JPH0314793B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a heat-resistant and oxidation-resistant molded article. [Prior art] Silicon nitride has excellent heat resistance and oxidation resistance, so it is molded into ceramics with excellent heat and oxidation resistance and used for gas turbine blades, engine parts, heat-resistant jig materials, etc. It will be done. However, conventional silicon nitride is produced by heating silicon powder to 1200-1300℃ in nitrogen or ammonia, or
Alternatively, it is obtained by heating in nitrogen or ammonia using a silicon-containing inorganic or organic monomer. [Problem to be solved by the invention] However, silicon nitride obtained by conventional methods can only be obtained in the form of powder, so in order to mold it using it, it is necessary to add a binder, such as an oxide such as magnesium oxide. As a result, the resulting molded product had the drawback of deteriorating various properties such as heat resistance and mechanical strength. [Means for Solving the Problems] As a result of research to provide a silicon nitride-based molded product free from such drawbacks, the present inventors found that by reacting a halogenated silane, a polyhydric alcohol, and ammonia, Silicon nitride in the desired shape can be obtained by synthesizing a resin compound, producing a desired shape with it, and then heating it in an ammonia or nitrogen gas atmosphere. If it is mixed or impregnated with carbon materials, ceramic materials such as silicon carbide, silicon nitride, alumina, ceramic fiber reinforced materials, etc. and heated in an ammonia or nitrogen gas atmosphere, silicon nitride will be contained in these materials. The present invention was completed based on the knowledge that the heat resistance and oxidation resistance of these materials are improved. The halogenated silane to be reacted with polyhydric alcohol such as glycerin and glycol in the present invention is one or more compounds represented by the following general formula. Si(X) ₄ , RSi(X) ₃ ,

【formula】

[Formula] where R: alkyl group, ethyl group, allyl group,
Hydrogen . The molded product of the resinous compound obtained by the above reaction or the molded product mixed or impregnated with the resinous compound is fired to 1300 to 1600° C. in an ammonia or nitrogen gas atmosphere. This converts the resinous compound into silicon nitride. When molding a resinous compound, it is heated above its melting point to become liquid or semi-molten, and then molded into a film, sheet, plate, fiber or desired shape by a conventional method. Further, impregnation with a resinous compound is similarly carried out in a liquid or semi-molten state by a conventional method. [Effects] The silicon nitride molded product obtained by the method of the present invention is molded without using a binder unlike conventional products, so it has extremely high purity and high mechanical strength. High heat resistance and oxidation resistance. Further, according to the present invention, carbon materials and carbon fibers impregnated with silicon nitride, which have not been obtained conventionally, can be obtained. [Examples] Next, embodiments of the present invention will be described with reference to Examples, but the present invention is not limited by these. Example 1 Mix 100g of glycerin with 100g of silicon tetrachloride.
20g of ammonium carbamate was added. Initially, the polycondensation was carried out at room temperature while stirring the reaction system, and the temperature was gradually raised to carry out the reaction at 65°C for 3 hours. By-produced NH ₄ Cl was removed along with excess glycerin to obtain a viscous white resin. A circular carbon fiber reinforced/carbon matrix composite material of 10 mm thickness x 100 mmφ prepared separately was impregnated with the resin under reduced pressure, and treated at 1000°C in an NH ₃ atmosphere.
It was further treated at 1500°C in an _N2 atmosphere. This operation of heat treatment to 1500° C. after resin impregnation was repeated three times. As a result, the bending strength of the composite material was 650Kg/cm ² , an increase in strength of approximately 20%. In addition, when this product was treated at 1000℃ for 1 hour under air circulation, the weight loss was 2.5%, and the impregnated composite material that was compared and tested at the same time showed a weight loss of 38%. Example 2 Methyltrichlorosilane (CH ₃・Si ・Cl ₃ )
50g was mixed into 100g of glycerin, 7.5g of ammonium carbamate was added little by little, and the mixture was reacted at 30°C for 4 hours. A white resinous substance was produced with vigorous foaming. What is obtained by removing excess glycerin is
The resin was white and viscous, and was suitable for impregnation into carbon and ceramic materials. When 150 g of xylene was used instead of glycerin and a similar reaction was carried out, infrared analysis confirmed the formation of silazane, but a white solid precipitate was formed and no resin was formed. The presence of glycerin was required for resin formation when such functional groups were included. The tensile strength of the obtained film was 5 Kg/cm ² . Example 3 Dimethyldichlorosilane ((CH ₃ ) ₂・Si・Cl ₂ )
100g of glycerin and 100g of glycerin were mixed, and 15g of ammonium carbamate was added and reacted at 30°C. The reaction was then continued for 4.5 hours at 60°C. The reaction product became a white resin. After adding 2.5 times the weight of alumina powder to this resin and thoroughly mixing it, it was placed in a mold having an internal volume of 10 mm thick x 50 mm wide x 80 mm and hot-press molded. This was then fired at 1300℃ in nitrogen gas to achieve a bending strength of 380.
A strong rectangular molded body weighing Kg/cm ² was obtained.

Claims (1)

[Claims] 1. A resinous compound made by reacting a halogenated silane, a polyhydric alcohol, and ammonia is molded, and the molded product is heated in an ammonia or nitrogen gas atmosphere to convert the resinous compound into silicon nitride. A method for producing a silicon nitride-based molded body, characterized by converting it into a silicon nitride-based molded body. 2 Mixing a resinous compound produced by reacting a halogenated silane with a polyhydric alcohol and ammonia with any one of carbon fiber, graphite material, carbon fiber reinforced carbon composite material, metal oxide, silicon nitride, and silicon carbide; or 1. A method for producing a silicon nitride-based molded body, which comprises impregnating the resinous compound with silicon nitride and heating the molded body in an ammonia or nitrogen gas atmosphere to convert the resinous compound into silicon nitride.