JPH05319928A - Production of highly functional carbon/ceramic composite material - Google Patents

Abstract

PURPOSE:To obtain a highly functional carbon/ceramic composite material having a homogeneous and dense ceramic coating film formed on the surface of a carbonaceous material or the inner surface of the pores of the material. CONSTITUTION:A polymer sol produced by hydrolyzing a metal alkoxide solution is impregnated under reduced or positive pressure into a porous carbonaceous material having an average pore diameter of 50-200mum and a porosity of 50-70% and the polymer sol is converted into an oxide and/or a carbide by heat-treating in a non-oxidizing atmosphere at >=500 deg.C. The metal of the metal alkoxide is preferably Ti, Al, Zr, Si, B or Mg.

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 a carbon / ceramic composite high-performance material having a composite structure in which a ceramic coating layer is formed on the surface of a porous carbonaceous substrate and on the inner surface of pores.

[0002]

2. Description of the Related Art Conventionally, many attempts have been made to form a ceramic coating layer for the purpose of imparting high functionality such as material strength and oxidation resistance to carbonaceous materials. For example, directly on the surface of a carbonaceous substrate by the CVD method, or SiO
A method for forming a SiC coating through an interfacial reaction between a gas and base carbon, and a ceramic coating layer formed by applying a slurry containing mullite particles and Al particles on the surface of a carbonaceous base material and then firing it at a temperature of 1000 ° C. Method (JP-A-60-1083)
No. 88), a method of spraying MgO or ZrO ₂ on the surface of a graphite material to form a ceramic layer (Japanese Patent Laid-Open No. 57-135771), and the like correspond to this. However, these conventional techniques generally require a complicated and large-scale and expensive coating facility, and cracks and peeling phenomena may occur in the coating layer formed.

The applicant of the present invention has proposed a method for solving such a problem and efficiently producing an oxidation resistant carbon material having high oxidation resistance by a simple process by hydrolyzing a metal alkoxide solution to obtain a polymer sol. Has been developed, and the polymer sol has been deposited on the surface of the carbon material and then heat-treated at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere to form a ceramic coating layer having a thickness of 1.0 μm or less. (JP-A-3-265582).

[0004]

According to the above-mentioned prior art, it is possible to coat the surface of the carbon material with a continuous, dense and gas-impermeable continuous thin film, and effectively improve the oxidation resistance. It will be possible. However, in this case, it becomes difficult to permeate the ceramic substance into the inside of the structure of the carbon base material, so that an unsolved problem remains when trying to form the entire structure into a carbon / ceramics composite form. ..

The present invention was developed to solve the above-mentioned problems, and an object thereof is to provide a carbon / ceramic composite system having a structure in which the surface of a carbonaceous material and the inner surfaces of tissue pores are covered with a ceramic film. It is to provide a manufacturing method for efficiently obtaining a highly functional material.

[0006]

The method for producing a carbon / ceramics composite high-performance material according to the present invention for achieving the above object has an average pore diameter of 50 to 200 μm and a porosity of 5.
A porous carbonaceous material having a property of 0 to 70% is impregnated with a polymer sol produced by hydrolyzing a metal alkoxide solution under reduced pressure and pressure, and then at a temperature of 500 ° C. or higher in a non-oxidizing atmosphere. The heat treatment is performed by means of the constitutional feature.

A porous carbonaceous material is selectively used for the base material of the present invention. The type and manufacturing history of this porous carbonaceous material are not particularly limited. Therefore, for example, in addition to the typical porous carbon manufacturing technology in which coke powder having a uniform particle size is kneaded with a carbonizing binder such as tar pitch, crushing, molding, and firing carbonization, resin foam such as polyurethane foam is heated. A method of impregnating with a curable resin liquid and firing and carbonizing after curing, carbon fiber or organic fiber pulp,
It is possible to use a porous carbonaceous material made of carbon or graphite obtained by various methods such as a method of molding with carbon powder, a binder component, etc., and then impregnating with a thermosetting resin liquid and firing and carbonizing. However, as a characteristic of the porous carbonaceous material, the average pore diameter by the mercury penetration method is 50 to 200 μm.
It is important to select one with m and a porosity of 50 to 70%. Average porosity is less than 50μm and porosity is 50%
When the ratio is below the range, the metal alkoxide polymer gel does not permeate smoothly into the inside of the tissue and the whole structure cannot be formed, and when the average pore diameter exceeds 200 μm and the porosity exceeds 70%, The strength of the base material is insufficient and cracks and damages occur during impregnation.

