JPH0848509A - Method for producing carbonaceous porous body - Google Patents

Abstract

(57) [Abstract] [Purpose] A novel carbonaceous porous material that has various useful physical properties as a functional material, such as a large specific surface area, good electrical conductivity, good thermal conductivity, and high temperature oxidation resistance. A method of manufacturing a body is provided. [Structure] A resin foam having a three-dimensional network structure is impregnated with a liquid composition of an organic liquid substance and an inorganic substance, and a three-dimensional structure is obtained by firing and carbonizing the composite after curing in an inert gas atmosphere. A method for producing a carbonaceous porous body in which a networked carbon porous body is obtained and the surface of the three-dimensional networked carbon porous body is coated with a metal carbide. [Effect] Due to the three-dimensional network structure carbon porous body obtained by firing the composite impregnated with the liquid composition, the difference in thermal expansion coefficient from the metal carbide coated on the surface for high temperature oxidation resistance and function improvement Can be adjusted, and the metal carbide can be coated on the surface of the porous carbon body without peeling or loss.

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 novel carbonaceous porous body, and more specifically, a highly functional carbon including conductive materials, heat conductive materials, heat storage materials, electrode materials and magnetic materials. The present invention relates to a method for producing a carbonaceous porous body which is useful as a material and has a porous body surface coated with a metal carbide.

[0002]

2. Description of the Related Art Carbon materials have low specific gravity, excellent heat resistance, corrosion resistance, and thermal shock resistance, and have unique properties such as electrical conductivity, thermal conductivity, lubricity, radiation resistance, and biocompatibility. There is. Taking advantage of these characteristics, as industrial materials, net-making electrodes, electric discharge machining electrodes, heating elements, resistors, carbon black, mechanical seals, bearings, molds, refractories, high temperature jigs, chemical industrial resistance Widely used in food materials and graphite materials for nuclear reactors. However, recent space and aviation engineering,
Along with the remarkable progress of advanced technologies such as energy engineering, electronic engineering, mechanical engineering, and biotechnology, carbon materials are required to have dramatically improved performance or new functions. It is difficult to deal with.

Recently, in order to meet these needs, a new carbon material and a carbon material by a new manufacturing method have been developed. Furthermore, for high strength, oxidation resistance, wear resistance, impermeability, high toughness, and high purification that cannot be handled by these carbon materials, carbon and synthetic resin are used according to their respective purposes.
Composites with metals, glass, ceramics, carbon fibers, etc. are being promoted.

Generally, the oxidation resistance and heat resistance of carbon materials,
Coating with a ceramic material is performed for the purpose of improving characteristics such as electric conductivity and thermal conductivity. The coating materials include metal carbides, metal nitrides, metal borides, and metal oxides. Among them, metal carbides have close thermal expansion coefficients to carbon materials and are less likely to peel off due to thermal shock, making them suitable as coating materials. . As the coating method for coating the surface of the carbon material with the metal carbide, a contact method of contacting the carbon material with a metal oxide that forms the metal carbide,
Alternatively, a conversion method in which the surface layer of the carbon material is kept at a high temperature and converted into a metal carbide by reacting with a metal oxide gas, or a metal carbide generated by reaction or decomposition of a raw material gas is deposited on the surface of the carbon material. A chemical vapor deposition method (hereinafter referred to as "CVD method") or the like is generally performed.

However, in the case of the above contact method, although the treatment is easy, there is a problem that it is difficult to produce a thick and dense material because the thickness of the film is thin, and in the case of the above conversion method, the film is formed. However, there is a problem that the metal carbide layer is likely to be porous in the manufacturing method. Further, in the above CVD method, the metal carbide coating is very dense, but the thickness of the coating is large. There is a problem that only thin materials such as several tens to several hundreds of μm can be produced. Moreover, the biggest problem of these three methods is that the thermal expansion coefficient of the carbon material as the base material and the metal carbide are different. The metal carbide was separated from the surface of the carbon material by the impact.

[0006]

The present invention can be used in order to solve the above-mentioned problems of the prior art, that is, the metal carbide does not peel off from the surface of the carbon material due to thermal shock and can be used even in a high temperature oxidizing atmosphere. It is also an object of the present invention to provide a method for producing a carbonaceous porous body which industrially advantageously produces a carbonaceous porous body coated with a metal carbide that exhibits useful properties such as good electrical conductivity and thermal conductivity.

