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.