2 </ Sub> Preparation And Properties Of Of Controlled Nano. Crystalline Phase Tio <sub>

Pure rutile nano-powder, pure anatase nano-powder and mixed-Phase TiO₂ were synthesized by hydrothermal method, using tetrabutyl titanate(TBT) as material, using high concentration of hydrochloric acid as acidic medium. The effects of experimental conditions to the structure of the products, such as structure guiding reagent and aging temperature and aging time, were examined via XRD, TEM, Raman, FT-IR, SPS and UV-vis characterization methods. The growth machanism of nano-TiO₂ was analysed under the different reaction conditions.The experimental results suggested that the type and amount of structure guiding reagent palyed a important role to controll crystalline phase. Hydrogen bonds or lipid bonds could be formed between sulfonic group in the DBS and hydroxyl group neighbor on the [TiO6] octahedron, and these would limit the structure of growth units, which has been formed from hydrolysate. The change of aging temperature could affect the disassociation of DBS, which would affect the concentration of sulfonic group. As a result, the structure of growth units were affected. The different aging time could control the crystal nuclear amounts of different crystalline phase and the concentration of dissociative Ti4+ in system. Consequently, nano-TiO₂ of different crystalline phase could be obtained.The mixed-Phase TiO₂ particles with good crystallization and dispersion were spherical morphology, and their diameter sizes were 4～15 nm. The experimental results suggested that the nano-powder containing 20% rutile and 80% anatase. The mixed-Phase TiO₂ showed the higher photocatalytic activity, which excelled P25 photocatalyst. The self-preparation suntan oil using pure rutile nano-powder has better UV-shielding properities and stability than chemistry suntan oil and physical suntan oil on the market. And it has the other advantages, such as non-toxic and no absorbed by skin.