Amorphous Nanohole Patterns Formed by Spinodal Decomposition of Nickel Superalloys for Solar-Selective Absorbers

Materials with tailored spectral absorptance properties are essential for the effective photothermal conversion of sunlight. This study demonstrates that solar-selective absorption properties can be achieved by the disordered amorphous pattern structures formed by the spinodal decomposition of a nickel superalloy, in contrast to many other techniques of tailoring spectral properties by employing ordered structures such as photonic crystals. The study reveals that short-range ordered structures can be obtained via spinodal decomposition by controlling the annealing conditions. Short-range ordered nanostructures are crucial to achieving high absorptance over a broad range in the solar spectrum and low emittance in the thermal radiation range from the absorber because of the Anderson localization effect. Corresponding to the spectrally selective absorption, the advantages of blackbody-like absorption are demonstrated by analyzing the performance factor of photothermal conversion. Using the spinodal decomposition process, it is possible to fabricate these structures on large-scale areas and nonplanar surfaces. Therefore, this technology is expected to increase the efficiency of various solar thermal energy systems.