Structure and thermal stability of spectrally selective absorber based on AlCrON coating for solar-thermal conversion applications

Abstract A novel four-layered Mo/AlCrON(HMVF)/AlCrNO(LMVF)/AlCrOx tandem coating was designed and fabricated by cathodic arc ion plating for solar-thermal conversion applications. The chemical composition, structures and thermal stability of the coating were systematically investigated by SEM, EPMA, XRD, TEM, XPS and Raman. The optical properties of the as-deposited and annealed coatings were measured by spectrophotometers. The high-temperature emittance of the coating was measured by a steady-state measurement system. Results showed that tandem coating exhibited a high solar absorptance of 0.921, and a low emittance of 0.12 at 25 °C, as well as emittance of 0.26–0.35 at temperatures range of 300−519 °C. The structure analysis showed that the nano-multilayered structured HMVF and LMVF layers, acting as the main absorber, were consisted of the Cr 2 Al nanograins embedding in the amorphous AlCrON phases. While the top AlCrOx layer was amorphous in nature, and could act as an antireflection layer. After heat-treatment at 600 °C in air for 7 days, only slight microstructure changes were observed from the tandem coating, and very similar solar selectivity of 0.922/0.14 to the as-deposited one was obtained, which indicated the relatively good thermal stability of the coating. These results indicated that the coating could be possibly applied to the high temperature solar-thermal conversion system.