The effect of calcination temperatures on the active species of WO 3 /SiO 2 catalysts for propylene production from metathesis of ethylene and 2-butene was studied to elucidate the structure-reactivity *** influence o...
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The effect of calcination temperatures on the active species of WO 3 /SiO 2 catalysts for propylene production from metathesis of ethylene and 2-butene was studied to elucidate the structure-reactivity *** influence of calcination temperatures on catalyst physicochemical properties,relating to the active species,was summarized from an array of characterization *** has been found that the surface tetrahedral tungsten species with high metal support interaction were formed on the catalyst calcined at 550℃ as confirmed by Raman,UV-Vis and H 2-TPR spectra,respectively.
High purity anatase nano-TiO2 powders with high photocatalytic activity were prepared by a hydrothermal synthesis method. X-ray diffraction （XRD）, field emission transmission electron microscopy （FETEM）, ultraviol...
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High purity anatase nano-TiO2 powders with high photocatalytic activity were prepared by a hydrothermal synthesis method. X-ray diffraction （XRD）, field emission transmission electron microscopy （FETEM）, ultraviolet-visible （UV-Vis） light absorption spectrum and photoluminescence （PL） spectrum were adopted to characterize the catalyst. Effects of temperature, time and sol concentration of hydrothermal synthesis on particle size and phases were investigated. Photocatalytic activities in the degradation of Rhodamine B Dye were studied. The experimental results indicated that photocatalytic activity of the nano-TiO2 powers was much higher than that of P25 （Degussa）.
Compounds Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 with filled tetragonal tungsten bronze structure were prepared,and the dielectric characteristics and ferroelectric transition were *** ceramics displayed weak frequency de...
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Compounds Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 with filled tetragonal tungsten bronze structure were prepared,and the dielectric characteristics and ferroelectric transition were *** ceramics displayed weak frequency dependence in room temperature dielectric constant,which decreased from 125 to 118 for Sr4Eu2Ti4Nb6O30,from 206 to 195 for Sr5EuTi3Nb7O30 in the frequency range of 10 kHz to 1 *** present ceramics showed a diffuse ferroelectric phase *** frequency independent transition temperature （Tm） indicated the above compounds had no relaxor *** diffuseness （γ） was 1.45 and 1.64 for Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 *** weak ferroelectric of the present materials are indicated from the P-E hysteresis loops,and a small 2Pr of 0.596 μC/cm2 and 0.068 μC/cm2 were observed for Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 respectively.
Effects of Al2O3 and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing T...
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Effects of Al2O3 and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing TiB2-30%Al2O3 can be attained due to the plate-like TiB2 particle and its random orientation and excessive Al2O3 grain growth. When sintering temperature is higher than 1 700 ℃, TiB2 grain growth can be found, which obvious improves flexural strength of TiB2 matrix but decreases toughness. It seems that mechanical properties of TiB2-Al2O3 composites are mainly depended on relative density besides grain growth. otherwise, they will be determined by relative density and TiB2 matrix strength together. Anyway, Al2O3 addition can weaken the grain boundary and thus improve the toughness of the materials. A flexural strength of 529 MPa, Vickers hardness of 24.8 GPa and indentation toughness of 4.56 MPa·m1/2 can be achieved inTiB2-30vol% Al2O3.
Multi-walled carbon nanotube （MWCNT）/TiO2/C60 composite catalysts were prepared by hydrothermal method. TiO2 was deposited on the MWCNT surface. Their photocatalytic activities for degradation of Rhodamine B dye wer...
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Multi-walled carbon nanotube （MWCNT）/TiO2/C60 composite catalysts were prepared by hydrothermal method. TiO2 was deposited on the MWCNT surface. Their photocatalytic activities for degradation of Rhodamine B dye were studied. X-ray diffraction, field emission transmission electron microscopy, ultraviolet-visible light absorption spectrum and photoluminescence spectrum were carried out to characterize the composite catalysts. The results indicated that MWCNTs and C60 could greatly enhance the photocatalytic activity of TiO2.
