JP4278802B2 - Method for producing sintered silicon carbide - Google Patents

Description

【００７５】
表１より、本発明の炭化ケイ素焼結体の製造方法を行うと、炭化ケイ素焼結体の純度、強度が向上することがわかる。
【００７６】
【発明の効果】
以上により、本発明によれば、高純度、且つ高強度な炭化ケイ素焼結体の製造方法を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a silicon carbide sintered body, and more particularly to a method for manufacturing a silicon carbide sintered body having high purity and high strength.
[0002]
[Prior art]
Conventionally, silicon carbide has attracted attention as a material used in a high temperature region because it has good strength, heat resistance, thermal shock resistance, wear resistance, etc. even at high temperatures exceeding 1000 ° C. It is used as an alternative material for quartz as a jig.
[0003]
As described above, silicon carbide has very good strength, heat resistance, thermal shock resistance, wear resistance, and the like. However, in recent years, higher performance silicon carbide has been demanded, especially for semiconductor-related parts. When using a sintered body, high purity and strength are required, and further improvements are desired.
[0004]
[Problems to be solved by the invention]
This invention is made | formed in view of the said prior art, ie, provides the manufacturing method of a silicon carbide sintered compact with high purity and high intensity | strength.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have reached the present invention. That is, the present invention
[0006]
<1> A step of producing a slurry-like silicon carbide mixed powder by dissolving and dispersing silicon carbide powder in a solvent, and pouring the slurry-like silicon carbide mixed powder into a mold, followed by drying. 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 a metal in the pores. The green body filled with silicon is immersed in an alkaline aqueous solution or an acid aqueous solution, and then heated to remove the metallic silicon from the pores, and the green body from which the metallic silicon has been removed from the pores is subjected to a vacuum atmosphere or in a non-volatile state. A step of immersing in molten metal silicon under an active gas atmosphere, and infiltrating the metal silicon into pores in the green body and filling the silicon carbide. A method for producing a sintered body.
[0007]
<2> A production method in which the silicon carbide powder includes a step in which a silicon compound and an organic compound that generates carbon by heating are dissolved in a solvent and dried, and the obtained powder is fired in a non-oxidizing atmosphere. The method for producing a silicon carbide sintered body according to <1>, wherein the silicon carbide sintered body is obtained.
[0008]
<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, and removing the metal silicon from the pores The green body is heated at 1450 to 1700 ° C. in a step of immersing the green body in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere and infiltrating the metal silicon into the pores of the green body and filling it. Then, the silicon carbide sintered body according to <1> or <2>, wherein the silicon carbide sintered body is immersed in molten metal silicon.
[0009]
<4> The 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, and removing the metal silicon from the pores In the step of immersing the green body in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere and infiltrating the metal silicon into the pores in the green body, the metal silicon has a total impurity content of 1 ppb. It is a manufacturing method of the silicon carbide sintered compact in any one of said <1>-<3> characterized by being less high purity metal silicon.
[0010]
<5> After the green body filled with metal silicon in the pores is immersed in an alkaline aqueous solution or an acid aqueous solution, the green body is heated at 1450 to 1700 ° C. in the step of removing the metal silicon from the pores by heating. The method for producing a silicon carbide sintered body according to any one of <1> to <4>, wherein the silicon carbide sintered body is heated by heating.
[0011]
<6> In the step of removing the metal silicon from the pores by immersing the green body in which the pores are filled with metallic silicon in an alkaline aqueous solution or an acid aqueous solution, The method for producing a silicon carbide sintered body according to any one of <1> to <5>, wherein heating is performed in an active gas atmosphere.
