Impact of Different Parameters on Symmetry and Size of Single Step Anodization Nanopores in Porous Alumina

Nanoporous Alumina is used widespread as a template material for nano scaled objects since mid-20th century. These nano scaled objects are in the form of nanowires, nanotubes and nanodots etc. In order to synthesize nanoporous alumina, two step anodization techniques has been reported. We have prepared porous alumina with the distinction that arrays of pores in alumina were created by single step anodization. We fabricate nanoporous alumina in 0.3 M oxalic acid for various anodization times at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2^{\circ}\mathrm{C}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$23^{\circ}\mathrm{C}$</tex> under constant voltage of 40 v. EDX graphs revealed that oxide layer of aluminum was formed on the metal surface of aluminum. SEM micrographs however, depicted a good estimate of pore symmetry under low temperature and resulted in small pores as compared to room temperature. Longer anodization time deepens the pores' depth, whereas at room temperature the acid invaded pores' wall. SEM images made the evident that the sample anodized sporadically has lower degree of pore symmetry than continuously anodized sample. It was also observed that at voltage other than self-ordering i.e. at 60 V, hexagonal symmetry of pores decreases.