JP3081915B2 - Method for producing metal-carbon composite fine particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing metal-carbon composite fine particles comprising fine metal particles and carbonaceous material. More specifically, the present invention relates to a method for producing fine particles obtained by immersing a metal electrode and a counter electrode installed in an electric discharge machining apparatus in a solvent containing carbon and causing discharge between the electrodes.

[0002]

2. Description of the Related Art Conventionally known methods for producing a metal-containing carbonaceous homogeneous material include a wet method, which comprises subjecting a polymer having a metal complex residue to thermal decomposition under an inert gas atmosphere or in vacuum; There are known a method of thermally decomposing a mixture of a metal complex derivative and a carbon source such as pitch in an inert gas atmosphere, and a method of directly thermally decomposing a metal complex derivative. As a dry method, an arc discharge method using a carbon electrode containing a metal is known.

Taking the iron complex as an example, the above-mentioned examples include 1) a method of thermally decomposing a copolymer of ferrocene-methylethylketone at 500 ° C. or poly (β-ferrocenylchloroacrolein) at 400 ° C. (LAAlie)
r et al., Dokl. Akad. Nauk SSSR, 194 , 843 (1970)) and 2)
In a vacuum, a polymer obtained by polycondensation of acetylferrocene and furfural with a sulfuric acid catalyst is used at 350 to 400.
C. (S. Yajima et al., Nature, 267 , 823 (1977)), or a method of thermally decomposing a 1-ferrocenylethanol-formaldehyde-phenol copolymer at 350-400.degree. C. (M. Omori et al., Bull. Chem.Soc.Jpn., 50 , 1157-11
60 (1977)) is known. The metal-containing carbonaceous material obtained by these methods is one in which fine particles of iron, iron oxide, or iron ions are highly dispersed in a carbon matrix. Since these methods require complicated pretreatments such as immobilization and polymerization before thermal decomposition, they cannot be said to be simple production methods.

[0004] As a method of utilizing the pitch or the like, 1)
Ferrocene with saturated benzene vapor in hydrogen stream 110
Pyrolysis at 0 ° C (Endo et al., Applied Treatment, 54 , 507-510)
(1985)), 2) A method of heat-treating a solvent-soluble mesophase pitch and a tris (acetylacetonato) iron (III) complex in an inert gas atmosphere at 400 to 1000 ° C. (1993)), 3) A polyacrylonitrile-based fine particle polymer was synthesized by seed polymerization using polystyrene as a core, and the resulting polyacrylonitrile-based fine particle polymer was reacted with two kinds of metal salts to obtain a polymer.
Synthesis of fine particle polymer complex with immobilized metals
Baking at 00 to 1000 ° C (Washimi et al., Polymer Pr.
eprints, 42 , 3660-3662 (1993)) and the like. The metal-containing carbonaceous material obtained by these methods is a material in which fine particles of iron or iron oxide are highly dispersed in a carbon matrix. This is not a simple synthesis method because it requires operations such as synthesis and polymerization of the iron complex as a raw material in advance.

The method of directly pyrolyzing a ferrocene derivative (Ushijima et al., Japanese Patent Application No. 6-68020) also requires the synthesis of a complex in advance.

As a dry method, an arc discharge method using a metal-containing carbon electrode (Yahachi Saito, Surface, 32 (4), 227-232 (199)
4)) are known. However, it is necessary to synthesize a carbon electrode containing a metal in advance by heat treatment at about 1800 ° C., the yield of the generated metal-carbon composite fine particles is low, and the fine particles are scattered in the reaction tube. It has drawbacks such as difficulty.

[0007]

An object of the present invention is to provide a method for synthesizing various metal-carbon composite fine particles by a simple method.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors immerse a metal plate electrode and a counter electrode installed in an electric discharge machine in an organic solvent containing carbon, By discharging between the two poles, the discovery that metal-carbon composite fine particles in which metal fine particles were included by decomposed carbon from an organic solvent was generated,
The present invention has been made. In this case, various kinds of metal-carbon composite fine particles can be easily synthesized by changing the type of the metal plate. Further, since the fine particles are generated in the solvent, collection is easy, unlike the dry method.

That is, according to the present invention, there is provided a method for producing various metal-carbon composite fine particles, characterized in that a discharge is caused between a metal electrode and a counter electrode provided in an organic solvent.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. In the method for producing metal-carbon composite fine particles of the present invention, various metal plates such as iron, cobalt, niobium, and platinum can be used as the metal raw material. In addition, brass, Hastelloy C, platinum rhodium, stainless steel SUS-316,
Various alloys such as a molybdenum alloy can also be used as the raw material plate. For the counter electrode, a metal having low electric resistance such as copper, graphite, brass, and copper tungsten is usually used. Its shape is a rod or a cylinder.

