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Modelling of Degradation in Black Copper Photothermal Collector Coatings

Research Area: Nanofabrication Year: 1988
Type of Publication: Article Keywords: photothermal collector, coating, degradation
Authors: Axel Scherer; O. T. Inal; R. B. Pettit
Journal: Journal of Materials Science Volume: 23
Number: 6 Pages: 1923-1933
Month: June
Abstract:
The degradation mechanism in black copper photothermal collector coatings was investigated through the use of kinetic analysis, microstructural determinations and optical modelling. The initial structure of black copper was identified using reflection electron diffraction, scanning electron microscopy and Auger electron spectroscopy sputter profiles. These results were used to develop an optical model of the as-deposited coatings. In this model, the coatings was best described as a two-layer film. The layer next to the substrate consists of dense copper oxide with metallic copper inclusions, while the rough outer layer is modelled as copper oxide dispersed in air. A substantial decrease in the solar absorptance (from 0.96 to 0.80) of coatings exposed to temperatures above 150°C in air was found to occur within 30 min and was explained by a decrease in the surface roughness of the coatings. After longer exposures, an increase in the thickness of the oxide layer near the substrate occurs at the expense of the surface layer. Incorporating this change in the model, the optical properties after thermal ageing were predicted.
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