JP2001089803A - Method of fabricating fine spherical metal powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of fabricating a fine spherical nickel metal which is a metal powder of narrow particle size distribution and is usable as an inner electrode of a multilayer ceramic capacitor. SOLUTION: An emulsion is used as a field of reaction. A W/O emulsion is prepared, and water is volatized from this emulsion and the colloid of the metal is allowed to gelatinize. If necessary, the resultant metal powder is subjected to heating treatment in an inert gas atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a fine spherical metal powder, and more particularly to a spherical metal powder having an average particle size in the range of 0.1 μm to several tens μm and a narrow particle size distribution. For example, the present invention relates to a method for producing a fine spherical metal nickel powder which can be suitably used as an internal electrode of a multilayer ceramic capacitor, or a fine spherical metal copper powder which can also be suitably used as an external electrode.

[0002]

2. Description of the Related Art In recent years, as electronic components have been reduced in size and capacity, multilayer ceramic capacitors have also been required to be more compact and higher in capacity. Multilayer ceramic capacitors print a paste containing precious metal powder for internal electrodes such as palladium and platinum on a dielectric green sheet composed of ceramic dielectric powder such as barium titanate and a binder such as polyvinyl butyral, and dried. Then, the internal electrodes are stacked so that they alternately overlap,
After thermocompression bonding, and then cutting it into appropriate dimensions, firing at a temperature of about 1300 ° C. to sinter the internal electrodes and the ceramic dielectric while removing the binder, and then, It is manufactured by forming electrodes.

Therefore, as a metal for the internal electrode,
It is necessary that the ceramic dielectric does not melt at the sintering temperature and is not oxidized.Thus, conventionally, as described above, expensive noble metals such as platinum and palladium are used, and Ceramic capacitors also have to be expensive.

[0004] In recent years, various studies have been conducted on practical applications as a low-cost multilayer ceramic capacitor using nickel as a base metal as an internal electrode instead of the above-mentioned expensive multilayer ceramic capacitor using platinum or palladium as an internal electrode. But there is a big problem here.

The internal electrodes of the multilayer ceramic capacitor are:
Limited by the size of the metal powder used for the internal electrode,
It cannot be made thinner than the particle size of the metal powder. Since the thickness of the internal electrode is usually 1 to 2 μm,
When particles larger than μm are used, the electrode layer becomes non-uniform, which may cause poor conduction. In addition, in the laminating step, the internal electrode layer penetrates the dielectric layer to cause poor insulation. Therefore, the nickel powder used for the internal electrode of the multilayer ceramic capacitor has a particle size of 0.1 to 1
It is about μm, and it is strongly required that the particle size distribution is narrow in consideration of the filling property.

For this reason, various methods for producing metallic nickel powder having such properties have been proposed in the prior art. However, any of these methods tends to produce particles having a cubic or other crystal habit. Therefore, Japanese Patent Application Laid-Open No. 4-36580
No. 6 proposes a method for producing fine spherical metallic nickel powder by reducing the partial pressure of nickel chloride and reducing it with hydrogen in the gas phase, but the production cost is extremely high.

Of course, as described in, for example, JP-A-53-16437, a method of reducing various compounds including metal oxides with pressurized hydrogen while heating them to a high temperature is also known. However, a method for producing fine spherical metallic nickel powder has not been known.

The present inventors have focused on a method of using an emulsion as a reaction field in order to produce fine spherical metal powder at low cost and easily, and as a result of intensive studies, they have found that a uniform fine particle size is obtained. Succeeded in obtaining a spherical metal powder having, and by performing a heat treatment under an inert gas atmosphere such as nitrogen as necessary, succeeded in obtaining a spherical metal fine powder, and completed the present invention. Things.

As a method of using an emulsion as a reaction field, a method of obtaining fine spherical nickel carbonate as described in, for example, JP-A-2-59432 has been known and attracted attention. . According to such a method, an aqueous solution of a water-soluble inorganic salt is added to a non-aqueous medium together with a surfactant, and the mixture is stirred to prepare a W / O type emulsion, and a suitable neutralizing agent (acid or alkali) is added thereto. )
The water-insoluble inorganic salt is precipitated as fine spheres in the fine droplets of the inorganic salt.

However, according to the method using the emulsion as a reaction field, the emulsion is easily broken by the influence of the acid and alkali used as the neutralizing agent, and the salt by-produced together with the water-insoluble nickel salt. Therefore, it is difficult to secure a stable reaction field throughout the entire reaction, and thus it is difficult to obtain spherical nickel salt particles having a uniform fine particle size.

