Selective surfaces of black chromium for use in solar absorbers

Abstract

One of the applications of selective surfaces is to improve performance of solar absorbers. The purpose of this work is to produces selective coatings with high absorption of solar radiation in the range of UV/Vis/NIR. It was prepared a selective surface composed of black chromium (Cr/Cr2O3) deposited on substrates of AISI 304 stainless steel using the technique of electrolytic deposition for application in solar thermal absorbers. The great parameters for deposition consisted of a continuous electric current of 2A for 90s, at a constant temperature of 40°C. After deposition, the samples under went to a heat treatment at 600°C for 2h for oxidation. The coatings thicknesses were determined. From the SEM analysis coupled with EDS, it was found that the microstructures reported sample of cermets. The XRD results show diffraction peaks related to metallic chromium (Cr) and chromium oxide (Cr2O3). Spectral absorptance values more 90.0% were found.