High-temperature AlN and Ti multilayer cermet for solar absorber coating: structural and optical properties

Ti/AlN/Ti multilayer solar absorber coating was deposited on modified stainless-steel substrate using sputtering. The coating was exhibited high solar absorptance (0.896) and low thermal emittance (0.190) with 4.72 selectivity (α/ɛ) in the solar and infrared spectrum, respectively. Similar work using AlN/Ti/AlN/Ti/AlN stacking sequence recorded low solar absorptance (0.82) and high thermal emittance (0.27), respectively, with 3.04 selectivity (α/ɛ). The novelty of the present work is evidenced. The coating was found to be thermally stable up to 500 °C in air. However, the optical properties of the coating were found to degrade at temperature of 600 °C and hence decrease in solar absorptance (from 0.896 to 0.791) and a rise in thermal emittance (from 0.190 to 0.210) were observed. The change in the optical properties is attributed to the decrease in surface roughness which led to increased surface reflectance as probed from AFM analysis.