Cr-(CrN/TiAlN)(m)-AlSiN-AlSiO open-air stable solar selective coating for concentrated solar thermal power applications

摘要

A novel spectrally selective multilayer coating: Cr-(CrN/TiAlN)(m) -AlSiN-AlSiO on SS316 substrate/tube was deposited via Cathodic Arc Physical Vapor Deposition (CAPVD) technique. The coating exhibited state-of-the-art absorptivity (alpha = 0.95-0.96) and emissivity (epsilon = 0.09-0.11). In view of open-air solar thermal application requirements, the coating has been systematically analysed for its thermal, environmental (corrosion) and mechanical stability. The thermal cycling studies carried out at 500 degrees C in open-air conditions have shown no change in optical properties for about 150 cycles. Further, accelerated thermal aging tests have shown an extrapolated service life of 25 years at 411 degrees C. In the case of corrosion studies, up to 520 h of exposure to 5% NaCl medium, no considerable change in optical properties was observed. Further, the coatings were well adherent to the substrates/tubes (6 N of critical load) with a considerable hydrophobicity (104 degrees contact angle). The observed results indicate that, Cr-(CrN/TiAlN)(2)-AlSiN-AlSiO coating may be a good choice for developing receiver tubes used in Concentrated Solar Power (CSP) systems with best solar selective properties and the capability to withstand harsh environments like solar flux variations, thermal shocks in the presence of open-air pollutants, dust and humidity.