JP2001146494A - Production process of sintered silicon carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for the production of a sintered silicon carbide having high purity and high strength. SOLUTION: The objective process for the production of a sintered silicon carbide comprises a step of dissolving or disperse silicon carbide powder in a solvent to produce a slurry of mixed silicon carbide powder, a step of casting the slurry in a mold and drying the molded product to obtain a green material, a step of immersing the green material in molten metallic silicon in vacuum or in an inert gas atmosphere to impregnate the metallic silicon into the void of the green material, a step of immersing the green material containing metallic silicon filled in the void in an alkaline aqueous solution or an acidic aqueous solution and heating the material to remove the metallic silicon from the void and a step of immersing the green material obtained by removing the metallic silicon from the void in molten metallic silicon in vacuum or in an inert gas atmosphere to impregnate the metallic silicon in the pore of the green material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a silicon carbide sintered body, and more particularly, to a method for manufacturing a high-purity and high-strength silicon carbide sintered body.

[0002]

2. Description of the Related Art Conventionally, silicon carbide has been attracting attention as a material used in a high temperature region because it has good strength, heat resistance, thermal shock resistance, abrasion resistance, etc. even at high temperatures exceeding 1000 ° C. In recent years, it has been used as a substitute for quartz as a jig for manufacturing semiconductors.

[0003] As described above, silicon carbide has very good strength, heat resistance, thermal shock resistance, abrasion resistance, and the like. In recent years, however, higher performance silicon carbide has been demanded, particularly for semiconductor-related parts. In the case of using a silicon carbide sintered body, high purity and strength are required, and further improvement is desired.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and has as its object to provide a method for producing a silicon carbide sintered body having high purity and high strength. I do.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have accomplished the present invention. That is, the present invention

<1> A step of dissolving and dispersing silicon carbide powder in a solvent to produce a slurry-like silicon carbide mixed powder, and pouring the slurry-like silicon carbide mixed powder into a mold and drying. A step of manufacturing a green body, and a step of immersing the green body in molten metal silicon under a vacuum atmosphere or an inert gas atmosphere to allow the metal silicon to penetrate pores in the green body and fill the same. A step of immersing the green body filled with metallic silicon in the pores in an aqueous alkali or acid solution and then heating to remove the metallic silicon from the pores. Dipping in molten metal silicon under an atmosphere or an inert gas atmosphere, and infiltrating and filling the pores in the green body with the metal silicon. A method for producing a silicon carbide sintered body.

<2> a process in which the silicon carbide powder is prepared by dissolving a silicon compound and an organic compound which generates carbon by heating in a solvent, drying the resultant, and firing the obtained powder in a non-oxidizing atmosphere. <1> The method for producing a silicon carbide sintered body according to <1>, wherein the method is a method for producing a silicon carbide sintered body.

<3> a step of immersing the green body in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere to infiltrate and fill the pores in the green body with metallic silicon; In a step of immersing the green body from which the metal has been removed in molten metal silicon under a vacuum atmosphere or an inert gas atmosphere to infiltrate and fill the pores in the green body with the metal silicon, the green body is treated with 1450 to 1700 The method for producing a silicon carbide sintered body according to the above <1> or <2>, characterized in that the sintered body is immersed in molten metal silicon heated at a temperature of ° C.

<4> a step of immersing the green body in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere to infiltrate and fill the pores in the green body with metallic silicon; The green body from which is removed is immersed in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere, and the metal silicon is penetrated into pores in the green body to fill the green body. The method for producing a silicon carbide sintered body according to any one of <1> to <3>, wherein the amount is high-purity metallic silicon having an amount of less than 1 ppb.

<5> After immersing the green body in which the pores are filled with metallic silicon in an alkaline aqueous solution or an acid aqueous solution, and heating to remove the metallic silicon from the pores, 1450 ~ 1700 ° C
The method for producing a silicon carbide sintered body according to any one of the above items <1> to <4>, characterized by heating.

<6> In the step of immersing the green body in which the pores are filled with metallic silicon in an alkaline aqueous solution or an acid aqueous solution, and then heating and removing the metallic silicon from the pores, the green body is vacuumed. <1> to heating under an atmosphere or an inert gas atmosphere.
<5> The method for producing a silicon carbide sintered body according to any one of <5>.

