Effect of solvent on the structural features and the degree of ordering of pore arrays in porous anodic alumina

Porous anodic alumina (PAA) films are usually fabricated in aqueous solutions. In this work, ethylene glycol (EG) as an organic solvent, is chosen to replace the conventional aqueous media. The anodization behaviors of aluminum in the EG solutions and the nanostructural characteristics of the as-fabricated PAA films were reported. In phosphoric and oxalic acid EG solutions, the ordered PAA films can be formed at room temperature by conventional low-field anodization. A fracture mode through the cell boundaries was found for the PAA films fabricated in the oxalic acid EG solution. These findings demonstrate that the solvents employed play a key role in the formation and self-ordering of PAA. Based on a model of field-induced plastic flow, a reasonable explanation of the experimental phenomena is proposed. The present results shed a new light on the formation mechanisms of PAA. The change of solvent also offers a novel tunability of morphology and cell size of PAA templates.