| Anodic aluminum oxide (AAO) film have attracted great attention in the areas of nanoscience and engineering due to their highly ordered pore arrangement, controllable pore diameter and well-characterized morphology. Therefore the study of electropolishing behaveiour of high-purity aluminum and growth kinetics of AAO film to further improve the performance of AAO film is of great significance.The electropolishing behavior of high-purity aluminum in perchloric acid ethanol electrolytes is studied by the electrochemical methods. The morphologies and composition of electropolished surface are examined. The results shows that the high-purity aluminum can be electrochemically polished in the mixed solution with volume ratios of 1:8 in the temperature range of 10-30℃. The electropolishing of high-purity aluminum follows dissolution product limited transport mechanism, a salt film precipitated on the electropolishing surface, consists of amorphous alumina. In addition, the effect of fierce stiring agitation and cavitation of ultrasonic agitation is to make ethanol molecule which is a polar molecule with a repulsive shield dispersion homogeneously dispersed, to shorten adsorption spacing on surface microscopic concave. The root-mean-square (RMS) surface roughness of the aluminum electropolished surface decreases from 23.5 nm to 17.4 nm and the self-organized nanostripes decreases from 212 nm to 54 nm after using the ultrasonic agitation.The growth kinetics of AAO films formed in 0.3 mol/L H2C2O4 under galvanstatic conditions shows that the film thickness increases with an increase in the current density in steady-state stage of AAO film formation, the film resistance and the ionic conductivity are also increased, which lead to voltage increases. It has been found that the film thickenss increases with the anodizing time and achives the limiting thickenss when the time is characteristic time, and then with the increase of the anodizing time, the film thickensss maintains certain or appreciably decreases. The chatacteristic time dencreases form 110 min to 80min and the limiting thickenss increases from 15.6μm to 23μm, increasing current density from 10 mA/cm2 to 20 mA/cm2. The film Growth can be expressed by the equationδp= k" it (t≤tc) and k" is a constant independent of the current density and the anodization temperature with a average value of 1.45×10-6 cm3/(mA·min).A method of fabrication of AAO film in in 0.3 mol/L H2C2O4 and 0.4 mol/L H3PO4 by adding 1,2-propanediol(PROH) and at sub-zero temperature has been proposed. The smallest pore diameter of AAO film is 56.29 nm, which is one quarter of those anodized in 20℃0.4 mol/L H3PO4. Sub-zero andization decrease the pore diameter possibly by retarding the ionic transport in the oxide and thus decreasing the rate of oxidation and dissolution. A uniform pore-size distribution with ordered pore arrangement of AAO films is observed in the SEM images. Moreover, the pore density and the porosity of AAO films were found to decrease with decreasing anodizing temperature hereby referred that the lower is the rate of formation of defect sites in the first place and less unit cells are developed around these centers for a given area with decreasing temperature. An increase of the volume percentage of PROH in electrolyte from 25% to 75% results in a corresponding increase in electrolyte viscosity and an accumulation of OH- in double layer causes the pore diameter, pore density and porosity of AAO film decreased.The electrochemical characteristics of the barrier and porous layers of AAO films before and after pore-filling are examined using electrochemical impedance spectroscopy (EIS). It is shown that the high and medium frequency range corresponds to the barrier layer properties and the low frequency ranges reflect the sealed porous layer properties. Calculated thickenss of the barrier layer is in the range of 1-18 nm. The resistance (Rb) and the thickness (8b) of the barrier layer increase and the capacitance of the barrier layer (CPEb) decreases with the volume percentage of PROH increasing from in electrolyte from 25% to 75%. The surface non-homogeneity of AAO film goes better by pore-filling, leads to decrease in the capacitance of porous layer (CPEp) and increase in the porous layer thickness.
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