SOLAR SELECTIVE COATING HAVING HIGHER THERMAL STABILITY USEFUL FOR HARNESSING SOLAR ENERGY AND A PROCESS FOR THE PREPARATION THEREOF

The present invention provides an improved solar selective multilayer coating having higher thermal stability and a process for the preparation thereof. Solar selective coatings having higher thermal stability are useful in solar steam generation, solar steam turbines to produce electricity and also...

Ausführliche Beschreibung

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Bibliographische Detailangaben
Hauptverfasser:	BARSHILIA HARISH CHANDRA, RAJAM KARAIKUDI SANKARANARAYANA, GRIPS VATIKA KRISHNAMURTHY WILLIAM
Format:	Patent
Sprache:	eng
Schlagworte:	CHEMICAL SURFACE TREATMENT CHEMISTRY COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL COATING MATERIAL WITH METALLIC MATERIAL COATING METALLIC MATERIAL DIFFUSION TREATMENT OF METALLIC MATERIAL ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR ELECTRICITY INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL LAYERED PRODUCTS LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT ORNON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM METALLURGY PERFORMING OPERATIONS PLASMA TECHNIQUE PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OFNEUTRONS PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMICBEAMS SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION TRANSPORTING
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Beschreibung
Zusammenfassung:	The present invention provides an improved solar selective multilayer coating having higher thermal stability and a process for the preparation thereof. Solar selective coatings having higher thermal stability are useful in solar steam generation, solar steam turbines to produce electricity and also on automobile engine components. In the present invention, a tandem stack of three layers of TiAlN, TiAlON and Si3N4 is deposited on metal and non-metal substrates at room temperature using a planar reactive direct current magnetron sputtering process. The first two layers function as the absorber and the third antireflection layer further enhances the coating's absorptance. The solar selective coatings were annealed in air and vacuum to test the thermal stability at different temperatures and durations. The coatings of the present invention deposited on copper substrates are stable in air up to a temperature of 625° C. for a duration of 2 hours and exhibit higher solar selectivity in the order of 9-10 and these coating also show no change in the absorptance and the emittance values even after vacuum annealing at 600° C. for 3 hours. Coatings deposited on copper substrates showed no significant degradation in the optical properties even after continuous heating in air at 525° C. for 50 hours. The solar selective coatings of the present invention exhibit high hardness, high oxidation resistance, chemical inertness and stable microstructure.