Improved oxidation resistance of Al2O3-SiC-C castables by introducing a small amount of andalusite fine powder.

In our previous study, high amounts of andalusite aggregates (about 19%) were used to improve the oxidation resistance of Al2O3-SiC-C castables, attributed to the transformation of andalusite. However, for andalusite aggregates with large particle size, only a small part of the silica-rich glass phase (about 20%) is extruded onto the surface of the particles to block the pores. Theoretically, the smaller particle size promotes the conversion of andalusite, and more silica-rich glass phase would be extruded to the particle surface to block the pores in the castables, which is speculated to favor the enhancement of the oxidation resistance of the castables. Therefore, in this work, andalusite fine powder (<0.055 mm) was employed to substitute the same-weight proportion of fused brown corundum fine powder in the castables. The results demonstrate that a small amount of andalusite fine powder can achieve the similar antioxidation enhancement compared with high addition content of andalusite aggregate. And the properties of castables fired at different temperatures proved that the thermal decomposition of andalusite fine powder into silica-rich glass and mullite is the key reason of elevated oxidation resistance as well as the improvement of strength and thermal shock stability. [ABSTRACT FROM AUTHOR]