JP2001048651A - Silicon carbide sintered body and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silicon carbide sintered body excellent in strength without occurrence of cracks or breakages. SOLUTION: The method for producing a silicon carbide sintered body comprises impregnating metallic silicon into a formed body containing silicon carbide and carbon under a vacuum atmosphere or non-oxidizing atmosphere to form an impregnated body and cooling the impregnated body under the condition such that the distribution of temp. in the impregnated body is in the range of 0.1 to 1.5 deg.C/cm. The silicon carbide sintered body is obtained by the production method for the silicon carbide sintered body mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide sintered body such as a boat for heat treatment of semiconductors and a liner tube, and a method for efficiently producing the silicon carbide sintered body.

[0002]

2. Description of the Related Art Conventionally, a compact containing silicon carbide and carbon is impregnated with metallic silicon in a non-oxidizing atmosphere.
Filling to form the impregnated body, when cooling the impregnated body, the excess metal silicon that did not react with the carbon, because of volume expansion during cooling and solidification, there is a problem that the impregnated body breaks there were. In particular, in the case of a long one, it hardened instantaneously with cooling of the furnace, so many accidents occurred, and it was difficult to reduce the defect rate even by adjusting the cooling rate.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, an object of the present invention is to provide a method for producing a silicon carbide-based sintered body that does not cause cracks or cracks, and a silicon carbide-based sintered body that is produced by the production method and has excellent strength and the like.

[0004]

Means for solving the above problems are as follows. That is, <1> for a molded article containing silicon carbide and carbon,
In a vacuum atmosphere or a non-oxidizing atmosphere, metal silicon is impregnated to form an impregnated body.
A method for producing a silicon carbide-based sintered body, comprising cooling the impregnated body while maintaining a temperature distribution of about 0.5 cm. <2> Before forming the impregnated body, the molded body is
The method for producing a silicon carbide sintered body according to <1>, wherein the sintered body is calcined at 400 ° C. <3> The metal silicon to be impregnated is 1420 to 1700 ° C.
The method for producing a silicon carbide-based sintered body according to <1> or <2>, wherein the sintered body is heated and melted. <4> A temperature distribution is provided by using two or more heaters,
The method for producing a silicon carbide-based sintered body according to any one of <1> to <3>, wherein the impregnated body is cooled by lowering the temperature of the two or more heaters at the same rate. <5> The method for producing a silicon carbide-based sintered body according to any one of <1> to <4>, wherein the rate of cooling the impregnated body is 50 ° C / h or less. <6> A silicon carbide based sintered body produced by the method for producing a silicon carbide based sintered body according to any one of <1> to <5>.

In the method for producing a silicon carbide sintered body of the present invention, first, the compact is impregnated with metallic silicon. At this time, the molten metal silicon penetrates into the compact by capillary action or the like. The infiltrated metallic silicon reacts with the carbon in the compact to form silicon carbide. Next, the impregnated body is cooled with a certain temperature distribution. As a result, the volume expansion during cooling and solidification by unreacted metallic silicon can be shifted from the low temperature side to the high temperature side, and a silicon carbide sintered body free from cracks and cracks can be obtained.

The silicon carbide sintered body of the present invention is excellent in strength because it is manufactured by the method of manufacturing a silicon carbide sintered body of the present invention.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a silicon carbide sintered body of the present invention has an impregnated body forming step and a cooling step, and may include other steps as required.

[Impregnated Body Forming Step] In the impregnated body forming step, a molded body containing silicon carbide and carbon is impregnated with metallic silicon in a vacuum atmosphere or a non-oxidizing atmosphere to form an impregnated body. It is a process.

(Molded Body) The formed body is obtained by forming a mixed powder of silicon carbide powder and an organic substance or carbon powder comprising at least one or more carbon sources in a slurry state, and molding the mixed powder. Can be The molded body obtained here may be called a green body, and is an unsintered silicon carbide-carbon molded body in which many pores obtained by removing the solvent from the slurry-like mixed powder are present. .

