Studies Of Bi-modified Titanium Oxide Nanotube Arrays

In this thesis, the modification of Bi element for the TiO₂ nanotube arrays was studied. The Bi-Ti alloys with different Bi contents were prepared firstly by a powder metallurgical method; then the Bi-doped TiO₂ nanotube arrays were obtained by anodisation of those Bi-Ti alloys. BiO_X（X=Cl, Br, I）-TiO₂ composite films were also obtained by vacuum impregnation and chemical precipitation methods. The morphologies, crystal structures, elementary compositions and the properties such as photocatalytic activity, and thermostability were characterized by SEM, XRD, XPS and UV-vis. The properties of photovoltaic conversion, photovoltaic energy storage and anti-corrosion properties of the samples were characterized by electrochemical analyzer at the same time.1. The Bi-Ti alloys with different bismuth titanium atom ratios（1:99, 3:97, 5:95, respectively） were obtained by a powder metallurgical method. The crystal structures and anti-corrosion properties of the Bi-Ti alloys were studied, respectively.2. The morphologies and crystal structures of the Bi-doped TiO₂ nanotube arrays which were obtained in glycol solution by anodic oxidation method were investigated. Results showed that the morphology and crystal structure of the TiO₂ nanotube arrays were not affected by the Bi doping. The samples were of anatase structure after annealed at 460 ℃.3. The effect of different concentrations of Bi-doping to the TiO₂ nanotube arrays was investigated in terms of photo-activity. Results show that the photovoltaic conversion property and photocatalytic activity of the samples were suppressed due to Bi-doping. The Bi-doped TiO₂ nanotube arrays had the best energy storage performance and anti-corrosion property when the Bi concentration was 3 mol %.4. The thermostability of Bi-doped TiO₂ nanotube arrays was studied and results demonstrated that part of nanotubes melt after annealed at 650 ℃ while most of nanotubes seriously melt at 750 ℃; Compared with the undoped samples, the thermostability of the Bi-doped samples decreased due to the Bi doping.5. BiO_X-TiO₂ composite films were obtained by vacuum impregnation and chemical precipitation and the morphologies, phase components and photocatalytic activities of those samples were studied in detail. Results showed that the morphologies of the composite films were obviously different with the different added halide ions. The photocatalytic activity of the samples decreased in the order X = Cl, Br and I. The methyl orange was chosen as degradation object and photocatalytic results showed that the decolorization ratios of both BiOCl-TiO₂ and BiOBr-TiO₂ composite films were much higher than that of the pure TiO₂ nanotube array film, while the decolorization ratio of BiOI-TiO₂ composite film was similar to that of the TiO₂ nanotube array film. The photocatalytic activity of BiOCl-TiO₂ was slightly higher than that of BiOBr-TiO₂.