A class of inorganic-oxide solar absorbers, prepared as bulk optical coatings by hydrothermal and co-precipitation ceramic methods to produce nanopowders, are stabilized to specific uni-metallic and poly-metallic phase configurations by pelletizing the inorganic reaction products and annealing them at elevated temperatures to ensure air-stability and high-temperature operation. These intrinsic absorbers, or homogeneous coating types that limit spectral intensity distributions of incident electromagnetic radiation compared to their multilayer counterparts, generally have easier manufacturability and deposition requirements at the cost of substandard absorptance capability. However, chemical reaction modifications to introduce surface texturing to the material can boost the overall solar absorptivity. For many energy applications these light-trapping structures correlate directly to increases in solar conversion efficiency and supporting spectrally-selective behavior, improving overall solar insolation from absorptivity in the UV-visible spectral ranges and limiting re-radiation of waste heat. In this work, two types of inorganic uni-metallic coatings (CuO and Co3O4) and two bi-metallic coatings (Cu0.15Co2.84O4 and Cu1.5Mn1.5O4), having been synthesized for solar energy applications, are analyzed via optical microscopy and field-emission scanning electron microscopy (FESEM) to determine approximate morphology at various spatial scaling. To infer the spectral absorptive performance of these coatings, we predict the extent of optical scatter based on image processing of microscopy data, correlating this data to the materials’ scattering events using a first-order Harvey-Shack scattering model and differential raytracing methods. Simulated scatter contributions are verified experimentally to the spectral irradiance profile of the material, therefore detailing how optimized surface structuring can best enhance solar absorptivity and the chemistry of synthesizing such coatings.

Scatter function determination of high-temperature, inorganic oxide solar absorber coating morphology

255th National Meeting (2018)

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