Reaction injection molding of silicon nitride ceramics having crystallized grain boundary phases
A reaction injection molding process is described for preparing a sintered, silicon nitride-containing ceramic article comprising; (1) injecting into a heated mold a fluid, nondilatant mixture comprising (a) at least 40% by volume of a powder mixture of (i) from about 20 wt.% to about 98 wt.% silicon nitride, (ii) from about 0.5 wt.% to about 20 wt.% of a silicate glass-forming sintering aid, and (iii) from about 0.001 wt.% to about 80 wt.% of a high metal content transition metal silicide or a transition metal or metal compound that forms a high metal content silicide with silicon nitride under the conditions defined in steps (2) or (3), and (b) a curable silicon nitride precursor binder that is a liquid below its curing temperature, to cure the binder and produce a hardened molded article, (2) heating the hardened mol suitable atmosphere to a temperature sufficient to convert the cured binder to a silicon nitride-containing ceramic, and (3) sintering the article by (i) heating at a temperature of 1,300 to 1,800 C until a silicate glass forms, and (ii) further heating at a temperature of 1,300 to 1,800 C under a vacuum until oxygen is removed from the silicate glass and the glass crystallizes.
- Assignee:
- IMS; EDB-93-135155
- Patent Number(s):
- US 5240658; A
- Application Number:
- PPN: US 7-851038
- OSTI ID:
- 5987334
- Resource Relation:
- Patent File Date: 10 Mar 1992
- Country of Publication:
- United States
- Language:
- English
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