Nanostructured Aluminum Oxide Black Coating: Electrochemical, Mechanical, and Optical Characterizations

Abstract

Nanoporous anodized aluminum oxide (AAO) template is continuously investigated since it is vital for producing a variety of promised nanomaterial. In this study, two steps anodization of aluminum working electrode was carried out in H2SO4 under control of temperature at 17 °C and revolution rate 150 rpm using thermostatic cooling system and revolution control mechanical stirrer, respectively. Different times 15 mins, 30 mins, and 45 mins of first anodization were used and followed by electrolytic detachment for 1 min. Then, second anodization was applied for 10 mins, 20 mins, 30 mins, and 40 mins. Each sample of the prepared nanoporous AAO was used as working electrode into the electrolytic coloring cell containing coloring salt solution of 40 g/l CuSO4. Copper ions were deposited into the porous layer by AC current with gentle agitation using magnetic stirrer. The surface was characterized by field-emission scanning electron microscope device (FESEM), atomic force microscope (AFM), microhardness, corrosion resistance, and optical characteristics. The optical characteristics and reflectivity measurements revealed that the prepared selective coating is promised for solar heating systems and solar water heaters (SWH).