Preparation and formation mechanism of fast-growing ZrO2 nanotubes and slow-growing TiO2 nanotubes

The preparation and application of porous anodic oxides have been widely studied, but their formation mechanism remains controversial. In this paper, TiO2 nanotubes and ZrO2 nanotubes were prepared in the same electrolyte at different voltages. The results show that the average growth rate of TiO2 nanotubes is slow, the length of nanotubes is short, and the length to diameter ratio is only 19. Under the same conditions, the average growth rate of the ZrO2 nanotubes is very fast, the length of the nanotubes is very long, the length to diameter ratio is up to 356. In addition, ZrO2 nanotubes are all burst nanotubes, while TiO2 nanotubes are mostly unburst nanotubes in SEM photos. All these interesting phenomena cannot be explained using the traditional field-assisted dissolution theory. In this paper, the oxygen bubble mold and the theory of electronic current were used to analyze the current-time curve of anodization. The total current was divided into ionic current and electronic current, and the growth mechanism and average growth rate of the two kinds of nanotubes were explained because of the difference of ionic current and electronic current.