The silicon carbide powder can be produced from silicon carbide powder such as α-type, β-type, amorphous or a mixture thereof by a method described below. In order to make the obtained silicon carbide sintered body a high purity silicon carbide sintered body, it is preferable to use a high purity silicon carbide powder as a raw material. The grade of the β-type silicon carbide powder is not particularly limited, and for example, generally commercially available β-type silicon carbide powder can be used.

The particle size of the silicon carbide powder is preferably small from the viewpoint of increasing the density.
It is preferably from 01 to 10 μm, more preferably from 0.05 to 5 μm. When the particle size is less than 0.01 μm, it may be difficult to handle in processing steps such as measurement and mixing, while when it exceeds 10 μm, the specific surface area is small, that is, The contact area of
It may be difficult to increase the density.

The high-purity silicon carbide powder is, for example,
A silicon source comprising at least one or more silicon compounds;
After dissolving at least one or more carbon sources containing an organic compound that generates carbon by heating and a polymerization / crosslinking catalyst in a solvent and drying, the obtained powder is fired under a non-oxidizing atmosphere. Obtainable.

As the silicon source, a liquid silicon source and a solid silicon source can be used in combination, but at least one of them must be a liquid silicon source.

As the liquid silicon source, (mono-,
And di-, tri-, tetra-) alkoxysilanes and polymers of tetraalkoxysilanes. Among the above alkoxysilanes, tetraalkoxysilanes are preferable, and specifically, methoxysilane, ethoxysilane, propoxysilane, butoxysilane, and the like are preferable, and ethoxysilane is particularly preferable in terms of handleability. As the polymer of the tetraalkoxysilane, the degree of polymerization is 2-1.
Examples include a low molecular weight polymer (oligomer) of about 5 and a liquid polymer such as a high polymerization degree silicate polymer. These polymers may be used in combination with silicon oxide, if desired. The silicon oxide includes, in addition to SiO, silica sol (colloidal ultrafine silica-containing liquid containing an OH group or an alkoxyl group therein), silicon dioxide (silica gel, fine silica, quartz powder) and the like. The silicon source is 1
The species may be used alone or in combination of two or more.

Among the above-mentioned silicon sources, an oligomer of tetraethoxysilane and a mixture of an oligomer of tetraethoxysilane and finely divided silica are preferred from the viewpoint of good homogeneity and handleability. Further, the silicon source is:
The purity is preferably high, and specifically, the initial impurity content is preferably 20 ppm or less, more preferably 5 ppm or less.

As the carbon source, in addition to a liquid carbon source, a liquid carbon source and a solid carbon source can be used in combination. Organic compounds that polymerize or crosslink are preferred. Specific examples thereof include phenolic resins, furan resins, polyimides, polyurethanes, monomers and prepolymers of resins such as polyvinyl alcohol, cellulose, sucrose, pitch,
A liquid carbon source such as tar is preferred. Among these, resol-type phenol resins are particularly preferred. These carbon sources may be used alone or in combination of two or more. In addition, the purity can be appropriately controlled and selected depending on the purpose. In particular, when high-purity silicon carbide powder is required, it is preferable to use an organic compound not containing 5 ppm or more of each metal.

The polymerization / crosslinking catalyst can be appropriately selected according to the carbon source. For example, when the carbon source is a phenol resin or a furan resin, toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalic acid and the like are used. And acids such as sulfuric acid. Among these, toluenesulfonic acid is more preferred.

When the high-purity silicon carbide powder is produced, the charging ratio of carbon to silicon (hereinafter abbreviated as C / Si ratio) varies depending on the pressure of the atmosphere.
Although it cannot be specified unconditionally, a mixture of each of the above-mentioned components is added to 100
It is defined by elemental analysis of a carbide intermediate obtained by carbonization at 0 ° C. Stoichiometrically, when the C / Si ratio is 3.0, the free carbon in the generated silicon carbide should be 0%. However, actually, the low C / Si ratio is low due to the volatilization of the simultaneously generated SiO gas. Free carbon is evolved in the ratio. It is important to determine the compounding amount in advance so that the amount of free carbon in the produced silicon carbide powder does not become an amount unsuitable for the production use of a sintered body or the like. Normally, 16
In baking at 00 ° C. or higher, the C / Si ratio is preferably 2.0 to 2.5 from the viewpoint of suppressing free carbon. However, when the C / Si ratio exceeds 2.5, although the generation of free carbon is significantly increased, the free carbon has an effect of suppressing the growth of the particles. It is also preferable that the C / Si ratio exceeds 2.5.

