Microstructure and phase evolution of alumina–spinel self-flowing refractory castables containing nano-alumina particles

The microstructure and phase composition of alumina–spinel self-flowing refractory castables added with nano-alumina particles at different temperatures are investigated. The physical and mechanical properties of these refractory castables are studied. The results show that the addition of nano-alumina has a great effect on the physical and mechanical properties of these refractory castables. With the increase of nano-alumina content in the castable composition, the mechanical strength is considerably increased at various temperatures. It is shown that nano-alumina particles can affect formed phases after firing. The platy crystals of CA6 are detected inside the grain boundaries of tabular alumina and spinel grains in samples fired at 1500 °C. CA6 phase can be formed at lower temperatures (1300 °C) with the addition of nano-alumina particles. As a result of using nanometer-sized alumina particles with high surface area, the solid phase sintering of the nano-sized particles and CA6 formation can occur at lower temperatures.