The anodization voltage influence on the properties ofTiO2 nanotubes grown by electrochemical oxidation

Abstract

A systematic study of titanium dioxide (TiO2) nanotubes (NTs) grown by electrochemical anodization inNH4F + glycerol electrolyte has been carried out in a broad range of anodizationvoltage of 5–350 V and acid concentration of 0.1–0.7 wt%. It is found thatNTs can be grown in the voltage range from 10 to 240 V. The maximumNH4F acid concentration at which NTs can be formed decreases with the anodization voltage(Va). The maximumNH4F acid concentrationis 0.7% for Va<60 V, and itdecreases to 0.1% at Va = 240 V. Glancing angle x-ray diffractometer (GAXRD) measurements show that as-grown amorphousTiO2 transforms to the anatase phase when annealed at400 °C, and further transforms to the rutile phase at annealing temperatures higher than500 °C. The transition temperature from anatase to rutile phase depends on the anodizationconditions. The electrical resistivity of the NT increases by eight orders of magnitude whenVa increases from 10 to 240 V.