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Proceedings Paper

Influence Of Surface Roughness On The Optical Properties Of Cermet Coatings
Author(s): Wolfgang Graf; Michael Kohl; Karlhanns Gindele
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Paper Abstract

Metal-dielectric composite materials (cermets) have been often investigated as solar thermal absorber coatings. The cermet, deposited on an infrared-reflecting metal substrate, is used as interference layer absorbing in the wavelength range of the solar irradiation. The attainable solar absorptance is limited by reflections at the cermet surface. A reduction of these reflection losses can be achieved by additional dielectric interference layers, grading of the filling factor of the metal in the cermet (decreasing from the substrate to the surface of the layer), or a suitable microroughness of the substrate-cermet interface and/or the surface of the coating. The latter way is described for microrough aluminium reflectors, deposited by physical vapour deposition on heated substrates, in combination with Ni/MgF2 cermet layers. The roughness parameters are evaluated by means of spectral reflectance measurements and scanning electron microscopy in order to investigate their dependence on the production parameters. The obtained optical properties are compared with those of absorber coatings produced according to the other methods mentioned above for achieving an enhanced absorptance of cermet absorber coating. The durability at temperature loads in air and in vacuum, respectively, is another topic of this paper.

Paper Details

Date Published: 6 March 1989
PDF: 8 pages
Proc. SPIE 1016, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion VII, (6 March 1989); doi: 10.1117/12.949944
Show Author Affiliations
Wolfgang Graf, University of Stuttgart (F.R.G.)
Michael Kohl, University of Stuttgart (F.R.G.)
Karlhanns Gindele, University of Stuttgart (F.R.G.)


Published in SPIE Proceedings Vol. 1016:
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion VII
Claes-Goeran Granqvist; Carl M. Lampert, Editor(s)

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