The nanoporous anodic alumina oxide formed by two-step anodization

The nanoporous anodic aluminum oxide (AAO) was fabricated by two-step anodization technique. The effects of anodization electrolyte and time on the pore diameter and structural properties of the AAO were investigated. The Field Emission-Scanning Electron Microscopy was used for the analysis of the surface morphology of AAO structure. The nanoporous structures with the pore size in the range of 31-113 nm and oxide layer thickness 3.4-33 μm were obtained. Wetting properties of these surfaces were characterized by measurements of the water contact angle. It was seen that the surface of the AAO became hydrophilic with the increase in the anodization time. Furthermore, we explored the mechanical properties and thermal stabilities of the AAO by microhardness and thermo-gravimetric analysis measurements. It was found that the AAO structures synthesized in the electrolyte containing ethylene glycol solution have the highest hardness and display well thermal stability among the other structures. The surface area and crystal structure of AAO were determined by surface area analysis and X-ray diffraction patterns measurements. Experimental results showed that the AAO structures have amorphous phase and the highest surface area is 2.59 m2/g.