| 摘要 |
PURPOSE:To simultaneously enhance strength and toughness by dispersing particles of nm order having a high coefft. of thermal expansion in silicon nitride grains and a grain boundary phase. CONSTITUTION:Particles having 1-500nm average particle diameter and >=5X10<-6>/ deg.C coefft. of thermal expansion are dispersed in silicon nitride and/or sialon grains having 0.05-3mum average minor axis size and <=10 aspect ratio and in a grain boundary phase. The resulting composite powder is press-molded and sintered to obtain a composite sintered body. By this method, residual compressive stress is produced in the silicon nitride grains by the difference in coefft. of thermal expansion at the time of cooling from the sintering temp. to room temp. Since this stress field is applied to the tips of cracks at the time of fracture, resistance to the occurrence and propagation of cracks is increased, fracture toughness is enhanced and strength and toughness are enhanced. |