The method for producing a silicon carbide sintered body of the present invention comprises:
Once the pores in the green body are filled with metallic silicon,
By removing the filled metallic silicon and refilling the metallic silicon, a high-purity and high-strength silicon carbide sintered body can be manufactured.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a silicon carbide sintered body of the present invention comprises the steps of dissolving and dispersing silicon carbide powder in a solvent to produce a slurry-like silicon carbide mixed powder (hereinafter referred to as silicon carbide mixed powder). Powder manufacturing step), and the slurry-like silicon carbide mixed powder is poured into a mold, dried,
A step of manufacturing a green body (hereinafter, referred to as a green body manufacturing step); and immersing the green body in molten metal silicon under a vacuum atmosphere or an inert gas atmosphere, so that the metal silicon becomes pores in the green body. A step of infiltrating and filling (hereinafter referred to as a silicon filling step) and a step of immersing the green body in which the pores are filled with metallic silicon in an alkaline aqueous solution or an acid aqueous solution and then heating the metallic body to remove the metallic silicon from the pores A step of removing (hereinafter, referred to as a silicon removing step), and immersing the green body from which the metal silicon has been removed from the pores in molten metal silicon under a vacuum atmosphere or an inert gas atmosphere, and placing the metal silicon in the green body (Hereinafter referred to as a silicon refilling step).

(Silicon Carbide Mixed Powder Production Step) The silicon carbide mixed powder production step is a step of dissolving and dispersing silicon carbide powder in a solvent to produce a slurry-like silicon carbide mixed powder. However, pores can be uniformly dispersed in the green body by sufficiently stirring and mixing during dissolution and dispersion in a solvent.

In the silicon carbide mixed powder production step, the solvent may be water. For example, a lower alcohol such as ethyl alcohol may be used for a phenol resin which is an organic compound which generates carbon by suitable heating. And ethyl ether, acetone and the like. In addition, it is preferable that the organic substance, the carbon powder, and the solvent composed of the carbon source have low impurity contents.

In the silicon carbide mixed powder production step, an organic binder may be added together with the silicon carbide powder. Examples of the organic binder include a deflocculant and a powder adhesive. As the deflocculant, when imparting conductivity, a nitrogen-based compound is preferable in that the effect is further enhanced. Ammonium acrylate and the like are preferably used. As the powdery adhesive, polyvinyl alcohol, urethane resin (for example, water-soluble polyurethane) and the like are preferably used. In addition, an antifoaming agent may be added. Examples of the antifoaming agent include a silicone antifoaming agent.

In the silicon carbide mixed powder production step, stirring and mixing can be performed by a known stirring and mixing means such as a mixer and a planetary ball mill. The stirring and mixing are preferably performed for 10 to 30 hours, particularly 16 to 24 hours.

Hereinafter, the silicon carbide powder will be described in detail. —Silicon Carbide Powder— The silicon carbide powder may be α-type, β-type, amorphous, or a mixture thereof. In order to obtain a high-purity green body or a silicon carbide sintered body, it is preferable to use a high-purity silicon carbide powder as a raw material silicon carbide powder.

As the grade of the silicon carbide powder,
There is no particular limitation, 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, and specifically, it is preferable that the particle size of the silicon carbide powder is 0.1.
About 01 to 10 μm, more preferably 0.05 to 5 μm
μm. If the particle size is less than 0.01 μm, the handling in the processing steps such as measurement and mixing tends to be difficult, and if it exceeds 10 μm, the specific surface area is small, that is, the contact area with the adjacent powder is small, It is not preferable because it is difficult to increase the density.

-Method for Producing Silicon Carbide Powder- The silicon carbide powder is prepared by dissolving a silicon compound, an organic compound which generates carbon by heating, and, if necessary, a polymerization or crosslinking catalyst in a solvent and drying. It is preferable that the powder is manufactured by a manufacturing method including a step of firing the obtained powder in a non-oxidizing atmosphere (hereinafter, may be referred to as a “silicon carbide powder manufacturing step”).

The silicon compound (hereinafter sometimes referred to as “silicon source”) is not particularly limited as long as it is a compound that generates silicon by heating, and may be either a liquid silicon compound or a solid silicon compound. May be
From the viewpoint of high purification and uniform dispersion, at least 1
Preferably, the seed is a liquid silicon compound.