[0012]
The method for producing a silicon carbide sintered body of the present invention has a high purity by once filling the pores in the green body with metallic silicon, removing the filled metallic silicon, and filling with metallic silicon again. In addition, a high-strength silicon carbide sintered body can be produced.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the method for producing a silicon carbide sintered body of the present invention, a silicon carbide powder is dissolved and dispersed in a solvent to produce a slurry-like silicon carbide mixed powder (hereinafter referred to as a silicon carbide mixed powder production process). When,
The slurry-like silicon carbide mixed powder is poured into a mold and dried to produce a green body (hereinafter referred to as a green body production process);
A step of immersing the green body in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere and infiltrating the metal silicon into pores in the green body (hereinafter referred to as a silicon filling step);
A step of immersing the green body in which the pores are filled with metallic silicon in an alkaline aqueous solution or an aqueous acid solution and then heating to remove the metallic silicon from the pores (hereinafter referred to as a silicon removal step);
A step of immersing the green body from which the metal silicon has been removed from the pores in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere and infiltrating the metal silicon into the pores in the green body (hereinafter referred to as silicon refilling). Called filling process).
Have
[0014]
(Silicon carbide mixed powder manufacturing process)
The silicon carbide mixed powder manufacturing process is a process of manufacturing a slurry-like silicon carbide mixed powder by dissolving and dispersing silicon carbide powder in a solvent. By stirring and mixing, the pores can be uniformly dispersed in the green body.
[0015]
In the silicon carbide mixed powder manufacturing process, the solvent may be water. For example, for a phenol resin that is an organic compound that generates carbon by suitable heating, lower alcohols such as ethyl alcohol and ethyl ether are used. , Acetone and the like. Moreover, it is preferable to use the organic substance, carbon powder, and solvent made of the carbon source having a low impurity content.
[0016]
In the silicon carbide mixed powder manufacturing process, an organic binder may be added together with the silicon carbide powder. Examples of the organic binder include a deflocculant and a powder pressure-sensitive adhesive. As the deflocculant, a nitrogen-based compound is preferable in terms of further enhancing the effect when imparting conductivity, for example, ammonia, Ammonium acrylate is preferably used. As the powder 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 defoaming agent include a silicone antifoaming agent.
[0017]
In the silicon carbide mixed powder manufacturing process, the stirring and mixing can be performed by a known stirring and mixing means such as a mixer or a planetary ball mill. The stirring and mixing is preferably performed for 10 to 30 hours, particularly 16 to 24 hours.
[0018]
The silicon carbide powder will be described in detail below.
-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 the raw material silicon carbide powder.
[0019]
There is no restriction | limiting in particular as a grade of the said silicon carbide powder, For example, the beta-type silicon carbide powder generally marketed can be used.
[0020]
The particle size of the silicon carbide powder is preferably small from the viewpoint of densification, specifically about 0.01 to 10 μm, and more preferably 0.05 to 5 μm. When the particle size is less than 0.01 μm, handling in processing steps such as weighing and mixing tends to be difficult, and when it exceeds 10 μm, the specific surface area is small, that is, the contact area with the adjacent powder is small, Since it becomes difficult to increase the density, it is not preferable.
[0021]
-Manufacturing method of silicon carbide powder-
The silicon carbide powder is prepared by dissolving a silicon compound, an organic compound that generates carbon by heating, and, if necessary, a polymerization or cross-linking catalyst in a solvent and drying the resulting powder in a non-oxidizing atmosphere. It is preferable to manufacture by the manufacturing method which has the process (henceforth a "silicon carbide powder manufacturing process") baked by.
[0022]
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. However, from the viewpoint of high purity and uniform dispersion, at least one of them is preferably a liquid silicon compound.
[0023]
Preferred examples of the liquid silicon compound include (mono-, di-, tri-, tetra-) alkoxysilanes and polymers of tetraalkoxysilanes.
[0024]
Preferred examples of the (mono-, di-, tri-, tetra-) alkoxysilane include tetraalkoxysilane. Specific examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like, and tetraethoxysilane is particularly preferable from the viewpoint of excellent handleability.
[0025]
The tetraalkoxysilane polymer may be a low molecular weight polymer (oligomer) having a degree of polymerization of about 2 to 15 (for example, a low molecular weight polymer such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane ( Suitable examples include oligomers)) and liquid high-polymerization silicic acid polymers.
