Growth Behaviors of Anodic Titanium Oxide Nanotubes in the Ethylene Glycol Solution According to Water Contents

摘要

TiO_2 nanotubes fabricated in aqueous HF-based electrolytes have been generally grown only to about 500nm in length because of the strong dissolubility of HF acid. In this paper, ethylene glycol solution has been applied for increasing the length of the anodic TiO_2 nanotubes, and the growth behaviors of the nanotubes according to water contents has been investigated. Anodization of Ti in ethylene glycol + 1 wt percent NH_4F (EG solution) with water additions up to 10 wt percent were carried out at the constant voltage of 20 V. The results show that a thin titanium oxide layer is formed in the initial stage and the nanotube structure grows underneath the initial layer. And the length of TiO_2 nanotubes decreases with the increasing water content in the solution. It can be ascribed to the locally acidified circumstance around the barrier layer inside the nanopore due to H~+ ion originated from water. The XPS for the nanotubes suggests that the spectra of Ti2p and O1s are the major chemical bonding states of the TiO_2, and those for F1s, N1s and C1s come from the compound of (NH_4)_2TiF_6.