[0007]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventor has made earnest studies to solve the problems of the conventional method for producing a porous carbon body composed of only carbon. A resin foam having an original network structure impregnated with a specific liquid composition is fired in a specific atmosphere after curing and carbonized to obtain a three-dimensional network structure carbon porous body. By coating the above with a metal carbide, the target method for producing a carbonaceous porous body was successfully obtained, and the present invention was completed. That is,

In the method for producing a carbonaceous porous material of the present invention, a resin foam having a three-dimensional network structure is impregnated with a liquid composition composed of an organic liquid material and an inorganic material, which is then cured with an inert gas. It is characterized in that a three-dimensional network structure carbon porous body is obtained by firing and carbonizing in an atmosphere, and the surface of the three-dimensional network structure carbon porous body is coated with a metal carbide. It is preferable that the organic liquid substance is composed of an initial condensate of an organic substance having a carbon residue yield of 5% or more or a solvent dissolved in a solvent by firing in an inert gas atmosphere. The inorganic substance is preferably at least one selected from the group consisting of graphite whiskers, highly oriented vapor phase pyrolytic graphite (HOPG), quiche graphite, natural graphite, artificial graphite, and carbon black fine powder. The firing and carbonization are preferably performed by heating at a temperature of 500 to 2500 ° C. in an inert gas atmosphere. The "inert gas atmosphere" defined in the present invention means an inert gas which does not react with a substance in the system such as a rare gas such as argon gas or a nitrogen gas in the gas phase in the reaction vessel during firing and carbonization. Gas phase state in which gas is filled to prevent excess or harmful effects by oxygen gas, etc., and also includes an inert atmosphere or non-oxidizing atmosphere commonly used in the industry. .

[0009]

In the present invention, the characteristics of the porous carbon body such as oxidation resistance, electric conductivity, and thermal conductivity are improved by coating the surface of the porous carbon body with a metal carbide film. The separation and cracking of metal carbide from the surface of the carbon porous body due to the difference in thermal expansion of the carbon is changed by changing the composition ratio of the inorganic material such as graphite and the binder carbon, that is, the thermal expansion coefficient of the carbon porous body is adjusted. It is a solution to this problem, which makes it possible to produce a porous carbon body with improved properties such as heat resistance, electrical conductivity, and thermal conductivity.

The contents of the present invention will be specifically described below. The method for producing a carbonaceous porous material of the present invention, a resin foam having a three-dimensional network structure, a composite obtained by impregnating a liquid composition comprising an organic liquid substance and an inorganic substance, in an inert gas atmosphere after curing. It is characterized in that a three-dimensional network carbon porous body is obtained by firing and carbonization, and the surface of the three-dimensional network carbon porous body is coated with a metal carbide. The resin foam having a three-dimensional network structure used in the present invention has a three-dimensional network structure and a porosity of 20 to 99.
%, Preferably 50 to 97% of thermosetting resin foam such as urethane foam and phenol foam.

The organic liquid substance used in the present invention is an organic substance which shows a carbon residue yield of 5% or more when fired in an inert gas atmosphere, and a substance which is not liquid at room temperature is an initial condensation of the substance. It is a substance that is made liquid by using a substance or a solvent. Specifically, it is an organic resin material having three-dimensional cross-linking, a natural organic material that solid-phase carbonizes, and the like, for example, an organic polymer substance and its monomers / oligomers, tar / pitches, carbonization pitches, heat Examples include one or a mixture of two or more types of prepolymers such as a plastic resin and a thermosetting resin.
If the residual carbon yield is less than 5%, the strength is weak and it becomes difficult to maintain the structure, which is not preferable.

Here, the organic polymer substance is a substance other than a thermoplastic resin and a thermosetting resin, which will be described later,
For example, compounds having condensed polycyclic aromatic compounds such as lignin, cellulose, tragacanth gum, gum arabic, natural gum and its derivatives, sugars, chitin and chitosan in the basic structure of the molecule, and a formalin condensate of naphthalene sulfonic acid, dinitro. Naphthalene, biren, pyrantrone,
Indusrene-based vat dyes derived from biolanthrone, benzoanthrone, and the like, and intermediates thereof are used.

