The effect of annealing under non-vacuum on the optical properties of TiALN non-vacuum solar selective absorbing coating prepared by cathodic arc evaporation

TiAlN solar selective absorbing coatings which were deposited on 304L stainless steel using cathodic arc evaporation method were annealed under non-vacuum at different temperatures with different times. The optical properties (absorptance and emittance) of the coatings were measured by a spectrophotometer. It was found that, after being annealed for 2 hours at different temperatures, the absorptance of the coatings reached the highest value of 0.92 at 700 °C while the emittance got the lowest value of 0.38 at 800 °C. When the coatings were annealed at 600 °C for 24 hours, the optical properties changed to 0.92/0.44 (absorptance/ emittance). By measuring the structure, morphology, elements and surface roughness of the coatings, it was found that both the elemental composition and the surface roughness of the coatings changed as a result of annealing, and these changes caused the change of the optical properties of the coatings.