Effects of porosity and pore size on mechanical and thermal properties as well as thermal shock fracture resistance of porous ZrB2–SiC ceramics

Abstract

Porous ZrB2–SiC (ZS) ceramics with different volume fractions of porosity, i.e. 8.7%, 17.9% and 27.3% and different mean pore diameter, i.e. 2.21, 3.65 and 4.23μm, were fabricated using partial hot pressing, in order to investigate the effect of the porosity and pore size on their mechanical and thermal properties as well as thermal shock performance. Particular emphasis was placed in the study on thermal shock fracture resistance. The critical temperature difference, ΔTc, of porous ZS herein was found to increase slightly with increasing porosity. This phenomenon is inconsistent with most previous researches on other material systems. However, it was well explained from the viewpoints of both physical properties and microstructures of the material, which provides new perspectives and a deeper understanding of how porosity and pore-size affect ΔTc. The ΔTc was also observed to increase as pore size decrease. It could tailor the thermal shock resistance of ZS ceramic and obtain porous ZS ceramic with both high thermal shock fracture resistance and high thermal shock damage resistance, using the above porosity and pore-size dependence of physical properties.