Examples of the thermoplastic resin include polyvinyl chloride, polyacrylonitrile, polyvinylidene chloride, chlorinated polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, polyvinylpyrrolidone, ethyl cellulose, carboxymethyl cellulose, polyvinyl chloride / vinyl acetate. Usual thermoplastic resins such as copolymers and polyphenylene oxide, polyparaxylene, polysulfone, polyamideimide, polybenzimidazole, polyoxadiazole and the like are used.

As the thermosetting resin, for example, a phenol resin, a furan resin, an epoxy resin, a xylene resin, a coplanar resin, or the like is used. An example thereof is one that exhibits a high carbon residue yield without performing a special carbon precursor treatment.

Examples of the above-mentioned pitches include petroleum pitch, coal tar pitch, asphalt, and dry-distilled pitches of hydrocarbon compounds such as these pitches and synthetic resins (carbon residue yield in treated products at 400 ° C. or lower. Is 75% ~
(95%) which has been subjected to non-graphitizing treatment such as oxidation treatment for the purpose of crosslinking.

Examples of the inorganic substance used in the present invention include graphite whiskers, highly-oriented vapor-phase pyrolytic graphite (HOP).
G), quiche graphite, natural graphite, artificial graphite, carbon black, fine powder of carbon fiber, etc., or a mixture of two or more thereof is used.

The liquid composition used in the present invention is obtained by mixing the above-mentioned one or more kinds of organic liquid substances and inorganic substances with a mixer or the like. Coefficient of thermal expansion of metal carbide,
For example, silicon carbide (SiC) is about 4 × 10 ⁻⁶ / ° C.,
Titanium carbide (TiC) is about 8 × 10 ⁻⁶ / ° C. and hafnium carbide (HfC) is about 7 × 10 ⁻⁶ / ° C. On the other hand, the coefficient of thermal expansion of an ordinary carbon material is about 2 × 10 ⁻⁶ / ° C., but in the case of graphite, it is 1 × 10 ⁻⁶ / ° C. on the basal plane, and the c-axis direction is 25 × 10 ⁻⁶ / ° C. It is about ℃. Therefore, as the inorganic substance used for adjusting the coefficient of thermal expansion, the above graphites are preferable because they can be easily adjusted. The compounding amount at that time varies depending on the shape of the porous body and the impregnation method, but is 1 to 90% by weight, preferably 5 to 30% by weight of the liquid composition.
Is.

In the production method of the present invention, first, the resin foam having the three-dimensional network structure is impregnated with the liquid composition containing the organic liquid substance and the inorganic substance. The impregnation method can be carried out by immersing a resin foam having a three-dimensional network structure in a liquid composition and, if necessary, impregnating it under conditions such as heating, depressurization and pressurization. Next, after removing the excess liquid composition that has not penetrated from the surface of the resin foam, the composite is cured. The curing operation here is to cure the resin when a liquid composition using a thermosetting resin is used, and to remove the solvent in the liquid composition using a solvent.

Next, the cured composite is subjected to a carbon precursor treatment, and the obtained carbon precursor is preferably heated at a temperature of 500 ° C. or higher in an atmosphere of an inert gas such as nitrogen or argon gas. Is 800 ° C or higher, more preferably 1000
It is heated to a temperature of ℃ or higher and carbonized. There is no upper limit to the firing temperature, and heating may be performed up to about 3000 ° C., if necessary, and preferably about 2500 ° C. The heating rate is 3 to 100 ° C / h up to 500 ° C, preferably 5
It is suitable to bake at ˜50 ° C./h, and has the drawback that the strength of the final product decreases as the heating rate increases. Therefore, it is better to avoid a heating rate of 100 ° C./h or more up to 500 ° C., and a heating rate of 500 ° C. or more depends on the heating method, but the heating rate is not particularly limited. The three-dimensional network carbon porous body obtained by the above method has different shrinkage rates depending on the type and blending composition of the organic and inorganic substances in the liquid composition, but is a product that faithfully maintains the shape of the original resin foam. is there.

Next, the surface of the obtained carbon porous body is coated with a metal carbide. As a coating method of the metal carbide, a contact method in which a metal oxide that forms a metal carbide is brought into contact, a conversion method in which the surface layer portion of the carbon material is kept at a high temperature and reacted with a gas of the metal oxide to convert into a metal carbide A CVD method in which a metal carbide generated by the reaction or decomposition of the raw material gas is deposited on the surface of the carbon material can be used. In the present invention, any of the metal carbide coating methods can be used,
The contact method and the CVD method are preferable, and the contact method is more preferable because it is possible to sufficiently coat the inside of the porous body and can be easily carried out industrially.

