Results 1 - 10 of 109
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[en] Novel nanostructured Pd-Zr oxides have been synthesized using chemical processing. The composition and structure have been investigated using X-ray diffraction and electron microscopy. The phase stability, thermal behavior and catalytic property under methane atmosphere have been examined by using thermogravimetric analysis, in situ gas environment high temperature X-ray diffraction and gas mass spectroscopy. The study indicated that the alloying of Zr improves the thermal stability and modifies the hysteresis characteristic of the phase transition between Pd-Zr metal and oxide during the thermal cycling
[en] Graphical abstract: - Highlights: • A facile and low-temperature method is developed for SnO2/graphene composite. • Synthesis performed in a choline chloride-based ionic liquid. • The composite shows an enhanced cycling stability as anode for Li-ion batteries. • 4 nm SnO2 nanoparticles mono-dispersed on the surface of reduced graphene oxide. - Abstract: A facile and low-temperature method is developed for SnO2/graphene composite which involves an ultrasonic-assistant oxidation–reduction reaction between Sn2+ and graphene oxide in a choline chloride–ethylene glycol based ionic liquid under ambient conditions. The reaction solution is non-corrosive and environmental-friendly. Moreover, the proposed technique does not require complicated infrastructures and heat treatment. The SnO2/graphene composite consists of about 4 nm sized SnO2 nanoparticles with cassiterite structure mono-dispersed on the surface of reduced graphene oxide. As anode for lithium-ion batteries, the SnO2/graphene composite shows a satisfying cycling stability (535 mAh g−1 after 50 cycles @100 mA g−1), which is significantly prior to the bare 4 nm sized SnO2 nanocrsytals. The graphene sheets in the hybrid nanostructure could provide a segmentation effect to alleviate the volume expansion of the SnO2 and restrain the small and active Sn-based particles aggregating into larger and inactive clusters during cycling
[en] Novel Pd-Mn oxides have been synthesized using chemical processing. The study indicated that the Pd-Mn oxide powders have nanometer structure. The alloying of Mn improves the thermal stability and modifies re-oxidation characteristic of the palladium oxide during the thermal cycling
[en] Highlights: • In this paper, a numerical code named MTC-H 2.0 based on unstructured mash was developed and validated. • In the code, a current density conservative scheme is used to ensure the conservative of current, Krylov subspace method and AMG method were used to improve the computing performance. • Both analytical and experimental cases were chosen to validate the code at high Hartmann number. • The code has good computing performance, and numerical results matched well with the analytical and experimental results. -- Abstract: In order to analyze the magnetohydrodynamic (MHD) effect in liquid metal fusion blanket, a parallel and high performance numerical code was developed to study MHD flows at high Hartmann Number based on the unstructured grid. In this code, the induced current and the Lorentz force were calculated with a current density conservative scheme, while the incompressible Navier–Stokes equations with the Lorentz force included as a source term was solved by projection method, a set of method were used to improve the computing performance such as Krylov subspace method and AMG method. To validate this code, three benchmarks of MHD flow at high Hartmann Number were conducted. The first benchmark was the case of Shercliff fully development flow, the second benchmark was the MHD flow in a circular pipe with changing external magnetic field, and the third benchmark was the MHD flow in a pipe with sudden expansion. In these cases the Hartmann Numbers were from 1000 to 6000. The code good computing performance, and numerical results show matched well with the analytical and experimental results
