JP2001019548A - Silicon carbide sintered compact and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silicon carbide sintered compact having no remaining silicon, excellent heat resistance and uniformity and high purity, capable of forming a porous body-like constitution and to provide a method for simply producing the sintered compact. SOLUTION: This silicon carbide sintered compact is obtained by a reaction sintering method having a process for dissolving or dispersing silicon carbide powder into a solvent to produce a slurry, pouring the slurry into a mold, drying a molded material and calcining the dried material in a vacuum atmosphere or in an inert gas atmosphere to produce a molding product and a process for immersing the molding product in a mixture composed of a liquid silicon source containing at least one or more of silicon compounds and a liquid organic substance composed of at least one or more carbon sources and sintering the immersed molding product at 1,600-2, 000 deg.C so that silicon in the liquid silicon source sucked up in pores in the molding product by capillarity is reacted with carbon generated from the carbon source in the molding product to form silicon carbide in the pores of the molding product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous material having fine voids, which is useful as a component for semiconductor manufacturing equipment, a component for electronic information equipment, a structural component such as a vacuum device, a membrane filter, and the like. The present invention relates to a high-purity and high-purity silicon carbide sintered body and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, silicon carbide has been attracting attention as a material used in a high temperature range because of its good strength, heat resistance, thermal shock resistance, and abrasion resistance even at high temperatures exceeding 1000 ° C. It is used as a substitute for quartz as a jig for manufacturing semiconductors. One of the methods for producing the above-mentioned sintered body made of silicon carbide is a reaction sintering method. In this reaction sintering method, first, a silicon carbide powder and a carbon powder are dissolved and dispersed in a solvent to produce a slurry-like mixed powder. Next, the obtained mixed powder is poured into a casting mold, an extrusion mold, a press mold, or the like and dried to obtain a green body. Next, the obtained green body is heated under a vacuum atmosphere or an inert gas atmosphere, immersed in molten metal silicon, and free carbon in the green body and silicon absorbed into the green body due to capillary action. To obtain a silicon carbide sintered body.

[0003] Such a silicon carbide sintered body is required to have high purity in order to be used for a jig for semiconductor production and the like.
It is difficult to achieve this. For example, a method of forming a SiO ₂ oxide film on the surface of a sintered body using an oxide film method, confining an impurity element in the film, dissolving and removing the oxide film with hydrofluoric acid or the like to achieve high purity, A method has been proposed in which, prior to impregnation, calcination is performed at about 2,000 ° C. under vacuum to remove impurities to achieve high purity.
The former requires a dedicated oxidizing furnace and processing equipment for handling the acid, and the latter requires one step. There is also a method of coating the surface of the sintered body by CVD, but in any case, the number of steps is increased and the cost is increased. Focusing on the purity, there remains a possibility that carbon such as carbon black used contains many impurity elements in its production or its properties such as adsorptivity.

[0004] In addition, unreacted metallic silicon may remain in the silicon carbide sintered body depending on the balance between carbon and silicon. However, there is a problem that the use is limited to the melting point (1420 ° C.) or less of the remaining metallic silicon. This unreacted silicon is prevented from remaining and S
When producing a slurry in which a predetermined amount of carbon powder is added to and mixed with silicon carbide powder in order to control the i / C ratio,
It is difficult to prepare a uniform slurry because the specific gravity and the particle size of the two powders are significantly different, and a method of increasing the amount of the dispersion medium or the amount of the surfactant has been adopted. However, the removal of the dispersion medium becomes complicated, and the latter has a concern that impurities resulting from the surfactant may increase, and any of these methods is not preferable. The silicon carbide sintered body used to be used for a jig requiring heat resistance is not necessarily a high-density product, for example, a porous body having fine through holes, such as used for a membrane filter. There is a demand for a porous body which is particularly excellent in heat resistance and suitable for a filter treatment for preventing contamination of impurities.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a silicon carbide sintered body which has no residual silicon, is excellent in heat resistance and uniformity, has high purity, and can be constituted as a porous body. An object of the present invention is to provide a body and a simple manufacturing method thereof.

