Effect of initial α-phase content on microstructure and flexural strength of macroporous silicon carbide ceramics

Abstract

The effects of the initial α-phase content on the microstructure and flexural strength of macroporous silicon carbide (SiC) ceramics were investigated. When β powder or a mixture of α/β powders containing small (≤3%) amounts of α powder were used, the grains showed a platelet-shape. In contrast, the grains had an equiaxed-shape when α powder or a mixture of α/β powders containing large (≥50%) amounts of α powder was used. The flexural strength increased with increasing α-SiC content in the starting composition, whereas the porosity decreased with increasing α-SiC content. The strength of the macroporous SiC ceramics was affected mostly by the porosity when the grain size was smaller than 10 μm, whereas the strength was controlled by pore size and grain size when the microstructure consisted of large (>10 μm) platelet grains.