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ABSTRACT
Current approaches to coat aluminum surfaces that use paints and organic coatings to protect them from corrosion and provide an aesthetic finish, are also energy intensive and involve high emissions of VOCs. The use of these coatings is becoming increasingly restricted by global efforts towards more environmentally sustainable surface finishing technologies. A recent development based on porous anodized aluminum (PAA) and metal nanowire deposits is presented here, which may become a competitive alternative to paint and organic coatings. Anodizing and electrodeposition do not emit VOCs and are less energy intensive. By controlling the conditions for anodizing and metal electrodeposition, coatings in a wide spectrum of colors can be produced, including greys, black, blues, purples and greens. Characterization of the coating morphologies and corresponding colors agrees with simulated results based on the Fresnel equations and Bruggeman Mixed Media Approximations.
anodic oxidation. As a result, one can obtain amorphous barrier-type oxides, crystalline barrier-type oxides or amorphous nanoporous oxides. Currently, highly-ordered nanoporous anodic aluminum oxides (AAO) are obtained with various electrolytes to form nanostructures with a range of geometrical features. This material can serve as a template for nanofabrication of variety of nanowires, nanotubes and nanodots. In this way, porous alumina can be fabricated electrochemically through anodic oxidation of aluminum, yielding highly ordered arrays of nano-holes several hundreds down to several tens of nanometers in size.
Sol-gel chemistry offers a flexible approach to obtain a diverse range of materials. It allows differing chemistries to be achieved as well as the ability to produce a wide range of nano-/micro-structures.