Suitable examples of the liquid silicon compound include (mono-, di-, tri-, and tetra-) alkoxysilanes and polymers of tetraalkoxysilanes.

The above (mono-, di-, tri-, tetra-)
Preferable examples of the alkoxysilane include tetraalkoxysilane. As tetraalkoxysilane,
Specifically, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like are preferably exemplified, and tetraethoxysilane is particularly preferred from the viewpoint of excellent handleability.

As the polymer of the tetraalkoxysilane, a low molecular weight polymer (oligomer) having a degree of polymerization of about 2 to 15 (eg, a low molecular weight polymer such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, etc.) Polymers (oligomers)) and liquid high-polymer silicate polymers are preferred.

Preferred examples of the solid silicon compound include silicon oxide. Here, the silicon oxide in the present invention means, in addition to SiO, silica sol (colloidal ultrafine silica containing liquid, containing OH group or alkoxyl group inside), silicon dioxide (silica gel, fine silica, quartz powder) Body) and the like.

Among the above-mentioned silicon compounds, low molecular weight polymer (oligomer) of tetraethoxysilane, and low molecular weight polymer (oligomer) of tetraethoxysilane, and fine powder silica are preferred because of their excellent homogeneity and handleability. And the like are particularly preferred. These silicon compounds may be used alone or in combination of two or more.

The total content of the impurity elements in the silicon compound is preferably 20 ppm or less, and more preferably 5 ppm.
The following is more preferred. However, the value is not necessarily limited to the numerical value within the above numerical range as long as it is within the allowable range of purification during heating and sintering.

The organic compound capable of generating carbon by heating (hereinafter, sometimes referred to as a “carbon source”) is not particularly limited, and any liquid or solid organic compound may be used. From the viewpoints of purification and uniform dispersion, it is preferable that at least one type is a liquid organic compound.

The organic compound which generates carbon by heating is preferably an organic compound which has a high residual carbon ratio and is polymerized and crosslinked by the presence of a catalyst and / or heating. As such organic compounds, for example, phenol resins, furan resins, polyimides, polyurethanes, resin monomers such as polyvinyl alcohol, and prepolymers, and liquid organic compounds such as cellulose, sucrose, pitch, and tar are preferably exemplified. . Among these, a phenol resin is preferable, and a resol-type phenol resin is particularly preferable. These organic compounds may be used alone or in combination of two or more.

The total content of the impurity elements in the organic compound which generates carbon by heating can be appropriately controlled and selected according to the purpose. In particular, in order to obtain high-purity silicon carbide powder, the total content of impurity elements is 5 ppm or less. Is preferred.

In the silicon carbide powder producing step,
Further, in addition to a polymerization or crosslinking catalyst, it is necessary to dissolve the silicon source and the carbon source in a solvent and dry the mixture of the silicon source and the carbon source to obtain a silicon carbide powder in order to obtain a powder. It is performed according to. 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 polymerization or crosslinking catalyst 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, sulfuric acid, maleic acid And amines such as hexamine. These mixed catalysts are 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. Among these, toluenesulfonic acid is preferably used.

In the silicon carbide powder production process, the ratio of carbon to silicon (hereinafter referred to as C / Si ratio) is defined by elemental analysis of a carbide intermediate obtained by carbonizing the mixture at 1000 ° C. You. Stoichiometrically, C
When the / Si ratio is 3.0, the free carbon in the generated silicon carbide should be 0%, but actually, the
Free carbon is generated at a low C / Si ratio due to the volatilization of the O gas. It is important to determine the composition in advance so that the amount of free carbon in the produced silicon carbide powder does not become an unsuitable amount for the production use of a sintered body or the like. Normally, 1
In firing at 600 ° C. or higher, the C / Si ratio is set to 2.0 to 2.
When it is 5, free carbon can be suppressed, and this range can be suitably used. When the C / Si ratio is 2.5 or more, the amount of free carbon increases remarkably. However, since this free carbon has an effect of suppressing grain growth, it may be appropriately selected according to the purpose of forming particles. However, when the atmosphere is fired at a low or high pressure, the C / Si ratio for obtaining pure silicon carbide varies.
The ratio is not limited to the range of the / Si ratio.