[0026]
A preferable example of the solid silicon compound is silicon oxide. Here, the silicon oxide in the present invention refers to silica sol (liquid containing colloidal ultrafine powder silica, containing OH group or alkoxyl group inside), silicon dioxide (silica gel, fine powder silica, quartz powder) in addition to SiO. Body) and the like.
[0027]
Among the silicon compounds, from the viewpoint of excellent homogeneity and handleability, a low molecular weight polymer (oligomer) of tetraethoxysilane, a mixture of the low molecular weight polymer (oligomer) of tetraethoxysilane and fine powder silica, etc. Is particularly preferred. Moreover, these silicon compounds may be used individually by 1 type, and may use 2 or more types together.
[0028]
The total content of impurity elements in the silicon compound is preferably 20 ppm or less, and more preferably 5 ppm or less. However, the value is not necessarily limited to the numerical value within the numerical range as long as it is within the allowable range of purification during heating and sintering.
[0029]
The organic compound that generates carbon by heating (hereinafter sometimes referred to as “carbon source”) is not particularly limited, and any organic compound in liquid or solid form may be used. From the viewpoint of uniform dispersion, at least one kind is preferably a liquid organic compound.
[0030]
The organic compound that generates carbon by heating is preferably an organic compound that has a high residual carbon ratio and that is polymerized / crosslinked by the presence of a catalyst and / or heating. Suitable examples of such organic compounds include monomers and prepolymers of resins such as phenol resins, furan resins, polyimides, polyurethanes, and polyvinyl alcohols, and liquid organic compounds such as cellulose, sucrose, pitch, and tar. . Among these, a phenol resin is preferable, and a resol type phenol resin is particularly preferable. These organic compounds may be used individually by 1 type, and may use 2 or more types together.
[0031]
The total content of impurity elements in the organic compound that generates carbon by heating can be appropriately controlled and selected according to the purpose, but in order to obtain high-purity silicon carbide powder, the total content is preferably 5 ppm or less.
[0032]
In the silicon carbide powder production process, a mixture of a silicon source and a carbon source is cured in order to further add a polymerization or crosslinking catalyst, dissolve the silicon source and the carbon source in a solvent, and dry to obtain a powder. The silicon carbide powder is also formed as necessary. Examples of the curing method include a method of crosslinking by heating, a method of curing with a curing catalyst, and a method using an electron beam or radiation.
[0033]
The polymerization or crosslinking catalyst can be appropriately selected according to the carbon source, but in the case of a phenol resin or furan resin, acids such as toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalic acid, hydrochloric acid, sulfuric acid, maleic acid, etc. Amines such as hexamine are used. These mixed catalysts are dissolved or dispersed in a solvent and mixed. Examples of the solvent include lower alcohols (for example, ethyl alcohol), ethyl ether, acetone and the like. Among these, toluenesulfonic acid is preferably used.
[0034]
In the silicon carbide powder manufacturing 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. Stoichiometrically, when the C / Si ratio is 3.0, the free carbon in the generated silicon carbide should be 0%. However, in practice, the low C / Si ratio is caused by volatilization of the SiO gas generated at the same time. Free carbon is generated in It is important to determine the blending in advance so that the amount of free carbon in the generated silicon carbide powder does not become an amount that is not suitable for manufacturing applications such as sintered bodies. Usually, in firing at 1600 ° C. or more near 1 atm, free carbon can be suppressed when the C / Si ratio is set to 2.0 to 2.5, and this range can be suitably used. When the C / Si ratio is 2.5 or more, free carbon significantly increases. However, since this free carbon has an effect of suppressing grain growth, it may be appropriately selected according to the purpose of grain formation.
However, when the atmosphere is fired at a low pressure or a high pressure, the C / Si ratio for obtaining pure silicon carbide varies, and in this case, it is not necessarily limited to the range of the C / Si ratio.
