Nanoscale toughening of low carbon Al2O3-C refractories by means of SiCnw/Al2O3 composite reinforcement

To improve the thermal shock resistance of low carbon Al2O3-C refractories, SiC nanowires (SiCnw) containing SiCnw/Al2O3 composite reinforcement were introduced. The specific fracture energy of the Al2O3-C refractory matrix was obtained by statistical grid nano-indentation. The reinforcement mechanism of SiCnw/Al2O3 on thermal shock resistance of refractories was investigated. The results revealed that the matrix-specific fracture energy of A6 (6 wt% SiCnw/Al2O3 added) was 217 N/m, which was 58.4% higher than reference sample A0 (137 N/m) and 18.6% higher than MA6 (183 N/m, 6 wt% SiC/Al2O3 added). A6 showed the highest residual strength ratio of 49.8%, which was 114.7 % higher than A0 (23.2%) and 82.4 % higher than MA6 (27.3%). The components with different morphology in SiCnw/Al2O3 cluster, especially SiC nanowires, promote the generation of microcracks, crack multi-deflection, and branching, which toughen the matrix and improve the thermal shock resistance of refractories. In comparison to the literature, A6 showed a higher rising in residual strength ratio than those with higher graphite content (4 wt% and 20 wt%), which will greatly reduce the consumption of carbon-containing refractories and contribute to the reduction of CO2 emission.