Abstract: The disclosure provides an improved solar selective multilayer coating having higher thermal stability and a process therefor. According to the disclosure, a tandem stack of three layers of TiAlN, TiAlON and Si3N4 is deposited on metal and non-metal substrates using a planar reactive magnetron sputtering process. The first two layers function as the absorber and the third antireflection layer further enhances the coating's absorptance. The solar selective coatings were annealed in air and vacuum to test the thermal stability at different temperatures and durations. The coatings deposited on copper substrates are stable in air up to a temperature of 625° C. and exhibit higher solar selectivity and these coatings also show no change in the absorptance and the emittance values even after vacuum annealing at 600° C. for 3 hours. The solar selective coatings exhibit high hardness, high oxidation resistance, chemical inertness and stable microstructure.

Abstract: The present invention provides an improved solar selective multilayer coating having higher thermal stability and a process for the preparation thereof. Solar selective coatings having higher thermal stability are useful in solar steam generation, solar steam turbines to produce electricity and also on automobile engine components. In the present invention, a tandem stack of three layers of TiAlN, TiAlON and Si3N4 is deposited on metal and non-metal substrates at room temperature using a planar reactive direct current magnetron sputtering process. The first two layers function as the absorber and the third antireflection layer further enhances the coating's absorptance. The solar selective coatings were annealed in air and vacuum to test the thermal stability at different temperatures and durations. The coatings of the present invention deposited on copper substrates are stable in air up to a temperature of 625° C.