TiO₂ Nanotubes – Annealing Effects on Detailed Morphology and Structure

Abstract

The present work deals with self-organized TiO 2 nanotube layers formed on a Ti metal substrate by anodization. For virtually any electrical or photoelectric application, these originally amorphous nanotube layers need to be converted to anatase. Most frequently, this is done by annealing at temperatures of approximately 450°C. In the present work we use TEM and XRD to compare the annealing at a significantly lower temperature of 350°C with that at the established 450°C. HRTEM results show that both annealing

TiO2‐Nanoröhren: Synthese und Anwendungen

“…[180] Weitere Berichte besagen, dass bei der anodischen Schichtbildung die Umwandlung des amorphen TiO 2 -Films in die kristalline Anatasphase nicht nur von der Anodisierungsdauer, sondern auch von der angelegten Spannung abhängen. [101,[206][207][208][209] Neben dem stöchiometrischen TiO 2 [103,118,214] berichten über die Gegenwart von Nanokristalliten in der Röhrenwand (insbesondere wenn die Anodisierung bei höheren Spannungen durchgeführt wurde). In einem sauren Elektrolyten (H 2 SO 4 ) kann der gebildete Oxidfilm je nach Anodisierungsbedingungen (Funkenentladung, potentiostatisch oder galvanostatisch) aus Anatas, einer Mischung aus Anatas und Rutil oder aus Rutilkristalliten bestehen.…”

Transport properties of single TiO2 nanotubes

“…The relatively simple way to produce such self-organized TiO 2 nanotubes on Ti substrates makes this approach cheap and efficient compared to other fabrication techniques. These TiO 2 tubes are usually amorphous after growing but can be converted to anatase by annealing at temperatures (T) higher than 300 C. 14,15 After annealing, the nanotubes are polycrystalline with an average grain size of 10 to 50 nm. 16,17 We have used impedance spectroscopy in order to discern between the mechanisms of conduction given by the possible electron pathways in the sample.…”

Key Oxidation Parameters that Influence Photo-Induced Properties and Applications of Anodic Titanium Oxides

“…Fig. 3 presents the cross-section images for selected samples (20,50 and 90 V on Ti foil in both electrolytes -S1, S2, S3 and P1, P2, P3) and there is a good correlation between the two methods. However a small difference can be observed due to two reasons: first, the layer thickness is not uniform and secondly, the porosity due to sparking.…”

“…18 It is well known that during annealing (thermal oxidation) of just a plain Ti substrate, thin rutile thermal oxide layers are obtained. [48][49][50] The rutile thermal layer grows from the titanium substrate 50 and augments the existing thickness of the compact oxide layer, and further anatase to rutile conversion inside the oxide layer takes place. This intermediate thermal layer observed by SEM (≈80 nm) corroborates the increase in thickness observed by spectrophotometry in Fig.…”