The effect of dissolution by periodic reverse current on the microstructure of bamboo-shaped porous anodic alumina

Abstract

• Periodic reverse current with small amplitude can promote the growth of the porous layer. • Periodic reverse current has the effect of pore expansion. • The water reduction speed increases during the reverse voltage stage. • The ions driven by the electric field change with the direction of current. • H+ (H2O) and OH− are the main ions that move in the reverse voltage stage. In this paper, the effects of a cyclic anodizing method with the introduction of periodic reverse current are reported. The effects of the periodic reverse current on the microstructure of bamboo-shaped porous anodic alumina (PAA) film are investigated using positive and negative current triangular waveforms. The results of the experiment showed that when the reverse current in each current cycle was I D ' = -5 mA, the growth velocity was the fastest. The analysis found that the introduction of the periodic reverse current was beneficial to increasing the growth velocity of the porous anodic alumina film and had the additional effect of pore expansion. However, with any further increase of the periodic reverse current, the growth velocity of the porous anodic alumina film gradually decreased, and the period length showed a decreasing trend. The main reason for this phenomenon is that in a larger reverse voltage phase, the ions driven by the electric field are mainly H + (H 2 O) and OH − . Then the reaction that occurs is mainly dissolution. With large pore size and adjustable period length, this porous anodic alumina film can be used as a template for the synthesis of nanomaterials, which have practical significance for the synthesis of nanodevices.