If desired, the silicon carbide powder may be produced after curing the mixture containing the silicon source and the carbon source. Examples of the curing method include a method of crosslinking by heating, a method of curing with a curing catalyst, and a method of electron beam or radiation. The catalyst used for the curing can be appropriately selected according to the carbon source.In the case of a phenol resin or a furan resin, toluene sulfonic acid, toluene carboxylic acid, acetic acid, oxalic acid, hydrochloric acid, hydrochloric acid, sulfuric acid, maleic acid and the like are used. Acids such as acids and amines such as hexamine are preferably exemplified. The catalyst is dissolved or dispersed in a solvent and mixed. Examples of the solvent include lower alcohols (for example, ethyl alcohol and the like), ethyl ether, acetone and the like.

The solvent for dissolving the silicon source, the carbon source, and the polymerization / crosslinking catalyst is not particularly limited, and includes a known organic solvent such as a lower alcohol and acetone. These may be used alone or in combination of two or more.

The drying method is not particularly limited, and a known drying method such as hot air drying, vacuum drying, and high frequency drying is preferably used.

The calcination is performed in a non-oxidizing atmosphere such as nitrogen or argon at 800 to 1000 ° C. for 30 to 120 minutes.
After heating and carbonizing to obtain a carbide, the obtained carbide is heated at 1350 to 2000 ° C. in a non-oxidizing atmosphere such as argon. The firing temperature and the firing time can be appropriately selected depending on the desired particle size of silicon carbide and the like.
900 ° C. is preferred in terms of production efficiency.

Also, at the time of the above-mentioned firing, the temperature is from 2000 to 2100 ° C.
By performing the heat treatment for 5 to 20 minutes, silicon carbide with higher purity can be obtained.

A method for obtaining a silicon carbide powder having a particularly high purity is described in Japanese Patent Application Laid-Open No. 9-48 filed earlier by the present applicant.
No. 605, a method for producing a raw material powder as described in the method for producing a single crystal, that is, a method for producing carbon by heating using at least one selected from high-purity tetraalkoxysilane and tetraalkoxysilane polymer as a silicon source. Using a pure organic compound as a carbon source, heating and firing a mixture obtained by mixing these homogeneously in a non-oxidizing atmosphere to obtain a silicon carbide powder; And a post-treatment step of heating at a temperature of 2000 to 2100 ° C. for 5 to 20 minutes at least once while maintaining the temperature at not less than 2000 ° C. and less than 2000 ° C. The method is preferred. According to this method, the content of the impurity element is 0.5 p
pm or less, high-purity silicon carbide powder can be obtained. However, since the high-purity silicon carbide powder obtained by this method is not uniform in size, it is preferable to treat the powder by pulverization and classification so as to conform to the particle size.

In the production of the silicon carbide powder, nitrogen can be introduced into the silicon carbide powder, if desired, for the purpose of imparting conductivity. In this case, first, the silicon source, the carbon source, the polymerization / crosslinking catalyst, and the organic substance composed of a nitrogen source are homogeneously mixed, but a carbon source such as a phenol resin and a nitrogen source such as hexamethylenetetramine are mixed. When the organic substance and a polymerization / crosslinking catalyst such as toluenesulfonic acid are dissolved in a solvent such as ethanol, it is preferable to sufficiently mix the organic substance with a silicon source such as an oligomer of tetraethoxysilane.

The slurry-like mixed powder is produced by dissolving and dispersing the silicon carbide powder and an organic substance or carbon powder comprising at least one or more carbon sources in a solvent.

