Transition metal based CuxNiyCoz-x-yO4 spinel composite solar selective absorber coatings for concentrated solar thermal applications

Solar selective absorber coatings, combining of nanostructured, ternary transition metal spinel structure and composite oxides were prepared by a series of transition metal (Co, Ni and Cu) based nitrate salts. A single layered structure of crystalline phase spinel-type oxide AB(2)O(4) in the framework of simple wet chemical route and dip coating method was prepared in the crystalline structure of CuxNiyCoz-x-yO4. The X-ray diffraction profile of the oxide film was found to coincide with that of crystalline [Cu0.3122+Co0.163+Co0.532+]A[Cu0.172+Ni0.163+Co1.673+]BO4 in the ICDD database. Precursor salts were heated at a particular temperature to form hydroxy nitrate solution followed by suitable solvent with different binders to form adherent sol for dip coating technique. By optimizing sol concentration, withdrawal speed and annealing temperature, uniform absorber layer with solar absorptance of 0.91 and emittance of 0.14 were achieved in a single layer coating with a composite oxide formation. The optical, structural and morphological properties of the optimized coatings of single layer CuxNiyCoz-x-yO4 spinel and composite oxide have been characterized by UV-Vis-NIR spectrophotometer, emissometer, X-ray diffraction, field emission - scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy.