JP2002154818A - beta-CRISTOBALITE, MANUFACTURING METHOD THEREFOR AND NON- OXIDE BASED CERAMIC MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce β-cristobalite and to provide its manufacturing method, by which stable β-critbalite is easily obtained without phase transfer, and to obtain a non-oxide based ceramic material whose oxidative degradation is suppressed and having excellent durability. SOLUTION: The β-cristobalite is obtained by mixing an alkoxide of silicon, silicon carbite or silicon nitride with a solution prepared by dissolving an aluminum halide and a calcium halide in a solvent, filtering solid substance not dissolved in the solvent and firing the same. The non-oxide based ceramic material is obtained by forming a coating layer based on a precursor of the β-cristobalite on the surface of a non-sintered compact (powder) or a sintered compact (molding) of the non-oxide based ceramic. By sintering it at 800-1,800 deg.C, the precursor of the β-cristobalite is converted to the β-cristobalite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a .beta.-cristobalite used as a material for a high-temperature turbine, a furnace material of a refuse incinerator, a reactor material of a nuclear reactor, a method for producing the same, and a non-oxide ceramic material. It is about.

[0002]

2. Description of the Related Art In general, cristobalite is synthesized by heating quartz, silicic acid or the like, and there are α-cristobalite and β-cristobalite. Conventionally, the following production method has been adopted to obtain β-cristobalite which has a small coefficient of thermal expansion and is used as a heat-resistant material. That is, first, a calcium component and an aluminum component are added to silicic acid, heated to 1750 ° C. or higher, and then cooled to produce glass as a sintered body. Subsequently, by firing the glass at 1400 ° C. for 3 hours, β-cristobalite can be generated in the glass (US Pat. No. 3,445,252).

On the other hand, silicon carbide (SiC) and silicon nitride (S
Since i ₃ N ₄ ) has excellent properties such as high-temperature strength, creep resistance and impact resistance, it has been attempted to use i ₃ N ₄ ) under high temperature or severe corrosive conditions where metallic materials cannot be used.

[0004]

However, according to the method disclosed in U.S. Pat. No. 3,445,252, it is necessary to generate glass as a sintered body of .beta.-cristobalite and then fire the glass. However, there is a problem that manufacturing efficiency is poor.

Although silicon carbide and silicon nitride form an oxide protective film of silicon oxide in a high-temperature oxygen atmosphere, a silicon oxide protective film formed in a high-temperature state particularly when a high-temperature state and a low-temperature state repeatedly act. Cracks occur due to volume expansion and volume shrinkage accompanying the phase transition, and oxygen infiltrates from these cracks. Therefore, oxidation of silicon carbide and silicon nitride inside the protective film layer progresses, and there is a problem that deterioration is large and durability is lacking. When cristobalite is used, the phase transition occurs at about 237 ° C., and the phase transition between the low-temperature type and the high-temperature type is repeated, and abrupt contraction or expansion occurs each time.

The present invention has been made by focusing on the problems existing in the prior art as described above. An object of the present invention is to provide a β-cristobalite capable of easily obtaining a stable β-cristobalite without a phase transition and a method for producing the same. Another object of the present invention is to provide a non-oxide ceramic material which is less deteriorated by oxidation even when a high-temperature state and a low-temperature state are repeatedly used and has excellent durability by using β-cristobalite having no phase transition. .

[0007]

In order to achieve the above-mentioned object, the β-cristobalite having no phase transition according to the first aspect of the present invention comprises an amorphous silicon oxide, silicic acid, calcium silicate, and an alkoxide compound of silicon. At least one selected from silicon carbide and silicon nitride is mixed with a solution in which aluminum halide and calcium halide are dissolved in a solvent, and the mixture is calcined to obtain a solid that does not dissolve in the solution.

According to the second aspect of the present invention, there is provided a phase transition-free β-
The method for producing cristobalite includes mixing at least one selected from amorphous silicon oxide, silicic acid, calcium silicate, an alkoxide compound of silicon, silicon carbide and silicon nitride into a solution in which aluminum halide and calcium halide are dissolved in a solvent. After that, the solid content not dissolved in the solution is fired at a temperature of 800 to 1800 ° C. for 1 to 10 hours.

A non-oxide ceramic material according to the third aspect of the present invention is a non-oxide ceramic material made of silicon carbide or silicon nitride. A coating layer based on a precursor of β-cristobalite is formed on a surface of a non-sintered or sintered body of non-oxide ceramics by coating a solution in which calcium is dissolved in a solvent and drying by heating. .