[0035]
In the silicon carbide powder manufacturing process, the baking is performed by dissolving a silicon source and a carbon source in a solvent and heating the dried powder at 1350 ° C. to 2000 ° C. in a non-oxidizing atmosphere such as argon. It is preferable to carry out by generating. The firing temperature and time can be appropriately selected according to the desired characteristics such as particle size, but firing at 1600 ° C. to 1900 ° C. is particularly preferred for more efficient production.
[0036]
In the silicon carbide powder manufacturing process, prior to the aforementioned firing, for the purpose of improving handling properties, removing volatile gas and moisture, the silicon source and the carbon source are dissolved in a solvent, and dried powder, Heat carbonization may be performed. The heating carbonization is preferably performed by heating the powder at 800 ° C. to 1000 ° C. for 30 minutes to 120 minutes in a non-oxidizing atmosphere such as nitrogen or argon.
[0037]
In the silicon carbide powder manufacturing process, at the time of firing, for the purpose of obtaining a higher purity silicon carbide powder, heat treatment may be performed at 1900 to 2100 ° C. for 5 to 20 minutes. Can be removed.
[0038]
In the silicon carbide powder production process, the stirring and mixing can be performed by a known stirring and mixing means such as a mixer or a planetary ball mill. The stirring and mixing is preferably performed for 10 to 30 hours, particularly 16 to 24 hours.
[0039]
In the silicon carbide powder production process, when it is particularly desired to obtain a high-purity silicon carbide powder, the raw material powder production method described in the method for producing a single crystal of JP-A-9-48605 filed earlier by the applicant of the present application, That is, one or more selected from high-purity tetraalkoxysilane and tetraalkoxysilane polymer is used as a silicon source, and a high-purity organic compound that generates carbon by heating is used as a carbon source. A silicon carbide production step of obtaining a silicon carbide powder by heating and firing the obtained mixture in a non-oxidizing atmosphere, and maintaining the obtained silicon carbide powder at a temperature of 1700 ° C. or higher and lower than 2000 ° C. And a post-treatment step of performing at least one heat treatment for 5 to 20 minutes at a temperature of 2000 ° C. to 2100 ° C. The content of each impurity element to obtain a silicon carbide powder is less than 0.5 ppm, can be used a method of manufacturing such a high-purity silicon carbide powder wherein the.
[0040]
Since the silicon carbide powder obtained as described above is non-uniform in size, a desired silicon carbide powder can be obtained by pulverization and classification.
[0041]
(Green body manufacturing process)
The green body manufacturing step is a step of manufacturing the green body by pouring the slurry-like silicon carbide mixed powder into a mold and drying. The green body is a silicon carbide molded body in which many pores are inherent.
[0042]
The green body manufacturing process involves casting the slurry-like silicon carbide mixed powder into a gypsum or resin molding die, leaving it to be removed, and then drying by heating or natural drying at a temperature of 50 to 60 ° C. It is preferable that the step is a step of producing a green body having a specified size by removing. Further, if necessary, the obtained green body is freed from trace amounts of moisture, peptizer, binder, etc., or contact between silicon carbide powders in the green body is sufficiently promoted to obtain contact strength. For the purpose, firing may be performed in a range of about 1200 ° C. to 2400 ° C. (the green body obtained thereby may be referred to as “calcined green body”).
[0043]
(Silicon filling process)
The silicon filling step is a step in which the green body is immersed in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere, and the metal silicon is infiltrated into the pores in the green body and filled.
[0044]
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 soaking the green body in the molten metal silicone, 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. The
[0045]
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.
[0046]
In the silicon filling step, the metal silicon is heated to 1450 to 1700 ° C., preferably 1550 to 1650 ° C., and melted. If the melting temperature is lower than 1450 ° C., the viscosity of the metal silicon increases. Therefore, it may be difficult to penetrate into the green body by inhalation, and when it exceeds 1700 ° C., evaporation may become remarkable and damage the furnace body and the like.
