JPS63192873A - Method for coating carbon material with metal - Google Patents

Abstract

PURPOSE:To uniformly coat a carbon material with a metal at a high sticking rate in a simple and safe manner by bringing the carbon material into contact with a soln. of a complex contg. the metal as the central atom and by depositing the constituent metal of the complex on the surface of the carbon material by heating. CONSTITUTION:A carbon material such as a carbon fiber or carbon powder is immersed in a soln. of a complex contg. a metal for coating such as Fe, Co or Ni as the central atom and brought into contact with the soln. A ligand which is easily released by decomposition at a relatively low temp., e.g., carbonyl or olefin is preferably used as the ligand of the complex. Diphenylmethane, alkylbenzene or the like is suitable for use as the solvent of the complex soln. The metal is then deposited on the surface of the carbon material by heating the material to a relatively low temp. of about 100-200 deg.C while in contact with the complex soln. to form a metallic film. The surface of the carbon material is preferably activated by oxidation treatment and treatment with a metallic salt soln. before immersion in the complex soln. so as to accelerate the decomposition reaction of the complex.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to carbon-metal composite materials, and particularly to a method for forming a stable metal film on the surface of a carbon material.

[Background of the invention]

Since carbon materials are lightweight and have excellent mechanical properties, they are used in various structural members, and in recent years, various studies have been conducted on composite materials of carbon materials and other materials. For example, carbon materials processed into particles, fibers, or cloth are attracting attention as materials for composites with metals and other materials due to their excellent properties.

By the way, when forming a composite material by combining such a carbon material and a base metal, a particular problem is the wettability or surface affinity of the two.

For example, various methods such as diffusion bonding, powder metallurgy, and molten metal infiltration have been proposed as methods for manufacturing FRM (fiber reinforced metal). Careful attention must be paid to the fact that mechanical properties may deteriorate due to problems occurring at the interface. Specifically, (a) physical wettability between carbon fiber and metal is poor, making it impossible to obtain strong adhesion at the interface, and (b) carbide is generated due to reactions at the interface during the manufacturing stage, and this is the carbon material. There are problems such as deterioration of strength.

Conventionally, in order to improve the wettability between carbon and metal and suppress carbide formation reactions, there has been a method in which the surface of a carbon material is coated with a specific metal in advance by methods such as electroless plating, vapor deposition, or sputtering. is proposed. However, in the above-mentioned electroless plating method, for example,
A method is used in which metals are deposited on the surface of carbon materials by reducing metal ions in an aqueous solution with formalin or the like, but generally the metal deposition rate by this method is extremely low. On the other hand, vapor deposition methods such as CVD and sputtering methods require complicated operating steps and complicated equipment, which not only brings various disadvantages in industrial and industrial applications, but also It takes a long time,
Furthermore, when the carbon material has a structure such as a cloth-like structure, it is difficult to coat the inside of the material with metal, and there is a problem that the coating state tends to be non-uniform.

[Summary of the invention]

The present invention has been made in view of the problems associated with the prior art as described above, and aims at the following points.

(a) To provide a method that can coat the surface of a carbon material with a metal using simple means.

(b) To prevent the formation of carbides as much as possible during the formation of a metal film.

(c) The carbon material is in the form of fine particles, powder, fibers or cloth;
To provide a method for forming a stable and uniform metal coating with a high adhesion rate, even when forming a fine or complicated structure such as a knitted fabric.

In order to achieve the above object, the method for coating a carbon material with a metal according to the present invention includes heating a carbon material and a solution of a complex having a central atom of the metal to be coated on the carbon material by bringing them into contact with each other. It is characterized in that the constituent metals of the complex are deposited on the surface of the carbon material.

Furthermore, in the method of the present invention, it is preferable that the surface of the carbon material is previously subjected to activation treatment prior to contact with the complex solution.

[Detailed description of the invention]

The present invention will be explained in more detail below.

The form of the carbon material to be coated with metal in the present invention is not particularly limited, but in the method of the present invention, carbon having a large specific surface area and a fine structure, such as carbon fiber or its knitted fabric, carbon powder, etc. Excellent coating effects can be obtained even when coating materials.

In the present invention, it is particularly preferable to previously perform activation treatment on the surface of the carbon material in order to promote the decomposition reaction of the complex prior to treatment with a complex solution to be described later. This activation treatment can be performed by combining an oxidation treatment and a treatment with a metal salt solution.

That is, as an activation treatment method, first, the carbon material is
For example, after performing oxidation treatment with a conventionally known oxidizing agent such as a sulfuric acid acidic potassium dichromate solution, a metal salt capable of reducing heavy metals or their salts having decomposition activity against the complex solution, such as stannous chloride, is used. This can be carried out by immersion treatment in an acidic aqueous solution, and then immersion treatment in an acidic aqueous solution of a heavy metal or its salt having decomposition activity against the complex solution to fix the active metal on the surface of the carbon material.

As the heavy metal or its salt having decomposition activity for the complex solution, palladium metal or palladium chloride can be preferably used.

