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Higher working temperatures could help to improve the solar-electricity efficiency of concentrating solar power plant. However, the high temperature also induces structure variations and optical degradation of solar absorbers, and how the structure evolutions affect the optical performances remains largely unclear. To address the problems, we conducted cyclic heat-treatment on the AlCrSiO-based solar selective absorbers at a temperature of 650 °C. Then the microstructures and optical properties of the absorbers before and after annealing were systematically investigated. Finite-Difference Time-Domain simulations were used to establish the relationships between the microstructures and optical properties. The results showed that the absorber can maintain its multilayered structure after cyclic heat-treatment at 650 °C in air with a solar selectivity of 0.928/0.171. Oxidation of micro-droplets on surface can enhance solar absorption in the UV–Vis region due to the reduction of backscattering. The weak oxidation of the absorbing layers would lead to the enhancement of interference effects in the whole solar spectrum. The combination of the above effects can actually enhance the solar absorptance. The diffusion of carbon from the substrate into the infrared reflective Cr layer would slightly improve the thermal emittance. These results suggested the AlCrSiO-based solar selective absorber can be a possible candidate for applications in the next-generation concentrating solar power plant system. • AlCrSiO-based solar absorber exhibited thermal stability at 650 °C in air with a selectivity of 0.93/0.17. • Oxidation of micro-droplets on absorber surface enhanced solar absorption in UV–Vis region. • Weak oxidation of absorbing layers led to enhancement of interference effects in whole solar spectrum. [ABSTRACT FROM AUTHOR]

The hydrolysis reactions of anhydride have been frequently used as important model reactions for thermal hazard study. The anhydride hydrolysis reactions are commonly heterogeneous liquid–liquid systems due to the low solubility of anhydride in water. However, since the hydrolysis product, namely organic acid, can increase the solubility of anhydride in water, the anhydride hydrolysis reaction will become homogenous with the reaction progressing. Meanwhile, an apparent autocatalytic feature could be observed in these hydrolysis reactions. This phenomenon brings a great challenge to model the anhydride hydrolysis reactions. In this article, the hydrolysis of propionic anhydride (PA) was taken as a model reaction to study. A reaction model considering both the reaction kinetics and anhydride solubility has been developed on the basis of the reaction mechanism. The reaction process and model parameters were studied using a real-time reaction calorimetry method. The hydrolysis reaction has been confirmed to be kinetically controlled by calculating the Hatta number and studying the influence of stirring speed on the heat flow profiles. The accuracy of this model has also been confirmed by comparing the simulated and experimental heat flow profiles. More importantly, the reason for the autocatalytic behavior of this hydrolysis reaction has been proven to be the enhanced concentration of PA in the aqueous phase, not the hydroxonium ion produced from the dissociation of propionic acid in the aqueous phase. [ABSTRACT FROM AUTHOR]

Higher operating temperature of concentrating solar power plant could help to improving the solar-electricity conversion efficiency. However, solar selective absorber with stability higher than 700 °C is still lacking. Here, we explored the potential of a tandem structure absorber of TiN/Ti 0.5 Al 0.5 N/Ti 0.33 Al 0.67 N/CrAlSiO. The as-deposited tandem absorber had a solar selectivity of 0.887/0.134, which was maintained at 800 °C for 1 h. With the annealing temperature increasing from 800 °C to 1000 °C, the solar absorptance first slowly decreased from 0.887 to 0.866, then dramatically decreased to 0.7 after annealing at 1100 °C. Optical simulation indicated that thermal annealing would induced higher optical constants both for the Ti 0.5 Al 0.5 N and Ti 0.33 Al 0.67 N layers, which is caused by the spinodal decomposition of the cubic TiAlN phase. While the thermal emittance slightly increased from 0.134 to 0.154, as the TiN IR reflector maintained its layer structure even up to 1100 °C. • TiN/Ti 0.5 Al 0.5 N/Ti 0.33 Al 0.67 N/CrAlSiO solar absorber with a selectivity of 0.887/0.134 was stable at 800 °C for 1 h. • Higher annealing temperature induced phase decomposition in cubic TiAlN, and resulted in decrease of solar absorptance. • The absorber remained a low thermal emittance of 0.15 up to 1100 °C with TiN IR reflector. [ABSTRACT FROM AUTHOR]