| 摘要 |
PURPOSE:To obtain a sintered product having excellent strength and fracture toughness while suppressing the formation of coarse defect of silicon carbide by adding a sintering assistant to crystalline composite powder composed mainly of silicon, nitrogen and carbon, having a crystallinity higher than a specific level and containing crystal phase consisting of alpha-phase silicon nitride and sintering the obtained mixture. CONSTITUTION:Amorphous composite powder composed mainly of Si, N and C is heat-treated in nitrogen atmosphere at 1550-1700 deg.C for >=3hr to obtain crystalline composite powder composed mainly of Si, N and C, having a crystallinity of >=65% and containing crystal phase consisting of alpha-Si3N4. A sintering assistant is added to the crystalline composite powder and the mixture is sintered to obtain the objective sintered product. Since crystalline composite powder is used as the sintering raw material, it is stable to oxidation and excess C, N, etc., are evaporated and removed from the raw material. Accordingly, the generation of CO gas is decreased to suppress the vapor-solid reaction of CO gas with Si and Si3N4, decrease the formation of coarse agglomerate texture of SiC and improve the strength of the sintered product. Since the crystallinity is >=65%, the above vapor-solid reaction is decreased to improve the strength and the toughness. |
