| dc.description.abstract | Abstract
With the addition of the trace elements and various process treatments, in this paper, the static capacity was investigated for the aluminum electrolytic capacitor of aluminum foils. The contents were divided into three parts－cathode foils, dielectric and high (low) voltage anode foils, accordingly. The microstructure and etching morphology were observed and discussed by the applications of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-Ray Diffraction, inductively coupled plasma atomic emission spectrometer (ICP-AES), metallurgical microscope, and electrochemical analytic system. Thus, the relationships among electrochemical behaviors, electric etching conditions and static capacity could be comprehended.
Firstly, the trace element of silver content was added for the cathode foils. With or without the stabilizing treatment, the variations for the metallurgical organization and microstructure were detected. After chemical etching, the form, size and distribution of etched holes were investigated so as to assess the variations of the static capacity. It was found that the silver content promoted the precipitations of Al-Fe-Mn and Al-Fe-Mn-Si, as well as enhanced etched surface. Thus, the static capacity effectively magnified. However, after the increment of silver content was up to 0.2%, the etched holes merged together due to over etching. This phenomenon caused the etched surface to lessen so as to reduce the static capacity. Also, the results showed that the stabilizing treatment could enhance re-crystallization for the aluminum foils. Therefore, the etched surface of the cathode foils effectively increased, a fact that increased the static capacity helpfully.
Secondly, after the addition of lead, aluminum foils of high voltage electrolytic capacitors proceeded with D.C. chemical etching. Thus, the form, size, and distribution of etched holes were observed to analyze the influence of the static capacitance. The results showed that the etched tunnels had square cross sections about 1.3μm per side. The inner tunnel sidewalls had a rough corrugated texture with regular ripples with a periodic interval of about 0.12μm. The addition of lead to high purity aluminum foils could effectively increase the number of grains and etched holes, which enhanced the etching of the surface as well as the static capacitance. However, the experiments showed that as the incremental addition of lead reached over 0.3ppm, the static capacitance reduced rapidly.
Also, in this study, different content of copper was added for the low-voltage anode foils of aluminum electrolytic capacitor. With A. C. chemical etching, the etched morphology and the influence of the static capacity were investigated. The results showed that the morphology of the low-voltage anode aluminum foils was spongy. As the content of copper increased, the expansive effect of the etched surface and the static capacity promoted. However, as the content of the copper was added over 49ppm, the phenomenon that the etched holes seriously merged together happened. Furthermore, the saw-tooth type of the etched surface boundary was inclined to be transferred to the line type, a fact that the static capacity reduced. By the electric chemical analysis of the polarised curve at fixed electric current circulation, the results showed that the more content of copper increased, the more serious extent of etching as well as the higher rate of the weight loss was obtained. | en_US |