EFFECTS OF POROSITY ON THERMAL SHOCK RESISTANCE OF SILICON NITRIDE CERAMICS

摘要

A water-quenching technique was employed to investigate the effect of porosity on the thermal shock behavior of Si_3N_4 ceramics. It is shown that the critical temperature difference for crack initiation decreases with increasing porosity. However, the presence of more pores increases the resistance to crack propagation. In low-porosity Si_3N_4, crack was observed to propagate catastrophically. In contrast, highly porous Si_3N_4 ceramics exhibited a quasi-static crack propagation and thus a gradual reduction in strength with quenching severity.