Solvothermal Synthesis of Cobalt and Copper Sulfides Nanoparticles with High Light Absorptance for New Solar Selective Coatings

New selective coating materials are developed and used in advanced solar collector and absorber designs with improved efficiency. Cobalt and Copper sulfides nanoparticles are high interest for absorbers of solar thermal collectors due to their optical properties and high absorptance in the solar wavelength range (> 96%). In the present work, Cobalt and Copper sulfides nanoparticles were synthesized successfully via a surfactant-assisted solvothermal process. The structural, morphological and optical characteristics of as-synthesized materials were investigated by X-ray diffraction, field emission scanning electron microscopy and diffuse reflectance spectroscopy.Evaluation of the obtained results indicated that the as-synthesized nanoparticles had well-defined morphology with very fine particles and higher light absorption in UV/vis region not only than the common inorganic pigments but also than common carbon black. Copper sulfide exhibited integral solar absorptance value equal to 0.97 that is very ideal for solar thermal collectors and thermal selective coatings. They also had low thermal emittances equal to 0.14 and 0.27 for cobalt and copper sulfides respectively.