Effect of the Thickness of Al₂O₃-TiO₂ Composite Oxide Films on the Electrical Properties of Anode Al Foils

Abstract:

High-voltage-etched Al foils with TiO₂ coating were fabricated via vacuum infiltration. Specimens subjected to different number of coating cycles (n = 0, 1, 2, 4, and 8) were annealed at 550 °C, and subsequently anodized at different voltages (100, 300, and 500 V). The microstructures of the specimens were observed by field emission scanning electron microscopy and field emission transmission electron microscopy. The results showed that uniform TiO₂ films (30 nm per coating cycle) were successfully formed on the high-voltage-etched Al foils. Its tunnels showed a dual-layer structure comprising an Al₂O₃ outer layer and an Al–Ti composite oxide inner layer after anodizing at 500 V. All the TiO₂-coated specimens anodized at different voltages could withstand the corresponding voltage. The thicker is the Al–Ti composite oxide layer, the higher is the specific capacitance of the anode Al foils. Compared to the specimens without the TiO₂ coating, the increasing ratios of the specific capacitances of the specimens coated 4 times reached the maximum values, which were 60.2%, 34.0%, and 30.2%, when anodized at 100 V, 300 V, and 500 V, respectively. These results suggest that the Al–Ti composite oxide layer is not only effective in enhancing the specific capacitance but also has a significant effect on the properties of the anode Al foils.

• Periodical: Key Engineering Materials (Volume 737)
• Pages: 143-149
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.737.143
• Online since: June 2017
• Authors: Lian Xiang, Sang Shik Park*
• Keywords: Al Electrolytic Capacitor, Al-Ti Composite Oxide Film, High-Voltage-Etched Al Foils, Vacuum Infiltration Method

References

[1] K. Watanabe, M. Sakairi, H. Takahashi, Anodizing of aluminum coated with silicon oxide by a sol–gel method, J. Electrochem. Soc. 148 (2001) B473–B481.

DOI: 10.1149/1.1408633

[2] X. F. Du, Y. L. Xu, Formation of Al2O3–Bi4Ti3O12 nanocomposite oxide films on low-voltage etched aluminum foil by sol–gel processing, Surf. Coat. Tech. 202 (2008) 1923–(1927).

DOI: 10.1016/j.surfcoat.2007.08.020

[3] S. S. Park, B. T. Lee, Anodizing properties of high dielectric oxide films coated on aluminum by sol–gel method, J. Electroceram. 13 (2004) 111–116.

DOI: 10.1007/s10832-004-5085-z

[4] K. Watanabe, M. Sakairi, H. Takahashi, Formation of Al–Zr composite oxide films on aluminum by sol–gel coating and anodizing, J. Electroanal. Chem. 473 (1999) 250–255.

DOI: 10.1016/s0022-0728(99)00121-7

[5] J. J. Chen, Z. S. Feng, M. L. Jiang, The effect of anodizing voltage on the electrical properties of Al–Ti composite oxide film on aluminum, J. Electroanal. Chem. 590 (2006) 26–31.

DOI: 10.1016/j.jelechem.2006.02.016

[6] F. Chen, S. S. Park, Formation behavior of multi-layer oxide films on etched Al foil by vacuum infiltration and anodization, ECS J. Solid State Sci. Technol. 4 (2015) P293–P297.

DOI: 10.1149/2.0051508jss

[7] M. Sunada, H. Takahashi, T. Kikuchi, Dielectric properties of Al–Si composite oxide films formed on electropolished and DC-etched aluminum by electrophoretic sol-gel coating and anodizing, J. Solid State Electrochem. 11 (2007) 1375–1384.

DOI: 10.1007/s10008-007-0316-2

[8] J. H. Jang, W. S. Choi, S. H. Lee, Fabrication and characterization of a thin film capacitor using Al anodizing and Ni electroless plating, Scripta Materialia 63 (2010) 269–272.

DOI: 10.1016/j.scriptamat.2010.04.004

[9] J. H. Liu, Q. Guo, M. Yu, Effect of TiO2 nanostructures on specific capacitance of Al2O3–TiO2 composite film on etched aluminum foil formed by the sol–gel and anodizing, Ceram. Int. 40 (2014) 3687–3692.

DOI: 10.1016/j.ceramint.2013.09.056

[10] X. F. Du, K. Men, Y. L. Xu, Enhanced capacitance performance of Al2O3–TiO2 composite thin film via sol–gel using double chelators, J. Colloid Interf. Sci. 443 (2015) 170–176.

DOI: 10.1016/j.jcis.2014.11.038

[11] L. Sun, J. F. Bu, W. X. Guo, Electrophoresis deposition of TiO2 nanoparticles on etched aluminum foil for enhanced specific capacitance, Electrochem. Solid-State Lett. 15 (2011) E1–E3.

DOI: 10.1149/2.013201esl

[12] J. F. Bu, L. Sun, Q. Wu, Al2O3–TiO2 composite oxide films on etched aluminum foil fabricated by electrodeposition and anodization, Sci. China Chem. 54 (2011) 1558–1564.

DOI: 10.1007/s11426-011-4377-9

[13] J. J. Chen, Z. S. Feng, B. C. Yang, Al2O3–TiO2 composite oxide films on etched aluminum foil by hydrolysis precipitation and anodizing, J. Mater. Sci. 41 (2006) 569–571.

DOI: 10.1007/s10853-005-2507-5

[14] L. Xiang, S. S. Park, Preparation of titanium dioxide films on etched aluminum foil by vacuum infiltration and anodizing, Appl. Sruf. Sci. 388 (2016) 245–251.

DOI: 10.1016/j.apsusc.2016.01.166

[15] L. Yao, J. H. Liu, M. Yu, Formation and capacitance properties of Ti–Al composite oxide film on aluminum, Trans. Nonferrous Met. Soc. China. 20 (2010) 825–830.

DOI: 10.1016/s1003-6326(09)60221-1

[16] R. S. Alwitt, C. K. Dyer, B. Noble, Voids in anodic aluminum oxide films, J. Electrochem. Soc. 129 (1982) 711–717.

DOI: 10.1149/1.2123956

[17] J. Yu, X. Zhao, Q. Zhao, Effect of film thickness on the grain size and photocatalytic activity of the sol–gel derived nanometer TiO2 thin films, J. Mater. Sci. Lett. 19 (2000) 1015–1017.

[18] L. H. Liu, Q. Guo, M. Yu, Formation and dielectric properties of Al-Ti-O nanocomposite oxide film on aluminum using sol–gel and anodizing, ECS J. Solid State Sci. Technol, 2 (2013) N55–N60.

DOI: 10.1149/2.007303jss