Of Titanium Dioxide Nanoparticles And Their Performance

Highly ordered nanomaterials are currently in great attention of many research fields. Titania has good photo electricity and gas sensation. It has been a hot spot at photo catalyzing degradation of pollutants, sensor and other important applications. In order to obtain the best performance and application, it is necessary to control the transformation From anatase to rutile phase. Phase-transformation of TiO₂ can be easily controlled by controlling the roasting time by KCl-NaCl composite molten salt method in the paper, and the nanomaterial has also been investigated in detail.The main results are as below:Phase-transformation controllable nanosized titania particles were fabricated by molten salt process through controlled the roasting time at 700℃. The anatase was obtained when roasting two hours, and the average size of product is about 20nm. The influences of a number of synthesis parameters for the preparation of titanium oxide nanoparticles such as roasting temperature, roasting time, and the ratio of the molten salt have been investigated. The microstructures and morphologies of the TiO₂ nanoparticles were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the roasting temperature was higher, the crystallization of titanium dioxide nano-materials was better; The ratio of malten salt had little influence with crystallization, while the roasting time exerted great influence with it and showed a certain regularity.The photoluminescence (PL) properties of the TiO₂ nanoparticles were discussed. There are two optical centers for the TiO₂ nanoparticles, the first originates from the F centers located at 465 nm, and the second is correlated with the electron transition in TiO₂ nanoparticles from the bottom of the conduction band to the top of the valence band which is ascribed to the quantum effect. The PL emission spectra can be useful to disclose the efficiency of temperature-induced structural transitions. There are two optical centres in the annealed TiO₂ nanoparticles. The first originates from the F centres located 465 nm, the second is correlated with the electron transition in anatase from the bottom of the conduction band to the top of the valence band located at 393 nm.The photocatalysis activities of TiO₂ nanoparticles were characterized by quantifying the degradation of methyl orange and Methylene Blue dye solution. The comparative of photocatalytic performance on phase-transformation controllable nanosized titania particles was investigated. The result indicated that the product after roasting for 6 hours exhibited the best photocatalytic efficiency. After 25 min, the degration ratio was about 22.28%.The reason may be the lower recombination efficiency of the electrons and holes after light activation due to the lower fluorescent energy. the degradation of methylene Blue dye solution, the result was regularity when roasting for 2 hours.The anatase nanoparticles were used as negative materials for lithium-ion battery, whose charge-discharge properties, cyclic voltammetry, electrochemical impedance spectroscopy and cycle performance were examined in detail. The results showed that there is a potential plateau at 1.73 V and 1.93 V in the process of Li insertion and extraction, between 1.0～2.5 V,at 0.25 C. The initial Li insertion /extraction capacity is 223mAh/g and 203.6mAh/g, respectively. In the 5th cycle, the discharge capacity is 213.2mAh/g,95.61% of initial discharge capacity was maintained; In the 10th cycle, the discharge capacity is 183.5mAh/g,83.29% of initial discharge capacity was maintained. In the 15th cycle,the discharge capacity is 160.1mAh/g,71.79% of initial discharge capacity was maintained,CV show TiO₂ electrode is reversible as the lithium cathode.