Structure, optical properties and thermal stability of SS/TiC–ZrC/Al2O3 spectrally selective solar absorber

Abstract

A tandem layer structured SS/TiC–ZrC/Al₂O₃ coating has been prepared by magnetron sputtering as a high temperature spectrally selective solar absorber. The coating consists of two layers; a TiC–ZrC layer and an Al₂O₃ layer. TiC and ZrC ceramics show inherent spectral selectivity, which is used to design spectrally selective solar absorbers. A co-sputtering technique was used to fabricate the absorptance layer (TiC–ZrC). The coating exhibits a high absorbance of 0.92 and a low emittance of 0.11, as well as good thermal stability with a selectivity of 0.92/0.13 even after annealing at 700 °C for 100 h under vacuum. The SS/TiC–ZrC/Al₂O₃ coating also shows good thermal stability at 400 °C for 5 h in air. The surface morphology, composition, structure and optical properties of the coating were characterized using SEM, XPS, XRD, Raman spectroscopy, UV-vis-NIR spectrophotometry and Fourier transform infrared spectroscopy. Benefiting from these advantageous features, the as-deposited SS/TiC–ZrC/Al₂O₃ coating can be a good candidate for concentrated solar power applications.