[0006]

Means for Solving the Problems As a result of diligent studies, the present inventors impregnated a compact of silicon carbide powder with a mixture of a liquid carbon generating substance and a liquid silicon generating substance, The present inventors have found that a silicon carbide sintered body meeting this purpose can be obtained, and completed the present invention. That is, the silicon carbide sintered body of the present invention comprises: <1> dissolving and dispersing silicon carbide powder in a solvent to produce a slurry, then pouring the slurry into a mold, drying, and drying in a vacuum atmosphere or an inert gas. A step of calcining in an atmosphere to produce a molded body, and forming the molded body into a liquid silicon source containing at least one or more silicon compounds, and a liquid organic substance comprising at least one or more carbon sources. After immersion in a mixture of
By sintering in the temperature range of ℃, the silicon in the liquid silicon source sucked up into the pores in the molded article by the capillary phenomenon reacts with the carbon generated from the organic substance consisting of the carbon source in the molded article. And forming silicon carbide in the pores of the compact by the reaction sintering method. <2> The silicon carbide powder has an average particle diameter in a range of 0.01 to 10 μm.

According to a third aspect of the present invention, there is provided a method for producing a silicon carbide sintered body, comprising the steps of: (3) dissolving and dispersing silicon carbide powder in a solvent to produce a slurry; Pouring into a mold, drying, and calcining under a vacuum atmosphere or an inert gas atmosphere to produce a molded body; and forming the molded body into a liquid silicon source containing at least one or more silicon compounds; After immersion in a mixture with an organic substance comprising at least one carbon source,
By sintering in the temperature range of ℃, the silicon generated in the liquid silicon material in the liquid silicon source and the carbon source generated from the liquid organic substance consisting of the carbon source sucked up into the pores in the formed body by the capillary phenomenon, in the formed body Reacting to form silicon carbide in the pores of the molded body.

[0008] The silicon carbide sintered body obtained by such a production method is manufactured by a reaction sintering method while producing silicon carbide.
Can be converted to SiC by reaction, so that there is no unreacted silicon remaining in the sintered body, excellent heat resistance, and a high-purity silicon carbide sintered body. By adjusting the mixing ratio and the supply amount of the silicon source and the carbon source in this way, it is also possible to obtain a porous body having controlled voids. In a preferred embodiment, <4> the mixture of the liquid silicon source and the organic substance comprising the carbon source is S
i / C ratio is adjusted to be in the range of 2.0 to 2.5, and <5> the liquid silicon source is a polymer of tetraalkoxysilane, and an organic substance comprising a carbon source Is a phenolic resin. Also, <6
> Step of forming the slurry, or, in the step of producing the green body by adding a substance serving as a nitrogen source, the volume resistivity is not more than 10 ⁰ Ω · cm,
A silicon carbide sintered body that can be subjected to electrical discharge machining can also be used.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The silicon carbide sintered body of the present invention is characterized in that a molded body obtained by casting with silicon carbide powder is impregnated with a mixture of a liquid carbon source and a silicon source and sintered.

[0009] The silicon carbide sintered body of the present invention is obtained by a reaction sintering method. The preferred reactive sintering method will be described in detail below. Generally, the reactive sintering method is a step of producing a silicon carbide powder, a step of producing a slurry containing the silicon carbide powder, and producing a green body from the slurry. And a step of producing a silicon carbide sintered body from the green body.
In the present invention, the green body refers to a silicon carbide molded body before reaction sintering having many pores and obtained by removing a solvent from a slurry-like mixed powder.

The step of producing the silicon carbide powder comprises the steps of: a silicon source containing at least one or more silicon compounds; a carbon source containing at least one or more organic compounds that generate carbon by heating; a polymerization or crosslinking catalyst; Is dissolved in a solvent, dried, and then the obtained powder is fired in a non-oxidizing atmosphere.

