effect of nanoporous anodic aluminum oxide (aao) characteristics on solar absorptivity

nanoporous anodic aluminum oxide (aao) has been used in many different fields of science and technology, due to its great structural characteristics. solar selective surface is an important application of this type porous material. this paper investigates the effect of nanoporous aao properties, including; film thickness, pore area percentage and pore diameter, on absorption spectra in the range of solar radiation. the parameters were verified individually depending on anodization condition, and the absorption spectra were characterized using spectrophotometer analysis.  the results showed that the absorptivity was increased with growth of the film thickness. furthermore, increasing the pore diameter shifted the absorption spectra to the right range, and vice versa. the investigation revealed the presence of an optimum pore area percentage around 14% in which the absorptivity was at its maximum value.