High-temperature photonics using self-organization of superalloys for solar selective absorbers

Making surface microstructures on refractory metal is one of the promising technologies of controlling optical property at high-temperature condition. However, the technique of fabricating microstructures for refractory metal is limited, such as using semiconductor technologies. Therefore, the large-area fabrication of periodic microstructures on refractory metals is a key technology supporting the practical application of controlling optical property using surface microstructures. This report describes large-area fabrication of two-dimensional submicron quasi-periodic microcavities using self-organization on a nickel-based superalloy. The surface microcavities on a bulk metal were obtained by appropriate heat treatments and simple chemical etching process. The spectrally selective property attributed to the confined modes inside cavities is observed. The selective absorbing property and thermal stability are also confirmed at 973 K. Therefore, this fabrication method can be applied for high temperature solar selective absorbers. The fabricated sample showed solar absorptance of 0.74 and emittance of 0.25 at 873 K. The performance of solar selective absorber is verified by simple heating test using the sample with randomly arrayed microstructures. It is indicated that the temperature of microstructured sample shows 30oC higher than that of a black-painted sample.