Novel process for the production of optically selective surfaces
AssigneeYeda Research and Development Co. Ltd.
InventorsMichael Epstein, Israel Dostrovsky
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Abstract
The invention relates to a process for the production of optically selective surfaces for use in solar collectors, having a predetermined ratio of absorbance .alpha..sub.s to emmitance .epsilon. of at least 10, which comprises effecting an anodic oxidation of copper, or copper applied to any substrate metal, in an alkaline bath at an elevated temperature between 50.degree. and 85.degree. C., preferably 70.degree. to 85.degree. C., and at a current density of above 1 mA/cm.sup.2 and up to 40 mA/cm.sup.2 until an increase of resistance is experienced. Substrate metals may be copper, copper plated steel, copper plated galvanized iron, copper plated nickel, nickel plated steel to which a layer of copper is applied, and the like.
Claims3
A process for the production of optically selective surfaces for use in solar collectors, having a ratio of absorbance .alpha..sub.s to emittance .epsilon. of at least 10, which comprises effecting an anodic oxidation of copper, or of copper applied to any metal substrate in alkaline, sodium hydroxide bath of from 0.35 N to 1.5 N sodium hydroxide, at a temperature between 50.degree. C. and 85.degree. C. and at a current density of from 1 mA/cm.sup.2 to 40 mA/cm.sup.2 until a increase of resistance is experienced.
Dependencies are inferred from the claim text.