Studies On Fabrication Properties Of Titania Nanocomposites

TiO₂ nano materials have been studied extensively and found a lot of applications in the last tens years due to their high photocatalytic activity, chemical stability, nontoxicity, and the degradation capability to organic pollutants.TiO₂ nanoparticles can be fabricated by various methods including sol-gel, hydrothermal method, microemulsion method, liquid phase deposition and chemical vapor deposition. In this thesis, TiO₂ nanoparticles were prepared by sol-gel. Different experimental conditions and different predecessors were investigated for the preparation of TiO₂ nanoparticle. It is also investigated to improve the performances of TiO₂ nanomaterial by doping it with different materials. However, only the ultraviolet light, a small portion (4-6%) of the solar spectrum can be absorbed by TiO₂ due to its large energy band gap (3.0-3.2 eV), which limits the application TiO₂ in photocatalytic field. It is important to improve the photocatlytic efficient of TiO₂ in the visible region. Various methods have been proposed to improve the photocatalytic performances of TiO₂, including the doping of metals or nonmetals, deposition of nobelmetals, modification of semiconductor composition, etc.In this thesis, the following work has been performed:(1) Mn-doped TiO₂ nanoparticles were prepared with sol-gel method and applied on glass fiber cloth to obtain thhe Mn-doped TiO₂ nanopartiles-coated film. The effect of sinter temperatue on the performance of the as-prepared film was investigated. The as-prepared film were characterized with field-emission scanning electron microscope (FE?SEM), energy dispersive x-ray (EDX), and X-ray diffraction (XRD).The results show that the crystal structure is dependent on the sinter temperature. The 450℃sintered TiO₂ is in anatase crystal with the best photocatalytica activity. The stability test show that the photocatalytic activity decreased after the first useage.(2) TiO₂ nanoparticles were prepared with sol-gel method using butyl titanate as precursor. The preparation conditions were optimized. The as-prepared catalyst powder was doped with Mo, and the photocatalytic performances of the Mo-doped TiO₂ particles were investigated with relative to the un-doped catalyst.The optimal preparation conditions are: water- ethanol mixture solvent, pH 2-3, the mole ratio of ethanol to butyl titanate ratio is 5:3, reaction temperature 35-40℃, Calcining temperature is in 600-700℃.(3) TiO₂ nanopowder was prepared with titanyl sulfate, the industry medium products, as precursors by uniform precipitation. The effects of the preparation and degradation conditions on the degradation efficiency were investigated. The lanthanum,selenium, and cerium-doped TiO₂ nanocomposits were prepared. The degradation experiments show that the best potocatalytic degradation rate is achieved with less than 1% of selenium dopant. While the doped elements are more than 2%, degradation rate of most the doped TiO₂ nanocomposites decreases greatly.