The step of producing a slurry from the silicon carbide powder is a step of dispersing the silicon carbide powder in a solvent. By sufficiently stirring and mixing in dissolving and dispersing in the solvent, the pores can be uniformly dispersed in the green body in the step of manufacturing the green body from the slurry.

The step of producing a green body from the slurry is a so-called cast molding step in which the slurry is poured into a mold. Here, in order to improve the shape retention during the subsequent immersion, the green body is calcined in a vacuum atmosphere or an inert gas atmosphere to obtain a silicon carbide molded body.

[0013] In the step of producing a silicon carbide sintered body from the molded body, the molded body is immersed in a mixture of a liquid silicon source and a liquid carbon source, and is immersed in a vacuum atmosphere or an inert gas atmosphere.
Heating to 1600 to 2000 ° C., sintering, and reacting silicon and carbon generated from a carbon source and a silicon source that has permeated into pores in the molded article by capillary action to generate silicon carbide in pores of the molded article. It is a process. By this process,
The molded body is subjected to reaction sintering to obtain a silicon carbide sintered body.

The step of producing the silicon carbide powder will be described in more detail. In the reaction sintering method, silicon carbide powder used as a raw material of the silicon carbide sintered body is α-type,
Examples thereof include β-type, amorphous, and mixtures thereof. In order to obtain a high-purity silicon carbide sintered body, it is preferable to use a high-purity silicon carbide powder as a raw material silicon carbide powder.

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.
About 10 μm, more preferably 0.05 to 5 μm
It is. If the particle size is less than 0.01 μm, handling in processing steps such as measurement and mixing tends to be difficult, and
If it exceeds 0 μm, the specific surface area is small, that is, the contact area with the adjacent powder is small, and it is difficult to increase the density, which is not preferable.

The high-purity silicon carbide powder includes, for example, a silicon source containing at least one or more silicon compounds, a carbon source containing at least one or more organic compounds that generate carbon by heating, a polymerization or crosslinking catalyst, Is dissolved in a solvent and dried, and then the obtained powder is calcined in a non-oxidizing atmosphere.

A silicon source containing the silicon compound (hereinafter, referred to as a silicon source)
As the silicon source), a liquid source and a solid source can be used in combination, but at least one type must be selected from liquid sources. As the liquid, a polymer of alkoxysilane (mono-, di-, tri-, tetra-) and tetraalkoxysilane is used. Among alkoxysilanes, tetraalkoxysilane is suitably used, and specific examples thereof include methoxysilane, ethoxysilane, propoxysilane, butoxysilane and the like, and ethoxysilane is preferred from the viewpoint of handling. Examples of the tetraalkoxysilane polymer include a low molecular weight polymer (oligomer) having a degree of polymerization of about 2 to 15 and a liquid silicate polymer having a higher degree of polymerization. Examples of solid materials that can be used in combination with these include silicon oxide. In the above reaction sintering method, silicon oxide includes, in addition to SiO, silica sol (colloidal ultrafine silica-containing liquid, containing OH groups and alkoxyl groups inside), silicon dioxide (silica gel, fine silica, quartz powder) and the like. . These silicon sources may be used alone or in combination of two or more.

Among these silicon sources, from the viewpoint of good homogeneity and handling properties, tetraethoxysilane oligomers and mixtures of tetraethoxysilane oligomers with finely divided silica are preferred. In addition, a high-purity substance is used for these silicon sources, and the initial impurity content is preferably 20 ppm or less, more preferably 5 ppm or less.

As the carbon source containing an organic compound which generates carbon by heating (hereinafter, appropriately referred to as a carbon source), in addition to a liquid source, a liquid source and a solid source can be used in combination. Organic compounds that have a high carbon content and polymerize or crosslink by catalyst or heating, specifically, for example, monomers and prepolymers of resins such as phenolic resins, furan resins, polyimides, polyurethanes, and polyvinyl alcohol are preferable, and cellulose, Examples thereof include liquid substances such as sucrose, pitch, and tar, and a resol-type phenol resin is particularly preferable. 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. Particularly, when high-purity silicon carbide powder is required, 5 ppm of each metal is used.
It is desirable to use an organic compound that does not contain the above.

