Effect of ZrO2-MoO3 on the properties of in situ synthesized corundum-mullite composite thermal storage ceramics

Based on the requirements for solar thermal storage materials, thermal storage ceramics must possess not only excellent thermal storage and thermal conductivity but also high strength and thermal shock resistance. This study investigates the effects of zirconia-molybdenum oxide composite additives on the properties of corundum-mullite composite ceramics. It has been shown that at high temperatures, the solid solution formed by the reaction between MoO 3 and Al 2 O 3 decomposes to generate highly reactive nano-sized alumina grains, which not only promote the densification process of the matrix but also act as a second phase to form an “intragranular” structure within the corundum grains. The “intragranular” structure, along with the presence of added zirconia, significantly enhances the mechanical and thermal shock resistance of the samples. After sintering at 1650 °C, the water absorption, porosity, bulk density, bending strength, thermal conductivity, and thermal storage density of the C3 sample containing 4 wt.% ZrO 2 and 3 wt.% MoO 3 were measured as 0.26%, 0.93%, 3.55 g/cm³, 245.06 MPa, 10.13 W·(m·K)⁻ 1 (25 °C), and 1363.54 kJ·kg⁻ 1 (1000 °C). After undergoing 30 thermal shocks, the bending strength of the C3 sample increased by 9.13%, reaching 267.44 MPa.