NiCrAlO/Al2O3 solar selective coating prepared by direct current magnetron sputtering and water boiling

Abstract

NiCrAlO/Al2O3 solar selective coating prepared by direct current (DC) magnetron sputtering and water boiling is demonstrated in this paper. Firstly, the coating consisting of tandem layers of Au/NiCrAl/Al with different NiCr volume fractions in NiCrAl sublayers is deposited solely by DC magnetron sputtering. Then the coating is boiled by deionized water and dehydrated by vacuum heating. The surface morphology, the depth distributions and relative chemical states of elements of the coating are characterized by scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It is found that Al in the coating is totally oxidized while most of NiCr and Au keep metallic after water boiling and vacuum dehydration, which forms the effective solar selective coating consisting of Au/NiCrAlO/Al2O3 with different metallic NiCr volume fractions. High near normal solar absorptance of 0.964 and low near normal thermal emittance of 0.066 are demonstrated by the reflectance measured by UV-VIS-IR spectrometer. The combination of DC magnetron sputtering and water boiling is very promising for fabrication of solar selective coating based on the dielectric aluminum oxide, as it is environmentally friendly and circumvents the radio frequency (RF) magnetron sputtering which needs RF automatic matching.