The polymerization and crosslinking catalyst used in the production of high-purity silicon carbide powder can be appropriately selected according to the carbon source. When the carbon source is a phenol resin or a furan resin, toluene sulfonic acid, toluene carboxylic acid, acetic acid Oxalic acid, sulfuric acid and the like. Among these, toluenesulfonic acid is preferably used.

The ratio of carbon to silicon (hereinafter abbreviated as C / Si ratio) in the step of producing high-purity silicon carbide powder, which is a raw material powder used in the above-mentioned reaction sintering method, is as follows. It is defined by performing elemental analysis on a carbide intermediate obtained by carbonization. Stoichiometrically, C /
When the Si ratio is 3.0, the free carbon in the generated silicon carbide is 0
%, But actually, the SiO
Free gas is generated at a low C / Si ratio due to gas volatilization. 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, 16
In the case of sintering at 00 ° C. or more, the C / Si ratio is 2.0 to 2.5
When it is set, 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, C to obtain pure silicon carbide is used.
Since the / Si ratio fluctuates, in this case, the C /
It is not limited to the range of the Si ratio.

In the reaction sintering method, a silicon source and a carbon source containing an organic compound which generates carbon by heating are dissolved in a solvent and dried to obtain a powder. The mixture with the carbon source is cured to form a powder, if necessary. As a curing method,
Examples thereof include a method of crosslinking by heating, a method of curing with a curing catalyst, and a method of electron beam or radiation. The curing catalyst can be appropriately selected according to the carbon source, but in the case of a phenol resin or a furan resin, toluene sulfonic acid,
Acids such as toluenecarboxylic acid, acetic acid, oxalic acid, hydrochloric acid, sulfuric acid, and maleic acid, and 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 and the like), ethyl ether, acetone and the like.

A silicon source and a carbon source containing an organic compound that generates carbon by heating are dissolved in a solvent, and the dried powder is heated and carbonized. This is performed at 800 ° C. to 1000 ° C. for 30 minutes to 12 minutes in a non-oxidizing atmosphere such as nitrogen or argon.
This is done by heating the powder for 0 minutes.

Further, the carbide is heated at 1350 ° C. to 2000 ° C. in a non-oxidizing atmosphere such as argon to form 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 desirable for more efficient production.

When a silicon carbide powder of higher purity is required, impurities can be further removed by performing a heat treatment at 2000 to 2100 ° C. for 5 to 20 minutes during the above-mentioned firing.

[0027] In particular, as a method of obtaining a high-purity silicon carbide powder, Japanese Patent Application Laid-Open No.
No. 8605, 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 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; ℃ to less than 2000 ℃,
While maintaining the temperature, at least one treatment of heating at a temperature of 2000 to 2100 ° C. for 5 to 20 minutes is performed.
And a method for producing a high-purity silicon carbide powder, wherein a silicon carbide powder having a content of each impurity element of 0.5 ppm or less is obtained by performing the above two steps. Can be used. Since the silicon carbide powder thus obtained is not uniform in size, it is processed by pulverization and classification so as to conform to the particle size.

Nitrogen can be introduced to impart conductivity to the obtained sintered body. When nitrogen is introduced in the step of producing silicon carbide powder, first, a silicon source, a carbon source, The organic substance consisting of a nitrogen source and the polymerization or crosslinking catalyst are mixed homogeneously, but as described above, a carbon source such as a phenol resin, an organic substance consisting of a nitrogen source such as hexamethylenetetramine, and toluenesulfonic acid. When the polymerization or cross-linking catalyst is dissolved in a solvent such as ethanol, it is preferable that the catalyst is sufficiently mixed with a silicon source such as an oligomer of tetraethoxysilane.

Next, the step of producing a slurry from silicon carbide powder will be described in more detail. The step of producing a slurry from silicon carbide powder involves dispersing the silicon carbide powder in a solvent to produce a slurry.When the slurry is dispersed in the solvent, it is uniformly mixed in the green body by sufficiently stirring and mixing. The pores can be dispersed in the pores.

