Effect of citric acid on microstructure and electrochemical characteristics of high voltage anodized alumina film formed on etched Al Foils

Aluminum capacitor foils with a tunnel etch structure were reacted with boiling water and then anodized at 530 V in boric acid solution or boric acid+citric acid mixed solution. The microstructure and crystallinity of the resulting anodized film were examined by TEM and XRD. The special capacitance,...

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Bibliographic Details
Published in:Transactions of Nonferrous Metals Society of China 2011, Vol.21 (1), p.133-138
Main Authors: BAN, Chao-lei, HE, Ye-dong, SHAO, Xin
Format: Article
Language:English
Subjects:
Al electrolytic capacitor
Al foil
Aluminum
anodized oxide film
Anodizing
Boric acids
Capacitance
citric acid
Crystallinity
Electric potential
Electrochemical impedance spectroscopy
electrochemical performance
High voltages
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Summary:Aluminum capacitor foils with a tunnel etch structure were reacted with boiling water and then anodized at 530 V in boric acid solution or boric acid+citric acid mixed solution. The microstructure and crystallinity of the resulting anodized film were examined by TEM and XRD. The special capacitance, resistance and withstanding voltage of the film were explored with electrochemical impedance spectroscopy (EIS), LCR meter and small-current charging. The results show that the high voltage anodized oxide film consists of an inner layer with high crystallinity and an outer layer with low crystallinity. However, the crystallinity of the film formed in boric acid+citric acid mixed solution is higher than that of the film formed in only boric acid solution, leading to an increase in film's field strength and special capacitance. Meanwhile, there are more defects from phase transformation in the out layer of the film formed in boric acid+citric acid mixed solution than in that of film formed in only boric acid solution, leading to a decrease in film's resistance and withstanding voltage.
ISSN:1003-6326
DOI:10.1016/S1003-6326(11)60689-4