Examples of the metal carbide coated on the surface of the carbon porous body include silicon carbide, titanium carbide, hafnium carbide, boron carbide and the like, but silicon carbide is used for improving high temperature oxidation resistance and thermal conductivity characteristics. preferable. In this way, it is possible to obtain a carbonaceous porous body having a target surface coated with a metal carbide.

The carbonaceous porous body obtained by coating the surface with a metal carbide obtained in the present invention can be used even in a high temperature oxidizing atmosphere without peeling of the metal carbide from the surface of the carbon material due to thermal shock, and has a specific surface area. It has greatly improved properties such as heat resistance, electrical conductivity, and thermal conductivity, and has high-temperature oxidation resistance, etc., including conductive materials, heat conductive materials, heat storage materials, electrode materials, and magnetic materials. It is useful as a highly functional carbon material.

[0023]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 The following operations were carried out to produce a carbon porous body. 75% by weight of a furan resin initial condensate (Hitafuran VF-302 manufactured by Hitachi Chemical Co., Ltd.), 5% by weight of dry distillation pitch (KH-1P manufactured by Kureha Chemical Industry Co., Ltd.), and natural scaly graphite fine powder having an average particle diameter of 1 μm (Nippon Graphite Co., Ltd.) Made C
10% by weight of SSP-B) and 10% by weight of carbon black (denka black manufactured by Denki Kagaku KK) were added and mixed with a mixer to prepare a liquid composition. Then, the above liquid composition was impregnated into a polyurethane foam having a three-dimensional network structure and a porosity of 60%. After removing the excess liquid composition, a curing reaction was carried out in a dryer at 100 ° C. for 3 hours. Next, a carbon precursor conversion treatment was performed in a 180 ° C. dryer for 10 hours. This precursor processed product is treated with 500 in nitrogen gas.
Up to ℃ at a heating rate of 20 ℃ / h, then 1000
The temperature was raised to 100 ° C./h, the temperature was maintained at 1000 ° C. for 3 hours, and then naturally cooled to obtain a carbon porous body.

Next, the following operation was performed in order to coat the surface of the obtained carbon porous body with a metal carbide. Alumina, silicon, and silicon carbide powder were placed in a graphite container, and a porous carbon material was embedded in the powder.
The temperature was raised to 50 ° C., the temperature was maintained for 2 hours, and then naturally cooled to obtain a carbonaceous porous body.

In order to confirm the oxidation resistance of the obtained carbonaceous porous material, the weight change was measured by holding it in an oxidizing atmosphere furnace heated to 1500 ° C. for 2 hours and then measuring the weight change, but no weight change was observed. . Further, the thermal stress test was conducted 10 times by conducting a heat cycle test in which the obtained carbonaceous porous body was heated to 1200 ° C. in an oxidizing atmosphere and then rapidly cooled to room temperature, and the thermal stress performance was examined. There was no next,
X-ray diffraction measurement of the surface of the obtained carbonaceous porous material confirmed silicon carbide. Further, when the cross section of the carbonaceous porous material was observed by an energy dispersive X-ray spectrometer (EDX), a silicon carbide layer having a thickness of 40 μm was confirmed. The thermal conductivity of the carbon porous body and the carbonaceous porous body having a surface coated with a silicon carbide layer was measured by the steady-state method and the comparative heat flow meter method, and it was found that the thermal conductivity of the carbon porous body was 10 W / mK. , 60W for carbonaceous porous material coated with silicon carbide layer
/ MK and improvement in thermal conductivity were also observed.

