Thermal shock behavior of porous ZrB₂-SiC ceramics

Porous ZrB₂-SiC (ZS) ceramics with different microstructures were fabricated by partial hot-pressing or pressureless-sintering, in order to obtain high thermal shock damage resistance. Their thermal shock behavior was investigated by water-quenching. The influences of various microstructural characteristics: porosity, pore size and sintering degree, on mechanical properties were investigated in detail, and their effects on critical crack size, critical thermal shock temperature (δT_c) and residual strength retention rate after thermal shock were also discussed. The pressureless-sintered ZS with 11% porosity had an optimum configuration of porosity and pore size, and exhibited the best combination of mechanical properties and thermal shock damage resistance. No cracks were visible under the scanning electron microscope on the surfaces of this specimen after thermal shock, showing its excellent structural stability.