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[en] A channeling study of TiOsub(x) crystals with different oxygen concentration has been performed. The results of planar channeling experiments show that the steering power of the pure oxygen planes appears to be weak to maintain a steered trajectory. The flux-peaking effect decreases with increasing O2 concentration and is destroyed at a high interstial concentration (O/Ti>1). The axial channeling experiments show a weak flux-peaking effect for the lowest oxygen concentration (10 at%) while at higher concentrations the angular dip of oxygen sublattice is observed
[en] Highlights: • TiO2/G with CTAB has been enhanced dispersibility and conductivity in result. • The TiO2/G with 7 wt% G and 30 wt% CTAB had the better conductivity in result. • CTAB only has an auxiliary role, not affects the crystalline structure of TiO2/G. • TiO2/G exists electron conductive paths for improving its conductivity.
[en] The sandwich-type polyoxometalate-based TiO2 nanofibres were prepared successfully by electrospinning combining with chemical reaction and employed in ultra-deep desulfurization. OTA–CoVW–TiO2 nanofibres (OTA = CH3(CH2)17(CH3)3N, CoVW = [Co4(H2O)2(VW9O34)2]10−) confirmed the excellent desulfurization performance in extraction catalytic oxidative desulfurization system (ECODS). At 323 K, the 500 ppm DBT (dibenzothiophene) model oil was entirely removed within 20 min using 0.010 g 45 wt% OTA–CoVW–TiO2 nanofibres as catalyst when O/S molar ratio was 4:1 and the dosage of model oil was 5 mL. The catalysts could be recycled and reused at least five times without remarkable decrease in catalytic activity. The desulfurization efficiencies for different substrates were shown as following order: DBT > 4,6-DMDBT (4,6-dimethyl-dibenzothiophene) > BT (benzothiophene). Moreover, the possible mechanism was also elucidated.
[en] A novel, facile, catalyst-free, and low temperature process for the synthesis of discrete anatase TiO2 nanocrystals has been developed in the absence of stabilizing agent. The product was shown to be discrete anatase TiO2 nanocrystals with a mean diameter of 4.97 ± 0.9 nm and a specific surface area of 393 m2/g. By varying the water content and precursor concentration, the particle size could be tuned. Also, the resultant colloid solution was quite stable even in the absence of stabilizing agent because of the coverage of EG molecules on the particle surface. In addition, the anatase TiO2 nanocrystals obtained in this work had highly thermal stability even at temperatures up to 800 oC. Also, as compared to Degussa P25 TiO2 powders, they exhibited stronger absorption at 200-350 nm and higher transmittance in the visible light region. Thus, the new approach proposed in this work was practicable for the synthesis of anatase TiO2 nanocrystals, particularly for those requested to have highly thermal stability and UVC-cut capability.
[en] When atomic layer deposition (ALD) is performed on a porous material by using an organometallic precursor, minimum exposure time of the precursor for complete coverage becomes much longer since the ALD is limited by Knudsen diffusion in the pores. In the previous report by Min et al. (Ref. 23), shrinking core model (SCM) was proposed to predict the minimum exposure time of diethylzinc for ZnO ALD on a porous cylindrical alumina monolith. According to the SCM, the minimum exposure time of the precursor is influenced by volumetric density of adsorption sites, effective diffusion coefficient, precursor concentration in gas phase and size of the porous monolith. Here we modify the SCM in order to consider undesirable adsorption of byproduct molecules. TiO2 ALD was performed on the cylindrical alumina monolith by using titanium tetrachloride (TiCl4) and water. We observed that the byproduct (i. e., HCl) of TiO2 ALD can chemically adsorb on adsorption sites, unlike the behavior of the byproduct (i. e., ethane) of ZnO ALD. Consequently, the minimum exposure time of TiCl4 (∼16 min) was significantly much shorter than that (∼71 min) of DEZ. The predicted minimum exposure time by the modified SCM well agrees with the observed time. In addition, the modified SCM gives an effective diffusion coefficient of TiCl4 of ∼1.78 Χ 10-2 cm2/s in the porous alumina monolith
[en] The electrochemical properties of n-type TiOsub(2-x) clectrode have been investigated in an aqueous 1M NaOH. The values of αnsub(a) from polarogram have been found to be 0.446-0.554. The diffusion coefficient of nsub(2) in 1M NaOH solution which is needed for the computation of reaction rate parameters mentioned above, has been measured by means of polarogram with DME. It has been to be 2.54x10sup(-5)cmsup(2)/sec at 25degC. Flatband potential and donor concentration by the Mott-Schottky plot have been estimated to be -0.63--1.50 V vs SCE and 2.07x10sup(19) -3.27x10sup(21)cmsup(-3), respectively. (author)
[en] TiO2 and N-substituted TiO2-xNx were synthesized by using precipitation method. TiO2-xNx compound absorbed whole UV light as well as long wavelength of visible light (400 - 700 nm) because of the change of band gap from 3.2 eV to 1.77 eV. Results obtained revealed that TiO2-xNx showed higher activity than pure TiO2 or P-25 for visible-photocatalytic degradation of 1,4-dichlorobenzene