Densification of silicon carbide using oxy-nitride additives for space-based telescope mirror applications

Abstract

Densification behavior of alpha silicon carbide (SiC) during vacuum hot pressing was studied up to 1900C with sintering additives based on AlN and Y 2 O 3 in different proportions. Near theoretical density was obtained with a total sintering additive content of 4 vol.. The microstructure of SiC sintered with AlNY 2 O 3 revealed fine equiaxed grains against the additional elongated grains exhibited by SiC sintered with AlN alone. The SiC having high density exhibited very good strength, elastic modulus, high thermal conductivity, low coefficient of thermal expansion and excellent polishability for telescope mirror applications. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).