A non-oxide ceramic material according to a fourth aspect of the present invention is the non-oxide ceramic material according to the third aspect, wherein the solution further comprises amorphous silicon oxide, silicic acid, calcium silicate and an alkoxide compound of silicon. At least one is included.

According to a fifth aspect of the present invention, there is provided the non-oxide ceramic material according to the third or fourth aspect, wherein the non-oxide ceramic material has a temperature of 800 to 1800 ° C.
It is obtained by baking for 10 hours to convert a precursor of β-cristobalite into β-cristobalite having no phase transition.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. First, β-cristobalite having no phase transition and a method for producing the same will be described. This β-cristobalite comprises at least one selected from amorphous silicon oxide (SiO ₂ ), silicic acid (H ₂ SiOx), calcium silicate, an alkoxide compound of silicon, silicon carbide and silicon nitride, and aluminum halide and calcium halide. Is mixed with a solution dissolved in a solvent, and the solid content not dissolved in the solution is calcined. Β-cristobalite of the present invention is aluminum,
Unlike the general β-cristobalite and α-cristobalite due to the solid solution of calcium, there is no phase transition even when heated to 237 ° C.
Even when the temperature reaches 0 ° C. or higher, the original shape is maintained. On the other hand, even if it is gradually cooled from a high temperature, no phase transition occurs, and it is stable.

Among the raw materials for obtaining β-cristobalite, silica gel or the like is used as amorphous silicon oxide. Silicic acid is a substance also called orthosilicic acid. As calcium silicate, zonotlite, tobermorite,
Low crystalline calcium silicate hydrate (CSH gel)
Is used to obtain cristobalite maintaining the outer shape of the raw material. Calcium and aluminum sources include nitrates, but halides have the highest accelerating effect.
Among them, chloride is preferred. A typical example of the silicon alkoxide compound is tetraethoxysilane (ethyl silicate). Silicon carbide and silicon nitride are both compounds that are extremely hard and have extremely high decomposition temperatures, and are suitable as high-temperature structural materials.

The aluminum halide to be reacted with these raw materials is aluminum chloride (AlC).
l ₃ ), and the like, and examples of the calcium halide include calcium chloride (CaCl ₂ ). Aluminum halide and calcium halide are used as a mixture, and can promote the formation reaction of β-cristobalite. In that case, 0.5 to 4 mol of aluminum halide is preferable per 1 mol of calcium halide, and 1.5 to 2.5 mol is more preferable. When the use ratio is less than 0.5 mol or more than 4 mol,
The synergistic effect obtained by using calcium halide and aluminum halide together is poor.

The aluminum halide and calcium halide are used as a solution dissolved in a solvent. Such solvents include water or alcohols such as ethanol.

[0016] Among the reaction products produced from the reaction raw materials, solids which are not dissolved in the above solution are filtered. The solid content obtained by filtration is fired, and specific firing conditions are a temperature of 800 to 1800 ° C. and a temperature of 1 to 1 ° C.
0 hours, preferably 1 to 3 hours. Firing temperature is 80
If the temperature is lower than 0 ° C., the reaction becomes insufficient or the reaction rate becomes slow. Thus, if it exceeds 1800 ° C., the stability of β-cristobalite obtained is impaired, which is not preferable. If the reaction time is less than 1 hour, the reaction is insufficient, and if it exceeds 10 hours, unnecessary heating is caused, which is not preferable in terms of energy cost.

As described above, the desired β-cristobalite having no phase transition can be obtained. Next, the non-oxide ceramic material is formed on the surface of the non-sintered or sintered non-oxide ceramic made of silicon carbide (SiC) or silicon nitride (Si ₃ N ₄ ) by the precursor of β-cristobalite. A body-based coating layer is formed. That is, a non-sintered body (powder) or a sintered body (molded body) of a non-oxide ceramic is immersed in a solution in which aluminum halide and calcium halide are dissolved in a solvent and dried by heating. Thus, a coating layer based on the precursor of β-cristobalite is formed on the surface of the non-sintered or sintered body of the non-oxide ceramic.

The form of the non-sintered or sintered body of the non-oxide ceramic may be either a powder or a compact having a predetermined shape. It is preferable that amorphous silicon oxide, silicic acid, calcium silicate, and at least one of silicon alkoxide compounds are further contained in addition to the aluminum halide and the calcium halide. As these compounds, those described for β-cristobalite having no phase transition are used. The amount of silicon alkoxide compound used is SiO ₂ per mole of calcium halide.
It is preferably 5 to 50 mol in conversion, and 10 to 30 mol.
More preferably, it is molar. When the amount is less than 5 mol, formation of a coating layer based on the precursor of β-cristobalite becomes insufficient. On the other hand, even if it is used in an amount exceeding 50 mol, all of the added compounds cannot contribute to the reaction, but remain in excess.

