Papers by Keyword: Titania (TiO₂)

Abstract: The diamond photonic crystals with the periodic arrangement of high dielectric constant (ε=100) were fabricated, and photonic band gap properties in the millimeter waveguides were investigated. Acrylic diamond lattice structures with TiO2 dispersion at 40 vol. % were fabricated by Micro-stereolithography. The forming accuracy was 10m. After sintering process, TiO2 diamond lattice structures are obtained. The relative density reached 96%. The millimeter wave transmittance properties were measured with network analyzer and W-band millimeter waveguide. The band gap was measured between 90 GHz and 110 GHz in the Γ-X <100> direction, which was well agreed with the results calculated by the plane wave expansion method and simulated by the Transmission Line Modeling method.

Abstract: Through a few examples, we present a short review on properties and applications of TiO2 films deposited by various CVD processes. The constraints due to the growth process make difficult optimization of properties that were correlated with microstructures. We focus on the photocatalytic activity in the visible range and on the antibacterial behavior of these functional thin layers.

Abstract: Composites of Sm doped TiO2 nanoparticles dispersed on carbon nanofibers (Sm-TiO2/CNFs) with different Sm contents were prepared by preoxidation, hydrolyzation and calcination of Sm-TiO2 precursor/PAN nanofibers. The characterizations of SEM, EDX, XPS and XRD showed that the CNFs surface was loaded by Sm-TiO2 nanoparticles with a uniform size of about 10nm, existing as anatase. It was concluded from XPS results that Ti element exist as Ti4+ and Sm doping increased the content of absorbed oxygen in composites. The effect of Sm doping on the photocatalytic activity of the Sm-TiO2/CNFs composite was investigated by the photocatalytic degradation of methyl orange aqueous solution under UV irradiation. It was found that Sm doping could improve the photocatalytic property of Sm-TiO2/CNFs effectively compared with the undoped specimen, and the photocatalytic activity of the Sm-TiO2/CNFs samples enhanced firstly and then reduced with Sm content increasing.

Abstract: Carbon/TiO2 composites were prepared via the reaction under Autogenic Pressure at Elevated Temperature (RAPET) using alkoxides as precursor, and then porous TiO2 hollow spheres were derived after removing the carbon ingredient by calcination at 600°C. The influence of surfactant additives, including the addition ratio and the nature of the surfactants, on the morphology and the structures of the Carbon/TiO2 composites and the derived TiO2 were also studied with scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectrophotoscopy (DRS) and nitrogen adsorption-desorption measurements. The results revealed that the morphology of the products turned to spherical and then fusiform and the structures turned from hollow to solid with the increasing of surfactant additive. The BET surface area of the hollow TiO2 was modified from 12m2/g to 57m2/g after calcinations. The XRD investigation indicates that the phases of the TiO2 in both the carbon/TiO2 composites and the derived TiO2 hollow spheres are anatase.

Abstract: This study investigated the effect of surface roughness on a coating of TiO2 submicron powders that had been applied on a stainless steel mesh using electrophoretic deposition (EPD). Roughness was provided to the surface of EPD coating using UV pre-illumination to the suspension prepared by isopropyl alcohol and commercial TiO2 powder. The Ra value was increased around 20% by this treatment. The rough coating provided a higher photocatalytic decomposition rate of 1,4-dioxane in water than a smooth coating obtained from the suspension without UV pre-illumination. That increase is attributable to the increase of the reaction field on the coating surface.

Abstract: The binding energy of anatase TiO2, in which the Ti was substituted by other transition metals in the 4th, 5th and 6th periods of the periodic system of the elements, has been calculated by using first principles method. The doping limits of V, Cr, Zr, Nb, Mo and W are 61.5%, 39.7%, 88.2%, 100.0%, 65.0%, and 63.2%, respectively predicted by the calculated binding energy, while the doping limits of other transition metals are much lower. So, these transition metals can easily be doped into the anatase structure theoretically while it is difficult for the others. And the band structure and density of states (DOS) of V, Cr, Zr, Nb, Mo and W doped anatase TiO2 have also been calculated and analyzed.

Abstract: To obtain porous and thick TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating technique on quartz glass substrates using this sol. The TiO2 films were calcined at 500-700 °C. The photocatalytic activity of the films was evaluated by examining decomposition of methylene blue in aqueous solution under UV light irradiation. The TiO2 film prepared from the sol with trehalose was more active than TiO2 film prepared from the sol without trehalose. The trehalose addition to the dip-coating solution was effective in improving the photocatalytic activity of the TiO2 film.

Abstract: F-doped TiO2 has exhibited superior photocatalytic activity. However, its electronic structures and photocatalysis mechanism are still unclear. In the present work, the structural optimization and electronic structure of F-doped anatase TiO2 have been investigated by means of the first-principles pseudopotential total energy method. It has been demonstrated that F doping would modify the valence band at the lower energy direction in the F-doped TiO2. Calculation results confirm that doping of fluorine would not shift the absorption edge into the visible light region. Instead, we attributed its photocatalytic activity to the enhancement of the oxidative power of F-doped TiO2.

Abstract: The porous TiO2 layer on the silicon surface not only acts as a buffer layer to relieve the strain associated with the volume expansion but also prevents the aggregation of the particles upon normal cycles of charging and discharging. The control of the optimum amount of catalyst has led to enhance the cycle performance of TiO2 coated silicon anode.

Abstract: Hybrid composite films made of an organic polymeric matrix and an inorganic nanosized filler, namely titania prolate nanoparticles, have been prepared and characterized both thermally and mechanically. The filler content has been varied, while still being kept in the regime of unsaturated, homogeneous nanocomposites. On increasing, the filler content there is an abrupt increase in hardness at an intermediate load, while the elastic modulus increases almost linearly. The glass transition temperature is also increased, with a tendency to saturation. The morphological characterization of the films confirms a lack of phase separation, with only a continuous, slight increase in surface roughness, and no major effects on the top film features.