Enhanced thermal stability of solar selective absorber based on nano-multilayered TiAlON films deposited by cathodic arc evaporation

Abstract

Titanium-nitride/oxynitride-based coatings have great potential for solar selective absorber applications in high temperatures. However, the recent developed absorbers suffered from poor thermal stability due to the columnar structure in these coatings. In this paper, we reported a solar selective absorber with excellent thermal stability up to 550 °C in air environment. The absorber with three-layered structure was constructed by nano-multilayered TiAlON films deposited by cathodic arc evaporation. We obtained the optical constants of the TiAlON films by carefully modelling the R and T spectra, and then based on the optical constants we built a three-layered structured solar selective absorber with a solar selectivity of 0.936/0.170. After heat-treatment at temperature of 550 °C for 50 h, only slight changes in optical performances could be detected, indicating the high thermal stability of the absorber. The high thermal stability could be attributed to the nano-multilayered structure in the TiAlON films, thus completely eliminating the columnar structure and suppressing the oxygen or nitrogen diffusion in the film. These results suggested that the TiAlON-based solar selective absorber could be possibly applied to concentrated solar thermal systems with temperature up to 550 °C.