Effect of hydration on microstructure and property of anodized oxide film for aluminum electrolytic capacitor
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Etched aluminum foil for aluminum electrolytic capacitor was first boiled in water for different time to form hydrous film on Al foil and then anodized in H3BO4 solution at 530 V to form anodic oxide barrier film as insulating dielectric layer. The obtained films were characterized by field-emission scanning electron microscopy, transmission electron microscope and X-ray diffraction for surface morphology, microstructure and crystallinity examination. Small-current charging, LCR meter and electrochemical impedance spectroscopy were exploited to measure the propertied of the anodized oxide film such as withstanding voltage (Uw), specific resistance (Rox) and specific capacitance (Cs and Cox) for its electrochemical performance. The results show that the hydrous film is pseudoboehmite (PB) with a dense inner layer and a fibrous outer layer. The crystallinity of the PB film increases with hydration time. During anodization, the PB film was transformed into anodic oxide (γ′-Al2O3) barrier film. Prolonging hydration time promotes transformating PB into γ′-Al2O3 and improves the crystallinity of the barrier film, leading to increase in Cs and Cox and decrease in Rox and Uw.
The work is financially supported by the Natural Science Foundation of Shandong Province, China (Grant No. ZR2017MEM019), Technology and Culture Innovation Fund for Student of Liaocheng Univerisy (Grant No. 26312171923) and Innovative Entrepreneurship training Program for College students of Liaocheng Univerisy (Grant No. 201710447009).
- 15.J.H. Lee, K.W. Jang, H.J. Oh, Mater. Sci. Eng. A 449–451, 314 (2007)Google Scholar