Thermal shock resistance of fibrous monolithic Si3N4/BN ceramics

Thermal shock resistance of fibrous monolithic Si3N4/BN ceramic was investigated by measuring the strength retention after varying the temperature difference (ΔT) up to 1400 °C and was compared with that of monolithic Si3N4. Monolithic Si3N4 showed catastrophic drop in flexural strength above ΔT of 1000 °C, while FM showed negligible reduction in flexural strength without critical temperature difference (ΔTc). Two parameters, such as the resistance to crack initiation (R′) and crack propagation (R⁗), were used in order to explain the thermal shock behaviors of fibrous monolith and monolithic Si3N4. Furthermore, crack interactions during flexural testing, such as delamination cracks and crack deflection, were characterized and were related to the work-of-fracture (WOF).