Characterization of high absorbance and high-emissivity black Ni[sbnd]Ce oxide composite coatings produced via photo-assisted electrodeposition

Abstract

Q235 steel, whose nominal composition (wt%) is 0.14–0.22 C, 0.30–0.65 Mn, ≤0.30 Si, ≤0.045 P, ≤0.055 S and Fe balance, has played an important role in the development of human history and the establishment of modern industry due to its excellent mechanical and engineering performance. In this study, black NiCe oxide composite coatings were electrodeposited on Q235 steel under photo-illumination and the effect of potential was studied. A 300 W ultra-high power xenon lamp with 300–2500 nm wavelength was the light source and provided 220,000 Lux irradiation intensity. After deposition of 40 min, black, uniform, and compact coatings were obtained; their colour gradually deepened when the potential changed from −0.7 to −0.9 V vs. saturated calomel electrode. The composite coatings improved the corrosion resistance of the substrate. Ni and Ce(III) content in the composite coating increased, whereas the hardness decreased at a more negative deposition potential. A black composite coating with both high absorptivity and high emissivity was obtained at a deposition potential of −0.8 V with photo-illumination, which exhibited an emissivity of 0.846 and absorptivity of approximately 95 % in the ultraviolet band, 90 % in the visible region, and 92 % in the near-infrared band. Exposure experiments showed that the absorptivity and emissivity decreased very little on exposing to a natural environment for one month. The electrodeposition mechanism and possible reasons for the above behavior are discussed in detail. The study provides an idea to prepare black coatings with high absorptivity and emissivity that are expected to be used in the naval, aerospace industry, photothermal conversion and optical instruments.