Effects of h‐BN on the thermal shock and oxidation resistance of SiO2‐bonded SiC refractories

Abstract

AbstractIn order to improve the thermal shock and oxidation resistance of the SiO2‐bonded SiC refractories, SiO2‐bonded SiC refractories incorporating h‐BN were prepared. The effects of h‐BN on mechanical properties, thermal shock, and oxidation resistance of the SiO2‐bonded SiC refractories were investigated. The flexural strength of the SiO2‐bonded SiC refractories was significantly increased with the addition of the h‐BN. Sample with 5 wt.% h‐BN addition exhibited highest flexural strength of 65.8 MPa which is much higher than that (30.8 MPa) of the samples without h‐BN addition. Because of the self‐healing caused by the oxidation, inhibited crystallization of the SiO2, and the toughing mechanism introduce by the plate‐like h‐BN, the thermal shock resistance of the SiO2‐bonded SiC refractories were significantly enhanced by the addition of h‐BN. Moreover, B2O3 produced from oxidation of the h‐BN combing SiO2 formed borosilicate glass inhibiting crystallization of the SiO2, thereby forming a more stable protective layer, consequently, the oxidation resistance of the SiO2‐bonded SiC refractories was enhanced. The enhanced thermal shock and oxidation resistance from addition of the h‐BN have important implications for its high‐temperature applications.