The growth rate of nanotubes and the quantity of charge during anodization

Abstract

Porous anodic oxides have attracted great attention because of their unique morphology and porous structure. At the same time, the study of the mechanism has become a hot topic. Here, in order to study the formation mechanism, the growth of porous oxides of Ti and Zr at different voltages has been studied. The results show that the growth rate of ZrO2 nanotube is much higher than that of TiO2 nanotube, and the length of ZrO2 nanotube is much longer than that of TiO2 nanotube. By comparing the current–time curves, it is found that the difference of growth rate of nanotube is related to the quantity of charge, that is, integral of current–time curve (Q=∫I dt). At the same time, it is also found that the growth rate of ZrO2 nanotubes is higher than that of TiO2 nanotubes. For example, the average growth rate of ZrO2 nanotubes is 0.422 μm/min, while the growth rate of TiO2 nanotubes is only 0.131 μm/min at 20 V. These interesting findings negate the idea of fluoride ion dissolution in the classical field-assisted dissolution theory. The oxygen bubble model and electronic current theory can well explain this conclusion.

Keywords

• Anodization
• Oxygen bubble model
• TiO2 nanotubes
• ZrO2 nanotubes