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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] We studied flux emergence events of sub-granular scale in a solar active region. The New Solar Telescope (NST) of the Big Bear Solar Observatory made it possible to clearly observe the photospheric signature of flux emergence with very high spatial (0.''11 at 7057 A) and temporal (15 s) resolution. From TiO observations with the pixel scale of 0.''0375, we found several elongated granule-like features (GLFs) stretching from the penumbral filaments of a sunspot at a relatively high speed of over 4 km s-1. After a slender arched darkening appeared at the tip of a penumbral filament, a bright point (BP) developed and quickly moved away from the filament, forming and stretching a GLF. The size of a GLF was approximately 0.''5 wide and 3'' long. The moving BP encountered nearby structures after several minutes of stretching, and the well-defined elongated shape of the GLF faded away. Magnetograms from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager and NST/InfraRed Imaging Magnetograph revealed that those GLFs are photospheric indicators of small-scale flux emergence, and their disappearance is related to magnetic cancellation. From two well-observed events, we describe detailed development of the sub-structures of GLFs and different cancellation processes that each of the two GLFs underwent.
[en] Palladium nanoparticles (PdNP) supported onto the anatase phase of TiO2 were successfully synthesised using a colloidal method. This synthesis method involved the reduction of K2PdCl4 solution by NaBH4 at different temperatures (1, 25, 50, 75 degree Celsius) and stabilised with PVA ligand. Transmission electron microscope (TEM) was used to determine the particle size of PdNP on the TiO2. Colloidal synthesis at 1 degree Celsius and 25 degree Celsius produced PdNP with less than a 3 nm diameter, whereas when the synthesis temperatures were higher than 25 degree Celsius, PdNP were produced with a size larger than 4 nm. The catalytic activity of Pd/ TiO2 was significantly improved when palladium (Pd) was produced at 1 degree Celsius with high selectivity towards the hydrogenation of cinnamaldehyde to hydrocinnamaldehyde. The conversion and selectivity trends from the cinnamaldehyde hydrogenation reaction demonstrated the influence of Pd nanoparticle size to provide active sites for the reduction of C=C and C=O bonds. Pd with a diameter of 2.58 nm favoured hydrogenation of C=C bond to produce high selectivity towards hydrocinnamaldehyde, meanwhile a large Pd diameter > 4 nm allowed simultaneaous reduction of C=C and C=O bonds to give comparable selectivity between hydrocinnamaldehyde and hydrocinnamylalcohol. (author)
[en] We detected 2.8 bright points (BPs) per Mm2 in the quiet Sun with the New Solar Telescope at Big Bear Solar Observatory, using the TiO 705.68 nm spectral line at an angular resolution ∼0.''1 to obtain a 30 minute data sequence. Some BPs formed knots that were stable in time and influenced the properties of the granulation pattern around them. The observed granulation pattern within ∼3'' of knots presents smaller granules than those observed in a normal granulation pattern, i.e., around the knots a suppressed convection is detected. Observed BPs covered ∼5% of the solar surface and were not homogeneously distributed. BPs had an average size of 0.''22, they were detectable for 4.28 minutes on average, and had an averaged contrast of 0.1% in the deep red TiO spectral line.