The solvent is for dissolving aluminum halide, calcium halide, amorphous silicon oxide, silicic acid, calcium silicate and an alkoxide compound of silicon, and specifically, water, ethanol and the like are used. . Aluminum halide and calcium halide are used by mixing them and dissolving them in a solvent.

A non-sintered or non-sintered non-oxide ceramic is immersed in the solution, and a film of the solution is formed on the surface thereof. At this time, when the non-oxide ceramic is a non-sintered body, that is, a powder, a filtration operation is performed after immersion, and the filtration residue is heated and dried. When the non-oxide ceramic is a sintered body, that is, a molded body, the non-oxide ceramic is immersed in a solution for several seconds to several minutes, pulled up, and dried by heating.

Next, the heating and drying is preferably performed at 100 to 40.
It is performed by heating at a temperature of 0 ° C. for 0.5 to 10 hours. If the heating temperature is lower than 100 ° C., it takes a long time for drying, which is not preferable. Conversely, a high temperature exceeding 400 ° C. is not preferable because excessive heat energy is consumed.

A non-oxide ceramic material having a coating layer formed of a β-cristobalite precursor on the surface is sintered at a predetermined temperature and for a predetermined time to form a β-cristobalite precursor. Is converted to β-cristobalite. The firing temperature is preferably 800
C. or higher, more preferably 800 to 1800C, and particularly preferably 900 to 1100C. The firing time is preferably 1 to 10 hours, more preferably 3 to 6 hours. If the sintering temperature is less than 600 ° C. or the sintering time is less than 1 hour, the sintering becomes insufficient. If the sintering temperature exceeds 1800 ° C. or the sintering time exceeds 10 hours, the product is easily decomposed. Is not preferred. Further, firing at a lower temperature in a shorter time is preferable from the viewpoint of energy cost.

The thickness of the precursor layer of β-cristobalite or the coating layer of β-cristobalite converted from the precursor is preferably 0.5 to 200 μm. When the thickness is less than 0.5 μm, the antioxidant effect and durability of the coating layer cannot be sufficiently exhibited,
If it exceeds 200 μm, the coating layer may be cracked or peeled off due to a slight difference in volume expansion coefficient between the non-oxide ceramic and the coating layer.

Since the non-oxide ceramic material thus obtained exhibits excellent durability due to its antioxidant effect, it can be used for materials for high-temperature turbines, furnace materials for refuse incinerators, and furnaces for nuclear reactors. It is suitably used as a structural material used at a high temperature, such as a material or a heating element.

The effects exerted by the above embodiments will be summarized below. According to the β-cristobalite described in the embodiment, since there is no phase transition when there is a temperature change, particularly when the high temperature state and the low temperature state are repeatedly applied, it is stable and durable without expansion and contraction. Excellent in nature.

The β-cristobalite reacts at least one selected from amorphous silicon oxide, silicic acid, calcium silicate, an alkoxide compound of silicon, silicon carbide and silicon nitride with aluminum halide and calcium halide in one stage After being baked, it is easily obtained.

Further, according to the non-oxide ceramic material, since a coating layer based on the precursor of β-cristobalite is formed on the surface thereof, particularly when the high temperature state and the low temperature state repeatedly act. , Silicon carbide or silicon nitride to an oxide can be prevented, and a phase transition of a β-cristobalite precursor can be prevented. Therefore, the non-oxide ceramic material is less deteriorated and has excellent durability.

Further, by performing sintering, the precursor of β-cristobalite forming the coating layer is converted into β-cristobalite, and the coating layer of β-cristobalite is formed on the surface of the non-oxide ceramic material. You.
Therefore, particularly when the high-temperature state and the low-temperature state repeatedly act, the change of silicon carbide or silicon nitride to an oxide can be prevented, and the phase transition of β-cristobalite is prevented. Therefore, the antioxidant effect is enhanced, and the durability is improved.

The solution contains at least one of amorphous silicon oxide, silicic acid, calcium silicate and an alkoxide compound of silicon, in addition to the aluminum halide and the calcium halide, so that a silicon (Si) source can be obtained. The base material of silicon carbide and silicon nitride is protected because the base material of silicon carbide and silicon nitride is not used. Therefore, the durability based on the fundamental protection effect and oxidation prevention effect of silicon carbide and silicon nitride of the base material is further improved.