The organic substance is a substance which generates carbon by heating, and is preferably conductive. Specifically, coal tar pitch, pitch tar,
Examples include various sugars such as phenolic resins, furan resins, epoxy resins, phenoxy resins, monosaccharides such as glucose, oligosaccharides such as sucrose, and polysaccharides such as cellulose and starch. These may be used alone or in combination of two or more. Further, for the purpose of homogeneously mixing with the silicon carbide powder, a substance that is liquid at room temperature, a substance that dissolves in a solvent, softens or becomes liquid by heating, and a thermoplastic or heat-meltable substance is preferably used. Among them, a phenol resin having a high strength of the obtained molded article, particularly a resol-type phenol resin, is preferably mentioned.

Examples of the carbon powder include pyrolytic carbon such as carbon black and acetylene black, graphite, activated carbon, and water-dispersible carbon, and are preferably conductive. Among these, conductive carbon black is particularly preferred.

As the solvent, water may be used. For example, for a phenol resin which is an organic compound which generates carbon by suitable heating, lower alcohols such as ethyl alcohol, ethyl ether, acetone and the like can be mentioned.
The organic substance, carbon powder, and solvent comprising the carbon source preferably have low impurity contents. When each of the components is dissolved and dispersed in the solvent, the components are sufficiently stirred and mixed to form uniformly dispersed pores in the green body.

In the production of the green body, an organic binder may be added, if desired. Examples of the organic binder include a deflocculant and a powder adhesive.
As the deflocculant, a nitrogen-based compound is preferable from the viewpoint of further improving the effect of imparting conductivity, and for example, ammonia, ammonium polyacrylate and the like are suitably used. As the powder adhesive, polyvinyl alcohol,
A urethane resin (for example, water-soluble polyurethane) is preferably used. In addition, if desired, an antifoaming agent may be added. Examples of the antifoaming agent include a silicone antifoaming agent.

The content of the organic substance in the green body is preferably 10 to 50% by carbon amount,
5 to 40% is more preferable. When the content is less than 10%, when impregnating metal silicon described below, carbon is insufficient, unreacted Si remains in the pores by 5% or more, and the conductivity may be reduced. On the other hand, if it exceeds 50%, the thixotropy of the slurry tends to be large and the moldability is poor, so that it may be difficult to carry out the method practically.

If nitrogen is introduced as desired, first, silicon carbide powder, an organic substance or a carbon powder composed of a carbon source, and an organic substance composed of a nitrogen source are homogeneously mixed. Black, an organic substance or a carbon powder composed of a carbon source such as a phenol resin, and an organic substance composed of a nitrogen source such as hexamethylenetetramine are mixed with water,
After dissolving and dispersing in a solvent such as ethyl alcohol, it is preferable to sufficiently stir and mix with the silicon carbide powder.

The stirring and mixing can be performed by known stirring and mixing means such as a mixer and a planetary ball mill. The stirring and mixing is performed for 10 to 30 hours, particularly 16 to 30 hours.
Preferably, it is performed for 24 hours.

The method of molding the slurry-like mixed powder is not particularly limited, and a known molding method can be used. In general, a casting method is preferably used. In the casting, the slurry-like mixed powder is poured into the casting mold, left, and after demolding,
By removing the solvent by heating or air drying under a temperature condition of 50 to 60 ° C., a molded body (green body) having a specified size can be obtained.

In the present invention, it is preferable in terms of strength and the like to calcine the molded body before impregnating the molded body containing silicon carbide and carbon with metallic silicon. The calcining temperature is preferably 1200 to 2400 ° C,
1450-2000 degreeC is more preferable. The temperature is 1
When the temperature is lower than 200 ° C., the contact between the silicon carbide powders in the green body is not sufficiently promoted, and the adhesive strength is not sufficient, so that the handleability may not be improved. When it exceeds, the powder growth of the silicon carbide powder in the green body becomes remarkable, and the impregnation of metal silicon described below may be insufficient.

