Thermal Shock Resistance of Porous Silicon Carbide Ceramics Prepared Using Clay and Alumina as Additives

Porous silicon carbide ceramics were prepared by an in situ reaction bonding process using clay and alumina as additives. The effects of alumina additive, pore former on phase composition, microstructure, flexural strength and thermal shock resistance of the ceramics were studied. Thermal shock resistance of porous SiC ceramics due to cooling was evaluated as a function of quenching temperatures and quenching cycles using water- and air-quenching technique. It was observed that residual strength of the quenched samples in water decreased with increase in the quenching temperature but was almost independent of quenching cycles. In water quenching, the surface of the sample cooled almost instantly but the inside remained hot which created an uneven thermal profile and generated microcracks in the sample; as a result sudden reduction of flexural strength was observed. The results showed that flexural strength and thermal shock resistance properties of the ceramics prepared with alumina are better than those of the ceramics prepared without alumina and the material was found suitable for hot gas filtration application.