In the step of producing a slurry from the silicon carbide powder, an organic binder may be added. Examples of the organic binder include a deflocculant, a powder adhesive, and the like.
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 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.

When imparting conductivity, when introducing nitrogen in this slurry production step, first, silicon carbide powder and an organic substance comprising a nitrogen source are mixed homogeneously, but a nitrogen source such as hexamethylenetetramine is mixed. Is dissolved and dispersed in a solvent such as water or ethyl alcohol, and then sufficiently stirred and mixed with the silicon carbide powder.

In this reaction sintering method, the stirring and mixing in each step can be performed by a known stirring and mixing means, for example, a mixer, a planetary ball mill or the like. Stir mixing
It is preferably performed for 10 to 30 hours, particularly for 16 to 24 hours.

The step of producing a green body from the slurry-like mixed powder will be described in more detail. In order to cast the slurry-like mixed powder into a mold, generally, casting is suitably used. The slurry-like mixed powder is poured into a molding die at the time of casting, left to stand, and then demolded.
A green body having a specified size can be obtained by removing the solvent by heating or air drying under a temperature condition of 0 to 60 ° C.

Here, before being immersed in the mixture of the liquid silicon source and the liquid carbon source, the green body is once calcined to produce a molded body. This calcining burns free carbon remaining in the green body. It is necessary to perform the reaction in a vacuum atmosphere or an inert gas atmosphere in order to give the reaction sintering in the next step without causing the reaction sintering. When this calcination is performed, a molded body is formed, and the shape retention and stability when the liquid silicon source and the carbon source mixture are introduced are increased. It is preferable from the viewpoint of improvement.

Next, the step of producing a silicon carbide sintered body from a compact will be described in more detail. The molded body manufactured through the above steps is immersed in a mixture of a liquid silicon source and a carbon source, and is immersed in a vacuum atmosphere or an inert gas atmosphere.
Sintering is performed by heating to a temperature range of 600 to 2000 ° C. By immersing the molded body in a mixture of a liquid silicon source and a liquid carbon source, the liquid mixture penetrates into pores in the molded body by capillary action, and silicon and carbon generated by heating react. By this reaction, silicon carbide is generated in the pores of the molded body, filling the pores, making the pores in the porous body smaller, increasing the bulk density, and improving the overall strength. The reaction between silicon and carbon was carried out in the range of 120,000 to 2000 as described in the step of producing silicon carbide powder.
Since sintering occurs at about ℃, sintering is performed in a temperature range of 1600 to 2000 ° C, and preferably in a range of 1600 to 1900 ° C. If the sintering temperature is lower than 1600 ° C., the reaction is not sufficiently performed, and if the sintering temperature is higher than 2,000 ° C., grain growth occurs, and on the contrary, the porosity increases. When the molded article is immersed in a mixture of a liquid silicon source and a carbon source, it is not necessary to immerse the entire molded article in the liquid mixture. The liquid mixture sequentially penetrates into the voids in the molded body. The time for immersing the molded article in the mixture is not particularly limited, and may be appropriately determined depending on the size and shape of the molded article, the state of the pores, and the like.

The liquid silicon source used here is a liquid silicon source used in the production of silicon carbide powder, that is, a mixture of alkoxysilane (mono-, di-, tri-, tetra-) and tetraalkoxysilane. Coalescing is used. Among the alkoxysilanes, tetraalkoxysilanes are suitably used, specifically, methoxysilane, ethoxysilane, propoxysilane, butoxysilane, and the like. As the polymer of tetraalkoxysilane, the degree of polymerization is 2 to 15. And low molecular weight polymers (oligomers) and silicic acid polymers having a higher degree of polymerization in liquid form. Among these silicon sources, tetraethoxysilane and its oligomers are preferred from the viewpoint of good homogeneity and handling properties. In addition, these silicon sources are made of high-purity substances and have an initial impurity content of 20 p.
pm or less, more preferably 5 ppm or less.

