Influence of powder characteristics on the sintering behaviour of reactive alumina powders

Fine reactive alumina powders have a significant impact on the properties of refractories at high temperatures. Except for the hydration of cement and in situ reactions, the performance of castables is also correlated with the sintering of reactive alumina. The characteristics of fine alumina powders produced by various manufacturers are quite different. This work aims to investigate the comprehensive influence of powder characteristics on the sintering behaviour of reactive alumina powders. Three types of commercial reactive alumina powders were selected for experiments. The linear shrinkage, bulk density, apparent porosity and microstructure of alumina compacts calcined at different temperatures were analysed. It was demonstrated that large specific surface area and higher SiO2 content had a positive effect on the densification of alumina compacts. The calculation based on the hypothetical composition of alumina grain boundary indicated that SiO2 mainly participated in the formation of liquid. Therefore, more liquid was generated at the grain boundary of alumina grains containing higher SiO2 content, which resulted in better sinterability of reactive alumina powders.