Fabrication of surface microstructures based on spinodal decomposition for high-temperature solar selective absorbers

Making periodically aligned microstructures with sub-micron size on a refractory metal is one of the promising technologies of increasing solar absorption selectively 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 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 microstructures using spinodal decomposition on a nickel-based superalloy. The surface microstructures were obtained only by appropriate heat treatments and simple chemical etching process. The size of microstructure; i.e. depth, width, can be controlled with heat treatment conditions and etching time. Solar selective absorptance of 0.82 and hemispherical total emittance of 0.31 at 600^oC can be obtained with the proper treatments.