Effect of different silicon sources on the properties of in-situ synthesized corundum-mullite composite thermal storage ceramics

Abstract

Thermal storage materials are typically made of materials with high thermal storage density, high thermal conductivity and high temperature stability. In this study, corundum-mullite composite thermal storage ceramics were prepared by solid-phase sintering using widely available and low-cost α-Al2O3, kaolin, and quartz as raw materials. The effects of silicon source and Al2O3/SiO2 ratio on the physical properties and structural properties of corundum-mullite composite ceramics were investigated. The results showed that the A3 sample (α-Al2O3: 85.77 wt%, kaolin: 14.23 wt%) after sintering at 1650 °C had the excellent performance, with thermal conductivity of 15.01 W (m K)−1 (25 °C), thermal storage density of 965.15 kJ kg−1, and bending strength of 145.9 MPa. The multiple ions introduced by kaolin can effectively promote the liquid-phase mass transfer at high temperatures, accelerate the diffusion rate of Si4+, increase the growth rate of mullite, and accelerate the densification process of the samples, which in turn improves the physical properties of the samples. When used in a solar thermal storage system, the A3 sample per unit volume can provide 911.53 kW h of electricity to the grid, saving 112.12 kg of coal and reducing 358.78 kg of CO2 emissions.