Thermal shock resistance and oxidation resistance of MgAl2O4–Si3N4 ceramics for solar thermal absorber: The effects of TiO2 additive content.

TiO 2 is employed to improve the performance of pressureless sintered MgAl 2 O 4 –Si 3 N 4 ceramics in this study, aiming to make the ceramics more suitable for solar thermal absorbing materials in concentrating solar power. Effects of TiO 2 content on the microstructure and properties of the composites were the focus, especially the thermal shock and oxidation resistance. The results show that composite with 2 wt% TiO 2 sintered at 1620 °C has the highest bending strength exceed 320 MPa, which contributes to resist the thermal stress. Instead of being damaged after 30 thermal shock cycles (ΔT ≈ 1100 °C), the bending strength of the sample increases 12.03%. The weight gain rate is only 0.8964 mg/cm2 when finishing the oxidized process at 1300 °C for 100 h, and the oxidation kinetic obeys the parabolic low. Solar absorptance and thermal conductivity of the composite reach 93.5% and 13.27 W/(m·K) respectively. MgAl 2 O 4 –Si 3 N 4 composite can be presureless sintered at lower temperature, and it has better high temperature stability than Si 3 N 4 and SiC ceramics prepared via the same procedure, which makes it an ideal choice for solar thermal absorbing material. [ABSTRACT FROM AUTHOR]