Thermal stability of nitride solar selective absorbing coatings used in high temperature parabolic trough current

This paper reports a new efficient solar selective surface in high temperature application. The influence of the monolayer’s microstructure and deposition rate was firstly discussed. Then the nitride nano-multilayer on the polished stainless steel (herein after referred as “SS”) substrate was prepared with Ti and Al metal targets by DC. and R.F. magnetron co-sputtering. The samples were annealed in air at different temperatures ranging from 350 to 800°C for 2 h to evaluate their thermal stability. The samples’ surface and cross-section morphology, crystal structure, phase composition, optical properties were analyzed by scanning electron microscopy, X-ray diffraction, UV-VIS-NIR spectrophotometer and infrared emissivity tester. The results show that the coatings exhibit high solar selectivity (α/ɛ) of 0.943/0.08 even after heat-treatment up to 400°C for 2 h in air. After heat-treatment at 600°C in air, the solar selectivity decreases to 0.92/0.16.