Preparation and characterization of corundum-based ceramics for thermal storage

Abstract

Corundum-based ceramics were prepared by two methods. The first used Fe2O3 and TiO2 as additives to react with α-Al2O3. The second made full use of Al2O3, SiO2 and TiO2 in calcined bauxite, and Fe2O3 was used as an additive. The SiO2-TiO2-Fe2O3 system was designed to influence corundum. The effects of Fe2O3, TiO2 and SiO2 on physical properties, phase transformation, microstructure, thermophysical properties and thermal shock resistance were investigated. Results showed that Fe2O3 and TiO2 realized densification sintering through entering in the lattice of corundum, and the solubility of Fe2O3 was higher than that of TiO2. In addition, the excess TiO2 tend to synthesize iron aluminum titanate in the grain boundaries, which could refine the grains and improve the mechanical properties. The SiO2-TiO2-Fe2O3 system reduced significantly the sintering temperature, but the imperfect microstructure impaired the properties. Corundum-based ceramics prepared by Fe2O3, TiO2 and α-Al2O3 had the optimal properties. The thermal conductivity and thermal storage density were 14.81 W/(m·K) (25 °C), 837 kJ/kg (25–800 °C), respectively. No cracks were formed after 30 thermal shock cycles (1100 °C-room, air cooling), and the bending strength increased by 2.59%. This study supports the application of corundum-based ceramics as a promising thermal storage candidate.