Optical Properties and Durability of Al_(2)O_(3)-NiP/Al Solar Absorbers Prepared by Electroless Nickel Composite Plating

摘要

A simple and low-cost method, electroless nickel composite plating, was used to deposit an Al_(2)O_(3)-NiP composite coating on an Al substrate to form an Al_(2)O_(3)-NiP/Al solar absorber. The effects of the Al_(2)O_(3) content in the Al_(2)O_(3)-NiP composite coating, the thickness of the coating, and the use of a double-layer Al_(2)O_(3)-NiP composite coating and a TiO_(2) antireflection (AR) layer on the optical characteristics of the Al_(2)O_(3)-NiP/Al absorbers were studied. The absorptance (alpha) and thermal emittance (epsilon) of the Al_(2)O_(3)-NiP/Al absorbers increased with the Al_(2)O_(3) content in the Al_(2)O_(3)-NiP composite coating and decreased as the thickness of the coating increased. A double-layer Al_(2)O_(3)-NiP/Al absorber with 2:1 thickness ratio of the top layer (Al_(2)O_(3)-NiP with 25 vol.percent Al_(2)O_(3)) to the inner layer (Al_(2)O_(3)-NiP with 7 vol.percent Al_(2)O_(3)) had the best optical properties (alpha/epsilon velence 0.746/0.103). The optimal double-layer Al_(2)O_(3)-NiP/Al absorber with a 106-nm-thick TiO_(2) AR layer achieved absorptance of 0.893 and thermal emittance of 0.111. The results of a thermal stability test and a condensation test revealed that the TiO_(2)-coated double-layer Al_(2)O_(3)-NiP/Al absorbers had excellent thermal stability, and their failure time in the condensation test exceeded 100 h.