Preceramic compositions
US4895889A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 12, 1988 |
| Grant date | Jan 23, 1990 |
| Priority date | — |
| Expiry date | May 12, 2008 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/2995
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
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 about 50-85% by weight of silicon nitride powder with about 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 about 1200.degree.-1450.degree. 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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.