Scanning Electron Micrograph and -Ray Diffraction

SEM investigations show that the breakdown sites are randomly distributed and there is no sign of self-organization at 

On the other hand, when using Ti thin film onto silicon substrates (Fig. 5.8), self-organized Ti02 nanotubes layers with thickness of about 600 nm are obtained after anodization under the same conditions. Moreover, the nanotube diameter and wall thickness are in the range 50-200 nm and about 20 nm, respectively. Hence, a layer of titania nanotubes is successfully fabricated on Ti foils and Ti thin films. Moreover, the titania nanotubes were heated at 450°C in air for 3 h and the nanotube morphology remained unmodified, as we will discuss later. 

XRD characterization can be helpful in knowing which Ti02 phase or which kind of amorphization is obtained just after anodization and thermal treatment. For that purpose, X-ray-diffraction (XRD) patterns were recorded at room temperature using a Siemens D5000 diffractometer with Cu Ka radiation (1.5406 A) with a recording scan 0.133°/min. 

The robustness of the two substrates should be addressed considering its integrity under these annealing conditions since no differences were observed by XRD and SEM. Moreover, the microstructure of the nanotubes remains basically unmodified as it can be seen from the SEM image given in Fig. 5.9. It is clear 

XRD patterns of (a] as-prepared and annealed ntTi02 nanotube layers on T1 foils with 600 nm length, [b] As-prepared and annealed ntT102 nanotube layers on T1 foils with 900 nm length, [c] As-prepared and after heat treatment at 450°C of TIO2 nanotube layers onto SI substrate. Note that reflections of anatase are written in the figure. 

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