In Situ Catalytic Synthesis of Si3N4 Nanowhiskers Reinforced SiC Refractories and Their High-Temperature Properties

Abstract

Silicon nitride (Si3N4)–bonded silicon carbide (SiC) refractory (Si3N4-SiC) is one of the most important nonoxide refractories, but its mechanical properties still suffer from the residual Si. Herein, we report that the nitridation of Si and properties of Si3N4-SiC refractories can be improved by in-situ formed CoOx catalysts. The room-temperature modulus of rupture (MOR), high-temperature MOR, thermal shock resistance, and oxidation resistance of as-prepared Si3N4(w)-SiC refractories with catalysts were investigated. The results showed that CoOx catalysts enhanced the nitridation of Si powders and promoted the formation of Si3N4 whiskers. The high-temperature MOR at 1573 K of as-prepared refractories was improved by 30%, compared with samples without catalysts. Moreover, the thermal shock resistance and oxidation resistance of the former was remarkably higher than that of the latter. The improvement was attributed to in-situ formation of Si3N4 whiskers network structure in the samples due to the catalytic effects of CoOx catalysts.