The metal alkoxide is a raw material component which is a raw material to be converted into a ceramic substance, and for the purpose of the present invention, the constituent metal species are one or more selected from Ti, Al, Zr, Si, B and Mg. A mixed system is preferably used.
The metal alkoxide is hydrolyzed in a solution state to form a polymer sol. At this time, in order to obtain a normal sol state, it is necessary to add a stabilizer or a deflocculant for delaying the reaction to the metal alkoxide solution and a catalyst for promoting the reaction to appropriately adjust the hydrolysis rate. Becomes For example, when zirconium butoxide [Zr (OC ₄ H ₉ ) ₄ ] having a fast hydrolysis reaction is used as the metal alkoxide, diethylene glycol, diethanolamine, triethanolamine, tripropanolamine, triethylene glycol, tetraethylene glycol is used. , Etc., while adding a mineral acid catalyst such as hydrochloric acid, nitric acid, sulfuric acid when using a raw material with a slow hydrolysis reaction such as ethyl silicate [Si (OC ₂ H ₅ ) ₄ ]. To do.

The above polymer sol is impregnated into the porous carbonaceous material under reduced pressure and pressure. This impregnation treatment is performed in a step of putting the porous carbonaceous material in a pressure vessel such as an autoclave to reduce the pressure inside the system, then inflowing the polymer sol until the porous carbonaceous material is immersed, and then pressurizing the inside of the system. Be done.
The degree of reduced pressure and pressure applied varies depending on the texture of the porous carbonaceous material to be treated and the viscosity of the impregnated sol, but generally the degree of pressure reduction is set to about 1 Torr and the degree of pressure is set to 5 kg / cm ² or more. Is appropriate.

The material after the impregnation treatment is dried and then Ar,
It is transferred to a heating furnace kept in a non-oxidizing atmosphere such as N ₂ gas and heat-treated at a temperature of 500 ° C. or higher to subject the sol component to a metal oxide layer, a mixed layer of metal oxide and metal carbide, or a metal carbide. Convert to a ceramic coating such as a layer. The above-mentioned impregnation-heating step is repeated a plurality of times as necessary, until the thickness of the ceramic coating reaches about 1 μm.

[0011]

According to the process of the present invention, a porous carbonaceous material having a specific pore structure is used as a base material, and a polymer sol obtained by hydrolyzing a metal alkoxide solution is forcibly impregnated under reduced pressure and pressure. The coalesced sol uniformly permeates not only the surface of the porous carbon material but also the inside of the pore structure to fill the entire pores. The polymer sol adhered to the surface of the porous carbonaceous material and the inner surface of the pores volatilizes the solvent component at the time of drying, and at the same time, the bond between the colloid particles progresses and gels into a network structure.

The formed gel layer is converted into a crystalline or amorphous metal oxide layer in the course of heat treatment at 500 ° C. or higher, and further, in a temperature range exceeding 1000 ° C., an interfacial reaction occurs with the base carbon. Carbonize gradually. Therefore, a complete metal carbide layer is finally obtained through the mixed layer of metal oxide and metal carbide. Efficient production of a carbon / ceramics composite high-performance material having a composite structure in which a uniform and dense ceramics coating layer is formed on the surface of the porous carbonaceous substrate and the inner surface of the pores by the action of each of these steps. Is possible.

[0013]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples, but the present invention is not limited to the scope of the illustrated examples.

Example 1 A porous carbon material having a mean pore size of 100 μm and a porosity of 68%, a length and width of 10 mm and a length of 25 mm (manufactured by Tokai Carbon Co., Ltd.) was used as a base material and set in an autoclave. The inside was depressurized at 1 Torr for 1 hour. Then, the titanium tetraisopropoxide _{[Ti (O-iC 3 H 7} ) 4 ] was diluted with absolute ethanol, water under stirring - ethanol - concentration 0.66mol of hydrochloric acid solution was gradually added dropwise to generate by hydrolysis / l Ti
The O ₂ sol was flowed into the autoclave until the substrate was immersed. Subsequently, the pressure in the system was increased to 6 kg / cm ² and the pressure was maintained for 1 hour for impregnation. The impregnated material is dried at room temperature for 24 hours and at 105 ° C. for 2 hours, and then N ₂
It was transferred to a heating furnace kept in an atmosphere and heated to 500 ° C. at a temperature rising rate of 5 ° C./min. For 3 hours for heat treatment.
This material was treated by repeating the sol impregnation under the same conditions and the heating step twice. The obtained material was further heat-treated at 1000 ° C. in an N ₂ atmosphere.