Conventionally, even if spherical nickel salt particles having a uniform and fine particle diameter can be obtained, for example, the spherical shape cannot be maintained in the process of oxidizing and reducing the nickel salt. It is difficult to obtain a uniform fine spherical metallic nickel powder, and it has been described by the present inventors that the present invention is disclosed in Japanese Patent Application Nos. 10-139683 and 10-139684.
It just looks at such methods.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the production of fine spherical metal powder, and has an average particle diameter of 0.1 μm to several tens μm.
It is an object of the present invention to provide a method for producing a fine spherical metallic nickel powder which is a spherical fine metal powder having a narrow particle size distribution and which can be suitably used as, for example, an internal electrode of a multilayer ceramic capacitor.

[0013]

The method for producing a fine spherical metal powder according to the present invention comprises mixing an aqueous colloidal solution of a metal selected from nickel, cobalt or copper with a non-aqueous medium to obtain a W / W
O-emulsion is formed, and then water is evaporated from the emulsion to gel these metal colloids. If necessary, the obtained metal powder is heated in an inert gas atmosphere. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aqueous metal colloid solution of the present invention can be obtained by a known method, but it is needless to say that this is limited to nickel, cobalt or copper. Such a metal colloid is prepared, for example, by dissolving a predetermined concentration of a water-soluble metal salt in a predetermined concentration aqueous solution of a protective colloid such as gelatin, polyvinyl alcohol or a dispersant, adding a reducing agent such as hydrazine under heating, and performing wet reduction. Can be prepared. The size of the metal colloid particles thus obtained can be adjusted by the concentration of the metal salt, the molar ratio with the reducing agent, the concentration of the protective colloid, and the like.

The method for producing fine spherical metal powder according to the present invention comprises a first step of producing fine spherical particles, and a heat treatment of the fine spherical particles in an inert gas atmosphere, if necessary, to obtain fine spherical metal particles. A second stage of powdering.

First, the first stage will be described. According to the present invention, an aqueous metal colloid solution obtained by a known method is mixed and stirred with a non-aqueous medium in the presence of a surfactant to prepare an emulsion according to a conventional method. Preferably, a nonionic surfactant having higher hydrophilicity is added to the aqueous metal colloid solution, and if necessary, the nonionic surfactant is dissolved by heating. To the non-aqueous medium, a nonionic surfactant having higher lipophilicity is added and, if necessary, dissolved by heating. Usually, while stirring the non-aqueous medium using a dispersing machine, the above-mentioned aqueous metal colloid solution is gradually added thereto to finely disperse the droplets of the aqueous metal colloid solution to prepare a W / O emulsion. Can be.

The particle size and particle size distribution of the spherical metal particles finally obtained in the first stage are appropriately determined according to the size and particle size distribution of the aqueous phase (droplets) in the emulsion, and further, the concentration of the aqueous metal colloid solution. The size and particle size distribution of the droplets in the emulsion can be adjusted according to the combination of surfactants used and their respective amounts, the type of disperser,
It can be adjusted by the stirring speed of the disperser.

The non-aqueous medium for preparing the emulsion is preferably a water-insoluble one which is hardly evaporated and stable in a heat treatment under reduced pressure or normal pressure as described later.
Therefore, those having a solubility in water of 5% or less and a boiling point higher than that of water are preferably used.

As such a non-aqueous medium, for example, n-
Octene, isooctene, squalane, aliphatic hydrocarbons such as kerosene, cycloaliphatic hydrocarbons such as cyclooctane, cyclononane, cyclodecane, aromatic hydrocarbons such as toluene, ethylbenzene, isopropylbenzene, cumene, mesitylene, tetralin, Ethers such as butyl ether and isobutyl ether, halogenated hydrocarbons such as dichloropentane, n-propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, isobutyl propionate, ethyl butyrate, butyl butyrate And the like, and mixtures thereof.

In addition to the above, synthetic oils such as natural oils such as mineral oils and animal and vegetable oils, hydrocarbon oils, ester oils, ether oils, fluorine-containing lubricating oils, phosphorus-containing lubricating oils, and silicon-containing lubricating oils are also available. Can be exemplified.

In particular, in the present invention, a hydrocarbon-based organic solvent which is insoluble in water and has a low vapor pressure is preferable, and specifically, an aliphatic hydrocarbon-based organic solvent having a boiling point of 100 ° C. or more at normal pressure is preferably used. .

