| 摘要 |
Low density silicon nitride ceramics having improved bending and specific strengths over known silicon nitride ceramics derived from silicon nitride powder and polysilazane precursors are prepared by (A) intimately mixing 50-85% by weight of silicon nitride powder with 15-50% by weight of a preceramic polysilazane binder, (B) pulverizing the mixture to form particles having a particle size smaller than 105 micrometers, (C) separating from those particles any particles having a particle size larger than about 105 micrometers, (D) molding the resultant composition having a particle size not larger than about 105 micrometers, and (E) pyrolyzing the molded composition in an inert atmosphere to a temperature of 1200-1450 DEG C.; said preceramic binder being at least one polysilazane prepared by reacting an organodihalosilane with ammonia, treating the ammonolysis product with a basic catalyst which is capable of deprotonating an NH group that is adjacent to an SiH group, and quenching the resultant product with an electrophilic quenching reagent. |