As the organic substance composed of a liquid carbon source, an organic compound which generates carbon by heating and is called a so-called carbon source is used.
They may be used alone or in combination of two or more.

As the organic compound which generates carbon by heating, those having conductivity are preferable. Specifically, coal tar pitch, pitch tar, phenol resin, furan resin, epoxy resin having a high residual carbon ratio are used. , Monosaccharides such as phenoxy resin and glucose, oligosaccharides such as sucrose,
Various sugars such as polysaccharides such as cellulose and starch are exemplified. These are preferably those that are liquid at room temperature, those that dissolve in a solvent, those that are softened by heating such as thermoplastic or heat-meltable, or those that become liquid, for the purpose of being homogeneously mixed with silicon carbide powder. Among them, a phenol resin having a high strength of silicon carbide which can obtain a large residual carbon ratio, particularly a resol type phenol resin is preferable.

A predetermined amount of a liquid silicon source and a liquid carbon source are weighed and uniformly mixed to prepare a mixture. Mixing may be performed by a known method for mixing liquid substances. Whether or not uniform mixing has been achieved can be confirmed by a viscometer. That is, the viscosity of the slurry is measured over time, and when the viscosity becomes constant, it is determined that the slurry is uniform. This measurement is usually performed at room temperature. If the temperature is higher than 50 ° C., the quality of the binder may be deteriorated, which is not preferable. As in the case of powder production, the mixing ratio of the silicon source / carbon source is such that C / Si is 2.0 to 2.0.
It is preferably in the range of 2.5. The liquid mixture adjusted at such a predetermined mixing ratio is infiltrated into the molded body, heated and baked, whereby the silicon source and the carbon source are thermally decomposed, and the generated silicon and carbon react with each other. Converted to silicon carbide, a sintered body composed of silicon carbide is obtained.

As described above, the generated carbon and silicon react with each other in the pores of the molded body to generate silicon carbide, so that the silicon carbide is filled and integrated into the pores in the molded body. By reducing the voids and increasing the contact between the particles to strengthen the wall surface, a high-purity and high-strength porous silicon carbide sintered body can be obtained. Also, by adjusting the ratio of the silicon source and the carbon source to be supplied, the stoichiometric balance between silicon and carbon is adjusted,
Since there is little residual metallic silicon component in the pores, the heat resistance is excellent, and since there is no residual carbon, the generation of particles is reduced, and a homogeneous and high-purity sintered silicon carbide can be obtained. According to the present method, the porosity of the porous body can be easily adjusted, and the reaction sintered body is filled with SiC. Therefore, during the sintering step, the silicon source and the carbon source other than silicon and carbon are contained. Atoms, for example, oxygen, hydrogen, etc. are released as water vapor and do not remain in the sintered body, but are discharged outside the system, and the impurities contained in the silicon source, the carbon source, and the like accompanying the release are also included. Since it is discharged out of the system, it can be said that this is a preferable reaction sintering method also from the viewpoint of purity.

When a molded body into which nitrogen is introduced by any of the above methods is used, a silicon carbide sintered body having good electric characteristics can be obtained. In order to achieve preferable conductivity, the content of nitrogen in the sintered body is 150 ppm or more, preferably 200 ppm or more. From the viewpoint of stability, it is preferable that nitrogen is contained in a solid solution state. Examples of the organic substance composed of a nitrogen source used when introducing nitrogen to impart conductivity to the silicon carbide sintered body include, for example, a polymer compound (specifically, a polyimide resin, a nylon resin, and the like), Organic amines (specifically, hexamethylenetetramine, ammonia, triethylamine, etc.
And their compounds and salts). Of these, hexamethylenetetramine is preferable. Further, it is a phenol resin synthesized using hexamine as a catalyst, and nitrogen derived from the synthesis step is 1 g of resin.
A phenol resin containing 2.0 mmol or more of the phenol resin can be suitably used as the nitrogen source. These organic substances comprising a nitrogen source may be used alone or in combination of two or more.

