Solar selective coating for harnessing solar energy, e.g. for solar steam generation, includes three solar absorber layers containing titanium aluminum nitride, titanium-aluminum-oxynitride and silicon nitride, respectively

摘要

A solar selective coating comprises first solar absorber layer of titanium aluminum nitride deposited on a substrate from glass, silicon or metal. The first absorber layer is deposited by another second solar absorber layer and a third antireflection layer of titanium-aluminum-oxynitride and silicon nitride, respectively. An independent claim is included for a process for the preparation of a solar selective coating comprising: (A) polishing and chemically cleaning the substrate by known methods, followed by subsequent cleaning by argon ion bombardment under vacuum at 1.0-6x10 -1Pa; (B) depositing a solar absorber layer of titanium-aluminum-nitride (TiAlN) on the above cleaned substrate by direct current (DC) magnetron sputtering of TiAl composite target in the presence of argon-nitrogen plasma, at 0.1-0.5 Pa, nitrogen of 2-3 standard cubic centimeter per minute (sccm), 2.25-6.25 W/cm 2and at a substrate of 25-50[deg]C; (C) depositing another solar absorber layer of TiAl-oxide (O)-N on the above layer of TiAlN deposited on the substrate by DC magnetron sputtering of TiAl composite target, in the presence of argon-oxygen-nitrogen plasma, at 0.1-0.5 Pa, nitrogen of 2-3 sccm, oxygen of 1-2 sccm, 2-6 W/cm 2and substrate of 25-50[deg]C; (D) further deposing a third antireflection layer of silicon nitride (Si 3N 4) on the above second solar absorber layer of TiAlON by using DC magnetron sputtering of silicon target, in the presence of argon-nitrogen plasma, at 0.1-0.5 Pa, nitrogen of 2-3 sccm, at 2-6 W/cm 2and at a substrate of 25-50[deg]C to obtain the desired solar selective coating of substrate/TiAlN/TiAlON/Si 3N 4. The substrate used is selected from the group consisting of copper, nickel, stainless steel, glass or nimonic. The vacuum chamber is maintained at a base of 3-6x10 -4Pa before deposition of the coatings. The coatings are deposited at 0.1-0.3 Pa. The coatings are deposited at a substrate to target distance of 4-6 cm. The thickness of the first absorber layer coatings is 300-500Å. The thickness of the second absorber layer coating is 400-800Å. The thickness of the third antireflection layer is 300-500Å.