Solar absorptivity of nano-porous anodic alumina (NPAA): effects of structural features

Great structural and geometrical characteristics of nano-porous anodic alumina (NPAA) would subject these type materials to a wide application in different fields of science and technology. Effect of anodizing parameters on structural features of NPAA has been the topic of a large number of studies. Nevertheless, the relation of NPAA characteristics with its optical properties has rarely been addressed. This paper investigates the effect of film thickness, beams incident angle, and average diameter, area percentage, and direction of pores on solar absorptivity. The results showed that, increasing of the film thickness, decreasing of the average pores' diameter, and distortion of pores enhanced the solar absorptivity. Furthermore, at an optimum value of pores' area percentage the absorptivity had a maximum value. Finally, increasing of the incident angle enhanced the solar absorptivity.