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Mesoporous composite of LiFePO_4 and carbon microspheres as positive-electrode materials for lithium-ion batteries

Particuology 2014年第6期12卷 106-113页

作者： Qiangqiang Tan Cheng Lv Yuxing Xu Jun Yang State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences

Mesoporous LiFePO4/C microspheres consisting of LiFePO4 nanoparticles are successfully fabricated by an eco-friendly hydrothermal approach combined with high-temperature calcinations using cost-effective LiOH and Fe3＋ salts as raw *** this strategy,pure mesoporous LiFePO4 microspheres,which are composed of LiFePO4 nanoparticles,were uniformly coated with carbon（1.5nm）.Benefiting from this unique architecture,these mesoporous LiFePO4/C microspheres can be closely packed,having high tap *** initial discharge capacity of LiFePO4/C microspheres as positive-electrode materials for lithium-ion batteries could reach 165.3 mAh/g at 0.1 C rate,which is notably close to the theoretical capacity of LiFePO4 due to the large BET surface area,which provides for a large electrochemically available surface for the active material and *** material also exhibits high rate capability（100 mAh/g at 8 C） and good cycling stability（capacity retention of 92.2%after 400 cycles at 8 C rate）.

关键词： LiFePO4 Composite Nanoparticle Hydrothermal approach Positive-electrode material Lithium-ion battery

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Experimental and modeling study on ignition delay times of dimethyl ether/ n -butane blends at a pressure of 2.0 MPa

Experimental and modeling study on ignition delay times of d...

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作者： Jiang, Xue Zhang, Yingjia Man, Xingjia Pan, Lun Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

In this study, the ignition delay times of dimethyl ether (DME)/n-C 4H10 fuel blends, neat DME, and neat n-C4H 10 diluted with argon were measured behind reflected shock waves. The experiments were performed in the temperature range of 1100-1600 K, at a pressure of 2.0 MPa, and equivalence ratios from 0.5 to 2.0. A latest kinetic mechanism NUIG Aramco Mech 1.3 was validated against the measured ignition data and used to conduct the chemical kinetic analysis. Results showed that different equivalence ratio-dependent behaviors were exhibited at different temperature regimes for DME, n-C4H10, and their blend. The ignition delay time of neat n-C4H10 was increased with an increase in the equivalence ratio. A strong inhibiting trend was exhibited at high temperatures. For the neat DME, however, an opposite influencing tendency from the equivalence ratio was presented in comparison to that on n-C 4H10. Ignition promotion becomes significant at relatively low temperatures. A 50% DME/50% n-C4H10 blend show a combined behavior of both n-butane and DME. Fuel reaction flux analysis, sensitive analysis, and mole fraction analysis were conducted for the understanding of the interaction between the ignition chemistries of DME and n-C4H10 at a pressure of 2.0 MPa. © 2014 American Chemical Society.

关键词： Ethers

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Convective heat transfer characteristics of supercritical hydrocarbon fuel in small non-circular cross-section Channels 11

Convective heat transfer characteristics of supercritical hy...

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AIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference 2014

作者： Guo, Yong Yang, Zhuqiang Jiang, Lei Liu, Zhaohui Bi, Qincheng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

ISBN: (数字)9781624102813

ISBN: (纸本)9781624102813

Convective heat transfer characteristics of supercritical pressure hydrocarbon fuel were experimentally investigated in electrically heated small non-circular channels with hydraulic diameter ranging from 2.00 to 3.00 mm. In this research, the system pressure and fuel mass velocity were maintained at supercritical (3.0 MPa) and 840.0 kg/(m2·s), while fuel inlet temperature varied from 200.0 ~ 450.0 °C. Heat transfer characteristics of various cross-section channels were obtained in view of the temperature profiles on the channel outside surface. Experimental results were compared among different non-circular channels. The effects of inlet fuel temperature, heat flux, aspect ratio or length to diameter ratio on the convective heat transfer characteristics were discussed. Due to the varieties of length to diameter ratio, the unique heat transfer characteristics of non-circular cross-section channels seemed to make them suitable for the application of hypersonic vehicle. However, this study did not consider the pyrolytic reaction in the high temperature range. The coking characteristics of small non-circular channels under high temperature may trade off the benefits acquired in the heat transfer characteristics.