In the above-mentioned silicon carbide powder production process, the firing is performed by dissolving a silicon source and a carbon source in a solvent, and drying the powder in a non-oxidizing atmosphere such as argon at 1350 ° C.
It is preferable to carry out by heating at 2000 ° C. to generate silicon carbide. The firing temperature and time can be appropriately selected according to the desired properties such as the particle size, but firing at 1600 ° C. to 1900 ° C. is particularly preferable for more efficient production.

In the above-mentioned silicon carbide powder production process, before the above-mentioned calcination, the above-mentioned silicon source and the above-mentioned carbon source were dissolved in a solvent and dried for the purpose of improving handling properties and removing volatile gas and moisture. The powder may be heated and carbonized. Heat carbonization is performed at 800 ° C. to 1000 ° C. for 30 minutes to 120 minutes in a non-oxidizing atmosphere such as nitrogen or argon.
It is preferably carried out by heating the powder.

In the above-mentioned silicon carbide powder production step, a heat treatment may be performed at 1900 to 2100 ° C. for 5 to 20 minutes for the purpose of obtaining a higher purity silicon carbide powder during the above-mentioned firing. Impurities can be further removed.

In the above-mentioned silicon carbide powder production process, the stirring and mixing can be performed by a known stirring and mixing means, for example, a mixer, a planetary ball mill or the like. The stirring and mixing are preferably performed for 10 to 30 hours, particularly 16 to 24 hours.

In the above-mentioned silicon carbide powder production step, particularly when it is desired to obtain a high-purity silicon carbide powder, the raw material powder described in the method for producing a single crystal of Japanese Patent Application Laid-Open No. 9-48605 filed by the present applicant has been filed. Production method, namely, high purity tetraalkoxysilane, at least one selected from tetraalkoxysilane polymers as a silicon source, a high purity organic compound that generates carbon by heating as a carbon source, and these are mixed uniformly. Heating the mixture obtained in a non-oxidizing atmosphere to obtain a silicon carbide powder, and subjecting the obtained silicon carbide powder to a temperature of 1700 ° C. to 20 ° C.
At a temperature of less than 00 ° C.
A post-treatment step of performing heating at a temperature of 0 ° C. to 2100 ° C. for at least 5 minutes for at least one time, and by performing the two steps, the carbon content of each impurity element is 0.5 ppm or less. A method for producing high-purity silicon carbide powder, which is characterized by obtaining silicon powder, can also be used.

Since the silicon carbide powder obtained as described above is not uniform in size, a desired silicon carbide powder can be obtained by pulverization and classification.

(Green Body Production Step) The green body production step is a step of pouring the slurry-like silicon carbide mixed powder into a mold and drying it to produce a green body. The green body refers to a silicon carbide molded body having many pores therein.

In the green body production step, the slurry-like silicon carbide mixed powder is cast into a gypsum or resin mold, left as it is, and then removed from the mold, and then heated and dried or naturally dried at a temperature of 50 to 60 ° C. To remove the solvent
Preferably, the process is a process for producing a green body having a specified size. Further, if necessary, the obtained green body may be removed from a trace amount of water, a deflocculant, a binder, or the like, or the contact between silicon carbide powders in the green body may be sufficiently promoted to obtain a contact strength. For the purpose, baking may be performed at a temperature in the range of about 1200 ° C. to 2400 ° C. (the green body thus obtained may be referred to as “calcined green body”).

(Silicon Filling Step) In the silicon filling step, the green body is immersed in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere, and the metal silicon is inhaled into pores in the green body by inhalation. This is the step of filling.

In the silicon filling step, the green body is immersed in molten metal silicon by heating to a temperature equal to or higher than the melting point of metal silicon, preferably 1450 to 1700 ° C., in a vacuum atmosphere or an inert gas atmosphere. By immersing the green body in the molten metal silicone in this way, the liquid metal silicon penetrates into the pores in the green body by inhalation, for example, capillary action, and the pores in the green body are filled with the metal silicon. You.

In the silicon filling step, the time for immersing the green body in the molten metal silicon is not particularly limited, and is appropriately determined depending on the size and the like.

