FABRICATION OF A " CONE PAA NANOSTRUCTURE" BY GRADUAL DECREASE OF VOLTAGE

The conical nanostructure improves the applications of alumina membranes and provides three dimensional nanometer scale systems to study the chemical and physical properties. In this study, the nano cone structure is produced in porous anodic alumina (PAA) by two-step anodizing. This conical nanostructure will improve the application of PAA membranes. This approach is novel generation of the so-called «gradually decreased voltage» technique, in which the voltage- time curve is divided into three stages and the effect of each step is investigated for different electrolytes. The effect of the decreasing voltage is examined in two types of electrolytes; oxalic and phosphoric acid with a constant decrease in voltage rate. The results of SEM, FE-SEM images show the slope of the inner cone layer in the oxalic acid to be considerably larger compared with phosphoric acid.