关键词： Aspect ratio

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Heat transfer characteristics of hydrocarbon fuel in a horizontal small tube under different pressures 11

Heat transfer characteristics of hydrocarbon fuel in a horiz...

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AIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference 2014

作者： Yang, Zhuqiang Bi, Qincheng Guo, Yong Liu, Zhaohui Jiang, Lei State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi' an 710049 China

ISBN: (数字)9781624102813

ISBN: (纸本)9781624102813

Experiments for heat transfer of a kerosene hydrocarbon fuel in a small horizontal tube have been conducted at subcritical and supercritical pressures. Parameters included the pressure of 2.0-5.0 MPa, mass flux of 822-2466 kg/ (m2·s) and heat flux up to 1500 kW/m2. The wall temperature and heat transfer performance at various operating conditions were captured in the experiments. Based on the results, the normal, improved and deteriorated heat transfer characteristics of the fuel were analyzed in detail. The effects of heat flux, pressure and mass flux on the heat transfer were discussed respectively. The heat transfer performed better when working pressure approached critical pressure. The deterioration in the large change of thermophysical properties region didn't occur at supercritical pressures. In the test, the increase of mass flux could enhance the heat transfer. But the effect of the enhancement decreased with mass flux increase. As to the pressure drop characteristics, low pressure and high mass flux both contributed to the increase of flow resistance.

关键词： Heat flux

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Microwave-hydrothermal preparation of a graphene/hierarchy structure MnO_2 composite for a supercapacitor

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Particuology 2014年第4期12卷 27-33页

作者： Zhong Chen Jianling Li Yu Chen Yakun Zhang Guofeng Xu Jun Yang Ye Feng State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing30 College Road State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences

Graphene/hierarchy structure manganese dioxide （GN/MnO2） composites were synthesized using a simple microwave-hydrothermal method. The properties of the prepared composites were analyzed using field emission scanning electron microscopy （FE-SEM）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and X-ray photoelectron spectroscopy （XPS） measurements. The electrochemical performances of the composites were analyzed using cyclic voltammetry, electrochemical impedance spectrometry （EIS）, and chronopotentiometry. The results showed that GN/MnO2 （10 wt% graphene） displayed a specific capacitance of 244 F/g at a current density of 100 mA/g. An excellent cyclic stability was obtained with a capacity retention of approximately 94.3% after 500 cycles in a 1 mol/L Li2SO4 solution. The improved electrochemical performance is attributed to the hierarchy structure of the manganese dioxide, which can enlarge the interface between the active materials and the electrolyte. The prepa- ration route provides a new approach for hierarchy structure graphene composites; this work could be readily extended to the preparation of other graphene-based composites with different structures for use in energy storage devices.

关键词： Graphene MnO2 Hierarchy structure Supercapacitor

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Visualization investigation of secondary flow on heat transfer deterioration in horizontal heat tube 22

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2014 22nd International Conference on Nuclear engineering, ICONE 2014

作者： Wu, Chao Li, Hui-Xiong Qian, Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

ISBN: (纸本)9780791845905

Mixed convection heat transfer in heated tubes has been studied extensively in the past decades, which is widely used in various industrial fields such as cooling of a nuclear reactor core. The secondary flow, which is induced by buoyancy force, has been found in previous research to have profound influence on the heat transfer difference on circumferential position and occurrence of heat transfer deterioration in horizontal heated channel. Therefore, understanding the secondary flow velocity field has important implications to prevent heat transfer deterioration and ensure the safe operation of nuclear power plants. Numerical methods have been adopted in literature to analyze the complex interaction between secondary flow and heat transfer deterioration. However, to the knowledge of the author, experimental measurement of secondary flow in the radial cross-section of a horizontal tube does not exist.. Copyright © 2014 by ASME.