[en] New solid polymer electrolytes (SPEs) comprised of lithium bis(fluorosulfonyl) imide (Li[N(SO_2F)_2], LiFSI) and polymeric ionic liquid (i.e., poly[N,N-dimethyl-N-[2-(methacryloyloxy) ethyl]-N-[2-(2-methoxyethoxy) ethyl]ammonium] bis(fluorosulfonyl) imide, P[C_5O_2N_M_A_,_1_1]FSI) have been prepared and characterized. For comparison, the corresponding SPEs, lithium bis(trifluoromethylsulfonyl) imide (Li[N(SO_2CF_3)_2], LiTFSI)/poly[N,N-dimethyl-N-[2-(methacryloyloxy) ethyl]-N-[2-(2-methoxyethoxy) ethyl]ammonium] bis(trifluoromethylsulfonyl) imide (P[C_5O_2N_M_A_,_1_1]TFSI), are also prepared and characterized. Their physicochemical properties have been investigated in terms of phase transition behavior, ionic conductivity, lithium-ion transference number (t_L_i"+), electrochemical stability, and with particular attention to the interfacial behavior between lithium electrode and SPEs. It has been demonstrated that the ionic conductivities of LiFSI/P[C_5O_2N_M_A_,_1_1]FSI electrolyte are higher than those of the corresponding TFSI-based one. The interface resistances of Li symmetric cell (Li metal | polymer electrolytes | Li metal) using LiFSI/P[C_5O_2N_M_A_,_1_1]FSI electrolyte are much lower than those using LiTFSI/P[C_5O_2N_M_A_,_1_1]TFSI electrolyte. These outstanding properties of the FSI-based electrolyte make it attractive as SPEs for Li battery
[en] Objective: To study the protective function of resveratrol on radiation-induced small intestine injury and lethal effect in mice. Methods: Mice were randomly divided into three groups: irradiation (IR) control, IR only, and IR+ resveratrol. 15 mice each group were irradiated on abdomen with 7.2 Gy γ-rays for cell lethal assay and 8 mice each group were irradiated with 6.5 Gy for small intestine injury assay. For the IR+ resveratrol group, the mouse was given resveratrol by intragastric administration 24 h before irradiation and then was fed with resveratrol daily for 5 days. The control and IR alone groups were fed with placebo. After 30 days of IR, mouse survival rate was detected. For small intestine injury experiments, 24 h after IR, the mice were terminated and the small intestines were treated with HE and immunohistochemical staining. Results: Compared with the irradiation group, resveratrol increased mouse survival by 33.3%, decreased apoptosis in intestinal crypt cells (t = 17.35, P < 0.05), and increased Ki67 expression (t = 13.62, P < 0.05). Conclusion: Resveratrol could protect small intestine injury from ionizing irradiation. (authors)
[en] Using the CGC formalism, we calculate the two-gluon rapidity correlations of strong colour fields in pp, pA and AA collisions, respectively. If one trigger gluon is fixed at central rapidity, a ridge-like correlation pattern is obtained in symmetry pp and AA collisions, and a huge bump-like correlation pattern is presented in asymmetry pA collisions. It is demonstrated that long-range ridge-like rapidity correlations are caused by the stronger correlation with the gluon of colour source. These features are independent of the azimuthal angular of two selected gluon. They are qualitatively consistent with current observed data at LHC. The transverse momentum and incident energy dependence of the ridge and bump-like correlations are also systematically studied. The ridge is more likely observed at higher incident energy and lower transverse momentum of trigger gluon.
