Yw. Kim et al., Effect of initial alpha-phase content on microstructure and mechanical properties of sintered silicon carbide, J AM CERAM, 81(12), 1998, pp. 3136-3140
By using alpha- and beta-SiC starting powders with similar particle sizes,
the effects of initial cu-phase content on the microstructure and the mecha
nical properties of the liquid-phase-sintered and subsequently annealed mat
erials were investigated. The microstructures developed were analyzed by im
age analysis. When beta-SiC powder was used, the grains became elongated. T
he average diameter decreased with increasing alpha-SiC content and the asp
ect ratio showed a maximum at 10% alpha-SiC and decreased with increasing a
lpha-SiC content in the starting powder. Such results suggest that microstr
ucture can be controlled by changing alpha-phase content in starting powder
s. The strength increased with increasing alpha-SiC content in the starting
powder while the fracture toughness decreased with increasing alpha-SiC co
ntent. There may be a trade-off in improving both the strength and toughnes
s in SiC ceramics sintered with oxide additives.