Absorption rate and thermal shock resistance of Co₂O₃-Fe₂O₃-mullite-based ceramics for solar heat absorbers

Mullite ceramic materials have a number of excellent properties that make them an excellent choice for solar heat absorber materials in Concentrating Solar Power (CSP) systems. In this study, the effects of adding Co2O3 and Fe2O3 on the properties of mullite-based ceramics were studied, aiming to get excellent absorption rate and thermal shock resistance. The results show that the sample C2 (45.05 wt% 75 calcined bauxite, 45.05 wt% Suzhou clay, 9 wt% Fe2O3, 3 wt% Co2O3) sintered at 1400 degrees C has the best comprehensive performance, with a bending strength of 143.28 MPa and a solar absorption rate of 92.2 % in the wavelength range of 0.3-2.5 mu m. The bending strength increased by 31.36 % after thermal shock cycles for 30 times (1000 degrees C similar to room temperature, air cooling). Generation of iron cobalt spinel and lattice distortion caused by Fe3+ and Co3+ into the mullite lattice combined to promote the absorption rate. In the meantime, the main crystalline phase columnar mullite showed a tight continuous interlaced network structure. The fracture mode was mainly transgranular fracture, which endowed C2 excellent thermal shock resistance.