JPH08319575A - Method for metal-plating carbon fine grain - Google Patents

Abstract

PURPOSE: To form a uniform metallic film on the surface of carbon fine grains. CONSTITUTION: Carbon fine grains constituted of mesophase spherulites are subjected to oxidation treatment, are deposited with Pd (NH3 )4 Cl2 by impregnation and are applied with electroless plating. By the oxidation treatment, acidic functional groups are introduced into the surface of the spherulites, Pd is deposided over the acidic functional groups, and by the electroless plating, a uniform metallic film can be formed via Pd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for metal plating of carbon fine particles capable of forming a uniform metal coating on the surface of carbon fine particles.

[0002]

2. Description of the Related Art By forming a ferromagnetic metal film on the surface of carbon fine particles having a particle size of several μm, it is possible to obtain a magnetic fluid for a vacuum seal of a rotary bearing, a filler of a paint for electromagnetic wave shielding and the like. . Further, by forming a general conductive metal film, it can be used for applications such as conductive toner and filler.

On the other hand, a so-called silane coupling method is known as a metal plating method for powder. This product is first subjected to a silane coupling treatment by diluting an aminosilane coupling agent in a mixed solvent consisting of water and ethanol and introducing powder. Then
Pd is supported on the powder by chemical bonding, and Pd is subjected to electroless metal plating.

[0004]

In the prior art, however, the problem that the silane coupling agent is extremely poisonous, the handling is troublesome, and the work management is extremely troublesome is unavoidable. Further, when general carbon black is used as the carbon fine particles, there is a problem that the whole is easily aggregated in a lump and it is extremely difficult to form a uniform film on the surface of each particle.

Therefore, in view of the problems of the prior art, an object of the present invention is to use mesophase spherulites as carbon fine particles, and replace Pd (N) with silane coupling treatment.
To provide a metal plating method for carbon fine particles, which is easy to handle and manage by employing H ₃ ) ₄ Cl ₂ impregnated and supported and which can form a uniform metal film on the surface of each particle. is there.

[0006]

Means for Solving the Problems The constitution of the present invention for attaining the above object is to carry out oxidation treatment of carbon fine particles composed of mesophase spherulites, impregnate and carry Pd (NH ₃ ) ₄ Cl _2, and carry out electroless plating. The point is to apply.

When performing electroless plating, a reducing agent and a complexing agent can be used together.

When performing electroless plating, the pH of the plating solution may be controlled.

[0009]

According to the structure of the invention, the mesophase spherulites have a lamellar structure in which the edge portion of the aromatic ring is exposed on the surface. Therefore, by oxidation treatment, hydrophilic acidic functional groups such as hydroxyl groups and carboxyl groups are formed. Can be introduced to the surface. The oxidation treatment can be carried out by immersing in an oxidant aqueous solution of nitric acid, sulfuric acid, hydrogen peroxide or the like having an appropriate concentration, or by performing heat treatment in the air.

Pd (NH ₃ ) ₄ Cl ₂ is impregnated and supported by, for example, a 5 mM aqueous solution of Pd (NH ₃ ) ₄ Cl ₂ (pH:
The spherulite that has been subjected to the oxidation treatment is put into 11) and the pressure is reduced. Since the acidic functional group on the surface of the spherulite releases a proton in a strongly alkaline aqueous solution and is negatively charged, [Pd (NH
₃ ) ₄ ] ²⁺ can be easily adsorbed.

The electroless plating depends on a plating bath. A plating solution composed of a Ni source or a Cu source, a reducing agent, and a complexing agent is prepared, and a spherulite carrying Pd is added to obtain a uniform N.
An i coating or a Cu coating can be formed on the spherulite surface.

As the Ni source, nickel sulfate, nickel chloride or the like can be used, and as the Cu source,
Copper sulfate, copper chloride, etc. can be used. Further, sodium hypophosphite, potassium borohydride, hydrazine and the like can be used as the reducing agent, and disodium malate, ammonia, ethylenediamine, glycine, pyridine and the like can be used as the complexing agent. The reducing agent reduces Pd on the surface of the spherulite, and the complexing agent prevents deterioration of the plating solution.

When electroless plating is performed, if the pH is controlled to be constant with an aqueous solution of NaOH, a more uniform thick film can be formed on the spherulite surface.

[0014]

As described above, according to the present invention, mesophase spherulites are used and Pd (NH ₃ ) Cl _{2 is used.}
By adopting the impregnating and supporting method, it is possible to uniformly support Pd on the spherulite surface through the hydrophilic oxidation functional group, and a uniform metal film can be formed through this Pd. There is an excellent effect that the handling and the work management as a whole are easy and the quality of the obtained product is extremely good.

[0015]

Example 1 Carbon fine particles having a particle size of 6 μm and made of mesophase spherulite were put into a 20% aqueous nitric acid solution, and the mixture was heated at 100 ° C.
Oxidized for a period of time. Almost no acidic functional groups were present on the untreated spherulite surface, but 5 on the spherulite surface after oxidation treatment.
There was about 175 μmol acidic functional group per 0 mg.

The oxidized spherulites are Pd (NH ₃ ) ₄ C
was placed in l ₂ of 5mM aqueous (pH 11), it was impregnated bearing 3 hours Pd at 90 ° C. using an evaporator. The amount of spherulite added was 58.2 mg per 20 ml of the aqueous solution.
And

The surface of the spherulites after impregnated and supported was uniformly covered with Pd, and neither agglomeration of spherulites nor agglomeration of Pd was observed.

Next, P was added to 200 ml of a plating solution containing nickel sulfate 2.5 mmol, sodium hypophosphite 6.5 mmol, and disodium malate 2.5 mmol.
50 mg of spherulite in which d was impregnated and supported was charged, and Pd was reduced and electroless Ni plating was performed by stirring at 60 ° C. for 30 minutes while maintaining pH 7.0 with an aqueous NaOH solution.

The surface of the obtained spherulite was uniformly covered with Ni, and no aggregation was observed. Note that Ni
Had a film thickness of about 0.8 μm, and its saturation magnetization was 27 emu / g, whereas the saturation magnetization of bulk Ni was 58.6 emu / g.

[0020]

Example 2 In Example 1, by maintaining the pH at 8.0 during electroless plating, the film thickness of Ni could be about 2 μm.

[0021]

[Example 3] In Examples 1 and 2, an equivalent Ni film could be formed by replacing nickel sulfate in the plating solution with nickel chloride.

Further, by using copper sulfate or copper chloride instead of nickel sulfate or nickel chloride, an equivalent Cu film could be formed.

[0023]

Comparative Example 1 In Examples 1 and 2, the oxidation treatment of mesophase spherulites was omitted.

The spherulite itself aggregated, Pd could not be uniformly supported on the spherulite surface, and a uniform Ni film could not be formed.

[0025]

[Comparative Example 2] In Example 1 and Example 2, Pd (NH
₃ ) Instead of impregnating and supporting ₄ Cl ₂ , reducing and supporting with PdCl ₂ was adopted.

The results were comparable to those of Comparative Example 1.

[0027]

Claims (3)

[Claims] 1. A carbon fine particle composed of mesophase spherulites is subjected to an oxidation treatment to impregnate and carry Pd (NH ₃ ) ₄ Cl ₂ .
A method for metal plating of carbon fine particles, which comprises performing electroless plating. 2. The method of metal plating of carbon fine particles according to claim 1, wherein a reducing agent and a complexing agent are used together when performing electroless plating. 3. The method of metal plating of carbon fine particles according to claim 1, wherein the pH of the plating solution is controlled during electroless plating.