Fabrication of TiO2 Nanotube Arrays by Rectified Alternating Current Anodization

Anodization is a popular method of preparing TiOnanotube array films(TiNTs) by using direct current(DC)power as the driving voltage.In this study,three driving voltage modes,namely,the sine alternating current(sine) mode,the full-wave rectification of sine waves via four diodes(sine-4D,where D means diode) mode,and the DC mode,were used to prepare TiNTs by anodization.At 20 V,TiNTs were formed under sine-4D mode but only irregular porous TiOfilms were formed under DC mode.At 50 V,TiNTs formed under both the sine-4D and DC modes.No TiNTs formed in the sine mode anodization at either 20 or 50 V.Compared with the DC mode,the sine-4D mode required a lower oxidation voltage for TiNT formation,which suggests that sine-4D is an economical,convenient,and efficient driving voltage for TiNT preparation by anodization.The morphologies and structures of TiNT samples anodized at 50 V in the sine-4D and DC modes at different oxidation time(1,5,10,30,60,and 120 min) were analyzed.TiNT growth processes were similar between the studied modes.However,the growth rate of the films was faster under the sine-4D mode than the DC mode during the first 30 min of anodization.