By performing the activation treatment in this manner, the metal, such as palladium metal, fixed on the surface of the carbon material by the treatment becomes a promoter for preferentially decomposing the complex on the surface of the carbon material in the subsequent complex solution treatment. At the same time, the important function of uniformly depositing the metal derived from the decomposed complex on the surface of the carbon material using the decomposition point as a nucleus is further promoted.

The concentration of each treatment solution described above does not need to be in a particularly limited range, and can be appropriately selected within a range that allows active metals such as PB that can act as a catalyst to be sufficiently fixed on the surface of the carbon material.

After performing the above activation treatment, treatment with a complex solution is performed.

The complex used in this treatment is selected from complex compounds that have a central atom of the metal to be coated on the carbon material, and among these, those that have a relatively low valence (including zero valence) metal as a central atom. Complexes are preferred.

The central metal is generally a metal such as iron, cobalt, or nickel, but is of course not limited to these, and other transition metals may be used as the central atom. Note that the metal coated on the carbon material has a melting point lower than that of the metal to be composited into the FRM in order to improve wettability with the metal used for FRM and to prevent material deterioration due to metal-carbon interaction. It is important to select a high metal species.

Examples of ligands constituting the complex include carbonyl, olefin, polyene, dipyridine, etc., but those that can be easily decomposed and released at relatively low temperatures and do not inhibit the cohesive growth of the metal on the surface of the carbon material. It is necessary that

Specific examples of complexes include F e 2 (CO) 5, F
e (Co)4, N i (Co)4, Co (C
Preferably used are carbonyl complexes such as O)s, dipyridyl complexes such as bisdipyridylnickel, and diene complexes such as bissilylooctadienenickel.

The solvent system for dissolving the above complex is not particularly limited as long as it is stable and inert up to the decomposition temperature of the complex and has sufficient solubility for the complex, but diphenylmethane, alkylbenzene, etc. It is a solvent that is easy to use.

The concentration of the above complex solution depends on the complex used, the type of solvent system,
The optimum value is selected depending on the amount of precipitation, the properties and structure of the carbon material, and the specific surface area, but it is usually appropriately selected within the concentration range of a saturated solution or less, and is not particularly limited.

In the present invention, it is preferable that a small amount of a specific metal such as palladium or palladium chloride or a salt thereof be coexisting in the complex solution as an additional component. Such components promote the decomposition of the complex during treatment with the complex solution, are included in the cohesive growth of the precipitated metal on the surface of the carbon material, further increase the coating speed, and further improve the coating state of the coated metal. It is effective in doing so.

The above-mentioned complex solution and the carbon material can be brought into contact by usually immersing the carbon material in the complex solution. By heating in a state of contact, the complex in the solution is decomposed, and the constituent metals of the complex are deposited on the surface of the carbon material, forming a metal coating film. The heating temperature in this case varies depending on the type of complex, but usually about 100 to 200°C is sufficient. As described above, the present invention is also excellent in that a metal coating can be formed at a relatively low temperature.

After forming a metal film on the surface of the carbon material as in step 2-2, post-treatments such as washing and drying are performed as necessary to complete the coating process.

In addition, when the treatment with the above-mentioned complex solution is carried out at a relatively low temperature range of about 150°C, for example, the metal precipitated on the surface of the carbon material tends to become an aggregate of colloidal particles, especially in the case of nickel and the like. This easily causes a reaction with oxygen in the air. Therefore, in order to prevent such problems, after a metal wave film is formed by complex solution treatment, it should be immediately dried in an inert gas such as nitrogen and heated to around 200°C. It is preferable to stabilize (inactivate) the metal wave film by changing the crystal form of the deposited metal.

As described above, according to the present invention, by a simple method,
Moreover, it is possible to form a metal film on the surface of the carbon material under relatively low temperature conditions, which is advantageous in terms of operation process, and also prevents as much as possible the formation of carbides during the formation of the metal film, which is the case with conventional methods. But it's excellent.

Furthermore, according to the method of the present invention, there is no restriction on the shape or structure of the carbon material to be coated, and even if the carbon material has a fine and complicated structure such as granules, fibers, or cloth, it can be coated uniformly. It is possible to form an even metal wave film.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the description of these Examples.

Example 1 100 g of carbon fiber or a carbon fiber cloth made from carbon fiber was mixed with 15 g of potassium dichromate in advance.

100ml of sulfuric acid. It was immersed in an oxidizing solution consisting of 150 ml of water at room temperature for 3 minutes to oxidize its surface, and then
% aqueous sodium hydroxide solution and water. This was further mixed with 5 g of stannous chloride and 20 ml of concentrated hydrochloric acid. A solution of the composition of 500 ml of water, then 0.1 g of palladium chloride and 1 ml of concentrated hydrochloric acid.
ml and 400 ml of water, respectively, for 3 minutes at room temperature to precipitate palladium metal on the carbon fiber surface.