[0030]

EXAMPLES Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples. Example 1 208.3 g (1 mol) of tetraethoxysilane, 28.4 g (0.12) of aluminum chloride hexahydrate
Mol) and 7.9 g of calcium chloride dihydrate (0.05 g).
Was dissolved in a mixed solution of 210 g of ethanol and 200 g of water to prepare a solution. In this solution, length 3mm,
A prismatic silicon carbide sintered body (about 0.9 g) having a width of 4 mm and a length of 5 cm was immersed for 3 minutes. Thereafter, the silicon carbide sintered body was pulled up from the solution, and subsequently dried at 140 ° C. to obtain a silicon carbide sintered body whose surface was coated with a coating layer of β-cristobalite precursor.

The coating layer of the obtained sintered body was 0.045 g.
(61.8 g / m ^{2 with} respect to the apparent surface area). Subsequently, the sintered body was fired at 1400 ° C.
A sintered body of silicon carbide covered with a coating layer of cristobalite was obtained.

(Example 2) Aluminum chloride hexahydrate 2
8.4 g (0.12 mol) and 7.9 g (0.05 mol) of calcium chloride dihydrate were dissolved in 210 g of ethanol to prepare a solution. In this solution, length 3mm,
A prismatic silicon carbide sintered body (about 0.9 g) having a width of 4 mm and a length of 5 cm was immersed for 3 minutes. Thereafter, the silicon carbide sintered body was pulled up from the solution, and subsequently dried at 140 ° C. to obtain a silicon carbide sintered body whose surface was coated with a coating layer of β-cristobalite precursor.

The coating layer of the obtained sintered body is 0.012 g
(17.0 g / m ^{2 with} respect to the apparent surface area). Subsequently, the sintered body was fired at 1400 ° C.
A sintered body of silicon carbide covered with a coating layer of cristobalite was obtained.

Example 3 Aluminum chloride hexahydrate 2
8.4 g (0.12 mol) and 7.9 g (0.05 mol) of calcium chloride dihydrate were dissolved in 210 g of ethanol to prepare a solution. In this solution, length 3mm,
A prismatic silicon carbide sintered body (about 0.9 g) having a width of 4 mm and a length of 5 cm was immersed for 3 minutes. Thereafter, the silicon carbide sintered body was pulled out of the solution, subsequently dried at 140 ° C., and immersed again in the solution for 3 minutes. Further, the silicon carbide sintered body was pulled up from the solution and subsequently dried at 140 ° C. Then, a sintered body of silicon carbide having a surface coated with a coating layer of a precursor of β-cristobalite was obtained.

The coating layer of the obtained sintered body is 0.015 g.
(20.1 g / m ^{2 with} respect to the apparent surface area). Subsequently, the sintered body was fired at 1400 ° C.
A sintered body of silicon carbide covered with a coating layer of cristobalite was obtained. The thickness of the coating layer of β-cristobalite is 90
μm.

(Comparative Examples 1 to 4) Calcium chloride (Comparative Example 1), aluminum chloride (Comparative Example 2), iron acetate (Comparative Example 3) and copper acetate (Comparative Example 4) were each added to ethanol to give a concentration of 1 mol. / L solution or suspension was prepared. A prism-shaped sintered body of silicon carbide (about 0.9 g) having a length of 3 mm, a width of 4 mm, and a length of 5 cm was immersed in this liquid for 3 minutes.
Thereafter, the silicon carbide sintered body was pulled up from the solution, and subsequently dried at 140 ° C., to obtain a silicon carbide sintered body having the adhered substance of each compound adhered to the surface.

The deposits on the surface of the obtained sintered body were 0.025 g, 0.012 g, 0.017 g, and 0.0025 g, respectively.
It was 15 g. Subsequently, the sintered body was fired at 1400 ° C. to obtain a silicon carbide sintered body as a comparative control.

(Test for Oxidation Degradation of Silicon Carbide) The sintered bodies of silicon carbide obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were heated at 1400 ° C. (heating rate 5 ° C./min) for 3 hours. The operation of the heat treatment and the operation of natural cooling to room temperature thereafter were repeated, and the rate of weight increase was measured each time to confirm the degree of oxidation deterioration of silicon carbide. At this time, untreated silicon carbide was similarly used as a control. The increase rate (%) for each sample and each number of treatments is shown in Table 1 and FIG.

