Cermet or ceramic/glass composites including self-reinforced beta -Silicon nitride, and method of making same

摘要

Infiltrate a porous, self-reinforced beta -Si3N4 preform with a metal or a crystallizable glass to yield a composite material. The preform possesses a low glass phase and has a density of from about 50 to about 70 percent of theoretical density. Prepare the beta -Si3N4 preform by subjecting a porous body formed from an alpha -Si3N4 powder composition to two sequential heat treatments. The first heat treatment occurs below the alpha - to beta - conversion temperature and results in a strengthened body that can be machined. The second heat treatment occurs above that temperature and yields the self-reinforced beta -Si3N4 preform. Conventional infiltration procedures with an infiltrant that is a metal or a glass results in a Si3N4/metal or Si3N4/glass composite material that has 50 to 70 percent of its volume occupied by beta -Si3N4 whiskers.