The metal plate and the counter electrode are usually used by immersing them in an organic solvent. The organic solvent used in this case is arbitrary as long as it contains carbon. Aliphatic hydrocarbons such as hexane, octane, kerosene, and liquid paraffin; aromatic hydrocarbons such as benzene, toluene, and xylene;
Monohydric or polyhydric alcohols such as methanol, ethanol, ethylene glycol and glycerin; ethers such as diethyl ether and dibutyl ether; fatty acids such as acetic acid and propionic acid; ketones such as acetone and methyl ethyl ketone; triethylamine and tripropylamine And aliphatic heterocyclic bases such as pyridine and quinoline, and aromatic ethers such as diphenyl ether. These can be used alone or as a mixture. In addition, alcohols and aliphatic amines can be used as a mixture with water. Generally, the diameter of fine particles of a metal or the like dispersed in carbon tends to be smaller for a solvent having a higher viscosity.
Therefore, solvents such as liquid paraffin and glycerin are particularly preferred. In this case, the viscosity of the organic solvent is usually 10 centipoise or more, preferably 100 to 2000 poise.

The electric discharge can be performed using an electric discharge machine or the like. The pulse width of the discharge is usually about 7 to 50 μsec, and the pause width is usually 12 to 80 μsec. Processing current is 2A
It is performed in the following, and is usually 0.2 to 1.0A. Also,
The voltage is between 10 and 150 volts. After the discharge, the solvent containing the metal-carbon composite fine particles, which is a product, can be easily separated by filtration. Unlike the dry method, there is no scattering of products.

The metal-carbon composite fine particles obtained by the wet discharge have a structure in which metal fine particles are embedded in carbonaceous material. The particle diameter of the metal fine particles contained in the carbonaceous material varies depending on the type of metal (such as melting point) and the type of solvent (such as boiling point). Generally, as the melting point of the metal is lower and the boiling point of the solvent is lower, the diameter of the metal fine particles tends to be larger. Particle size measurement and transmission electron microscope observation confirmed that the particle size was in the range of several nm to several tens nm.

According to this discharge method, metal-carbon composite fine particles whose surface is coated with carbon and have excellent oxidation resistance can be efficiently obtained by a simple method, and can be used in many fields of material development. It is.

[0015]

Next, the present invention will be described in more detail with reference to examples.

Example 1 Using a steel plate (2 cm × 4 cm × 0.5 cm) as an electrode and a copper pipe (outer diameter 0.5 cm, length 5 cm) as a counter electrode, discharge was performed by dipping in liquid paraffin as a solvent. The generated iron-carbon composite fine particles accumulate in liquid paraffin. After reacting for 70 hours, the product was filtered, washed and dried to obtain 3.28 g of metal-carbon composite fine particles. In this method, metallic iron fine particles (several nanometers) are dispersed in a carbon structure, and one whole particle (particle size distribution measuring method, average 31
0 nm) was found from powder x-ray and TEM observations. The surface area (BET method) and metal content (calculated by elemental analysis, mol%) were as shown in Example 1 shown in Table 1.

Examples 2 to 11 The same procedures as in Example 1 were carried out except that nickel, tin, molybdenum, niobium, titanium, cobalt, copper, lead, silver and platinum were used as metal plates and the reaction time was slightly changed for each metal. When the reaction was performed in the same manner, the results shown in Table 1 were obtained. It was similar to iron in that metal (carbide) particles were dispersed in the structure of carbon to form one whole particle. The metal species in the product was a mixture of molybdenum and molybdenum carbide in molybdenum, and a carbide in niobium and titanium.
In each case, each metal fine particle was observed.

Example 12 A reaction was carried out in the same manner as in Example 2 except that glycerin was used as a solvent. As a result, the overall particle size was almost the same as in Example 2, but the metal species (nickel and nickel oxide) were used. Was a little larger than 3 to 100 nm.

[0019]

[Table 1]

The particle diameter (total) of the metal-carbon composite material fine particles shown in the table indicates the average particle diameter, the metal particle diameter indicates the minimum particle diameter and the maximum particle diameter, and the crystallite is powder X. Shows the value calculated from the line.

[0021]

According to the present invention, fine metal particles coated with carbonaceous material can be produced efficiently and by a very simple method. Because the product accumulates in the solvent,
The collection of generated fine particles is much easier than the dry arc discharge method. These are extremely important in the field of material development as a method of producing materials that can be applied not only as metal particles with excellent oxidation resistance but also as materials for conductive or new catalytic materials, magnetic fluids and electrorheological fluids. Has meaning.

Claims (2)

(57) [Claims] 1. A method for producing metal-carbon composite fine particles, comprising discharging between a metal electrode and a counter electrode provided in an organic solvent. 2. The method for producing metal-carbon composite fine particles according to claim 1, wherein a highly viscous organic solvent is used as said organic solvent.