Highly-dispersed ZrO2 nanoparticles (NPs) were successfully synthesized via sol-gel and supercritical fluid drying (SCFD) method with zirconium oxychloride as the source. The as-synthesized ZrO2 was characterized by X...
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Highly-dispersed ZrO2 nanoparticles (NPs) were successfully synthesized via sol-gel and supercritical fluid drying (SCFD) method with zirconium oxychloride as the source. The as-synthesized ZrO2 was characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetary (CV). The results indicate that the nearly spherical ZrO2 three-dimensional network NPs possess diameters of about 10nm, and the pure ZrO2 after SCFD treatment maintains uniform crystal structure while the 3Y-ZrO2 have many crystal defects. The electrochemical performance of ZrO2 NPs showed that the pure ZrO2 NPs after SCFD treatment have very small electrochemical impedance and well-performance of cyclical stability, which provide a new orient of lithium batteries materials.
Dominant heat-carrying modes in skutterudites are associated with vibrations of the pnicogen rings. Apart from filling the structural cages with foreign species, disrupting the pnicogen ring structure by substitutiona...
Dominant heat-carrying modes in skutterudites are associated with vibrations of the pnicogen rings. Apart from filling the structural cages with foreign species, disrupting the pnicogen ring structure by substitutional alloying should be an effective approach to reduce thermal conductivity. In this paper we explore alloying configurations of pnicogen rings (Sb rings in the case of CoSb3) that yield particularly low values of the thermal conductivity. We find that IV-VI double substitution (replacing two Sb atoms with one atom each from the column IV and column VI elements to achieve an average charge of two Sb atoms) is a very effective approach. Our ab initio calculations, in combination with a cluster expansion, have allowed us to identify stable alloy configurations on the Sb rings. Subsequent molecular and lattice dynamics simulations on low energy configurations establish the range of atomic displacement parameters and values of the thermal conductivity. Theoretical results are in good agreement with our experimental thermal conductivity values. Combining both approaches of compensated double substitution and filling of structural cages should be an effective way of improving the thermoelectric figure of merit of skutterudites.
Anchored periplasmic expression (APEx) technology aims to express and localize proteins or peptides in the Escherichia coli periplasm. Some reports have suggested that transmembrane segments of integral membrane prote...
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Anchored periplasmic expression (APEx) technology aims to express and localize proteins or peptides in the Escherichia coli periplasm. Some reports have suggested that transmembrane segments of integral membrane proteins can be used as membrane anchors in the APEx system. In this study, a series of hydrophobic anchors derived from the first putative transmembrane helix of a Bacillus subtilis integral membrane protein, MrpF, and its truncated forms were investigated for anchored periplasmic expression of alkaline phosphatase (PhoA) in E. coli. Anchoring efficiency of hydrophobic anchors was evaluated by monitoring the expression and activity of anchored PhoA. The length of hydrophobic anchors was found to be critical for anchoring proteins to cell membranes. This study may open new avenues for applying transmembrane segments derived from native membrane proteins as membrane anchors in the APEx system.
Two types of Mg-Cu composition system graded density impactors used for complex loading （shock loading and quasi-isentropic compression） are designed by the elastic-plastic hydrodynamic method in this paper. Mixture...
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Two types of Mg-Cu composition system graded density impactors used for complex loading （shock loading and quasi-isentropic compression） are designed by the elastic-plastic hydrodynamic method in this paper. Mixtures of metal powders in the Mg-Cu system are cast into a series of 17 and 25 uniform compositions ranging from 100% Mg to 100% Cu. The graded den- sity impactors are launched to the stationary 10 Ixm aluminum film and 12 mm LiF window targets by a two-stage light-gas gun in the National keylaboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, CAEP, and the resulting wave profiles are measured with the DISAR system. Hydrodynamic simulation results are perfectly consistent with the experiments. Our work in this paper will set up a foundation for further research of controllable loading/releasing routes and rate experiments in the future.
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