文摘
Solar thermal coatings play important role in solar heat utilizations, which is considered as one of the most critical factor in solar thermal system. In the past several years we have researched and developed our coatings based on the destructive-interference absorption principle. The multi-layer structured coating mainly consist of metal layer, double metal-ceramic layers, and ceramic layer, each of the layer functions as infrared anti-reflecting layer, solar spectrum absorber, and transparence enhancing layer, respectively. Meanwhile the degradation of the absorption coatings draw much attentions from either the investor or the researchers because the degradation is also known as the key to understand the service lifetime of the solar thermal receivers. In this paper we present the experimental results of the accelerating testing on the coatings, with or without the involvement of the oxygen from the environment. The analytical experimental results show the macro structure of the coatings were destroyed due to the relaxing of the thermal stress. It also indicates that the oxidation serves as the other main reason for the degradation in the coatings after thousands of hours continuously high temperature annealing in air environment. While in the vacuum case the coatings were annealed for longer time than it had been done in air environment, the optical function of the coatings decreased greatly correspondingly. Series of analytical experiments were done to investigate the process of the degradation. Self-diffusion and reaction diffusion theory were employed to study the structure evolving inside the coatings.
