COMPOSITE SILICON NITRIDE SINTER AND PRODUCTION THEREOF.

摘要

A composite silicon nitride sinter comprising a silicon nitride matrix and, dispersed therein, silicon carbide grains with a size of several to several hundred manometers, wherein the total amount of the silicon carbide dispersed in the sinter is 1 to 40 vol.% and the amount of the silicon carbide dispersed in the silicon nitride grains is 5 to 99 vol.% of the total amount of dispersion, the rest being present exclusively in the silicon nitride grain boundaries. The production process comprises compacting the starting material comprising amorphous composite powder composed of a silicon, nitrogen and carbon elements together with a sintering aid, subjecting the compacted powder to primary sintering at 1,350 to 1,650 DEG C in a nitrogen atmosphere followed by secondary sintering at 1,600 to 1,900 DEG C, and causing silicon carbide deposited in the silicon nitride grains at 1,800 to 2,200 DEG C to migrate toward the grain boundaries. The process can provide ceramic material which is excellent in strengths and fracture toughness and can be used as high-temperature structural material for automotive engines and so forth.