The surfactant used for preparing the emulsion is appropriately selected depending on the non-aqueous medium used.
Although not particularly limited, in particular, in order to obtain a stable emulsion, the metal colloid aqueous solution (aqueous phase) is previously added with H
A highly hydrophilic surfactant having an LB value of 10 or more is dissolved, while a highly lipophilic surfactant having an HLB value of 10 or less is dissolved in a non-aqueous medium (oil phase). The phase and the oil phase should be mixed.

The amount of these surfactants used may be appropriately selected depending on the W / O ratio and the required particle size of the emulsion, and is not particularly limited, but is usually 20% by weight based on the emulsion. Or less, preferably,
It is in the range of 0.5 to 15% by weight. As will be described later, when the surfactant is dissolved in both the aqueous phase and the oil phase, it is usually 20% by weight or less, preferably 0.5 to 10%, based on the water or the non-aqueous medium. % By weight.

Further, the W / O ratio in the emulsion is
Although it depends on the amount and properties of the non-aqueous medium used, particularly on the viscosity and on the properties of the surfactant used, especially on the HLB value, a stable emulsion is usually obtained in the range of 3/2 to 1/10. Yes, preferably in the range of 1/1 to 1/5, particularly preferably in the range of 1/3 to 1/5. However, it is not limited to this.

Nonionic surfactants having an HLB value of 10 or more, such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, and polyoxyethylene sorbitan monostearate, which are used for preparing the above emulsion, ,
Polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan trioleate, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, Polyoxyethylene fatty acid esters such as polyethylene glycol monooleate, polyoxyethylene higher alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene Polyoxy such as octyl phenyl oleyl ether and polyoxyethylene nonyl phenyl ether Ethylene luxury, and the like alkyl aryl ethers.

Assuming that the HLB value is 10 or less,
For example, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate and other sorbitan fatty acid esters, glycerin monostearate, glycerin monooleate Examples include glycerin fatty acid esters such as ate.

After preparing an emulsion in which droplets of the aqueous metal colloid solution are finely dispersed in a non-aqueous medium in this manner, preferably under normal pressure while slowly stirring, or under reduced pressure as necessary. The metal gels in the aqueous solution of the metal colloid by heating and evaporating the water, thereby causing the metal to gel in the droplets of the aqueous metal colloid solution. Medium dry,
If the metal thus obtained is centrifuged, washed and dried, for example, the desired fine spherical metal particles can be obtained.

According to the present invention, in order to evaporate water from the emulsion, there is no particular limitation as long as the emulsion is not destroyed during that time. Aeration under normal pressure,
Alternatively, suction may be performed under reduced pressure. In particular, suction is preferably performed under reduced pressure while heating the emulsion.

According to the present invention, when the emulsion is sucked under reduced pressure, the temperature and pressure conditions are particularly
Although not particularly limited, it is usually sufficient if the pressure is reduced under a reduced pressure (vacuum) of 400 mmHg or less.
It is about. Also, the temperature may range from 0 to 90 ° C, but preferably ranges from 10 to 80 ° C, and most preferably ranges from 20 to 70 ° C.

In the present invention, the emulsion is used in an amount of 20 to
Good results can be obtained by evaporating water from the emulsion while heating to a temperature in the range of 70 ° C. under reduced pressure using an aspirator, and thus under reduced pressure of about 10 to 50 mmHg.

However, according to the present invention, in order to evaporate water from the emulsion containing the droplets of the aqueous metal colloid solution, the emulsion may alternatively be simply stirred under normal pressure. As another method, air may be blown into the emulsion, that is, aerated while heating under normal pressure, if necessary.

After treating the emulsion in this way, the obtained metal is filtered, washed, and dried, usually to have a particle size of 0.1 to 15 μm and an average particle size of 0.2 to 5 μm. And spherical and fine metal particles having a uniform particle diameter can be obtained.

Next, according to the present invention, if necessary, as a second step, the uniformly fine metal particles thus obtained are subjected to a heat treatment in an inert gas atmosphere, so that the particle size is usually reduced to 0. 0.1 to 15 μm, average particle size 0.2 to 5
A uniform fine spherical metal powder having a diameter of μm can be obtained.

In the present invention, the heat treatment is carried out in an inert gas atmosphere, usually in nitrogen, at a heating rate of 100 ° C./hour or less, preferably 60 ° C./hour or less.
To 800 ° C, preferably 500 to 700 ° C.

