Effect of Al2O3 addition on properties of non-sintered SiC–Si3N4 composite refractory materials

•The non-sintering SiC–Si3N4 refractories with Al2O3 addition were prepared.•The Al2O3 additive benefited to enhance compressive and flexural strengths.•The oxidation and cryolite resistance of refractories were improved by adding Al2O3.•The oxidation and cryolite resistance of the matrix were analyzed comprehensively.

Preparation of SiC–Si3N4 composite refractory materials without sintering entails only low energy consumption and incurs little cost compared with traditional preparation methods. This paper investigated the effect of Al2O3 addition on bulk density, apparent porosity, linear shrinkage and oxidation resistance of as-fabricated non-sintered SiC–Si3N4 composite refractory materials. Meanwhile, the compressive and flexural strengths both before and after heat treatment were analyzed. The mechanisms of oxidation resistance and cryolite resistance of the SiC–Si3N4 composite refractory materials are discussed. Increasing amounts of Al2O3 reduced linear shrinkage but increased oxidation resistance and cryolite resistance. Moreover, compressive and flexural strengths initially increased and then decreased, with maximum values achieved at an Al2O3 addition of 8% w/w.

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