Application of titanium containing amorphous hydrogenated carbon films (a-C : H/Ti) as optical selective solar absorber coatings

摘要

A combined PVD/PECVD process for the vacuum deposition of titanium containing amorphous hydrogenated carbon films is described. Elemental compositions of the deposited films have been determined by in situ core level photoelectron spectroscopy (XPS). The long-term stability of the plasma process has been demonstrated. Target poisening has not been observed. We have fabricated optical selective surfaces by the deposition of a-C:H/Ti multilayers onto aluminum substrates. Eventhough we have not optimized layer thicknesses and stoichiometries so far, the experimental results are promising: solar absorptance alpha(S) of 0.876 and thermal emittance epsilon(100 degrees C) of 0.061 have been achieved yielding an optical selectivity s:= alpha(S)/epsilon(100 degrees C) of 14.4. Accelerated aging tests of these coatings have demonstrated their aging stability: the service lifetime is predicted to amount to more than 25 years. Raman spectroscopy has been used to monitor changes in the structure of the aged coatings. Degradation mechanisms are being discussed. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 24]