Effect of different carbon allotropes on optical properties of CoCuMnOx solar selective coating

Abstract

This study investigates the inclusion of different forms of carbon in CoCuMnOx solar selective coating via the low-energy consumption method “sol-gel technique”. The usage of carbon as an additive in CoCuMnOx was an attempt to enhance the spectral selectivity. Four allotropes of carbon (graphene nanoplatelets (GNP), carbon nanotubes (CNT), graphite, and charcoal) were embedded in the selective coating with different concentrations and then were deposited on smooth and roughened stainless-steel sheets. In an additional attempt to improve CoCuMnOx selectivity, three different coatings (silica, charcoal@silica, and CNT@silica) were individually applied on top of it. Each carbon allotrope showed distinct structural and optical properties of the coating. Using charcoal as an additive achieved a solar absorptance of 0.964 and a thermal emittance of 0.095, thus providing superior optical properties compared to the other allotropes. The characteristics of the coatings were detected by X-ray diffraction, Energy Dispersive X-Ray analysis, and Scanning Electron Microscope.