The amount of the organic substance comprising the nitrogen source is preferably such that when the silicon source and the carbon source are simultaneously added during the step of producing the silicon carbide powder, nitrogen is contained in an amount of 1 mmol or more per gram of the silicon source. Preferably, 80 μg to 1000 μg per 1 g of silicon source, and at the time of producing a slurry from silicon carbide powder,
When added simultaneously with silicon carbide powder and an organic substance comprising at least one or more carbon sources, 1 g of silicon carbide powder
Since nitrogen preferably contains 0.7 mmol or more, 200 μg to 20 μg per 1 g of silicon carbide powder.
00 μg is preferred, and 1500 μg to 2000 μg is more preferred.

The silicon carbide sintered body of the present invention preferably has a total content of impurity elements of preferably less than 10 ppm, more preferably less than 5 ppm. Although the impurity content of the silicon carbide sintered body of the present invention is preferably less than 10 ppm, 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 unevenly distributed.
Therefore, those skilled in the art generally evaluate the extent to which impurities contaminate the silicon carbide sintered body under predetermined heating conditions by using various practical devices. Here, the impurity element belongs to a group 1 to group 16 element in the periodic table of the revised edition of the 1989 IUPAC inorganic chemical nomenclature,
In addition, it refers to an element having an atomic number of 3 or more and excluding a carbon atom, a nitrogen atom, and a silicon atom.

The apparatus used in the production method of the present invention includes:
In the reaction sintering method, there is no particular limitation as long as the heating conditions can be satisfied, and a known heating furnace or a known reactor can be used.

The silicon carbide sintered body of the present invention is subjected to processing such as processing, polishing, washing and the like according to the purpose of use. The silicon carbide sintered body obtained by the production method of the present invention can be subjected to the use of semiconductor production parts, electronic information equipment parts, and the like by electric discharge machining, and is controlled porous, It can be suitably used as a filter material requiring heat resistance and purity.

[0046]

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. (Example 1) As silicon carbide powder, a central particle diameter of 1.1 µm
m high-purity silicon carbide powder (impurity content 5 pp manufactured according to the manufacturing method described in JP-A-9-48605).
m or less of silicon carbide: containing 1.5% by weight of silica) 10
00 g and polyammonium acrylate 1 as a deflocculant
0 g was dissolved in 400 g of water and dispersed and mixed in a ball mill for 6 hours. Then, 30 g of water-soluble polyurethane ("U-coat" manufactured by Sanyo Chemical Co., Ltd.) was used as a powder adhesive, and a silicone defoaming agent ("Shin-Etsu Chemical Co., Ltd.") KM72A "), and further dispersed and mixed in a ball mill for 10 minutes to produce a slurry having a viscosity of 3 poise.

The slurry was 100 mm long and 50 m wide.
m, cast into a 5 mm thick gypsum mold, air-dried (22 ° C.) for 24 hours, and calcined at 1800 ° C. for 0.2 hours to produce a molded body.

Next, 0.4 kg of liquid tetraethoxysilane (product name: ES40 Colcoat Co., Ltd.) as a silicon source, 0.9 kg of phenol (manufactured by Sumitomo Chemical Co., Ltd.) as an organic substance consisting of a carbon source, and a solvent were used. Immersed in a homogeneous mixture with ethanol as a sample, and allowed to penetrate into the pores of the molded article by capillary action, and then immersed in an
C. and maintained at that temperature for 30 minutes to allow the silicon generated from the silicon source penetrated into the molded article by the capillary action to react with the carbon generated from the carbon source, and to cause the pores of the molded article Example 1 by generating silicon carbide
Was manufactured. (Si / C ratio: 2.
4)

Comparative Example 1 In Example 1, 150 g of carbon black powder was added to silicon carbide powder to prepare a slurry. However, a uniform slurry could not be formed, and 5 g of peptizer and 100 g of water were added. To produce a slurry. Thereafter, a molded body was prepared in the same manner as in Example 1, and the molded body was subjected to an inner diameter of 200 mm and a height of
155 mm in a graphite crucible under an argon atmosphere.
By immersing in a high-purity metallic silicon powder (manufactured by Kojundo Chemical Laboratory) heated to 0 ° C. and molten for 30 minutes, the carbon in the molded body and the molten metal permeated into the molded body due to the capillary phenomenon The silicon carbide was reacted with silicon, and pores in the compact were filled with the generated silicon carbide to produce a silicon carbide sintered body of Comparative Example 1.