The rate of temperature rise during the calcination is 800
The temperature is preferably from 1 to 3 ° C./min up to ° C., and from 5 to 8 ° C./min. Is preferable from 800 ° C. to the maximum temperature. it can.

The maximum holding time of the calcination is 10 to
120 minutes is preferred, 20 to 60 minutes is more preferred,
It can be appropriately determined in consideration of the shape and size of the green body. The calcination is preferably performed in a vacuum atmosphere or an inert gas atmosphere from the viewpoint of preventing oxidation.

The calcination is performed using a known apparatus such as a vacuum sintering furnace, an atmosphere furnace, and a sintering furnace.

(Metal Silicon) The metal silicon is high-purity metal silicon (metal silicon having an impurity content of less than 1 ppm), and is heated to a temperature not lower than its melting point, melted, and impregnated into the molded body. .

The metallic silicon which has been liquefied by the impregnation penetrates into the molded body by capillary action or the like,
The metal silicon reacts with the free carbon in the compact. By this reaction, silicon carbide is generated, pores and the like in the compact are filled with the silicon carbide, and the silicon carbide-based sintered body of the present invention having high density, strong, and good conductivity is obtained. be able to.

The heating temperature of the metal silicon is 14
20-1700 degreeC is preferable and 1550-1650 degreeC is more preferable. When the heating temperature is lower than 1420 ° C., the viscosity of the metal silicon increases, so that the metal silicon may not penetrate into the molded body due to capillary action or the like. In addition, the evaporation of the metal silicon becomes remarkable and may damage the furnace body and the like.

The time of the impregnation is not particularly limited, and can be appropriately determined depending on the size of the compact and the amount of free carbon in the compact. Examples of the metallic silicon include various shapes such as powder, granules, and lump, and have a diameter of 2 to 5
A suitable example is a lump of metallic silicon of mm.

The total content of the impurity elements in the impregnated body is:
It is preferably at most 10 ppm, more preferably at most 5 ppm. However, from the viewpoint of application to the semiconductor industrial field, the impurity content obtained by these chemical analyzes has only a meaning as a reference value. Practically, depending on whether the impurities are uniformly distributed or locally unevenly distributed,
The evaluation differs, and in general, it is possible to evaluate the extent to which the impregnated body is contaminated with impurity elements by using various means under a predetermined heating condition using a practical apparatus.

[Cooling Step] The cooling step is a step of cooling the impregnated body with the impregnated body having a temperature distribution of 0.1 to 1.5 ° C./cm. By cooling the impregnated body with such a temperature distribution,
The volume expansion when unreacted metallic silicon is solidified by cooling can be shifted from the low temperature side to the high temperature side, and a silicon carbide sintered body free of cracks and cracks can be obtained.

[0045] In the cooling step, the impregnated body is filled with 0.1%.
Cooling in a state having a temperature distribution of 1 to 1.5 ° C./cm means that if the temperature distribution is less than 0.1 ° C./cm, absorption of volume expansion during cooling and solidification of silicon metal is sufficient. On the other hand, if it exceeds 1.5 ° C./cm, the temperature distribution becomes large, and conversely, a difference in expansion causes cracks. In the present invention, 0.5 to the impregnated body is used.
Cooling in a state of having a temperature distribution of about 1.0 ° C./cm is more preferable because internal strain is less generated. The direction in which the impregnated body has a temperature distribution is not particularly limited and may be appropriately selected depending on the intended purpose.For example, when the impregnated body is a rod-shaped body, its longitudinal direction is preferable. If there is no longitudinal direction in the impregnated body, any direction may be used.

The method of giving the impregnated body a temperature distribution is as follows:
Although there is no particular limitation, for example, two or more heaters are provided in a heating furnace, and the heating temperature of the heater is gradually lowered from one end of the heating furnace to the other end, so that the impregnation is performed by giving a certain temperature gradient. There is a method of giving a temperature distribution to the body.

