METHOD FOR PRODUCING BRITTLE SILICON NITRIDE

摘要

PURPOSE: To produce a friable silicon nitride body by infiltrating a fluid which expands by freezing into the outer surface and the center core of a silicon nitride body having a specified density and then freezing the fluid on the outer surface faster than the fluid in the center core. CONSTITUTION: A fluid which expands by freezing is infiltrated into the outer surface and the center core of a silicon nitride body having >=1.5 g/cc density. Then the fluid infiltrated into the body is frozen in such a manner that the fluid on the outer surface freezes faster than the fluid in the center core. Then the frozen silicon nitride body is defrosted to produce a friable silicon nitride body. The friable silicon nitride body broken and then milled into proper flakes to obtain powder. The fluid which expands by freezing is preferably water, and infiltration of the fluid into the body is preferably carried out in about <=100 mmHg vacuum state.