When the heating temperature is lower than 400 ° C., it may not be possible to obtain denser metal particles. On the other hand, when the heating temperature is higher than 800 ° C., the metal particles become spherical due to firing. Sometimes the form cannot be maintained. Thus, when the heating temperature is out of the above range, it is difficult to finally obtain a uniform fine and solid spherical metal powder.

When the heating rate is higher than 100 ° C./hour, spherically-shaped metal powder is likely to be generated depending on the heat treatment temperature. In the case of nickel, for example, such a metal powder is not preferable as an internal electrode material of a multilayer ceramic capacitor. The lower limit of the heating rate is not limited at all in terms of the properties of the obtained metal powder, but is usually 10 ° C./hour or more, preferably 20 ° C./hour or more from the viewpoint of productivity. is there.

As described above, according to the present invention, the uniform fine spherical metal particles obtained in the first step are subjected to a heat treatment in an inert gas atmosphere as necessary, so that the particle size distribution is narrow and uniform. Fine metal powder can be obtained.

[0038]

As described above, according to the method of the present invention,
In the first step, an aqueous metal colloid solution obtained by a known method is mixed with a non-aqueous medium to form a W / O emulsion, and the emulsion is then heated or suctioned under reduced pressure to obtain an aqueous solution of the metal colloid. By evaporating water from the mixture, and further drying in oil if necessary, a spherical metal having a uniform and fine particle size can be obtained as a precipitate.

According to the present invention, the metal colloid gels in the droplets and precipitates as metal during the process of evaporating water from the emulsion, so that spherical metal particles having a uniform and fine particle size can be obtained. .

The metal particles obtained by the method of the present invention have a uniform and fine particle size in the case where the conventional metal particles are non-spherical. Accordingly, by performing heat treatment in an inert gas atmosphere, a uniform and fine spherical solid metal powder having a narrow particle size distribution can be obtained.

As described above, according to the present invention, it is possible to easily and inexpensively obtain a uniform and fine spherical solid metallic nickel powder. It can be suitably used as a material.

[0042]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

Example 1 To 20 g of gelatin was added 500 ml of water, and the mixture was heated to 60 ° C. and dissolved. This solution was added to commercially available nickel chloride (Ni
A solution prepared by previously dissolving 100 g of Cl ₂ .6H ₂ O) in 400 ml of water was added to make the total amount 1000 ml, and the mixture was thoroughly stirred and mixed to prepare a 0.42 mol / L aqueous solution as nickel. The aqueous solution was heated to 80 ° C., 60 g of commercially available hydrazine (nickel / hydrazine = 1/3 molar ratio) was quickly added, and a few drops of palladium nitrate (50 g / Las Pd) aqueous solution were added as a catalyst to start the reaction. The mixture was stirred at 80 ° C. for 2 hours to obtain a colloidal aqueous solution of nickel.

5 g of polyoxyethylene sorbitan monooleate having an HLB value of 15 nonionic surfactant (Rhodol TW-O120 manufactured by Kao Corporation) was added to 650 g of the aqueous nickel colloid solution thus obtained.
Stir at <RTIgt; C </ RTI> to dissolve. Separately, as a non-aqueous medium,
To 350 g of super squalane having a boiling point of about 280 ° C. (Squalane Co., Ltd.), 10 g of a nonionic surfactant sorbitan monooleate having an HLB value of 4.3 (Rhodol SP-O10 manufactured by Kao Corporation) was added.
Stir at <RTIgt; C </ RTI> to dissolve.

Next, an aqueous solution of nickel colloid in which a surfactant was dissolved and a non-aqueous medium were mixed, and the mixture was stirred at 3000 rpm for 10 minutes using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). An emulsion of the type was prepared.

At a temperature of 50 ° C., the emulsion was sucked under a reduced pressure of 20 to 30 mmHg to evaporate water, and the suction was continued to obtain a nickel-in-oil separated liquid. The solution is filtered, washed sufficiently in the order of hexane, methanol and water, and dried at a temperature of 100 ° C. for 2 hours to obtain a spherical metal having a particle size of 0.1 to 2.0 μm and an average particle size of 0.78 μm. 10 g of nickel powder was obtained.

X-ray diffraction confirmed that the particles thus obtained were metallic nickel. At this time, the size of the nickel crystallite was 175 ° (angstrom). FIG. 1 shows a scanning electron micrograph of the metallic nickel powder thus obtained, and FIG. 2 shows the particle size distribution.