The cooling of the impregnated body is not particularly limited as long as the impregnated body can be cooled while having a constant temperature distribution. For example, the inside of the heating furnace having the above-mentioned constant temperature gradient is cooled. A method of moving the impregnated body in parallel from a high temperature side to a low temperature side at a constant speed is exemplified. Further, in the heating furnace having the above-mentioned constant temperature gradient, the impregnated body is stopped without being moved in parallel, and the heating temperature of the two or more heaters is reduced at the same speed, so that the constant temperature gradient is obtained. In a state where the temperature is maintained.

The cooling rate of the impregnated body is preferably 50 ° C./h or less, more preferably 5 to 20 ° C./h. If the cooling rate exceeds 50 ° C./h, internal strain may occur and cracks may occur.

When the impregnated body is cooled by moving the impregnated body from the high temperature side to the low temperature side in the heating furnace, the moving speed of the impregnated body is appropriately selected so as to be a preferable cooling rate of the impregnated body. Can be. Further, the cooling of the impregnated body with the predetermined temperature distribution in the longitudinal direction of the impregnated body may be performed at least until the temperature on the high temperature side of the impregnated body reaches 1400 ° C. If the temperature is lower than or equal to ° C., the molten metal silicon is completely solidified, so that the metal silicon may be cooled without having a temperature distribution.

[Others] The production apparatus used in the method for producing a silicon carbide sintered body of the present invention is not particularly limited as long as the heating conditions of the present invention can be satisfied.
Known heating furnaces and reaction devices are exemplified.

The method for producing a silicon carbide sintered body of the present invention prevents cracks and cracks during cooling and solidification, and is excellent in production efficiency. Further, the obtained silicon carbide-based sintered body is dense and strong, and has excellent strength and the like.

Further, according to the method for producing a silicon carbide based sintered body of the present invention, the total content of impurity elements in the obtained silicon carbide based sintered body can be reduced to 10 ppm or less. Here, the impurity element refers to the IUP in 1989.
It belongs to Group 1 to Group 16 elements in the periodic table of the revised version of AC Inorganic Chemical Nomenclature and has atomic numbers of 6 to 8 and 14
Means three or more elements excluding.

Further, according to the method for producing a silicon carbide-based sintered body, the obtained silicon carbide-based sintered body has a density of 2.
It becomes a high-density product of 9 g / cm ³ or more, and tends to be a polycrystalline semiconductor exhibiting conductivity. That is, conduction electrons contributing to electric conduction flow between silicon carbide crystals with the grain boundaries interposed therebetween, and therefore, the junction between the grain boundary phase and silicon carbide is also important for the development of conductivity.

Further, the silicon carbide sintered body obtained by the method for producing a silicon carbide sintered body of the present invention has high bending strength. The bending strength of a general silicon carbide sintered body is 240 MPa or more at room temperature, and 1500 or more.
Although the bending strength at 5 ° C. is 55.0 to 80.0 MPa, the bending strength of the silicon carbide based sintered body obtained by the method for producing a silicon carbide based sintered body of the present invention is 350 MPa or more as a bending strength at room temperature. .

[0055]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to these examples.

Example 1 As a silicon carbide powder, a high-purity silicon carbide powder having a center particle diameter of 0.8 μm (Japanese Patent Laid-Open No. 9-4)
3400 g of silicon carbide having an impurity content of 5 ppm or less and containing 1.5% by weight of silica produced according to the production method described in No. 8605, and carbon black (“# SL200” manufactured by Nippon Kayaku) as carbon powder 600 g and 2200 g of water in which 44 g of polyammonium ammonium acrylate was dissolved as a deflocculant, and dispersed and mixed in a ball mill for 16 hours. 4 g of a silicone antifoaming agent (“KM72A” manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and the mixture was dispersed and mixed by a ball mill for 10 minutes, and the viscosity was 1.8 Pa.
・ S slurry-like mixed powder was produced.

The obtained slurry-like mixed powder was mixed with 800
Cast into a gypsum mold of × φ20, φ200 × 15t,
After leaving it for 6 hours, it was removed from the mold and dried (50 ° C.) for 12 hours to produce a green body containing free carbon. The formed compacts were four 800 × φ20, φ20
0 × 15t is two sheets.

