Boric acid-free electrodeposition process and solar–thermal energy conversion of and Ni-carbon black nanocomposite coatings

Abstract This work focuses on the development of a multi-layered system, of bright nickel electrodeposited on a steel substrate, and a second layer composed of black nickel either with or without carbon black nanoparticles (CB NPs), aiming for an efficient conversion of incident solar radiation into heat, for the fabrication of solar collectors. The structural characterization, revealed that the bright nickel film was composed of metallic nickel, while the black coatings contained amorphous nickel compounds. SEM analysis unveiled the presence of pinholes on the surface of the bright nickel film, suggesting that the black nickel coating was ineffective in sealing them. The appearance of cracks with the increase in the deposition time was observed. With the nanocomposite of black nickel and CB NPs, these cracks can be avoided and the pinholes sealed. The CB NPs were found to reduce reflectance, enhancing the conversion of solar energy into heat. Graphical abstract