Solar Performance Analysis of ZrOx/ZrC-ZrN/Zr/SS Spectrally Selective Coating Under Extreme Thermal Environment

ZrOx/ZrC-ZrN/Zr absorber-reflector tandem solar selective coatings (ARTSSCs) on stainless steel (SS) substrates are investigated under extreme thermal conditions. The deposited coatings are heated upto 900 °C at 5 °C/min heating rate in nitrogen and air environments to explore the structure-property correlation and their impact on thermal degradation. We observed that tetragonal, monoclinic and cubic zirconium oxide phases are present only for heat-treated ARTSSC structures, suggesting the partial conversion of nitride and carbide phases from absorbers layer of as-deposited structures. Surface roughness ~13.75 nm, in as-deposited structures, has increased upto 22.67 ± 0.05 nm and 26.21 ± 0.08 nm in nitrogen and air heat-treated coatings, respectively. This increased surface roughness and dominant zirconium oxide phases, in heat-treated ARTSSCs, resulted into poor hardness ~13.3 GPa and ~6.64 GPa for samples heat treated in nitrogen and air ambient, with respect to ~18.88 GPa for as-deposited structures. Such degradations have impact on spectral emissivity, which enhanced upto 0.25 and 0.28 for heat-treated ARTSSCs structures in nitrogen and air ambient, with respect to 0.04 for as-deposited coatings.