Papers by Keyword: Anatase

Abstract: In order to avoid the damage on mesostructure by the high temperature treatment, inorganic titanium species were used as the precursors for the preparation of mesoporous TiO2 of crystalline framework at mild conditions. The influences of the precursor, additive, reaction pH and temperature on phase and textural structures of the products were investigated. The samples were characterized by XRD, N2 adsorption/desorption, FT-IR and SEM. The results show that anatase mesoporous TiO2 with large surface area could be obtained without calcination with Ti(SO4)2 as precursor or TiCl4 when SO42- was added. And the template could be completely removed by Soxhlet extraction.

Abstract: A comprehensive analysis of structural-reactivity relations on TiO2 nanocrystals is presented. Using an interplay between TEM, X-ray diffraction and vibrational spectroscopy of well-defined anatase and rutile TiO2 nanocrystals correlations between the adsorbate structure of formic acid and the corresponding photo-induced decomposition rate are described. It is demonstrated that the detailed bonding configuration determines the decomposition rate. Generalizations and implications of the findings are discussed.

Abstract: A high efficiency nanocomposite photocatalyst is reported. Multiwall carbon nanotubes (MWNTs) were coated with titania. Two distinct types of nanocomposites were synthesized with variation in the synthetic procedure. One of the nanocomposites is based on a core of arc-discharge synthesized multiwall carbon nanotubes; whereas the other is based on a core of chemical vapor deposition (CVD) grown MWNTs. The nanocomposites have a similar appearance in transmission electron microscopy pictures in that they have a core of MWNTs that are chemically bonded to a few nanometer thick layer of pure anatase phase of titania. Yet they show a dramatically different photocatalytic behavior when they are compared on the basis of rates of photocatalytic decomposition of an organic dye in aqueous media following the Langmuir-Hinshelwood mechanism. This article focuses on the analysis of the differences in the nanocomposites using X-Ray Photoelectron Spectroscopy (XPS). XPS spectra of these materials indicate that there are distinct differences. However, they also show that both share C-O-Ti bonds that transform the carbon in the carbon nanotubes into a dopant for the anatase titania. This doping seems to be essential for long wavelength, i.e. visible light induced photocatalysis.

Abstract: In this study, titania (TiO2) nano powders were synthesized by a new method. TiO2 nano-sized powders were prepared by a gel-casting method. Crystalline structure, morphology and mineral phase analysis of TiO2 powder have been characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Results show that different preparation conditions of gel such as reactants concentration, accelerator, starter concentration, time and temperature of calcination have a large influence on the properties of the produced powder. Calcination time and temperature can improve the crystallization of TiO2 powders and can be an accelerator factor for converting amorphous phase to anatase or rutile phase. The results obtained show that the anatase to rutile transformation is started at about 750oC and the best size of produced powder grain is 20-25 nm.

Abstract: Nowadays, different production methods of nanoparticles have been developed. Among novel wet-chemical processes, the Chemical Bath Deposition (CBD) method is used to synthesize nanoparticles more easily than the other method. In this investigation, titanium dioxide (TiO2) nanoparticles were synthesized by the Chemical Bath Deposition (CBD) method. Tetraisopropyl titanate (C12H28O4Ti), sodium hydroxide (NaOH) and ethanol were used as initial materials. Appropriate solvents were used for preparation of samples. CBD process was carried out at 50°C for 90 min and the obtained materials washed and then dried at room temperature for 48 hrs. For determining particle size and evaluation of morphological characteristics, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used. The TEM observation indicated that the average particles size of powder is about 10-30 nm and the shape of product is semi-spherical shape. The final results present that the CBD method is more suitable than the other process because of it showing a low processing cost and fine powders.

Abstract: The utilization of Al2O3 and Li2O as dopants that promote the anatase-to-rutile (A-R) phase transition in TiO2 nanoparticles during calcinations is studied. X-Ray Diffraction and SEM techniques were employed for the evaluation of phase transformation and particle size coarsening in pure TiO2, TiO2-Al2O3 and TiO2-Li2O mixtures. For the Li-Ti-O pseudobinary systems some complex oxides may be formed during phase transformation that occurs at significantly lower temperatures compared to pure TiO2 or TiO2-Al2O3 mixtures. Al2O3 doping in TiO2 only increases the anatase-to-rutile transition rate once the phase transformation has been initiated.

Abstract: Titanium oxide TiOx material is used as electron transporter in organic photovoltaic cells (OPV). The layer was prepared between P3HT:PCBM as the active layer and the and aluminum electrode by spin coating technique. The synthesis and characterization of TiOx is described. Using Raman spectroscopy technique TiOx crystals show anatase structure. Varied concentrations of TiOx and isopropanol solvent were performed. The most optimized device efficiencies up to 2,0% was achieved at a 1:20 ratio, which indicated more than 50% efficiency enhancement comparing with the device without TiOx layer. The major improvement of the cell was originated from photocurrent enhancement.

Abstract: Titanium dioxide has been successfully synthesized via an evaporation-induced self-assembly method. Here, TiCl4 was chosen as a precursor and CTAB as a surfactant. The SEM images revealed that hydrochloric acid, added during reaction, obviously enlarges the particle size of TiO2 since a larger size was obtained. The X-ray diffraction (XRD) results confirmed the appearance of both the anatase and rutile structures of TiO2 after titania film was calcined at 450°C for 1 hour. The TEM results showed that the evaporation temperature had no significant impact upon the particle size of TiO2.

Abstract: Crystal-oriented and crack-free thin TiO2 films with a good interfacial adhesion on indium-tin oxide (ITO) glass substrates for photoelectrodes were fabricated by the electrophoretic deposition (EPD) method in a 12 T strong magnetic field. A binder-free suspension for the EPD was prepared by dispersing TiO2 in the mixture of 2-propanol and 2,4-pentanedione. The electrophoretic mobility and the sedimentation rate were measured at various ratios of the mixed solution. The optimized state of the suspension exhibiting the highest surface charge potential and producing deposits with the highest green density was obtained at the 50:50 mixing ratio. The TiO2 films were characterized by XRD and SEM analyses. The photo-current measurement was also conducted to investigate the relation between the photo-anode characteristics of a dye-sensitized solar cell and the plane orientation of the TiO2 films

Abstract: In this paper, nano-sized titanium dioxide particles were prepared by homogeneous precipitation method using industrial TiOSO4 as raw material. The morphology, crystal structures and the crystal transformation were characterized using transmission electron microscopy (TEM), X-ray Diffraction (XRD), and thermogravimetry-differential thermogravimetric analyzer (TG-DTA) respectively. The impact factors on the production rate and the diameters of nano-TiO2 were investigated. The factors include the reaction temperature, the concentrations of reactants, the molar ratios of reactants, the reaction time, the calcination temperature, and the calcination time. The results indicated that nano anatase titanium dioxide in uniform phase could be obtained under a reaction temperature of 90°C, the concentration of TiO2+ at 0.8mol/L, the reaction time of 4h, the ratio of CO(NH2)2 to TiOSO4 as 1:3, followed by a calcination period of 2h under 600°C,