Optical properties and thermal stability of CrxOy/Cr/Cr2O3 multilayer absorber coatings for solar selective applications

Selvakumar, N and Barshilia, Harish C and Rajam, KS and Biswas, A (2009) Optical properties and thermal stability of CrxOy/Cr/Cr2O3 multilayer absorber coatings for solar selective applications. In: 23rd International Conference on Surface Modification Technologies, November 2-5, 2009, IGCAR, Kalpakkam.

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Abstract

Spectrally selective CrxOy/Cr/Cr2O3 multilayer absorber coatings were deposited on copper (Cu) substrates using a pulsed sputtering system. The Cr targets were sputtered using asymmetric bipolar-pulsed DC generators in Ar+O2 and Ar plasmas to deposit a CrxOy (bottom layer)/Cr/Cr2O3 (top layer) coating. High absorptance (0.899-0.912) and low emittance (0.05-0.06) was achieved by optimizing the composition and thicknesses of the individual layers. In order to study the thermal stability of the CrxOy/Cr/Cr2O3 coatings, they were subjected to heat treatment (in air and vacuum) at different temperatures and durations. The coating deposited on Cu substrates exhibited high solar selectivity (/) of 0.895/0.06 even after heat-treatment in air up to 300 °C for 2 h. In the case of vacuum annealing, for temperatures greater than 500 °C the outward diffusion of Cu was the dominating degradation mechanism. Studies on the accelerated aging tests indicated that the absorber coatings on Cu were stable in air up to 250 h at 250 °C with a solar selectivity of 0.898/0.11

Item Type: Conference or Workshop Item (Paper)
Subjects: RENEWABLE ENERGY > Solar Energy
PHYSICS > Optics
Depositing User: Mr N Selvakumar
Date Deposited: 27 Jul 2011 06:31
Last Modified: 27 Jul 2011 06:31
URI: http://nal-ir.nal.res.in/id/eprint/9688

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