Method of manufacturing a sintered composite body of silicon nitride and

Abstract

A sintered composite body of silicon nitride and silicon carbide is manufactured by mixing a silicon powder with a carbonaceous powder and a sintering additive, producing a mixture, molding the mixture into a molded body, heat-treating the molded body in an atmosphere containing a nitrogen gas for thereby simultaneously nitriding and carbonizing silicon contained in the molded body, and subsequently firing the molded body in a nitrogen gas atmosphere. A composite powder of silicon nitride and silicon carbide which is produced by simultaneously nitriding and carbonizing silicon contained in the molded body has a content of .alpha.-type silicon nitride which is at least 30% of all silicon nitride in the composite powder. To produce such a composite powder, a silicon powder is mixed with a carbonaceous powder and a sintering additive, producing a mixture, and the mixture is heat-treated in an atmosphere containing a nitrogen gas at a temperature of at most 1450.degree. C. for thereby simultaneously nitriding and carbonizing silicon contained in the mixture, the arrangement being such that the temperature of the mixture is increased at a rate lower than 2.degree. C./minute from a temperature before the silicon starts being nitrided and carbonized up to the temperature of at most 1450.degree. C.