[0047]
In the silicon filling step, examples of the metal silicon include powder, granule, and bulk metal silicon, and a bulk metal silicon of 2 to 5 mm is preferably used. The metal silicon is preferably high-purity metal silicon having a total impurity content of less than 1 ppb.
[0048]
In the silicon filling step, the green body is preferably once cooled to room temperature after filling the pores with metallic silicon.
[0049]
(Silicon removal process)
The silicon removing step is a step of removing the metallic silicon from the pores by immersing a green body having pores filled with metallic silicon in an alkaline aqueous solution or an aqueous acid solution and then heating the green body. By heating the green body in which the pores are filled with metallic silicon, the metallic silicon is melted or evaporated to be removed from the pores.
[0050]
In the silicon removal step, the green body is immersed in an alkaline aqueous solution or an acid aqueous solution, and then heated, and heated at 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 doing so, it is preferable to remove the metal silicon in the green body.
[0051]
In the silicon removal step, examples of the aqueous alkali solution include an aqueous alkali hydroxide solution. Examples of the acid aqueous solution include hydrofluoric acid aqueous solution, nitric acid aqueous solution, sulfuric acid aqueous solution, hydrochloric acid aqueous solution, hydrogen peroxide water, ozone water, and mixed acid aqueous solutions thereof. Examples of the mixed acid aqueous solution include a hydrofluoric acid aqueous solution, a mixed acid aqueous solution of hydrofluoric acid and sulfuric acid, and a mixed acid aqueous solution of hydrofluoric acid and hydrochloric acid.
[0052]
In the silicon removing step, the green body is heated to 1450 to 1700 ° C., preferably 1550 to 1650 ° C., to remove metallic silicon in the green body. When the melting temperature is less than 1450 ° C., Since the viscosity of the metal silicon increases, it may be difficult to remove from the green body, and when the temperature exceeds 1700 ° C., evaporation may become remarkable and the furnace body and the like may be damaged.
[0053]
(Silicon refilling process)
The silicon refilling step is a step of immersing the green body from which the metal silicon has been removed from the pores in molten metal silicon in a vacuum atmosphere or an inert gas atmosphere, and infiltrating the metal silicon into the pores in the green body to fill the pores. It is preferable to carry out in the same manner as the silicon filling step.
[0054]
(Other)
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 electrical conductivity. As a method for introducing nitrogen, at least one nitrogen-containing compound (hereinafter sometimes referred to as “nitrogen source”) is added in the silicon carbide powder manufacturing step or the silicon carbide mixed powder manufacturing step. Can be introduced.
[0055]
The nitrogen source is preferably a substance that generates nitrogen by heating, such as a polymer compound (specifically, polyimide resin, nylon resin, etc.), organic amine (specifically, hexamethylenetetramine, ammonia, And various amines such as triethylamine and the like, and compounds and salts thereof. Among these, hexamethylenetetramine is preferable. A phenol resin synthesized using hexamine as a catalyst and containing 2.0 mmol or more of nitrogen derived from the synthesis step with respect to 1 g of the resin can also be suitably used as a nitrogen source. These nitrogen sources may be used alone or in combination of two or more.
[0056]
When the nitrogen source is introduced in the silicon carbide powder production process, it is preferable to add the nitrogen source simultaneously with the silicon source and the carbon source. The amount of the nitrogen source added is preferably 80 μg to 1000 μg with respect to 1 g of the silicon source because it is preferable to contain 1 mmol or more of nitrogen per 1 g of the silicon source.
[0057]
In the case where the nitrogen source is introduced in the silicon carbide mixed powder production step, a method of simultaneously adding and dissolving the nitrogen source in the solvent when dissolving and dispersing the silicon carbide powder in the solvent is preferable. . Further, the nitrogen source is preferably added in an amount of 0.7 mmol or more per 1 g of silicon carbide powder, and is preferably 200 μg to 2000 μg, more preferably 1500 μg to 2000 μg, per 1 g of silicon carbide powder.
