Papers by Keyword: Titania (TiO₂)

Abstract: In order to develop an ideal material for the nozzle used in steel continuous casting process, the hydration resistance of some CaO-containing complex oxides and CaO-NiO solid solutions were investigated systematically. The hydration resistance of the complex oxides was CT >CZ>CS>CF>CB3BTB2 B>CB2BS>>CB2BF>CB3BA>CAB2B>CaO. CT should be a promising material for the nozzle. A large number of fine secondary-NiOss particles were separated from the CaOss crystal grains in CaO-NiO solid solution and improved the hydration resistance.

Abstract: Lightweight fine open-cell porous Si/SiC ceramic filter was fabricated using polyurethane sponge. The thickness of the strut and the cell size of porous Si/SiC ceramics were almost the same size of the original sponge. This porous ceramic was an ideal structure for photocatalyst supports. The contact probability between photocatalyst and pollutant could be easily increased by using this ceramic filter coated with photocatalyst. The TOC value of Orange II solution, coloring matter, could decrease remarkably using this photocatalytic ceramic filter and germicidal lamp.

Abstract: TiO2 has been intensively studied as a wide band-gap transition metal oxide partially due to the multi-valence nature of its cation. Here, density-functional theory calculations within the supercell approximation are carried out to determine the preferred charge state of point defects in rutile TiO2. The first component of this work is to investigate the dependence of the defect formation energies on supercell size and the electrostatic Makov-Payne correction. The results show that the Makov-Payne correction improves the convergence of defect formation energies as a function of supercell size for positively charged titanium interstitials and negatively charged titanium vacancies. However, in the case of positively charged oxygen vacancies, applying the Makov-Payne correction gives the wrong sign for the defect formation energy correction. This is attributed to the shallow nature of the transition levels for this defect in TiO2. Finally, we combine the calculated defect formation energies with thermodynamic data to evaluate the influence of temperature on the relative stabilities of point defects. The results indicate that when the Makov- Payne correction is applied, a stable charge transition occurs for titanium interstitials. In addition, as the temperature increases, the dominant point defect in TiO2 changes from oxygen vacancies to titanium interstitials.

Abstract: The coating of polymer surfaces with ceramics up to now is basically only accomplishable by vacuum-based technologies such as sputtering, because the thermal load is low compared to other methods such as sol-gel processing. Since the investment costs for the equipment required are considerably high and the coating is limited to line-of sight deposition, simple and cost-effective processing routes are sought. In all higher organisms inorganic materials are synthesized at ambient temperatures under physiological conditions. Therefore the study of biomineralization processes has gained considerable academic attention in the last decades. One of the key features of inorganic material deposition in vito is the interaction between supersaturated solutions and specifically modified surfaces. Following this paradigm so-called bio-inspired approaches can be developed which go beyond the current limitations of synthetic techniques. One example is the mineralization of planar polymer surfaces with TiO2 at 50oC. Using polystyrene latex particles as templates, all four stages commonly found in natural biomineralization can be emulated in a completely artificial system.

Abstract: Fibrous TiO2 with ca. 0.16 mm in width and 5 - 6 cm in length was prepared by drying a suspension of monodispersed anatase particles at 363 K in air. The TiO2 fibers thus obtained were thermally treated at the temperatures ranging from 363 to 1273 K for 1 h in air. Elevating the treating temperature increases the crystallinity of anatase phase and reduces the specific surface area from 98 to 5 m2/g due to the sintering of particles. The rutile phase appears at 1273 K by transformation of anatase phase. A photocatalytic activity of the fibers was examined by decomposition of methylene blue (MB) in water under UV irradiation centered at 365 nm. The fibers decomposed the MB in aqueous media under UV irradiation, indicating that the fibers possess a high photocatalytic activity. The catalytic activity is considered to be enhanced on increasing the crystallinity of anatase phase, nevertheless, that decreased with generation of rutile phase.

Abstract: An electrophoretic solution using TiO2 nano particles is the most promising candidate in electronic paper industry because it offers various advantages such as ink-on-paper appearance, good contrast ratio, wide viewing angle, image stability in the off-state and extremely low power consumption. To prepare an electrophoretic solution of TiO2 nano particles with low apparent gravity for electronic paper, TiO2 powders were mixed with polyethylene powders using high energy planetary-mill in cyclohexane with low dielectric constant and transparency. The zeta-potential value of raw TiO2 particles in cyclohexane was measured about -80mV but that of polyethylene-coated TiO2 particles by milling was measured over -110mV, with showing good dispersibility by surfactant attached to them. Thus it was possible to control surface charge on the TiO2 particle by using optimum amount of surfactant after polyethylene coating on them for enhancement of dispersion stability.

Abstract: An apparatus which presents a mechanical milling with electric discharge is introduced. As a model experiment, an anatase TiO2 nanopowder was processed by the method using NH3(10%)/N2 gas. The influences of specific surface area, crystal structure, and optical property were investigated. Relatively high specific surface areas exceeding 250m2/g were observed for all processed powders. The crystal structure and crystallinity of TiO2 did not change by the milling with electric discharge. On the other hand, noticeable absorption in Vis light range was observed, suggesting nitrogen doping into the powder.

Abstract: TiO2 sol with steady suspension and high photocatalytic activity was prepared via a precipitation-peptization method. The XRD results indicate that the TiO2 sol exhibited an anatase structure. TiO2 films on woven fabrics (carbon, PET and Nylon), prepared via dip-coating with TiO2 sol, were characterized by XRD and SEM analysis. The dependence of the woven fabrics properties on the amount of TiO2 coated and photocatalytic activity were also studied. When the diameter of fibers is smalle, large quantity of TiO2 is coated on woven fabrics leading to an improvement in the photocatalytic activity. It is observed that the photocatalytic activity of TiO2 film coated on woven fabrics exceeds that of TiO2 film coated on common glass substrate with the same surface area.

Abstract: Nanostructured and conventional Al2O3, ZrO2, and TiO2 were deposited using an atmospheric plasma spraying (APS). The size of commercial nano-ceramic powders was varied from 5nm up to 150nm. The microstructure and phase composition of the plasma sprayed coatings on metallic substrate were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that nano-sized ceramic powders enhanced the deposition efficiency on the metallic substrate rather than the micro-sized conventional commercial powders. Density and mechanical property such as microhardness were better in the case of the nano-sized ceramic powders than that of the conventional micro-sized ceramic powders, which are associated with the fine surface roughness and less size in pores of the coating layers. The wear rate of the nanostructured coating was lower than that of the conventional coating. The results were explained in terms of their microstructure of the coatings layers. Also, photocatalytic characterization of the plasma sprayed coatings, using nanocrystalline size TiO2 as feedstock with various powder sizes and shapes as well as adding with different photocatalytic oxides, was performed. The photocatalytic reactivity using plasma sprayed coating layers can be utilized into various applications.