[0039]

[Table 1]

As shown in Table 1, in Examples 1 to 3,
It can be seen that there is no weight increase after the β-cristobalite film, which is an oxide film, is formed in the first treatment and increases in weight, and the progress of oxidation is suppressed. In contrast, in Comparative Examples 1 to 4, it was clarified that each time heating and cooling were repeated, they were oxidized, and silicon carbide continued to deteriorate to silicon oxide.

Example 4 Tetraethoxysilane 20
8.3 g (1 mol), aluminum chloride hexahydrate
6. 4 g (0.12 mol) and calcium chloride dihydrate
9 g (0.05 mol) of ethanol 630 g and water 20
The solution was dissolved in 0 g of a mixed solution to prepare a solution. 1.0 g of powdered needle-shaped silicon carbide (specific surface area: 3 m ² / g) in this solution
Was immersed and mixed by stirring, followed by filtration. Thereafter, the residue was dried at 140 ° C. to obtain silicon carbide powder whose surface was coated with a coating layer of a precursor of β-cristobalite.

The solid matter (coating layer, β-cristobalite precursor) attached to the obtained silicon carbide powder was 0.36
g (0.12 g / m ^{2 with} respect to the specific surface area). Subsequently, the silicon carbide powder was fired at 800 ° C.
-A silicon carbide needle powder coated with a coating layer of cristobalite was obtained. Further, this was sintered at 1400 ° C. to obtain a silicon carbide molded body whose surface was covered with β-cristobalite.

(Example 5) Aluminum chloride hexahydrate 2
8.4 g (0.12 mol) and 7.9 g (0.05 mol) of calcium chloride dihydrate were dissolved in 630 g of ethanol to prepare a solution. 1.0 g (specific surface area: 3 m ² / g) of powdered silicon carbide was immersed in this solution, and the mixture was stirred and mixed, followed by filtration. Then, the filtration residue is
After drying at 40 ° C., a silicon carbide powder whose surface was coated with a coating layer of a precursor of β-cristobalite was obtained.

The solid matter (coating layer, precursor of β-cristobalite) adhering to the obtained silicon carbide powder was 0.14.
g (0.05 g / m ^{2 with} respect to the specific surface area). Subsequently, the silicon carbide powder was fired at 800 ° C.
-A silicon carbide needle powder coated with a coating layer of cristobalite was obtained. Further, this was sintered at 1400 ° C. to obtain a silicon carbide molded body whose surface was covered with β-cristobalite.

(Example 6) Aluminum chloride hexahydrate 2
8.4 g (0.12 mol) and 7.9 g (0.05 mol) of calcium chloride dihydrate were dissolved in 630 g of ethanol to prepare a solution. 1.0 g (specific surface area: 3 m ² / g) of powdered silicon carbide was immersed in this solution, and the mixture was stirred and mixed, followed by filtration. Then, filtration residue 14
After drying at 0 ° C., the obtained dried product was immersed again in the dissolving solution, stirred and mixed, and filtered.
After drying at 0 ° C., a silicon carbide powder whose surface was coated with a coating layer of a precursor of β-cristobalite was obtained.

The solid matter (coating layer, precursor of β-cristobalite) adhering to the obtained silicon carbide powder was 0.23
g (0.08 g / m ^{2 with} respect to the specific surface area). Subsequently, the silicon carbide powder was fired at 800 ° C.
-A silicon carbide needle powder coated with a coating layer of cristobalite was obtained. Further, this was sintered at 1400 ° C. to obtain a silicon carbide molded body whose surface was covered with β-cristobalite.

Example 7 Tetraethoxysilane 20
8.3 g (1 mol), aluminum chloride hexahydrate
6. 4 g (0.12 mol) and calcium chloride dihydrate
9 g (0.05 mol) of ethanol 210 g and water 20
The solution was dissolved in 0 g of a mixed solution to prepare a solution. 0.9 g of prismatic silicon nitride having a length of 3 mm, a width of 4 mm and a length of 5 cm was immersed in the solution for 3 minutes. Then, it was pulled up from the solution and dried at 140 ° C. to obtain silicon nitride whose surface was coated with a coating layer of β-cristobalite precursor.

0.034 g of solids (coating layer, precursor of β-cristobalite) attached to the obtained silicon nitride
(46.9 g / m ^{2 with} respect to the apparent surface area). Subsequently, the silicon nitride is fired at 1400 ° C.
Obtaining silicon nitride coated with a coating layer of cristobalite.