[0058]
In the method for producing a silicon carbide sintered body of the present invention, there is no particular limitation on the production apparatus and the like as long as the heating conditions can be satisfied, and a known heating furnace or reaction apparatus can be used.
[0059]
The silicon carbide sintered body produced as described above is usually processed into a predetermined shape and subjected to treatments such as polishing and cleaning. As this processing method, since the silicon carbide sintered body has good conductivity, electric discharge machining or the like is preferably used.
[0060]
In the method for producing a silicon carbide sintered body of the present invention, the silicon carbide is sintered by once filling the pores in the green body with metallic silicon, removing the filled metallic silicon, and filling with metallic silicon again. For example, a silicon carbide sintered body having a total content of impurity elements of preferably 10 ppm or less, more preferably 5 ppm or less, and more preferably 1.5 ppm or less can be obtained. Is also possible. It is considered that the impurity is transferred into the metal silicon filled in the green body, and by removing this, the impurity is removed together, so that it can be highly purified.
[0061]
As for the total content of the impurity elements, the impurity content by chemical analysis has only a meaning as a reference value. Practically, the evaluation differs depending on whether the impurities are uniformly distributed or locally distributed, but in the present invention, values measured by the solution ICP-MS method are used.
[0062]
The impurity element is an element that belongs to group 1 to group 16 in the periodic table of the 1989 IUPAC Inorganic Chemical Nomenclature Revision and has an atomic number of 3 or more, excluding atomic numbers 6 to 8 and 14. Say.
[0063]
In the method for producing a silicon carbide sintered body of the present invention, the silicon carbide is sintered by once filling the pores in the green body with metallic silicon, removing the filled metallic silicon, and filling with metallic silicon again. For example, it is possible to produce a silicon carbide sintered body having a bending strength of preferably 350 to 380 MPa.
[0064]
When other suitable physical properties of the silicon carbide sintered body produced by the method for producing a silicon carbide sintered body of the present invention are examined, for example, Young's modulus is 3.5 × 10. ^Four ~ 4.5 × 10 ^Four Vickers hardness is 204 MPa (2000 kgf / mm ² ), Poisson's ratio is 0.14 to 0.21, and thermal expansion coefficient is 3.8 × 10 ^-6 ~ 4.2 × 10 ^-6 (℃ ^-1 ), Thermal conductivity is 150 W / m · K or more, specific heat is 0.68 to 0.76 j / g · ° C. (0.15 to 0.18 cal / g · ° C.), and thermal shock resistance is ΔT of 500 to 700 ° C. It is.
[0065]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.
[0066]
(Comparative Example 1)
As silicon carbide powder, high-purity silicon carbide powder having a center particle diameter of 0.8 μm (silicon carbide having an impurity content of 5 ppm or less produced according to the production method described in JP-A-9-48605: 1.5 wt% 850 g of silica (containing silica) was placed in 500 g of water in which 9 g of ammonium polyacrylate was dissolved as a peptizer and dispersed and mixed in a ball mill for 16 hours, and then 30 g of water-soluble polyurethane (“Yukot” manufactured by Sanyo Kasei) as a powder adhesive And 1 g of a silicone antifoaming agent (“KM72A” manufactured by Shin-Etsu Chemical Co., Ltd.), and further dispersed and mixed with a ball mill for 10 minutes to form a slurry-like mixed powder having a viscosity of 0.09 Pa · s (0.9 poise) The body was manufactured.
[0067]
This slurry-like mixed powder was cast into a gypsum mold having a length of 70 mm and a diameter of 10 mm, left for 6 hours, then demolded and dried (50 ° C.) for 12 hours to produce a green body.
[0068]
The obtained green body was melted in a carbon crucible having an inner diameter of 60 mm and a height of 80 mm by raising the temperature to 1550 ° C. under an argon atmosphere (2-5 mm lump high-purity metal silicon (manufactured by Okuyama Corporation: total) The silicon carbide sintered body of Comparative Example 1 was manufactured by immersing it in an impurity amount of 1 ppb or less and holding it for 30 minutes so that the molten metal silicon penetrates and fills the pores in the green body.
