Thermal shock resistance and dimensional stability of zirconia-corundum-mullite composites for solar thermal storage

Abstract

Zirconia-corundum-mullite composites were prepared from andalusite, ZrO2, and α-Al2O3 and evaluated for application as solar thermal storage materials in this study. The effects of ZrO2 concentration (0–25 wt%) and sintering temperature(1500–1650°C) on the bending strength, phase composition, microstructure, dimensional stability, and thermal shock resistance of the samples were investigated. The results showed that sample C2 (containing 10 wt% ZrO2) sintered at 1600°C exhibited the best properties. A portion of Y2O3 existed in ZrO2, which excited a small amount of t-ZrO2 in the sample after sintering, while the other portion of Y2O3 was separated from ZrO2 and participated in the formation of a high-temperature liquid phase. The liquid phase reduced the dimensional stability of the sample. However, the liquid phase could also promote sintering, reducing the optimal sintering temperature, with lower sintering temperatures increasing the dimensional stability of the sample. Once again, the C2 sample exhibited the highest thermal shock resistance, with a strength loss of 2.76 MPa after 30 thermal shock tests. The thermal storage density(25–1100°C) of C2 was 1121 kJ/kg. In summary, sample C2 exhibits a high degree of dimensional stability and thermal shock resistance and can thus be used as a reliable solar thermal storage material.