Electrochemical impedance spectroscopic study of barrier layer thinning in nanostructured aluminium

Abstract

The electrochemical behaviour of electropolished and anodised aluminium was studied by electrochemical impedance spectroscopy (EIS). Freshly electropolished aluminium behaves as a pure capacitor exhibiting Warburg impedance at low frequencies. Storage of the electropolished aluminium, even in an air-tight bottle, results in the reconstruction of a uniform compact barrier layer. The impedance response of a stored electropolished aluminium as well as anodised aluminium after oxide removal, done by chemical etching, exhibits only a capacitive loop in the complex plane. The effect of the oxide layer thickness on the impedance data was investigated for layers formed during anodising at a cell potential of 15 or 23 V. Impedance measurements carried out over a wide range of frequencies gave useful information on the efficiency of the thinning of the barrier layer at the bottom of porous aluminium oxide layers. The rate of thinning of the barrier layer was estimated for samples anodised at different voltage.

Fluid streaming above interdigitated electrodes in dielectrophoresis experiments

“…No bubbles were visible at the IDE structure itself despite the local high field strength. This might be explained by the oxide layer which usually covers aluminium [24,25] and could be dense enough to prohibit any direct current which would lead to electrolytic decomposition of water. The connecting electrodes were made of gold and therefore allowed quasi-static direct current within each half cycle of the 10 Hz field, i.e.…”

Porous anodic alumina formed by anodization of aluminum alloy (AA1050) and high purity aluminum

“…During this process, the AAO templates are immersed in usually in a H 3 PO 4 solution and subjected to chemical etching. In most cases, nanoporous AAO membranes are synthesized by a two-step, voltage-controlled anodization carried out in sulfuric acid [12][13][14][15][16], oxalic acid [17,18], and phosphoric acid [19,20] solutions. The best nanopore order is observed at a certain value of the anodizing potential, known as a self-ordering regime.…”

Structural features of self-organized nanopore arrays formed by anodization of aluminum in oxalic acid at relatively high temperatures

“…The laboratory-made AAO templates used for fabrication of nanomaterials are usually prepared by a self-organized two-step anodizing in a sulfuric [29][30][31][32][33][34][35], oxalic [36,37] and phosphoric acid solutions [38]. However, oxalic acid as an anodizing electrolyte is frequently used, the range of temperature balances usually between 0 and a few • C and the duration of anodization exceeds often several hours.…”