Synthesis And Properties Of TiO₂ Nanotubes

Anodic titanium oxide nanotube arrays（TNTs）is one of the most extensive studied materials in the fields of catalysis and dye-sensitized solar cells in recent years.TNTs exhibit high surface area and controllable nanoscale geometry.Compared to other preparation technology of titanium oxide nanotube arrays,anodic oxidation process exhibit improved properties due to its simplification and excellent performance of TNTs.To explore the precise regulation of exterior morphology of the conditions for the preparation of TiO₂ nanotubes using has a very large value.Though about the preparation of TiO₂ nanotubes has caused the attention of many people and preparation conditions have also been relatively mature,the magnetic of TiO₂ nanotubes,and the source of the magnetic everyone still heavy said,for the electrical research also are relatively rare.Therefore,we have fabricated the TiO₂ nanotubes by anodic oxidation,and characterized the microstructure,magnetism and electrical property by field-emission scanning electron microscope（SEM）,physical property measurement system（PPMS）,x-ray energy dispersive spectroscopy（EDS）and so on.（1）Highly ordered TiO₂ nanotubes are prepared using NH₄ F glycol solution by the two step anodization at room temperature.This article discussed the impact of oxidation time,oxidation voltage,electrolyte,moisture content in the electrolyte and the distance between the cathode and anode on the morphology of TiO₂ nanotubes.The experimental results show that these factors are mutually restricted,and the relatively important factors are oxidation time,the distance between the cathode and anode and oxidation voltage.In this article,we got the longest nanotube is about 23 microns.Although the preparation is limited by many conditions,we can control the microstructure accurately,and the application will more extensive in the future.（2）Characterized the magnetism of TiO₂ nanotubes using PPMS,and prepared Ag/TiO₂ / Ti devices on the base of TiO₂ nanotubes.The experimental results show that the TiO₂ nanotubes have weaker ferromagnetic at room temperature.For the I-V measurement,there is stable bipolar resistive switching behavior in TiO₂ nanotubes.Studied the relationship between the resistance state and magnetism of TiO₂ nanotubes,and realized the electric field induced ferromagnetic.Analysis that the room-temperature ferromagnetism of TiO₂ nanotubes and the characteristics of bipolar resistance switch are from the oxygen vacancy in the inside and outside wall of the nanotube,and the large magnetic anisotropy and the intensity of magnetization on different annealing conditions support this analysis.Experiment shows a ferromagnetic signal that is much stronger perpendicular to the TiO₂ nanotubes films than it is parallel to the film surface,and the magnetization can be controlled by annealing conditions.When Ag/TiO₂ / Ti devices in different resistance state,the oxygen vacancy will change,thus the magnetism of TiO₂ nanotubes will have corresponding change,and the electric field induced ferromagnetic will be realized.The application of TiO₂ nanotubes in the field of spintronics and multi-functional storage will more extensive in the future.