|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.
[Keywords: Porous ceramics, Thermal shock, Mechanical strength, Microstructure]