Effect of removal of silicon on preparation of porous SiC ceramics following reaction bonding and recrystallization

Porous α-SiC ceramics with distributed pore structure were prepared by recrystallization method using silicon as the template. The microstructure evolution of this material (sintered at 2100 °C) was investigated by varying particle size of the silicon powders (3.5 μm and 37 μm). The results demonstrated that finer silicon powder could strengthen grain growth along close-packed directions and made the material easily to form plate-like SiC crystals. Pore diameter was mainly controlled by silicon raw powder when the silicon had a greater median diameter value than the SiC powder. In this study, grain growth was determined by a mixed mechanism during silicon removing. The porosity increased with the increasing of silicon contents while the strength was in a reverse proportional relationship. High porosity ceramics with relative high strength, which were sintered at 2100 °C for 15 min, were obtained using 3.5 μm silicon powder as the template.