Aqueous solution-chemical derived Ni-Al2O3 solar selective absorbing coatings

Here we report the preparation of Ni-Al2O3 absorbing coatings by a facile aqueous solution-chemical method. In this approach, aluminum nitrate and nickel nitrate were simply mixed in water as precursor solution together with a chelating agent and a wetting agent, all of which were of low cost and available commercially. At high temperature and in N-2 atmosphere, aluminum ions were converted into an Al2O3 matrix and nickel ions were in situ reduced into nano-size nickel particles embedded in the Al2O3 matrix. The optimum single layer attained a high normal solar absorptance of 0.85 and a low normal thermal emittance of 0.03. A three-layer coating, i.e. double absorption layers together with one top anti-reflection layer, exhibited better optical properties of absorptance/thermal emittance = 0.93/0.05, respectively, and was stable in air up to 300 degrees C. (c) 2012 Elsevier B.V. All rights reserved.