Oxidation resistance of andalusite-bearing Al2O3–SiC–C castables containing reduced anti-oxidant

Abstract

Our work previously found that the addition of andalusite aggregate enhanced the oxidation resistance of Al2O3–SiC–C castable. Therefore, it is speculated that the addition of andalusite can reduce the dosage of anti-oxidant. In this work, decreasing amounts of anti-oxidant Si (1.5 wt% - 0 wt%) are employed to further reveal the influence of andalusite aggregate on the oxidation resistance of Al2O3–SiC–C castable. The oxidation resistance of the specimens is evaluated by the oxidation index after the thermal shock resistance test. The phases composition of the castables were characterized via XRD, and its microstructures were tested via SEM. The Al2O3–SiC–C castables containing andalusite aggregate and reduced amount of antioxidant Si demonstrate better oxidation resistance as the SiO2-rich liquid glass from andalusite transformation enters the pores under capillary force, blocks the pore channels and thus prevents the inward diffusion of oxygen. Additionally, partial silica-rich liquid glass produced by the converted andalusite particle would have a reaction with Al2O3 in the castables to form secondary mullite, contributing to a denser structure, which is also conducive to blocking oxygen entry and consequently improving the oxidation resistance of the castables.