| dc.description.abstract | This work studies the effects of etching parameters and foil manufacturing process of the aluminum foils used in electrolytic capacitors. There are three parts of this survey showed as below :
Part1 :
This part focus on the survey of 540VF aluminum foil primarily. By changing concentration, current density and etching temperature. We investigated the effects of etching morphology on the surface increment. This experiment first used potentiostat to observe the relationship between potential-time under different etching parameters. Thus we could predict the reaction during etching. According to the selected parameters of electrochemical etching, the aluminum foils have been etched, and the capacitance was measured under EIAJ specifications. For surface, oxide replicas and cross section morphology studies, the samples were examined in the SEM, SEM and OM respectively
From the experiments, it was found that there was a proper sulfuric and hydrochloric acid concentration for tunnel etching. At this concentration we could get a fine microstructure for increasing capacitance. Phosphoric acid could grow a passive film, which protected aluminum from Cl- corrosion. Although high current density had large corrosive current, the current efficiency was bad too. Increased etching temperature could accelerate the diffusion of Cl-. There also had proper current density and temperature for etching process.
Part2 :
This part studies the effects of current frequency and current density on etching morphology, microstructure and static capacity of the aluminum foils used in electrolytic capacitors. The behavior associated with electrochemical etching during an anodic half cycle was investigated by a potentiostat. The oxide covering of the anode, which protected aluminum from etching, thickened as the frequency increased. Increasing the current density inhibit the passing of chlorine ions through the passive cover. The static capacity increased to 70 uF/cm2 with 20 VF forming voltage by optimization the etching parameters used herein this work.
Part3 :
First of all, the chemical compositions of high purity aluminum foils were determined before etching by using the analysis of ICP-AES. This research will examine different parameter of procedure such as different homogenization treatment, cold rolling, hot rolling, and stabilizing treatment. The texture of Al-foil was analyzed by pole figure, and microstructure observation was used by transmission electron microscope (TEM).After electrochemical etching, we forming according to EIAJ standard and measures its capacitance and rate of weight loss. To discuss the effect of capacitance caused by etched structure, the morphology of etched surface and cross section was observed by scanning electron microscope (SEM) and optical microscope (OM).From the observation of etched microstructure, the effect of procedure factors on the etching behavior of high purity aluminum foils could be studied in details.
In the results of experiment, it was found that the capacitance is similar under different cold-rolled. When the temperature of homogenization treatment and hot-rolled was raised, the capacitance will be increase. And then it had fine pit which distributed uniform .The fitting of stabilizing treatment could scatter dislocation. And the sample of stabilizing treatment was carry out , it had better capacitance than not stabilizing treatment. | en_US |