[en] Abstract: Amorphous Ni–P–C films are fabricated by combining the electrodeposition of Ni–P films from a eutectic-based ionic liquid and the direct current magnetron sputtering of amorphous carbon top-layer. The carbon top-layer with a thickness of about 10 nm is homogeneously coated on the surface of the Ni–P films. A comparison study is undertaken between Ni–P and Ni–P–C films to evaluate the microstructure and the electrochemical performances of the composite films as anode materials for lithium ion batteries, which allow the decoupling of the effect of the carbon layer. It is found that at lower discharge–charge current densities, the cyclability of both Ni–P and Ni–P–C films is similar. As the discharge–charge current density increases, the Ni–P–C film exhibits improved capability and reversibility over the Ni–P film. The Ni–P–C film delivers an initial discharge capacity of 1060 mAh g−1 at 250 mA g−1 and the capacity retention after 50 cycles is 62%, much higher than that of the Ni–P film (51%). The cyclability of Ni–P–C film at different discharge–charge current densities from 200 to 500 mA g−1 is also much better than those of Ni–P film. This study indicates that the introduction of a carbon top-layer on Ni–P film could significantly improve the electrochemical performances due to the decreased interface electric resistance and the structure stability
[en] Highlights: • LiFNFSI-based electrolyte does not decompose after storage at 85 °C for two weeks. • Decompositions of LiPF_6-carbonate electrolyte would be initialized by the presence of trace amounts of HF and protic impurities. • SEI films formed on graphite anode in the LiFNFSI-based electrolyte are majorly dominated by the reductive products of FNFSI"− anions. • Graphite/LiCoO_2 cells with LiFNFSI show better higher-temperature storage, current-rate and cycling performances than those with LiPF_6. - Abstract: Lithium (fluorosulfonyl)(n-nonafluorobutanesulfonyl)imide (LiFNFSI) is investigated as conducting salt to replace conventional used LiPF_6 for lithium-ion batteries. The stabilities of electrolytes of 1.0 M LiFNFSI- and LiPF_6-ethylene carbonate (EC)/ethyl methyl carbonate (EMC) are comparatively studied at both room (25 °C) and elevated temperatures (60 and/or 85 °C) by using NMR. It is found that the electrolyte of LiFNFSI does not decompose after storage at 85 °C for 14 days; however, both LiPF_6 and carbonate solvents occur degradations even after storage at 25 °C, and degrade prominently with increasing the temperature. A new mechanism for continuous decompositions of both LiPF_6 and carbonate solvents, being initialized by trace amounts of HF and protic impurities, has been suggested. The electrochemical performances of LiFNFSI for graphite/LiCoO_2 Li-ion cells have been comparatively investigated with those of LiPF_6 at both 25 and 60 °C, with particular attention to characterizing the electrode/electrolyte interphases formed on both electrodes by using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). It is demonstrated that LiFNFSI is advantageous over LiPF_6 in the high-temperature storage, current-rate and cycling tests, particularly at elevated temperature; however, the impedances are all larger for the LiFNFSI-based cells than for the LiPF_6-based ones. Analyses of XPS reveal that the chemical compositions of electrode/electrolyte interphases formed on both electrodes are highly dependent on the types of lithium salts. Particularly, on graphite anode, the solid-electrolyte-interphase (SEI) films formed in the LiFNFSI-based electrolyte are majorly dominated by the reductive products of FNFSI"− anions, and are relatively stable at elevated temperature, while those formed in the LiPF_6-based electrolyte are largely governed by the reductive products of carbonate solvents, and occur significant dissolutions and regrowth at elevated temperature. All above results suggest that the improved capacity retention for the cells with LiFNFSI is mainly attributable to the robust nature of the SEI films formed on graphite anode, and the superior stability and absence of HF contamination for the LiFNFSI-based electrolyte, while the rapid capacity fading of the cells with LiPF_6 is essentially due to the decompositions and regrowth of SEI films on graphite anode, and the detrimental impact of HF and protic residues in the electrolyte of LiPF_6.
[en] High-T c superconducting (HTS) coated conductor stacks have been demonstrated as very promising superconducting permanent magnets (PMs), to be used in applications like rotary motors and levitation devices. In this paper, we present a novel magnetization method to address a key problem in the application of HTS stacks, which is effective magnetization with compact, light and efficient setups. The proposed method, transformer–rectifier flux pumping, uses the mechanism developed for HTS coils to magnetize the modified HTS stacks. The accumulation of flux with time is achieved in the HTS stacks. The results show that the flux pump can effectively magnetize long HTS stacks with a magnetic field applied to a much smaller area. Operational characteristics of the flux pump are experimentally studied and some explanations are proposed for the distinct behaviors observed in the experiments. This study heralds a new direction in the magnetization of superconducting PMs and has the potential to be a practical method for industrial applications. (paper)