Example 8 Aluminum chloride hexahydrate 2
8.4 g (0.12 mol) and 7.9 g (0.05 mol) of calcium chloride dihydrate were dissolved in 210 g of ethanol to prepare a solution. In this solution, length 3mm,
Silicon nitride 0.9 in the form of a prism 4 mm wide and 5 cm long
g was soaked for 3 minutes. Then, withdraw from the solution,
Drying was performed at 40 ° C. to obtain silicon nitride whose surface was coated with a coating layer of a precursor of β-cristobalite.

0.009 g of solid matter (coating layer, precursor of β-cristobalite) attached to the obtained silicon nitride
(12.9 g / m ^{2 with} respect to the apparent surface area). Subsequently, the silicon nitride is fired at 1400 ° C.
Obtaining silicon nitride coated with a coating layer of cristobalite.

(Example 9) Aluminum chloride hexahydrate 2
8.4 g (0.12 mol) and 7.9 g (0.05 mol) of calcium chloride dihydrate were dissolved in 210 g of ethanol to prepare a solution. In this solution, length 3mm,
Silicon nitride 0.9 in the form of a prism 4 mm wide and 5 cm long
g was soaked for 3 minutes. Then, withdraw from the solution,
It was dried at 40 ° C. and immersed again in the solution for 3 minutes. Further, the sintered body of silicon carbide is pulled out of the solution,
Dried at 40 ° C. Then, silicon nitride whose surface was coated with a coating layer of a precursor of β-cristobalite was obtained.

The solids (coating layer, precursor of β-cristobalite) attached to the obtained silicon nitride were 0.011 g.
(15.3 g / m ^{2 with} respect to the apparent surface area). Subsequently, the silicon nitride is fired at 1400 ° C.
Obtaining silicon nitride coated with a coating layer of cristobalite. The thickness of this coating layer was about 65 μm.

Example 10 Tetraethoxysilane 20
8.3 g (1 mol), aluminum chloride hexahydrate
6. 4 g (0.12 mol) and calcium chloride dihydrate
9 g (0.05 mol) of ethanol 630 g and water 20
The solution was dissolved in 0 g of a mixed solution to prepare a solution. 1.0 g of powdered silicon nitride (specific surface area: 7 m ² / g) was immersed in the solution, mixed by stirring, and then filtered. afterwards,
The filtration residue was dried at 140 ° C. to obtain a silicon nitride powder whose surface was coated with a coating layer of a precursor of β-cristobalite.

The solid matter (coating layer, precursor of β-cristobalite) attached to the obtained silicon nitride was 1.05 g (1.5 g / m ^{2 based on the} specific surface area). Subsequently, the silicon nitride was fired at 800 ° C. to obtain a silicon nitride powder coated with a coating layer of β-cristobalite. This was further sintered at 1400 ° C. to obtain a silicon nitride molded body covered with a coating layer of β-cristobalite.

Example 11 28.4 g (0.12 mol) of aluminum chloride hexahydrate and 7.9 g (0.05 mol) of calcium chloride dihydrate were dissolved in 630 g of ethanol to form a solution. Prepared. 1.0 g of powdered silicon nitride (specific surface area: 7 m ² / g) was immersed in the solution, mixed by stirring, and then filtered. Then, the filtration residue is
After drying at 40 ° C., a silicon nitride powder whose surface was coated with a coating layer of a precursor of β-cristobalite was obtained.

The solid matter (coating layer, precursor of β-cristobalite) attached to the obtained silicon nitride was 0.53 g (0.8 g / m ^{2 based on the} specific surface area). Subsequently, the silicon nitride was fired at 800 ° C. to obtain a silicon nitride powder coated with a coating layer of β-cristobalite. This was further sintered at 1400 ° C. to obtain a silicon nitride molded body covered with a coating layer of β-cristobalite.

Example 12 28.4 g (0.12 mol) of aluminum chloride hexahydrate and 7.9 g (0.05 mol) of calcium chloride dihydrate were dissolved in 630 g of ethanol to form a solution. Prepared. 1.0 g of powdered silicon nitride (specific surface area: 7 m ² / g) was immersed in the solution, mixed by stirring, and then filtered. Then, the filtration residue is
After drying at 40 ° C., the obtained dried product was immersed again in the dissolving solution, stirred and mixed, and filtered.
After drying at 0 ° C., a silicon nitride powder whose surface was coated with a coating layer of a precursor of β-cristobalite was obtained.

The solid matter (coating layer, precursor of β-cristobalite) attached to the obtained silicon nitride was 0.74 g (1.1 g / m ^{2 based on the} specific surface area). Subsequently, the silicon nitride was fired at 800 ° C. to obtain a silicon nitride powder coated with a coating layer of β-cristobalite. This was further sintered at 1400 ° C. to obtain a silicon nitride molded body covered with a coating layer of β-cristobalite.

