Porosity and hole diameter tuning on nanoporous anodic aluminium oxide membranes by one-step anodization

Nanoporous Aluminium (III) oxide was fabricated and characterized to determine its suitability as a microfiltration membrane and an antireflection coating. Aluminium (III) oxides were obtained using a one-step anodization process with Phosphoric acid (H3PO4) as electrolyte. The effect of the anodization voltage and electrolyte concentration were studied. Semi-ordered nanotubes were observed using a Scanning Electron Microscope. Porosity, pore diameter and interpore distance were obtained and were found to increase with an increase in anodization voltage. While the pore diameter and porosity increased with an increase in electrolyte concentration, the interpore distance was found to remain stable. The porosity was found to vary from 16% to 28% in the investigated range of parameters, while the pore diameter varied from 120 to 178 nm. Reflectance curves showed a wide range of low reflectance in the visible light region, which validates their applicability in the field of anti-reflection coatings.