How does thermal shock crack ceramic refractory materials?

Thermal shock in ceramic refractory materials occurs primarily during rapid cooling from high temperatures. When a refractory object is subjected to this sudden temperature change, the surface layers contract against the inner layers of the material. This differential contraction generates significant tensile stress, which leads to the propagation of cracks throughout the ceramic structure.1

While ceramics are inherently brittle, their resistance to this phenomenon can be improved by modifying their microstructure during processing. Refractory materials often feature a coarse microstructure containing large filler grains and a high degree of porosity. These structural characteristics can help blunt the tips of developing cracks, thereby reducing the material's overall susceptibility to thermal shock. However, there is a trade-off: while porosity and large grains enhance thermal shock resistance, they can also reduce the load-bearing strength of the refractory and may be undesirable in environments where the material must resist corrosion from molten substances.1