METHOD FOR PRODUCING DENSE SILICON NITRIDE CONTAINING YTTRIUM OXIDE AND ALUMINUM OXIDE AND HAVING HIGH TEMPERATURE STRENGTH AND OXIDATION RESISTANCE

摘要

METHOD FOR PRODUCING DENSE SILICON NITRIDE CONTAINING YTTRIUM OXIDE AND ALUMINUM OXIDE AND HAVING HIGH TEMPERATURE STRENGTH AND OXIDATION RESISTANCE The addition of controlled amounts of A1203 to high purity Si3N4 powder (containing less then 0.1 weight percent cation impurities and containing Y203 as a densifying additive) enables shorter sintering times to achieve polycrystalline Si3N4 bodies having densities approaching theoretical density, while a postsintering crystallization heat treatment results in strengths at high temperatures not otherwise obtainable in the presence of A1203. Resulting Si3N4 bodies are useful as engine parts and components or a regenerator or recuperator structures for waste heat recovery. In addition, such Si3N4 bodies containing A1203 exhibit good oxidation resistance.