Method of forming a densified silicon nitride article

Abstract

A method is disclosed in this specification for forming a densified silicon nitride article. The method is initiated by forming a reaction bonded article of moderate density. This moderate density reaction bonded article has a primary phase of substantially pure grains of silicon nitride surrounded by a secondary grain boundary phase. The secondary grain boundary phase contains silicon nitride, silicon dioxide and a densification aid incorporated in the reaction bonded article of moderate density. The compounds forming the secondary grain boundary phase are present either in their pure forms or interacted with one another. The reaction bonded article is packed in a packing powder which contains portions of the pure compounds found in or interacted with one another to define the secondary grain boundary phase. The reaction bonded article of moderate density is heated in the packing powder to a temperature and for a time whereby interaction of the secondary grain boundary phase and the packing powder may take place. The interaction takes place so that a new grain boundary phase can be developed about the substantially pure grains of silicon nitride. The new grain boundary phase developed is a unitary phase of a selected composition.

Dependencies are inferred from the claim text.