[0069]
(Example 1)
The silicon carbide sintered body of Comparative Example 1 (a green body in which pores are filled with metallic silicon) was immersed in an aqueous alkali solution or an aqueous acid solution, and then heated to 1550 ° C. in an argon atmosphere, and the metallic silicon in the pores Was removed.
[0070]
The green body obtained by removing metallic silicon from the pores was melted in a carbon crucible having an inner diameter of 60 mm and a height of 80 mm in an argon atmosphere by raising the temperature to 1550 ° C. (Okuyama Co., Ltd .: total impurity amount of 1 ppb or less) immersed in and held for 30 minutes to infiltrate and fill the pores in the green body with the silicon carbide sintered body of Example 1 Manufactured.
[0071]
<Evaluation>
For the obtained silicon carbide sintered bodies of Example 1 and Comparative Example 1, the following evaluation, three-point bending test, and purity measurement were performed, respectively. The results are shown in Table 1.
[0072]
(3-point bending test)
A three-point bending test of the silicon carbide sintered body was performed according to JIS R1601.
[0073]
(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]

[0075]
From Table 1, it can be seen that when the method for producing a silicon carbide sintered body of the present invention is performed, the purity and strength of the silicon carbide sintered body are improved.
[0076]
【The invention's effect】
As described above, according to the present invention, a method for producing a silicon carbide sintered body with high purity and high strength can be provided.

Claims (6)

A step of producing a slurry-like silicon carbide mixed powder by dissolving and dispersing silicon carbide powder in a solvent;
Pouring the slurry-like silicon carbide mixed powder into a mold and drying to produce a green body;
Immersing the green body in molten metal silicon under a vacuum atmosphere or an inert gas atmosphere, and infiltrating the metal silicon into pores in the green body, and filling,
A step of removing the metallic silicon from the pores by 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;
Dipping the green body from which the metal silicon has been removed from the pores into molten metal silicon in a vacuum atmosphere or an inert gas atmosphere, and infiltrating the metal silicon into the pores in the green body and filling the pores. A method for producing a silicon carbide sintered body. The silicon carbide powder is obtained by a production method having a step of dissolving a silicon compound and an organic compound that generates carbon by heating in a solvent and drying, and firing the obtained powder in a non-oxidizing atmosphere. The method for producing a silicon carbide sintered body according to claim 1, wherein 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, and a green body from which the metal silicon has been removed from the pores. In the step of immersing in molten metal silicon in a vacuum atmosphere or inert gas atmosphere and infiltrating the metal silicon into the pores in the green body, the green body is heated and melted at 1450 to 1700 ° C. 3. The method for producing a silicon carbide sintered body according to claim 1 or 2, wherein the silicon carbide sintered body is immersed in the metal silicon. 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, and a green body from which the metal silicon has been removed from the pores. In the step of immersing in molten metal silicon in a vacuum atmosphere or inert gas atmosphere and infiltrating the metal silicon into the pores in the green body, the metal silicon has a high total impurity content of less than 1 ppb. It is a purity metal silicon, The manufacturing method of the silicon carbide sintered compact in any one of Claims 1-3 characterized by the above-mentioned. The green body in which the pores are filled with metal silicon is immersed in an alkaline aqueous solution or an acid aqueous solution and then heated to remove the metal silicon from the pores, and the green body is heated at 1450 to 1700 ° C. The manufacturing method of the silicon carbide sintered compact in any one of Claims 1-4 characterized by the above-mentioned. In the step of removing the metal silicon from the pores by immersing the green body in which the pores are filled with metal silicon in an alkaline aqueous solution or an acid aqueous solution and then heating the green body, the green body is subjected to a vacuum atmosphere or an inert gas atmosphere. It heats under, The manufacturing method of the silicon carbide sintered compact in any one of Claims 1-5 characterized by the above-mentioned.