Papers by Keyword: Anatase

Abstract: Quasi-solid state dye-sensitized solar cells (DSSC) having bilayer structure were made by using nanocrystalline anatase-rutile TiO₂ to enhance the photovoltaic performance. The bilayer structures were coated to FTO glass using doctor blade technique with total active area of 0.4 cm². Cyanidin dye extracted from mangosteen pericarp was used as photosensitizer. Bilayer anatase-anatase was formed with surface area of 99.9 m²/g and pore volume of 0.23 cc/g while anatase-rutile structure has surface area of 103.5 m²/g and pore volume of 0.21 cc/g. Overall energy conversion efficiencies under illumination of 10 mW/cm² of 0.461% and 0.1365% were achieved for DSSC employing anatase-anatase and anatase-rutile TiO₂ structure, respectively. Both efficiencies were higher than that of monolayer anatase and rutile TiO₂ structure whose efficiencies in the range of 0.02% to 0.037%. The photocurrent action spectra of bilayer structures performed high efficiency spectrum in the wavelength range of 420 480 nm owing to cyanidin effect of dye.

Abstract: Films of titanium dioxide (TiO₂) were deposited by aerosol deposition at room temperature. Anatase TiO₂ powders were used. The crystal structure of these films was a mixture of the anatase and brookite TiO₂ phases, while the rutile TiO₂ phase was observed at high carrier gas flow rates. The TiO₂ film thickness increased in proportion with the scan time and the carrier gas flow rate. Film thickness was constant at constant total deposition times. Flake-like and mesh-like surface morphologies were observed on the films. The direct-current resistivity was estimated from the dielectric constant and the loss tangent; it was found to be much smaller than that of bulk TiO₂. We speculate that this low resistivity is due to reduction of TiO₂ particles during room-temperature impact consolidation in a N₂ atmosphere.

Abstract: The lattice parameters (lattice constants a, c), elastic properties (elastic constants, bulk modulus, shear modulus) and optical parameter (dielectric function) are investigated from a theoretical perspective using computer simulation in the frame of density functional theory. The calculated lattice constants and elastic moduli are in agreement with the theoretical results. We found that anatase can retain its stability in the pressure interval 020Gpa. The anisotropy of this compound is found to increase with applied pressure. Moreover, the dielectric functions are also discussed. The plasma frequency and static dielectric constant of TiO₂ are 16eV and 6.1, respectively. * Corresponding author: Dong CHEN

Abstract: The new technique for the TiO₂ photocatalyst manufacturing with titanium tetrachloride alcoholic solution using was revealed. The ammonium titanate precursor was precipitated by double-jet method with TiCl₄ alcoholic and ammonium aquatic solutions using. The TiO₂ nanopowders were prepared by precursors calcinations at 400, 500, 600, 700 and 800°C. The photocatalytic activity determination was made by the way of dye photodegradation technique (methyl orange). The difference in adsorption ability of TiO₂ dispersion reference to organic dyes was found. The conditions for the synthesis of TiO₂ anatase effective photocatalyst synthesis were revealed.

Abstract: Simple sol-gel route was used to synthesis the TiO₂ nanoparticles and examined by X-ray diffraction (XRD). The small particle size and uniform morphology of the TiO₂ were found at different calcination temperatures. The kinetic study of phase changes from the anatase to rutile using the X-ray diffraction data with Avrami equation was investigated. The transformation of anatase to rutile was started after 500 °C and above by decreasing of XRD peaks intensity of anatase with rutile increased. The activation energy of the rutile phase was found lower which indicated that uniform shape and morphology of TiO₂ nanoparticles. At same time, changes of activation energy value depended on the experimental conditions was observed.

Abstract: TiO₂ thin films with a thickness of about 150 nm were deposited by spin coating method on sapphire substrate from a sol-gel system. The hydrogen sensing properties of TiO₂ films annealed at various temperatures were studied and correlated with their structure, optical and electrical properties. The annealing temperatures in the range of 600 800 °C lead to anatase films with a roughness in the range of 0.6 0.9 nm. Their sensitivity towards hydrogen is low. The thin films annealed at temperatures in the range 900 1000 °C consist of rutile phase and their roughness increased to 11.7 13.5 nm. They showed good hydrogen sensitivity with optimal operating temperature 200 250 °C. The structure and sensing properties of the prepared films are compared with those synthesized with magnetron sputtering. The maximum of sensitivity was measured on the thin films with diameter of the grains about 100 nm in both cases, i.e. on thin films prepared by sol-gel method as well as on thin films prepared by magnetron sputtering. The maximum sensitivity correlates with the diameter of the grains and dont depend on the allotropy of the titanium dioxide anatase or rutile.

Abstract: Nanocrystallization of anatase phase was established in BaO-TiO2-B2O3 glass system. Crystallization kinetics of anatase phase in these glasses were investigated using non-isothermal differential scanning calorimetry (DSC) at three different heating rates (10, 20 & 30 K/min). Scanning Electron Microscopy (SEM) carried out on heat treated (at 920 K) glasses confirmed bulk nucleation and three-dimensional growth. Johnson-Mehl-Avarami model could not be applied for this system suggesting considerable overlap of the nucleation and growth involving complex transformation process. However, modified Kissinger and Ozawa models were used to calculate the effective activation energy associated with anatase crystallization. The kinetic exponent n was found to be temperature dependent indicating the change in the crystallization mechanism. This was attributed to the high entropy fusion of anatase phase, fast crystallization rate and nano dimension of the anatase phase.

Abstract: The purpose of this research is to study the effect of synthesis temperature in order to produce anatase TiO₂ nanoparticles (NPs) without using strong acids. In this research TiO₂ nanoparticles was prepared by the hydrolysis and condensation of titanium (IV) isopropoxide in water at synthesis temperature of 0°C ± 0.1°C which produced anatase TiO₂ crystallite size of 4.66 nm. XRD (X-ray diffraction) was used to analyse the crystal structure of the TiO₂ and to calculate the crystallite size of the TiO₂ nanoparticles. Transmission electron microscope (TEM) was also used to characterise the morphology of the TiO₂ nanoparticles.

Abstract: Sodium hydroxide (NaOH)-, heat- and autoclave-treated Ti metal did not form apatite in simulated body fluid (SBF) within 7 days although certain amounts of sodium (Na) still remained on the Ti metal surface even after the autoclave treatment. When hot water treatment was applied between NaOH and heat treatment, the Ti metal formed apatite within 7 days in SBF. Anatase-type TiO₂ was partially precipitated by the NaOH and heat treatment but it was disappeared by the subsequent autoclave treatment. When the hot water treatment was applied between the NaOH and heat treatment, considerable amount of anatase-type TiO₂ was formed and it still remained even after the autoclave treatment. The zeta potential of the Ti metal with the hot water treatment was almost zero in SBF. These results indicate that Ti metal can show apatite-forming ability in SBF even after autoclave treatment, when hot water treatment is applied between the NaOH and heat treatment, and that anatase-type TiO₂ might play an important role in the apatite formation rather than the amount of Na and/or the zeta potential.

Abstract: This paper report the effect of milling time on the structural properties of TiO₂ nanopowder prepared from sol-gel milling process. The synthesized TiO₂ nanopowders have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR). XRD result reveals that the TiO₂ nanopowder in anatase phase is detected. The morphology of the TiO₂ nanopowder change obviously with the increase of the milling time. Further, FTIR results found the sharp peaks of Ti-O-Ti and Ti-O bonding at below 600 cm^-1 for all TiO₂ nanopowder.