The obtained green body (green body) was
Calcination at 0 ° C for 1 hour (temperature rise up to 800 ° C at 1 ° C / min,
5 ° C./min up to 1800 ° C., atmosphere is vacuum. )
After that, it was held for 10 minutes to obtain a calcined molded body. By bonding the two calcined plate-like members to both ends of the four calcined cylindrical members, a molded body in the shape of a wafer boat was produced.

The obtained wafer boat-shaped formed body was melted by heating to 1550 ° C. in an argon atmosphere in a carbon crucible having an inner diameter of 60 mm and a height of 80 mm.
5mm lump high-purity metallic silicon (manufactured by High-Purity Chemical Laboratory)
By immersion in the molded product and holding for 30 minutes, the free carbon in the molded product was reacted with the molten metal silicon permeated into the molded product by capillary action, thereby producing an impregnated product.

1.5 ° C./c in the longitudinal direction of the obtained impregnated body
The sample was cooled at a rate of 50 ° C./h with a temperature distribution of m. In the method of giving the impregnated body a temperature distribution, three heaters were installed in the longitudinal direction of the atmosphere furnace (longitudinal direction of the impregnated body), and the temperature distribution was controlled. One temperature controller is provided for each of the three heaters, and a main temperature controller that supervises these temperature controllers is connected to the three temperature controllers. The method of cooling the impregnated body was controlled by a main temperature controller, and the heating temperatures of the three heaters were all cooled at a rate of 50 ° C./h.

Example 2 Example 1 was the same as Example 1 except that the impregnated body was cooled at a rate of 20 ° C./h with a temperature distribution of 1.0 ° C./cm in the longitudinal direction. In the same manner as described above, a silicon carbide sintered body was produced.

Example 3 Example 1 was the same as Example 1 except that the impregnated body was cooled at a rate of 5 ° C./h with a temperature distribution of 0.25 ° C./cm in the longitudinal direction. In the same manner as described above, a silicon carbide sintered body was produced.

In Examples 1 to 3, cracks and cracks did not occur, and the production efficiency was excellent. Further, each of the obtained silicon carbide-based sintered bodies was dense and strong, and was excellent in strength and the like.

Comparative Example 1 In Example 1, except that the impregnated body was cooled without having a temperature distribution in the longitudinal direction,
In the same manner as in Example 1, a silicon carbide sintered body was produced. In Comparative Example 1, two of 800 × φ20 were cracked near the center.

[0065]

According to the present invention, it is possible to provide a method for producing a silicon carbide sintered body free from cracks and cracks, and a silicon carbide sintered body produced by the production method and having excellent strength and the like. it can.

Claims (6)

[Claims] 1. A molded body containing silicon carbide and carbon is impregnated with metallic silicon in a vacuum atmosphere or a non-oxidizing atmosphere to form an impregnated body.
A method for producing a silicon carbide-based sintered body, comprising cooling the impregnated body while maintaining a temperature distribution of 5 ° C./cm. 2. Before forming the impregnated body, the molded body is
The method for producing a silicon carbide-based sintered body according to claim 1, wherein the sintered body is calcined at 0 to 2400 ° C. 3. The method according to claim 1, wherein the metallic silicon to be impregnated is 1420-17.
The method for producing a silicon carbide sintered body according to claim 1, wherein the silicon carbide sintered body is heated and melted at 00 ° C. 4. 4. The silicon carbide material according to claim 1, wherein a temperature distribution is provided by using two or more heaters, and the impregnated body is cooled by lowering the temperature of the two or more heaters at the same speed. A method for manufacturing a sintered body. 5. The method for producing a silicon carbide sintered body according to claim 1, wherein the rate of cooling the impregnated body is 50 ° C./h or less. 6. A silicon carbide-based sintered body produced by the method for producing a silicon carbide-based sintered body according to any one of claims 1 to 5.