The material produced in the above process was cut from the center and the cut surface was inspected. As a result, the material structure of the heat treatment at 500 ° C. was a uniform dense Ti with a thickness of about 1 μm on the inner surface of the pores.
It was confirmed that it had a carbon / ceramics composite system structure in which an O ₂ coating was formed. FIG. 1 is a scanning electron micrograph showing the particle structure inside the tissue in the porous carbon substrate before coating with TiO ₂ , and FIG. 2 is the same enlarged size as FIG. 1 showing the particle structure inside the tissue after coating with TiO ₂ . 3 is a scanning electron micrograph of FIG. Fig. 3 shows Ti with a higher magnification than Fig. 1.
Scanning electron micrograph showing the particle structure inside the tissue in the porous carbon substrate before O ₂ coating, FIG. 4 shows the particle structure inside the tissue after coating with TiO ₂ and the scanning type of the same enlarged size as FIG. 3. It is an electron micrograph. Further, it was confirmed that in the structure after heating at 1000 ° C., a part of the coating film was a mixed composite layer converted to TiC.

Comparative Example 1 A graphite material having an average pore diameter of 4 μm and a porosity of 23% [G340 manufactured by Tokai Carbon Co., Ltd.] was used as a base material, and the degree of vacuum was 10
A TiO ₂ film was formed under the same impregnation-heat treatment conditions as in Example 1 except that the pressure was set to Torr and the pressure was set to 200 kg / cm ² . When the center portion of the obtained material was cut and the cut surface was inspected, the presence of TiO ₂ was not found in the internal structure other than the surface.

Comparative Example 2 A porous graphite material having an average pore diameter of 300 μm and a porosity of 85% (manufactured by Tokai Carbon Co., Ltd.) was used as a base material, and the rest was treated in the same process as in Example 1. However, the base material was cracked during the impregnation treatment, and a normal composite material could not be obtained.

Example 3 A porous carbon material having an average pore diameter of 130 μm and a pore diameter of 58% (manufactured by Tokai Carbon Co., Ltd.) was used as a base material, and zirconium butoxide [Zr (OC ₄ H ₉ ) ₄ was used as an impregnating material. ] Was mixed with isopropanol at a ratio of 0.05 mol, ethylene glycol (stabilizer) in an amount twice that of zirconium butoxide was added thereto, and the polymer sol was hydrolyzed gradually with automatic stirring. Otherwise, impregnation and heat treatment were performed under the same conditions as in Example 1 to form a ZrO ₂ coating inside and outside the structure. When the obtained material was cut from the center and the internal structure was inspected, it was found that it had a carbon / ceramics composite morphology in which a uniform and dense ZrO ₂ coating with a thickness of about 1 μm was formed on the inner surface of the pores of all the structures. Admitted.

[0019]

As described above, according to the present invention, a carbon / ceramic composite material having a structure in which a uniform and dense ceramic coating is formed on the surface of the porous carbonaceous material and the inner surface of the pores can be efficiently produced. .. Therefore, it can be expected to be useful as a high-performance material for various applications.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph showing a grain structure inside a tissue in a porous carbon substrate before coating with TiO _{2 in} Example 1.

2 is a scanning electron micrograph of the same enlarged size as FIG. 1, showing the particle structure inside the tissue after coating with TiO _{2 in} Example 1. FIG.

FIG. 3 is a scanning electron micrograph showing the grain structure inside the structure of the porous carbon substrate before coating with TiO ₂ which has a higher magnification than that of FIG. 1.

FIG. 4 is a scanning electron micrograph showing the particle structure of the pore structure after coating with TiO ₂ and having the same enlarged size as in FIG.

Claims (2)

[Claims] 1. An average pore diameter of 50 to 200 μm and a porosity of 5.
A porous carbonaceous material having a property of 0 to 70% is impregnated with a polymer sol produced by hydrolyzing a metal alkoxide solution under reduced pressure and pressure, and then at a temperature of 500 ° C. or higher in a non-oxidizing atmosphere. A method for producing a carbon / ceramics composite-based high-performance material, which is characterized by performing heat treatment with 2. The metal species constituting the metal alkoxide is T
The carbon / ceramic composite according to claim 1, which is a mixed system of one or more selected from i, Al, Zr, Si, B and Mg, and the formed ceramic form is an oxide and / or a carbide. -Based high-performance material manufacturing method.