Optimized microstructure with nano-alumina and its effects on properties of corundum spinel castables

The mechanical properties, thermal shock resistance, and microstructure evolution of corundum spinel castables with different nano-alumina contents were investigated. The results show that the addition of nano-alumina has advantages on the microstructure evolution and properties of castables. An optimum nano-alumina amount is 2 wt%. When nano-alumina addition changes from 0 to 2 wt%, the cold modulus of rupture (CMOR) and cold compressive strength (CCS) improved by 69.7% and 78.1% after firing at 1100 degrees C, respectively. The CMOR and CCS increased by 42.5% and 35.2% after firing at 1500 degrees C, respectively. Meanwhile, the hot modulus of rupture (HMOR) was enhanced by 21.5% to 13.4 MPa. The retained Young's modulus values of castables were improved from 49.6% to 59.6% after eight thermal shock cycles. Furthermore, the HMOR and the retained Young's modulus values of castables slightly reduced when nano-alumina content up to 3 wt%. XRD, DSC, SEM, and EDS analyses revealed that the addition of nano-alumina leads to the formation of calcium dialuminate (CaO center dot 2Al(2)O(3)) at 1100 degrees C and it is beneficial to the formation of more platelet hibonite (CaO center dot 6Al(2)O(3)) at 1500 degrees C. As a result of using nano-alumina with large surface area, the solid phase sintering of the nanoscale particles can occur at lower temperatures. Moreover, the mechanical properties and thermal shock resistance of the castables were improved remarkably.