Example 13 28.4 g (0.12 mol) of aluminum chloride hexahydrate and 7.9 g (0.05 mol) of calcium chloride dihydrate were mixed with 2000 g of methanol.
To prepare a solution. 3m in length in this solution
A prismatic sintered body of silicon carbide (approximately 0.9 g) having a length of 5 mm, a width of 4 mm and a length of 5 cm was immersed for 20 seconds. Thereafter, the sintered body of silicon carbide was pulled up from the solution and subsequently dried at 140 ° C. Then, a sintered body of silicon carbide having a surface coated with a coating layer of a precursor of β-cristobalite was obtained. Subsequently, the sintered body was fired at 1400 ° C. to obtain a sintered body of silicon carbide whose surface was covered with a coating layer of β-cristobalite. The thickness of the coating layer of β-cristobalite is 5 μm
Met.

Example 14 Tetraethoxysilane 20
After hydrolyzing 8.3 g (1 mol) by adding 200 g of water, the mixture was heated at 500 ° C. for 5 hours to have a surface area of about 530 m ^2.
/ G of silica gel. 1 mol of this silica gel was added to a solution prepared by dissolving 28.4 g (0.12 mol) of aluminum chloride hexahydrate and 7.9 g (0.05 mol) of calcium chloride dihydrate in 210 g of ethanol. The solid was filtered. Then, the solid content at 1000 ° C. is 6
By firing for a time, β-cristobalite having no phase transition was obtained.

Example 15 1.0 g of silicon carbide powder
Was added to a solution prepared by dissolving 28.4 g (0.12 mol) of aluminum chloride hexahydrate and 7.9 g (0.05 mol) of calcium chloride dihydrate in 210 g of ethanol. Filtered. And the solid content is 100
By baking at 0 ° C. for 6 hours, powdery β-cristobalite having no phase transition was obtained.

(Example 16) One mole of silica gel obtained by treating calcium silicate with an acid was mixed with 28.4 g (0.12 mole) of aluminum chloride hexahydrate and 7.9 g of calcium chloride dihydrate ( (0.05 mol) was added to a solution in which 210 g of ethanol was dissolved, and then the solid content was filtered. The solid was fired at 1000 ° C. for 6 hours to obtain β-cristobalite having no phase transition.

Example 17 Tetraethoxysilane 20
8.3 g (1 mol) of aluminum chloride hexahydrate 2
After adding 8.4 g (0.12 mol) and 7.9 g (0.05 mol) of calcium chloride dihydrate to 210 g of ethanol, the solid content was filtered. The solid content was calcined at 1000 ° C. for 6 hours to obtain powdery β-cristobalite having no phase transition.

Example 18 698 g (about 1 mol) of zonotolite was mixed with 28.4 g of aluminum chloride hexahydrate.
(0.12 mol) and 7.9 g of calcium chloride dihydrate
(0.05 mol) was added to a solution in which 210 g of water was dissolved, and then the solid content was filtered. And the solid content is 1
By baking at 000 ° C. for 6 hours, β-cristobalite having no acne morphology of zonotolite and having no phase transition was obtained.

The above embodiment may be modified as follows. -Non-oxide ceramics such as boron nitride and boron carbide may be added to silicon carbide or silicon nitride constituting the non-oxide ceramics. Further, a mixture of silicon carbide and silicon nitride may be used.

As a method of coating a solution of aluminum chloride, calcium chloride, or tetraethoxysilane in a solvent on the surface of silicon carbide or silicon nitride, a solution is applied to the surface of silicon carbide or silicon nitride. A method of applying with a tool, a method of spraying with a sprayer, and the like may be adopted.

Further, the technical idea grasped from the above embodiment will be described below.・ Non-sintered or sintered non-oxide ceramics
The non-oxide ceramic material according to any one of claims 3 to 5, which is a powder or a compact having a predetermined shape.
With this configuration, the form of the non-oxide ceramic material can be selected according to the application.

The thickness of the coating layer is 0.5 to 200 μm
The non-oxide ceramic material according to any one of claims 3 to 5, wherein m is m. With this configuration, the effect of preventing the non-oxide ceramic material from being oxidized can be enhanced, and the durability can be reliably improved.

[0069]

As described above, according to the present invention, the following effects can be obtained. Β- according to the invention of claim 1
According to cristobalite, a stable state can be maintained without phase transition due to a temperature change.

