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

摘要

Densification behavior of alpha silicon carbide (SiC) during vacuum hot pressing was studied up to 1900℃ with sintering additives based on AIN and Y_2O_3 in different proportions. Near theoretical density was obtained with a total sintering additive content of < 4 vol.%. The microstruc-ture of SiC sintered with AIN + Y_2O_3 revealed fine equiaxed grains against the additional elongated grains exhibited by SiC sintered with AIN 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.