In the silicon filling step, the metal silicon is heated up to 1450-1700 ° C., preferably 1
The material is heated to 550 to 1650 ° C. to be melted. If the melting temperature is lower than 1450 ° C., the viscosity of the metallic silicon increases, so that it may be difficult to infiltrate the green body by inhalation, and may exceed 1700 ° C. In some cases, evaporation may be remarkable, resulting in damage to the furnace body and the like.

In the silicon filling step, examples of the metal silicon include powder, granules, and bulk metal silicon, and bulk metal silicon having a size of 2 to 5 mm is preferably used. Preferably, the metal silicon is high-purity metal silicon having a total impurity content of less than 1 ppb.

In the silicon filling step, the green body is preferably cooled to room temperature once after filling the pores with metallic silicon.

(Silicon Removal Step) The silicon removal step is a step of immersing a green body in which pores are filled with metallic silicon in an alkaline aqueous solution or an acid aqueous solution and then heating the green body to remove the metallic silicon from the pores. is there. By heating the green body filled with metallic silicon in the pores, the metallic silicon melts or evaporates,
Removed from pores.

In the silicon removing step, the green body is immersed in an alkaline aqueous solution or an acidic aqueous solution and then heated to a temperature equal to or higher than the melting point of metallic silicon, preferably 1450 to 1700, in a vacuum atmosphere or an inert gas atmosphere.
It is preferable to remove metallic silicon in the green body by heating up to ℃.

In the silicon removal step, examples of the aqueous alkali solution include an aqueous alkali hydroxide solution. Examples of the acid aqueous solution include a hydrofluoric acid aqueous solution, a nitric acid aqueous solution, a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, a hydrogen peroxide solution, an ozone water, and a mixed acid aqueous solution thereof. Examples of the mixed acid aqueous solution include a hydrofluoric nitric acid aqueous solution, a mixed acid aqueous solution of hydrofluoric nitric acid and sulfuric acid, and a mixed acid aqueous solution of hydrofluoric acid and hydrochloric acid.

In the silicon removing step, the green body is heated to 1450 to 1700 ° C., preferably 1550 ° C.
迄 1650 ° C. to remove metallic silicon in the green body. If the melting temperature is less than 1450 ° C., the viscosity of the metallic silicon increases, so that it may be difficult to remove the metallic silicon from the green body. On the other hand, when the temperature exceeds 1700 ° C., the evaporation is remarkable and the furnace body or the like may be damaged.

(Silicon refilling step) In the silicon refilling step, the green body obtained by removing metal silicon from the pores is
This is a step of dipping in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere to infiltrate and fill the pores in the green body with the metal silicon, and is preferably performed in the same manner as the silicon filling step.

(Others) The silicon carbide sintered body obtained by the method for producing a silicon carbide sintered body of the present invention may contain nitrogen for the purpose of imparting conductivity. As a method for introducing nitrogen, in the silicon carbide powder production step or the silicon carbide mixed powder production step, at least one or more nitrogen-containing compounds (hereinafter, sometimes referred to as “nitrogen source”) are added. Can be introduced by

As the nitrogen source, a substance that generates nitrogen by heating is preferable. For example, a polymer compound (specifically, a polyimide resin and a nylon resin), an organic amine (specifically, hexamethylenetetramine) , Ammonia, triethylamine and the like, and compounds and salts thereof), and among these, hexamethylenetetramine is preferable. Also, a phenol resin synthesized using hexamine as a catalyst and containing 2.0 mmol or more of nitrogen derived from the synthesis process per 1 g of the resin can be suitably used as a nitrogen source. These nitrogen sources may be used alone or in combination of two or more.

In the case where the nitrogen source is introduced in the silicon carbide powder production step, the nitrogen source and the silicon source are
Preferably, a nitrogen source is added. The amount of nitrogen added was 1 mmol / g of silicon source.
Since the above content is preferable, the content is preferably 80 μg to 1000 μg with respect to 1 g of the silicon source.

When the nitrogen source is introduced in the silicon carbide mixed powder production step, when dissolving and dispersing the silicon carbide powder in the solvent, the nitrogen source is simultaneously added to the solvent to dissolve and disperse. The method is preferred. Since the amount of nitrogen added is preferably 0.7 mmol or more per 1 g of silicon carbide powder, the amount is preferably 200 μg to 2000 μg, more preferably 1500 μg to 2000 μg per 1 g of silicon carbide powder.

