Trace nanoscale Al2O3 in Al2O3-MgAl2O4 castable for improved thermal shock performance

Abstract

Al2O3–MgAl2O4 castables are prepared using tabular alumina, fused spinel, α-Al2O3 micro-powder, calcium aluminate cement and nano-Al2O3 particles as starting materials. The effects of trace nano-Al2O3 particles (0.2–0.8 wt%) on the thermal shock resistance (TSR) and microstructure of Al2O3–MgAl2O4 castable are investigated. The results show that trace addition of nano-Al2O3 particles contributes to CA6 crystal development and microstructure optimisation. The platelet CA6 crystals form an interlocking network structure creating a toughening effect, which leads to a significant improvement in TSR. In addition, CA6 formation accompanied by volumetric expansion generates many microcracks, which are beneficial for relieving thermal stress during the thermal shock process and enhancing the TSR of the Al2O3–MgAl2O4 castable.