<Evaluation> The obtained silicon carbide sintered bodies of Example 1 and Comparative Example 1 were subjected to the following evaluation, measurement of density and porosity by Archimedes method, and heat resistance test, respectively. Further, the amount of impurities was measured. Table 1 shows the results.

(Method for Measuring Density and Porosity by Archimedes Method)
Performed according to SR1634.

(Heat resistance test) 150 under argon atmosphere
After heating to 0 ° C., the weight change before and after the heat treatment was observed.

(Measurement of Impurities) After the surface of the sample was washed with a mixed acid of hydrofluoric acid / nitric acid / sulfuric acid = 5/2/3, the sample was decomposed with the same mixed acid. This decomposition was performed twice, and the third decomposition liquid was used as a sample, and each element was analyzed by ICP-MS.

[0054]

[Table 1]

As shown in Table 1, the silicon carbide sintered body of Example 1 had a low impurity content, a high density and good heat resistance. In the silicon carbide sintered body of Comparative Example 1, formation of a thin metallic silicon deposition film on the surface was observed.

[0056]

As described above, the silicon carbide sintered body of the present invention has no residual silicon, is excellent in heat resistance and uniformity, has high purity, and can be configured as a porous body. It had excellent characteristics. Further, according to the production method of the present invention, a silicon carbide sintered body having the above excellent characteristics can be easily produced.

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Claims (6)

[Claims] Claims 1. A silicon carbide powder is dissolved and dispersed in a solvent to produce a slurry, which is then poured into a mold.
Drying and calcining in a vacuum atmosphere or an inert gas atmosphere to produce a molded body; and forming the molded body into a liquid silicon source containing at least one or more silicon compounds; After immersion in a mixture with a liquid organic substance comprising a carbon source,
By sintering in the temperature range of 2000 ° C., the silicon in the liquid silicon source sucked into the pores of the molded body by the capillary phenomenon reacts with the carbon generated from the organic substance comprising the carbon source in the molded body. A step of producing silicon carbide in pores of a molded body at least, and a sintered silicon carbide obtained by a reaction sintering method comprising: 2. The silicon carbide powder having an average particle size of 0.0
2. The silicon carbide sintered body according to claim 1, wherein the silicon carbide sintered body is in a range of 1 to 10 [mu] m. 3. A step of producing a slurry by dissolving and dispersing silicon carbide powder in a solvent, pouring the slurry into a mold, drying, and calcining under a vacuum atmosphere or an inert gas atmosphere to form a slurry. A step of producing a body; and immersing the molded body in a mixture of a liquid silicon source containing at least one or more silicon compounds and an organic substance comprising at least one or more carbon sources.
By sintering in a temperature range of 0 ° C., the silicon generated in the liquid silicon source and the carbon generated from the liquid organic substance consisting of the carbon source sucked up into the pores in the molded body by the capillary phenomenon are converted into the molded body. Reacting in step (a) to generate silicon carbide in the pores of the molded body; and a method for producing a silicon carbide sintered body. 4. The mixture of the liquid silicon source and the organic substance comprising a carbon source is adjusted so that the Si / C ratio is in the range of 2.0 to 2.5. 3. The method for producing a silicon carbide sintered body according to item 3. 5. The production of a silicon carbide sintered body according to claim 3, wherein the liquid silicon source is a polymer of tetraalkoxysilane, and the organic substance comprising the carbon source is a phenol resin. Method. 6. The method for producing a silicon carbide sintered body according to claim 3, wherein in the step of forming the slurry or the step of producing the molded body, a substance serving as a nitrogen source is added. .