According to the method for producing β-cristobalite according to the second aspect of the present invention, stable β-cristobalite can be easily obtained without phase transition due to temperature change. According to the non-oxide-based ceramic material of the invention according to claim 3, due to the precursor of β-cristobalite forming the coating layer, even when the high-temperature state and the low-temperature state repeatedly act, deterioration due to oxidation is small, Has excellent durability.

According to the non-oxide ceramic material of the invention described in claim 4, a precursor of β-cristobalite forming the coating layer can be obtained without using silicon carbide or silicon nitride as a base material as a raw material. Therefore, the effect of the invention described in claim 3 can be further improved.

According to the non-oxide ceramic material of the invention described in claim 5, the same effect as the effect of the invention described in claim 3 or 4 is exhibited by β-cristobalite forming the coating layer. be able to.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the number of repetitions and the rate of weight increase in Examples, Comparative Examples and Control Examples.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C04B 35/58 102P 102X (71) Applicant 596095389 Kaichi Fujiyoshi 27 Kamono, Kamono-cho, Minokamo-shi, Gifu Prefecture No. 2 (71) Applicant 596097486 Yasuyuki Nomura 1729, Nishiho, Kobe-cho, Anpachi-gun, Gifu Prefecture (71) Applicant 500518360 Shingo Ishida 1-3, Rokutanda-cho, Shimotsurin, Nishikyo-ku, Kyoto, Kyoto 145 (71) Application No. 500518371 Nobuyuki Takeuchi 38, Takamine Former Doi-cho, Kita-ku, Kyoto, Kyoto Prefecture (72) Inventor Kaichi Fujiyoshi 27-2, Kamono, Kamono-cho, Minokamo-shi, Gifu (72) Inventor Yasuyuki Nomura Anhachi-gun, Gifu 1729, Nishiho, Kobe-cho Former Takamine Doi-cho 1 38 (72) Inventor Minoru Hirai 2093 Akasaka-cho, Ogaki-shi, Gifu Prefecture Kawai Lime Co., Ltd. (72) Inventor Kazuhiko Kikuchi 2093 Akasaka-cho, Ogaki-shi, Gifu Kawai Lime Co. In-house (72) Inventor Kenji Kido 2093 Akasaka-cho, Ogaki-shi, Gifu Prefecture Kawai Lime Industry Co., Ltd. (72) Inventor Koichiro Sasaki 1372, Tokiguchi, Tokizu-cho, Toki-shi, Gifu Prefecture Inside Shinmei Kogyo Co., Ltd. (72) Inventor Hayato Minamisato 1-1, Makiyama Shinmachi, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture F term (reference) 4G001 BA03 BA04 BA07 BA22 BB03 BB04 BB07 BB22 BC32 BC72 BD12 4G072 AA32 BB09 FF02 GG03 HH16 HH23 HH30 HH33 KK07 LL06 LL11 MM31 MM36 NN21 RR12 TT30 UU30

Claims (5)

[Claims] At least one selected from the group consisting of amorphous silicon oxide, silicic acid, calcium silicate, an alkoxide compound of silicon, silicon carbide and silicon nitride is mixed with a solution in which aluminum halide and calcium halide are dissolved in a solvent. .Beta.-cristobalite having no phase transition obtained by calcining a solid that is not dissolved in the solution. 2. At least one selected from amorphous silicon oxide, silicic acid, calcium silicate, an alkoxide compound of silicon, silicon carbide and silicon nitride is mixed with a solution in which aluminum halide and calcium halide are dissolved in a solvent. Thereafter, the solid content not dissolved in the solution is reduced to 800 to 18%.
A method for producing β-cristobalite having no phase transition, wherein the method is calcined at a temperature of 00 ° C. for 1 to 10 hours. 3. The surface of a non-sintered or sintered non-oxide ceramic made of silicon carbide or silicon nitride is coated with a solution of aluminum halide and calcium halide dissolved in a solvent, and dried by heating. A non-oxide ceramic material having a coating layer based on a precursor of β-cristobalite formed on a surface of a non-oxide ceramic body or a sintered body of the non-oxide ceramic body. 4. The non-oxide ceramic material according to claim 3, wherein the solution further contains at least one of amorphous silicon oxide, silicic acid, calcium silicate and an alkoxide compound of silicon. 5. The non-oxide ceramic material according to claim 3 or 4 at a temperature of 800 to 1800 ° C.
A non-oxide ceramic material obtained by baking for 10 hours to convert a precursor of β-cristobalite into β-cristobalite having no phase transition.