Example 2 The following operations were carried out to produce a carbon porous body. 70% by weight of chlorinated vinyl chloride resin (T-742 manufactured by Nippon Carbide Co., Ltd.) was dissolved in tetrahydrofuran to form a liquid, in which 5% by weight of dry distillation pitch (KS manufactured by Kureha Chemical Industry Co., Ltd.) and an average particle diameter of 3 μm
15% by weight of Kish graphite fine powder (KH manufactured by Kowa Seiko Co., Ltd.) and 10% by weight of carbon black (chemical Denka Black manufactured by Denki Kagaku) were added and mixed with a mixer to prepare a liquid composition. Next, it has a three-dimensional network structure and a porosity of 80.
% Polyurethane foam was impregnated with the above liquid composition. After removing the excess liquid composition, 2 hours at 100 ° C dryer, 2 hours at 120 ° C, 2 hours at 140 ° C,
The carbon precursor treatment was performed at 160 ° C. for 2 hours and at 180 ° C. for 10 hours. The precursor-treated product is heated in nitrogen gas up to 500 ° C. at a heating rate of 15 ° C./h, then heated up to 1000 ° C. at 50 ° C./h, and heated at 1000 ° C. for 3 hours.
After being kept for a while, it was naturally cooled to obtain a carbon porous body.

Next, the following operation was performed to coat the surface of the obtained carbon porous body with a metal carbide. Alumina, silicon, and silicon carbide powders were placed in a graphite container, and a carbon porous material was embedded in the powder.
The temperature was raised to 00 ° C., the temperature was maintained for 3 hours, and then naturally cooled to obtain a carbonaceous porous body.

In order to confirm the oxidation resistance of the obtained carbonaceous porous body, the weight change was measured by keeping it in an oxidizing atmosphere furnace heated at 1500 ° C. for 2 hours and then measuring the weight change, but no weight change was observed. . Further, the thermal stress test was conducted 10 times by conducting a heat cycle test in which the obtained carbonaceous porous body was heated to 1200 ° C. in an oxidizing atmosphere and then rapidly cooled to room temperature, and the thermal stress performance was examined. There was no next,
X-ray diffraction measurement of the surface of the obtained carbonaceous porous material confirmed silicon carbide. When the cross section of the carbonaceous porous material was observed by an energy dispersive X-ray spectrometer (EDX), a silicon carbide layer having a thickness of 50 μm was confirmed. The thermal conductivity of the carbon porous body and the carbonaceous porous body having a surface coated with a silicon carbide layer was measured by the steady-state method and the comparative heat flow meter method. The thermal conductivity of the carbon porous body was 12 W / mK. , 70 W for a carbonaceous porous body coated with a silicon carbide layer
/ MK and improvement in thermal conductivity were also observed.

[0030]

According to the present invention, there has been a problem in coating a surface of a conventional carbon material with a metal carbide by using a surface coating method such as a contact method or a chemical vapor deposition method (CVD method).
It becomes possible to control peeling, cracking, etc. of the coating material due to thermal stress by examining the ratio of graphite etc. to resin carbon and adjusting the thermal expansion coefficient when producing the carbon porous body as the base material. Therefore, it is possible to obtain a carbonaceous porous body coated with a metal carbide that is free from peeling and cracking even at high temperatures.

Furthermore, since the carbon carbide is coated on the porous carbon body in which an inorganic substance such as graphite having good thermal conductivity and electric conductivity is homogeneously composite-dispersed, the oxidation resistance is higher than that of the conventional porous carbon body. It is possible to obtain a carbonaceous porous body having excellent properties, such as improved thermal conductivity and the like, and is therefore useful as a method for producing a holding material such as a latent heat storage material in a heat storage device.

Claims (4)

[Claims] 1. A composite obtained by impregnating a resin foam having a three-dimensional network structure with a liquid composition composed of an organic liquid substance and an inorganic substance is baked in an inert gas atmosphere after curing,
A carbon porous body having a three-dimensional network structure is obtained by carbonization,
A method for producing a carbonaceous porous body, which comprises coating the surface of this porous carbon body having a three-dimensional network structure with a metal carbide. 2. The carbon according to claim 1, wherein the organic liquid substance comprises an initial condensate of an organic substance having a residual carbon yield of 5% or more or a solvent dissolved in a solvent by firing in an inert gas atmosphere. Method for producing porous body. 3. The inorganic material comprises at least one selected from the group consisting of graphite whiskers, highly oriented vapor phase pyrolytic graphite (HOPG), quiche graphite, natural graphite, artificial graphite and carbon black fine powder. Item 2. A method for producing a carbonaceous porous body according to Item 1. 4. The method for producing a carbonaceous porous body according to claim 1, wherein the firing and carbonization are performed by heating at a temperature of 500 to 2500 ° C. in an inert gas atmosphere.