In the method for producing a silicon carbide sintered body of the present invention, as long as the heating conditions can be satisfied, there is no particular limitation on the production apparatus and the like, and a known heating furnace or reactor can be used. .

The silicon carbide sintered body manufactured as described above is usually processed into a predetermined shape, and is subjected to processing such as polishing and washing. As the machining method, electric discharge machining or the like is preferably used because the silicon carbide sintered body has good conductivity.

The method for producing a silicon carbide sintered body of the present invention comprises:
Once the pores in the green body are filled with metallic silicon,
By removing the charged metallic silicon and refilling the metallic silicon, the silicon carbide sintered body can be highly purified. For example, the total content of impurity elements is preferably 10 ppm or less, more preferably Can be 5 ppm or less, more preferably 1.5 ppm or less. It is considered that this is because impurities in the green body migrate into the metal silicon filled therein, and by removing this, the impurities are removed together, so that high purity can be achieved.

As for the total content of the impurity elements, the impurity content obtained by chemical analysis has only a meaning as a reference value. In practice, the evaluation differs depending on whether the impurities are uniformly distributed or locally unevenly distributed. In the present invention, values measured by the solution ICP-MS method are used.

The above-mentioned impurity element is defined in IUPA 1989
C refers to an element belonging to Group 1 to Group 16 elements in the periodic table of the revised inorganic chemical nomenclature for C, having an atomic number of 3 or more, and excluding atomic numbers 6 to 8 and 14.

The method for producing a silicon carbide sintered body of the present invention
Once the pores in the green body are filled with metallic silicon,
By removing the filled metallic silicon and refilling the metallic silicon again, the silicon carbide sintered body can be made to have a high strength.
It is also possible to produce a silicon carbide sintered body of 50 to 380 MPa.

According to the method for producing a silicon carbide sintered body of the present invention,
Other suitable physical properties of the silicon carbide sintered body
Considering that, for example, the Young's modulus is 3.5 × 10^Four
~ 4.5 × 10^Four, Vickers hardness is 204 MPa (2
000kgf / mm^Two) Above, Poisson's ratio is 0.14 ~
0.21, thermal expansion coefficient 3.8 × 10^-6~ 4.2 × 10
^-6(℃^-1), Thermal conductivity is 150W / mK or more, specific heat is
0.68 to 0.76 j / g · ° C. (0.15 to 0.18 c
al / g · ° C), thermal shock resistance ΔT is 500-700 ° C
It is.

[0065]

EXAMPLES The present invention will be specifically described below with reference to examples, but is not limited to the examples unless it exceeds the gist of the present invention.

Comparative Example 1 As a silicon carbide powder, a high-purity silicon carbide powder having a center particle diameter of 0.8 μm (JP-A-9-4)
850 g of silicon carbide having an impurity content of 5 ppm or less produced according to the production method described in No. 8605 and containing 1.5% by weight of silica) in 500 g of water in which 9 g of ammonium polyacrylate was dissolved as a deflocculant. After adding and dispersing and mixing in a ball mill for 16 hours, 30 g of a water-soluble polyurethane ("Yukote" manufactured by Sanyo Chemical) as a powdery adhesive and a silicone antifoaming agent ("KM72A" manufactured by Shin-Etsu Chemical Co., Ltd.) 1
g, and further dispersed and mixed in a ball mill for 10 minutes.
A slurry-like mixed powder having a viscosity of 0.09 Pa · s (0.9 poise) was produced.

The slurry-like mixed powder was 70 m long.
m, cast into a gypsum mold having a diameter of 10 mm, left for 6 hours, demolded, and dried (50 ° C.) for 12 hours to produce a green body.

The obtained green body was heated to 1550 ° C. and melted in a carbon crucible having an inner diameter of 60 mm and a height of 80 mm under an argon atmosphere to form a block of high-purity metallic silicon of 2 to 5 mm (Okuyama Corporation) Made: Total impurities 1
ppb or less) and held for 30 minutes to allow the molten metal silicon to permeate and fill the pores in the green body, thereby producing a silicon carbide sintered body of Comparative Example 1.

