A Study On Anodic Porous Stucture

Anodic aluminium oxide (AAO) was fabricated by applying different voltages in0.3M oxalic acid and0.3M sulfuric acid separately. The relationship between porediameters and voltages was studied. The correlation between the oxalic acid concertrationand AAO pore diameters was obtained from a series of samples made in different oxalicacid concertrations at40V.The desired pore opening duration was oachived and therelationship between pore diameter and pore widening duration was also established..AAOs with pore diameters12~70nm were prepared by anodized in both sulfuric acidand oxalic acid solution.The pore sizes were studied by field effect scanning electronmicroscopy (FE-SEM) and statistics analysis, the pore diameter increased with theincreasing of voltages,and there is liner relationship between anodizing voltage and porediameter.6%phosphoric acid solution at30℃was applied for pore widing of the specimenprepared in0.3M oxalic acid solution at40V,the micromorphology of pore bottom ofdifferent immerse duration were analysied by FE-SEM.The result demonstrates that45minis a proper duration to completely remove the barrier layer. Appropriately prolong theimmersion time can improve the degree of porous order.The porous sample prepared in0.3M oxalic at40V was immersed in6%phosphoricacid solution at30℃to widen the pore.The pore diameteris propotional to the immersingduration, and degree of order can be improved after pore widening. However, if thewidening process is too long, the sidewall of the pore will crash and thus form thealuminium oxide nanowire.The different concentrations of oxalic acid solutions were studied at40Vcondition.The pore diameter increases with higher concentration, while concentration doesnot correlate the level of pore diameter.Different voltages were applied in0.6M oxalic acid to obtain the porous structure, andthe diameter of pore is linear to the voltages. The upper limit voltage in0.6M oxalic acidfor a stable growth is50V, and further increase the voltage will lead to the failure in pore growth.At the same time, the porous silicon obtained through anodize process has also beenstudied. The porosity of porous silicon prepared in different hydrofluoric acid (HF)concentrations and current densities was calculated. The porosity decreases withincreasing HF concentrations and finally saturates, and it increases with increasing thecurrent density.The porous structures have been systematically studied. The porous structures andanodize conditions could establish quantitative relationship as guidance for further studies.