Ceria doped solar selective coating for solar thermal application

High-velocity oxygen-fuel (HVOF) sprayed WC-Co-Cr based coating has been investigated for possible solar thermal applications. In order to have better performance of the base coating, ceria (CeO2) has been used as the dopant. These coatings have been sprayed on stainless steel (SS-304) substrates and subsequently various investigations are done to understand the metallurgical, mechanical, physical, and solar absorptive characteristics. The investigations primarily include raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA) and solid particle erosion for metallurgical, mechanical and physical characteristics. To understand solar absorptivity and reflectivity from the surface of the sample, UV-vis spectroscopy has been done and results depicted that CeO2 inclusion of enhanced target properties up to significant level. Using HVOF thermal spray method enhanced metallurgical phases are formed in the coating structure which resulted in better erosion and corrosion resistance of the coated surface. Thermal gravimetric analysis of the coated surface depicted that the surface is thermally stable up to 650 K. While, UV-vis spectroscopy revealed an optimal reflectivity of 10.17 % while peak absorptivity of the surface has reached approximately 90 % after CeO2 addition in the base composition. It is also notable that absorptivity and reflectivity of coated stainless-steel (SS) substrate is approximately 76 % and 20 % respectively at 600 nm wavelength, at this wavelength, the photon density is high, and when results of WC-Co-Cr/CeO2 coated substrate are compared to bare SS-substrate (without any coating) it shows an increment of 12 % in absorptivity and 4 % in reflectivity results.