Microstructure and properties of porous silicon carbide ceramics fabricated by carbothermal reduction and subsequent sintering process

Porous silicon carbide (SiC) ceramics were prepared from a carbon-filled polysiloxane by carbothermal reduction and subsequent sintering process. Their microstructure, pore size distribution, compressive strength, and flexural strength were evaluated as a function of sintering temperature. The grain morphology was transformed from small, equiaxed grains to large, platelet grains with increasing sintering temperature. The porosity decreased with increasing sintering temperature from 55% for the 1800 °C-sintered specimen to 40% for the 1950 °C-sintered specimen, while the pore size distribution ranged from 0.003 to 30 μm. The volume fractions of both submicron- and micron-size pores decreased significantly with increasing sintering temperature. Both compressive and flexural strengths were increased with increasing sintering temperature, due to both the decreased porosity by densification and the strut strengthening by necking at higher temperatures.