 2 CuS0 ₄ · 5H ₂ 0 0.85M

II ₂ SO ₄ 0.55M

PA5000 2X 10— ⁵ M

CNF 2 gZL

(Note that PA5000 is polyacrylic acid with a molecular weight of 5000, and CNF is carbon fiber: fine carbon fiber.)

Scanning electron micrograph of the film deposited on the surface of the cathode electrode when electrolysis was performed for 20 minutes at a current density of 25 ° (: 5 A / dm ²⁾ with stirring using the above electrolyte. These are shown in Figures 3 and 4. As can be seen in Figures 3 and 4, a large number of CNFs are incorporated into fine spherical copper particles with a particle size of about 10 to 30. The u-CNF composites were formed, and these composites could be easily separated from the cathode electrode and formed into particles by ultrasonic irradiation in compressed air blown acetone.

As is clear from Example 1 and Example 2, a granular composite can be obtained by increasing the current density and making it slightly burnish. It can also be seen that the size of the granular material can be controlled by changing the electrolysis conditions (electrolysis time). Example 3

_{_{CuS0 4 · 5H 2 0 2 2}} 0 g / L

II ₂ SO ₄ 5 5 g / L

PA5000 0.2 5 g / L

C F 10 g / L

(Note that PA5000 is polyacrylic acid with a molecular weight of 5000)

A scanning electron micrograph of the film deposited on the surface of the force source electrode when electrolysis was performed for 10 minutes at 25 ° C and a current density of 40 AZdm ² with stirring using the above electrolytic solution. See Figure 5. As can be seen in Fig. 5, the particle size is about 10 to 30 W

7

A large number of CNFs are incorporated into fine spherical copper particles of Hm to form a CU-CNF composite having a pinion-like appearance. When the content of CNF in this composite was measured, it was about 7 vol%. Example 4

_{_{CuS0 4 · 5H 2 0 2 2}} 0 g / L

II 2 SO ₄ 5 5 g / L

PA5000 0.2 5 g / L

CNF 20 g / L

Scanning electron micrograph of a film deposited on the surface of a force source electrode when electrolysis was performed for 10 minutes at a current density of 25 ° (:, 40 A / dm ²⁾ with stirring using the above electrolytic solution. Fig. 6. As can be seen in Fig. 6, Cu-CNF has a ゥ -like appearance in which a large amount of CNF is incorporated into fine spherical copper particles having a particle size of about 10 to 30 m. A complex was formed, and the content of CNF in the complex was measured to be about 15 vol%.

As is clear from Examples 3 and 4, the CNF content in the CU-CNF composite can be increased by increasing the CNF content in the electrolytic solution. Example 5

_{_{CuS0 4 · 5H 2 0 1 g}} / L

H ₂ S0 ₄ 1 5 0 g / L

Polyoxyethylene (10) octyl phenyl ether (dispersant)

2 g

CNF 20 g / L

Using the above electrolyte solution, stirring, 2 when 5 ° C, 1 0 was for 10 minutes electrolysis at a current density of A / dm ^2, scanning of the film deposited on the surface of the cathode one cathode electrode An electron micrograph is shown in FIG. In this example, CNF having higher activity on the outer peripheral surface than the CNF used in Examples 1 to 4 was used. By using such a CNF, as shown in Fig. 7, a Cu-CNF composite with copper beads attached to the surface of the CNF is formed. Example 6

CuS0 ₄ · 5H ₂ 0 1 g

H ₂ S0 ₄ 50 g / L

Polyoxyethylene (10) octylphenyl ether (dispersant)

2 g

CNF 20 g / L

Using the above electrolyte solution, under stirring, in the case of performing 1 0 minute electrolysis at 2 5 ° C, 40 current density A / dm ^2, a scanning electron micrograph of a film deposited on the surface of the force cathode electrode See Figure 8. In this example, CNF having higher activity on the outer peripheral surface than the CNF used in Examples 1 to 4 was used. By using such a CNF, as shown in FIG. 8, a CU-CNF composite in which copper is attached in a dendritic manner to the CNF surface is formed. Example 7

CNF 10 g / L

PA5000 0.5 g / L

Using the above electrolyte solution, under stirring, in the case of performing 1 0 minute electrolysis at 2 5 ° C, 40 current density A / dm ^2, a scanning electron micrograph of a film deposited on the surface of the force cathode electrode Figure 9 shows. In this way, it is possible to electrolytically deposit metals other than copper If it is a suitable metal, a composite electrolytic powder with CNF can be obtained. The invention's effect

As described above, according to the present invention, the particle size of metal particles can be adjusted from an extremely fine particle size of several hundred nm to several tens of meters / m, which is easy to handle, and the amount of fine carbon fibers mixed can be controlled. It is also possible.

Claims

The scope of the claims

1. Electrolyzing the electrolytic solution in which the fine carbon fibers are dispersed to precipitate metal particles mixed with the fine carbon fibers on the force source electrode;

Separating the precipitated metal particles from above the cathode electrode.

2. The method for producing metal particles according to claim 1, comprising a step of collecting, washing and drying the separated metal particles.

3. The method for producing metal particles according to claim 1 or 2, wherein the electrolysis conditions are adjusted to precipitate the metal particles in an average particle size of several hundred nm to several tens / zm.

4. The method for producing metal particles according to any one of claims 1 to 3, wherein the metal particles are copper metal particles.

5. The metal particle according to any one of claims 1 to 4, wherein the force particle electrode on which the metal particle is deposited is immersed in acetone, and the metal particle is separated by irradiating an ultrasonic wave. Production method.

6. The method according to claim 1, wherein compressed air is blown onto the force source electrode on which the metal particles are deposited, or impact or vibration is applied to the cathode electrode during electrolysis to separate the metal particles from the force source electrode. 5. The method for producing metal particles according to any one of claims 1 to 4.

7. The method for producing metal particles according to any one of claims 1 to 6, wherein a fine carbon fiber is dispersed in the electrolytic solution by adding a dispersant comprising an organic compound.

8. The method for producing metal particles according to claim 7, wherein polyacrylic acid having a molecular weight of 500 or more is used as the dispersant.

9. The method for producing metal particles according to any one of claims 1 to 8, wherein an electrode having a roughened surface is used as the cathode electrode.

10. Metal particles produced by the method for producing metal particles according to any one of claims 1 to 9. Corrected form (Rule 91)

11. A composite material obtained by melting the aggregate of metal particles according to claim 10.

Corrected form (Rule 91)