Titanium oxide nanotubes anodized in aqueous and non-aqueous electrolytes

Titanium oxide nanotubes having a very large surface area are very attractive for battery, gas sensor, photo catalytic applications, and as biomaterials. Titanium of 99.7% purity was anodized in 1 M potassium phosphate monobasic (KH2PO4) water solution, glycerine, and ethylene glycol with 0.15 M, 0.17 M, and 0.075 M NH4F. Titanium oxide nanotubes were fabricated at an anodization maximum potential of 25 V in the aqueous solution, 50 V in glycerine, and 60 V in the ethylene glycol solution. The maximum lengths of nanotubes were 3.0 mu m, 14 mu m, and 164 mu m, respectively. The diameter and length of the titanium oxide nanotubes were compared. The diameters of nanotubes were from 100 urn to 150 urn in the aqueous and ethylene glycol solutions but on the other hand the diameter was 60 nm in glycerine. These differences come from the properties of the anodization solution such as the viscosity and ionic strength of the solutions (electric conductance) and these are key factors for titanium anodization. After anodization, annealing at 500 degrees C for 30 minutes was followed and the anatase phase appeared on the surface of the titanium nanotube. From electron-diffraction patterns obtained by the fast Fourier transform (FFT) of HRTEM images, the measured angle between the (011) and (101) planes was 82.2 degrees, which was consistent with the theoretical value of the anatase structure. From results of this study we could control the morphology of titanium oxide nanotube arrays by anodization.