Preparation and Thermal Shock Resistance of Mullite Ceramics for High Temperature Solar Thermal Storage

Abstract

Mullite thermal storage ceramics were prepared by low-cost calcined bauxite and kaolin. The phase composition, microstructure, high temperature resistance and thermophysical properties were characterized by modern testing techniques. The experimental results indicate that sample A3 (bauxite/kaolin ratio of 5:5) sintered at 1 620 °C has the optimum comprehensive properties, with bulk density of 2.83 g·cm⁻³ and bending strength of 155.44 MPa. After 30 thermal shocks (1 000 °C-room temperature, air cooling), the bending strength of sample A3 increases to 166.15 MPa with an enhancement rate of 6.89%, the corresponding thermal conductivity and specific heat capacity are 3.54 W°(m°K)⁻¹ and 1.39 kJ°(kg°K)⁻¹ at 800 °C, and the thermal storage density is 1 096 kJ°kg⁻¹ (25–800 mullite ceramics; sintering properties; high-temperature thermal storage; thermal shock resistance). Mullite forms a dense and continuous interlaced network microstructure. which endows the samples high thermal storage density and high bending strength, but the decrease of bauxite/kaolin ratio leads to the decrease of mullite content, which reduces the properties of the samples.

Keywords

mullite ceramics / sintering properties / high-temperature thermal storage / thermal shock resistance