Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (06): 1291-1305.doi: 10.3866/PKU.WHXB201204093

• REVIEW • Previous Articles     Next Articles

Research Progress in Formation Mechanism of TiO2 Nanotubes and Nanopores in Porous Anodic Oxide

ZHU Xu-Fei1, HAN Hua2, SONG Ye1, DUAN Wen-Qiang2   

  1. 1. Key Laboratory of Soft Chemistry and Functional Materials of Education Ministry, Nanjing University of Science & Technology, Nanjing 210094, P. R. China;
    2. The National Engineering and Technology Research Center for ASIC Design, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, P. R. China
  • Received:2012-02-22 Revised:2012-04-01 Published:2012-05-17
  • Contact: ZHU Xu-Fei
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (61171043, 51077072) and National Science and Technology Major Project of the Ministry of Science and Technology of China (2009ZX01021-002).

Abstract: Self-ordered porous anodic TiO2 nanotubes and other porous anodic oxides (PAO) have received considerable attention because of their potential for high technological application in a number of fields. The anodization of valve metals has been widely investigated over the last eight decades. The formation mechanisms of hexagonal cells and nanotubes, however, have remained unclear until now. Simply reviewing the mechanisms of PAO formation was not the aim of this research and we were more interested in reviewing the forming processes of compact anodic oxides (CAO) and investigating the relationship between the PAO and CAO, to better understand the pore generating mechanisms. The present work introduces the differences between PAO and CAO films, as well as reviewing the traditional theories of PAO films and their deficiencies. Recent progress in the formation mechanism of PAO, including the viscous flow, breakdown, equifield strength, and oxygen bubbles models has been reviewed in detail. The perspective on future developments for the PAO forming mechanism has been tentatively discussed. Based on sufficient analysis of the latest findings, it has been proposed that several approaches may be employed for investigating the pore forming and self-ordering mechanisms. These new approaches include ultrasound-assisted anodizing, anodizing under vacuum or high pressure and adding sodium carbonate or a reducing agent to the PAO-forming electrolytes. An investigation of changes in the current and anodizing efficiencies would also be an effective approach for better understanding the physical nature of fieldassisted dissolution (FAD).

Key words: Compact anodic oxide, Porous anodic oxide, Formation mechanism, Anodization, Self-ordering


  • O646