Fabrication of porous SiC ceramics through a modified gelcasting and solid state sintering

With starch as pore forming agent, porous silicon carbide (SiC) ceramics were successfully fabricated by gelcasting. A novel and simple gelling system of isobutylene and maleic anhydride (Isobam) can gel in air at room temperature was used. The rheological behaviors of SiC slurries were investigated as a function of starch content. The gelled SiC green bodies were sintered at 2050-2150 °C through solid state sintering with B4C and carbon as sintering additives. Porosity of the porous SiC ceramics sintered at 2100 °C was well controlled from 34.20% to 42.68% with the starch content increasing from 0 to 20 wt%. With increasing the sintering temperature from 2050 to 2150 °C, flexural strength and porosity of porous SiC ceramics with 20 wt% starch varied from 61.0 to 128.0 MPa and 48.1% to 34.2%, respectively. The porous SiC ceramics fabricated with 20 wt% starch addition and sintered at 2100 °C were proved to possess excellent thermal shock resistance. The ceramics after water-quenching at 1500 °C showed an average flexural strength of 95.8 MPa, which was higher than the strength of samples without quenching.