Example 1 A silicon carbide sintered body (a green body in which pores were filled with metallic silicon) of Comparative Example 1 was immersed in an aqueous alkali solution or an aqueous acid solution, and then heated to 1550 ° C. in an argon atmosphere. Thus, metallic silicon in the pores was removed.

The green body obtained by removing metallic silicon from the pores was heated to 1550 ° C. in a carbon crucible having an inner diameter of 60 mm and a height of 80 mm and heated to 1550 ° C. in an argon atmosphere to form a 2 to 5 mm lump. By immersing in pure metal silicon (manufactured by Okuyama Co., Ltd .: total impurity amount of 1 ppb or less) and holding for 30 minutes, the molten metal silicon was infiltrated into the pores in the green body and filled, and the silicon carbide fired in Example 1 was filled. A compact was produced.

<Evaluation> The obtained silicon carbide sintered bodies of Example 1 and Comparative Example 1 were subjected to the following evaluation, three-point bending test, and measurement of purity. Table 1 shows the results.

(Three-point bending test) The three-point bending test of the silicon carbide sintered body was performed according to JIS R1601.

(Measurement of Purity) The purity of the silicon carbide sintered body was measured by measuring the content of each impurity element using an ICP-mass spectrometer.

[0074]

[Table 1]

Table 1 shows that the purity and strength of the silicon carbide sintered body can be improved by performing the method for producing a silicon carbide sintered body of the present invention.

[0076]

As described above, according to the present invention, high purity,
Further, it is possible to provide a method for producing a silicon carbide sintered body having high strength.

Claims (6)

[Claims] A step of dissolving and dispersing the silicon carbide powder in a solvent to produce a slurry-like silicon carbide mixed powder; pouring the slurry-like silicon carbide mixed powder into a mold, drying; A step of manufacturing a green body, the green body under a vacuum atmosphere or an inert gas atmosphere,
A step of immersing the metal body in a molten metal silicon to fill the pores in the green body by infiltrating the metal silicon, and a step of immersing the green body filled with the metal silicon in the pores in an aqueous alkali solution or an acid solution and then heating And removing the metal silicon from the pores, and immersing the green body from which the metal silicon has been removed in a molten metal silicon under a vacuum atmosphere or an inert gas atmosphere,
A step of infiltrating and filling metallic silicon with pores in the green body. 2. The method according to claim 1, wherein the silicon carbide powder comprises a step of dissolving a silicon compound and an organic compound that generates carbon by heating in a solvent, drying the powder, and firing the obtained powder in a non-oxidizing atmosphere. The method for producing a silicon carbide sintered body according to claim 1, wherein the method is obtained by a production method. 3. A step of immersing the green body in molten metal silicon under a vacuum atmosphere or an inert gas atmosphere to infiltrate and fill the pores in the green body with the metal silicon, and to remove the metal silicon from the pores. In the step of immersing the removed green body in molten metal silicon under a vacuum atmosphere or an inert gas atmosphere to fill the pores in the green body by infiltrating the metal silicon, the green body is heated to 1450 to 1700 ° C. 3. The method for producing a silicon carbide sintered body according to claim 1, wherein the substrate is immersed in molten metal silicon heated by the method described in claim 1. 4. A step of immersing the green body in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere to infiltrate and fill the pores in the green body with the metal silicon, and to remove the metal silicon from the pores. In the step of immersing the removed green body in a molten metal silicon under a vacuum atmosphere or an inert gas atmosphere to fill the pores in the green body by infiltrating the metal silicon, the metal silicon has a total impurity content. Is a high-purity metallic silicon of less than 1 ppb. The method for producing a silicon carbide sintered body according to any one of claims 1 to 3, wherein 5. A step of immersing the green body in which the pores are filled with metallic silicon in an alkaline aqueous solution or an acid aqueous solution, and then heating the green body to remove the metallic silicon from the pores. The method for producing a silicon carbide sintered body according to any one of claims 1 to 4, wherein the heating is performed at 1700 ° C. 6. A step of immersing the green body in which the pores are filled with metallic silicon in an alkaline aqueous solution or an acid aqueous solution, and then heating the green body to remove the metallic silicon from the pores. The method for producing a silicon carbide sintered body according to any one of claims 1 to 5, wherein heating is performed in an inert gas atmosphere.