METHOD OF MAKING AN ANISOTROPIC SILICON NITRIDE COMPRISING OBJECT BY USE OF HIGHER DENSITY AND FULLY REACTED PREFORMS

摘要

Method of densifying a silicon nitride compact having 5-17 wt.% yttrium silicon oxynitride and having a density of 2.0-2.6 g/cm3 comprises: (a) partially sintering the compact at 3000-3200 deg.F for 0.5-72 h. to form a semi-dense body with density 2.9-3.15 g/cm3; (b) hot pressing a stacked assembly of such bodies in the hot zone of a hot pressing cavity to form fully dense anisotropic products, each body being separated from the next within the assembly by a distance no greater than 0.030 inch, the stacked assembly occupying the entire length of the hot pressing cavity, and including at least 5 bodies of height ratio 1:3 to 1:40.