Example 2 The nickel metal powder obtained in Example 1 was heated at 20 ° C./hour in a nitrogen stream of 5 L / min and heat-treated at 700 ° C. for 3 hours to obtain a particle size of 0.1 to 0.1 μm. A spherical nickel metal powder having a diameter of 1.0 μm and an average particle diameter of 0.43 μm was obtained. At this time, the size of the nickel crystallite was 476 ° (angstrom). FIG. 3 shows a scanning electron micrograph of the metallic nickel powder thus obtained, and FIG. 4 shows the particle size distribution.

Example 3 To 20 g of gelatin was added 500 ml of water, and the mixture was heated to 60 ° C. and dissolved. This solution is added to commercially available copper chloride (CuCl ₂
2H ₂ O) A solution prepared by previously dissolving 65 g in 400 ml of water was added to make the total amount 1000 ml, and the mixture was thoroughly stirred and mixed.
A 0.38 mol / L aqueous solution was prepared as copper. This aqueous solution is heated to 80 ° C. and 38 g of commercially available hydrazine
(Copper / hydrazine = 1/2 molar ratio) was quickly added, and palladium nitrate (50 g / LasPd) was further used as a catalyst.
A few drops of an aqueous solution were added to start the reaction, followed by stirring at 80 ° C. for 2 hours to obtain a copper colloid aqueous solution.

5 g of polyoxyethylene sorbitan monooleate having an HLB value of 15 nonionic surfactant (Reodol TW-O120 manufactured by Kao Corporation) was added to 650 g of the aqueous copper colloid solution thus obtained. To dissolve. Separately, as a non-aqueous medium, a nonionic surfactant sorbitan monooleate having an HLB value of 4.3 (Rheodor SP- manufactured by Kao Corporation) is added to 350 g of super squalane having a boiling point of about 280 ° C. (Squalane Co., Ltd.). O10) (10 g) was added, and the mixture was stirred at 80 ° C. and dissolved.

Next, a copper colloid aqueous solution in which a surfactant was dissolved and a non-aqueous medium were mixed, and the mixture was stirred at 3000 rpm for 10 minutes using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), and the W / O An emulsion of the type was prepared.

At a temperature of 50 ° C., the emulsion was sucked under a reduced pressure of 20 to 30 mmHg to evaporate water, and the suction was continued to obtain a copper in-oil separated liquid. This liquid is filtered, washed sufficiently in the order of hexane, methanol and water, and dried at a temperature of 100 ° C. for 2 hours to obtain a spherical metal having a particle diameter of 0.1 to 3.0 μm and an average particle diameter of 0.96 μm. 10 g of nickel powder was obtained.

The particles obtained in this manner were confirmed to be metallic copper by X-ray diffraction. At this time, the crystallite size of copper was 243 ° (angstrom). FIG. 5 shows a scanning electron micrograph of the metallic copper powder thus obtained, and FIG. 6 shows the particle size distribution.

Example 4 The metallic copper powder obtained in Example 3 was heated at 20 ° C./hour in nitrogen at 5 L / min, and heat-treated at 700 ° C. for 3 hours to obtain a particle size of 0.1 to 2 0.0 μm, average particle size 0.53 μm
m spherical metallic copper powder was obtained. The crystallite size of copper at this time was 790 ° (angstrom). FIG. 7 shows a scanning micrograph of the metallic copper powder thus obtained, and FIG. 8 shows the particle size distribution.

Example 5 To 20 g of gelatin was added 500 ml of water, and the mixture was heated to 60 ° C. and dissolved. This solution was added to commercially available cobalt chloride (CoC).
l ₂ · _{6H 2} O) 85g of a solution prepared by dissolving in water of 400ml was added, the total volume of 1000 ml, were well stirred and mixed,
A 0.36 mol / L aqueous solution was prepared in advance as cobalt. This aqueous solution was cooled to room temperature, and 27 g of commercially available sodium borohydride (cobalt / sodium borohydride = 1/2 molar ratio) was dissolved in an aqueous solution prepared by adding 500 ml of water to 10 g of sodium hydroxide in advance. The reaction was carried out by gradually adding the aqueous solution, followed by stirring for 30 minutes to obtain an aqueous colloidal solution of cobalt.

