Reaction injection molding of silicon nitride ceramics, with a crystalline grain boundary phases

摘要

A sintered, Si.sub.3 N.sub.4 -containing ceramic article is prepared by a reaction injection molding process comprising (1) injecting into a heated mold a fluid, nondilatant mixture of (a) at least 40% by volume of a powder mixture of (i) Si.sub.3 N.sub.4, (ii) a silicate glass- forming sintering aid and (iii) a high metal content silicide, and (b) a curable Si.sub.3 N.sub.4 precursor binder, to cure the binder and produce a hardened molded article, and (2) heating the molded article under a suitable atmosphere to convert the cured binder to a Si.sub.3 N.sub.4 - containing ceramic. The molded article is then sintered under a vacuum to crystallize the silicate glass phase by deoxygenation.