The carbon fibers treated in this way are immersed in an approximately 3% solution of iron pentacarbonyl in diphenylmethane and heated to approximately 180°C. The iron pentacarbonyl in the solution decomposes on the carbon fiber surface, and iron metal precipitates. The carbon fiber surface could be uniformly coated with iron metal. After the reaction, the mixture was passed through the mouth, washed three times with 500 ml of hexane, and dried. In this thermal decomposition reaction, carbon monoxide was generated quantitatively and could be recovered. The particle size of the iron metal particles deposited on the carbon fiber surface was 2 to 4 μm. The amount of iron metal precipitated depends on the amount of iron pentacarbonyl added, but about 60% of iron pentacarbonyl decomposed on the carbon fiber surface and precipitated as an iron metal film.

Example 2 If palladium metal is added during the thermal decomposition reaction of Example 1, the thermal decomposition reaction of iron pentacarbonyl can be promoted, and a uniform iron metal coating can be formed as in Example 1. did it. The rate of decomposition depends on the amount of palladium metal added, but when 6 mol % palladium metal was added, it was about four times faster than when it was not added.

Example 3 Even when nickel metal was used instead of palladium metal in the same manner as in Example 2, the decomposition reaction was promoted and an iron coating could be formed in the same manner.

Example 4 In the same manner as in Example 2, decomposition was promoted even when palladium chloride was used instead of palladium metal, and carbon fibers could be coated with iron metal.

Example 5 In the same manner as in Example 2, even when silver metal was used instead of palladium metal, decomposition was promoted and a uniform iron coating could be formed.

Example 6 Even if diiron nonacarbonyl is used instead of iron pentacarbonyl, a film can be formed with iron metal by the same treatment as in Examples 1 and 2, but in this case, the solubility of diiron nonacarbonyl is low. Therefore, the diiron nonacarbonyl that remained undissolved decomposed independently and became iron metal particles.

Example 7 Although carbon fibers could be coated with ferrous metal even without any pretreatment of the carbon fibers as in Example 1, many ferrous metals were reduced to particles of approximately Lμm. It precipitated independently on areas other than the fiber surface.

Example 8 Carbon fibers treated in the same manner as in Example 1 were immersed in an approximately 3% solution of cobalt octacarbonyl in diphenylmethane.
When heated to 50° C., the cobalt octacarbonyl in the solution decomposed on the surface of the carbon fibers, making it possible to uniformly coat the carbon fibers with cobalt metal. The reaction was completed in about 6 hours. The amount of cobalt metal precipitated on the fiber surface varies depending on the amount of cobalt octacarbonyl used, but is about 60~
70% of cobalt metal was deposited. The deposited cobalt metal has a cubic system. After separation, the cobalt metal coated carbon fibers were washed with hexane and dried.

Example 9 Carbon fibers treated in the same manner as in Example 1 were immersed in an approximately 3% solution of nickel tetracarbonyl in diphenylmethane and heated to approximately 150°C. The nickel tetracarbonyl in the solution was separated onto the carbon fibers. , carbon fiber could be coated with nickel. The reaction took about 6 hours, but the amount of nickel precipitated was about 60% of nickel tetracarbonyl.
%Met. As in the case of cobalt metal, it was separated from the reaction solution, washed with hexane, and dried. Note that this operation must be performed under complete sealing due to the toxicity of nickel tetracarbonyl. In the case of air activation, depending on the state of nickel precipitation, annealing treatment was performed at about 200° C. under an inert gas.

Example 10 Carbon fibers treated in the same manner as in Example 1 were immersed in an approximately 3% diphenylmethane solution of biscyclooctadiene nickel and heated to approximately 180°C, and the biscyclooctadiene nickel decomposed on the surface of the carbon fiber. As a result, nickel metal precipitated and the carbon fiber surface was able to be coated uniformly with nickel metal. The reaction was completed in about 1 hour. Although the amount of nickel metal precipitated depends on the amount of biscyclooctadiene nickel, about 50 to 60% of nickel metal was precipitated on the carbon fiber surface. The deposited nickel metal has cubic and hexagonal crystals. After separating the carbon fibers from the liquid, they were washed with hexane and dried.

Example 11 In the same manner as in Example 1, carbon fibers could be similarly coated with nickel metal by using bis-2,2'-dipyridine nickel instead of biscyclooctadiene nickel. The amount of nickel metal precipitated was 20-30%.

Example 12 Carbon black (average particle size 100 μm) pretreated in the same manner as in Example 1 was used, and Examples 1, 8.
Iron and cobalt in the same manner as 9.

Alternatively, when coating was performed using a nickel carbonyl complex, results similar to those obtained with carbon fiber were obtained.

Claims (1)

[Claims] 1. By bringing a carbon material into contact with a solution of a complex having a central atom of a metal to be coated on the carbon material and heating it, the constituent metals of the complex are precipitated on the surface of the carbon material. A method for coating a carbon material with metal, characterized by: 2. The method according to claim 1, wherein the surface of the carbon material is subjected to activation treatment before contacting with the complex solution.