5 g of polyoxyethylene sorbitan monooleate having an HLB value of 15 nonionic surfactant (Reodol TW-O120 manufactured by Kao Corporation) was added to 650 g of the aqueous copper colloid solution thus obtained. To dissolve. Separately, as a non-aqueous medium, a nonionic surfactant sorbitan monooleate having an HLB value of 4.3 (Rheodor SP- manufactured by Kao Corporation) is added to 350 g of super squalane having a boiling point of about 280 ° C. (Squalane Co., Ltd.). O10) (10 g) was added, and the mixture was stirred at 80 ° C. and dissolved.

Next, a copper colloid aqueous solution in which a surfactant was dissolved and a non-aqueous medium were mixed, and the mixture was stirred for 10 minutes at 3000 rpm using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) An emulsion of the type was prepared.

At a temperature of 50 ° C., the emulsion was sucked under a reduced pressure of 20 to 30 mmHg to evaporate water, and the suction was continued to obtain a copper in-oil separated liquid. This liquid is filtered, washed sufficiently in the order of hexane, methanol and water, and dried at a temperature of 100 ° C. for 2 hours to obtain a spherical metal having a particle diameter of 0.1 to 5.0 μm and an average particle diameter of 1.15 μm. 10 g of nickel powder was obtained.

As a result of X-ray diffraction, it was confirmed that the particles thus obtained were metallic cobalt. At this time, the crystallite size of cobalt was 105 ° (angstrom). FIG. 9 shows a scanning electron micrograph of the metal cobalt powder thus obtained, and FIG. 10 shows the particle size distribution.

Example 6 The metal cobalt powder obtained in Example 5 was heated at 20 ° C./hour in nitrogen at 5 L / min, and treated at 700 ° C. for 3 hours to obtain a particle size of 0.1 to 3.0. 0 μm, average particle size 0.59 μ
m spherical metal cobalt powder was obtained. At this time, the crystallite size of cobalt was 397Å.

(Angstrom). FIG. 11 shows a scanning micrograph of the metal cobalt powder thus obtained, and FIG. 12 shows the particle size distribution.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph of an example of a metallic nickel powder obtained in Example 1.

FIG. 2 is a particle size distribution diagram of the metallic nickel powder obtained in Example 1.

FIG. 3 is a scanning electron micrograph of the metallic nickel powder obtained in Example 2.

FIG. 4 is a particle size distribution diagram of the metallic nickel powder obtained in Example 2.

FIG. 5 is a scanning electron micrograph of an example of a metallic copper powder obtained in Example 3.

FIG. 6 is a particle size distribution diagram of the metallic copper powder obtained in Example 3.

FIG. 7 is a scanning electron micrograph of the metallic copper powder obtained in Example 4.

FIG. 8 is a particle size distribution diagram of the metallic copper powder obtained in Example 4.

FIG. 9 is a scanning electron micrograph of an example of the metallic cobalt powder obtained in Example 5.

FIG. 10 is a particle size distribution chart of the metallic cobalt powder obtained in Example 5.

FIG. 11 is a scanning electron micrograph of the metallic cobalt powder obtained in Example 6.

FIG. 12 is a particle size distribution diagram of the metallic cobalt powder obtained in Example 6.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Hatanaka 5-1-1 Ebisshima-cho, Sakai-shi, Osaka Sakai Chemical Industry Co., Ltd. (72) Inventor Toshihiro Sugaya 5-1-1 Ebisshima-cho, Sakai-shi, Osaka Sakai Chemical Inside (72) Inventor Minoru Yoneda 5-1-1 Ebishima-cho, Sakai-shi, Osaka Sakai Chemical Industry Co., Ltd. (72) Inventor Hideto Mizutani 5-1-1 Ebisushima-cho, Sakai-shi, Osaka Sakai Chemical Industry Co., Ltd. (72) Inventor Chiyo Honda 5-1-1 Ebishima-cho, Sakai City, Osaka Prefecture F-term (reference) 4K017 AA03 BA03 BA05 CA01 CA07 DA01 EJ01 EJ02 EK08 FA02 FA03 FB11

Claims (2)

[Claims] An aqueous colloidal solution of a metal selected from nickel, cobalt and copper is mixed with a non-aqueous medium to form a W / O emulsion, and water is evaporated from the emulsion to gel these metal colloid particles. A method for producing a fine spherical metal powder. 2. The method according to claim 1, wherein the fine spherical metal particles are placed in an inert gas atmosphere.
The method for producing a fine spherical metal powder according to claim 1, which is subjected to a heat treatment.