关键词： Numerical methods

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Flame-front instabilities of outwardly expanding isooctane/ n -butanol blend-air flames at elevated pressures

Flame-front instabilities of outwardly expanding isooctane/ ...

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作者： Zhang, Xinyi Tang, Chenglong Yu, Huibin Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Experiments were conducted in a constant volume bomb filled with isooctane/n-butanol blend-air mixtures over a wide range of n-butanol blending ratios, equivalence ratios, and initial pressures. High-speed schlieren photography was used to measure the critical radius for the onset of flame-front instability. Results show that, for a given n-butanol blending ratio, cellular instabilities appear earlier and the critical Peclet number, which represents the onset of instability, is decreased with the increase of the initial pressure and equivalence ratio. Under fuel-rich conditions, the critical Peclet number increases with the increase of the n-butanol blending ratio. Theoretical calculation of the critical Peclet number was also conducted to interpret the effects of n-butanol on the flame-front instabilities of the blends. Results show that, for rich mixture conditions, with the increase of the n-butanol blending ratio, the overall activation energy of the mixtures is decreased and, thus, the thermal-diffusional instabilities are suppressed. While under fuel-lean conditions, the thermal-diffusional instabilities are favored. As a consequence, with an increasing n-butanol blending ratio, the critical Peclet number is expected to be decreased under fuel-lean conditions and increased under fuel-rich conditions. © 2014 American Chemical Society.

关键词： Mixtures

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A multi-scale architecture for multi-scale simulation and its application to gas-solid flows

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Particuology 2014年第4期12卷 160-169页

作者： Bo Li Guofeng Zhou Wei Ge Limin Wang Xiaowei Wang Li Guo Jinghai Li State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences

A multi-scale hardware and software architecture implementing the EMMS （energy-minimization multi-scale） paradigm is proven to be effective in the simulation of a two-dimensional gas-solid suspension. General purpose CPUs are employed for macro-scale control and optimization, and many integrated cores （MlCs） operating in multiple-instruction multiple-data mode are used for a molecular dynamics simulation of the solid particles at the meso-scale. Many cores operating in single-instruction multiple- data mode, such as general purpose graphics processing units （GPGPUs）, are employed for direct numerical simulation of the fluid flow at the micro-scale using the lattice Boltzmann method. This architecture is also expected to be efficient for the multi-scale simulation of other comolex systems.

关键词： General purpose graphics processing unit（GPGPU）Many integrated core （MIC）Meso-science Multiple-instruction multiple-dataSingle-instruction multiple-dataVirtual process engineering

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Influence of phase and microstructure on the rate of hydrochloric acid leaching in pretreated Panzhihua ilmenite

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Particuology 2014年第3期12卷 83-90页

作者： Qingshan Zhu Jianbo Zhang Hongzhong Li State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences

The present study investigated the influence of high temperature oxidation and reduction pretreatments on the leaching rate ofPanzhihua ilmenite. The as-pretreated ilmenite was leached with 20% HCI at 105 ℃, The leaching process was controlled by the phases and microstructures that evolved during the pretreatment processes. The leaching kinetics of pure hematite, ilmenite and pseudobrookite were characterized to clarify the phase effect on the iron-leaching rate; the rate of iron leaching occurs in the following order in the HCI solution： hematite （ferric iron）〉 ilmenite （ferrous iron）〉〉 pseudobrookite （ferric iron）. Therefore, the often-cited notion that ferrous iron dissolves faster in HCl solutions than ferric iron when explaining the pretreatment effects is inaccurate. Moreover, the oxidation pretreatment （at 600-1000 ℃ for 4 h） cannot destroy the dense structure of the Panzhihua ilmenite. Therefore, the influence exerted by the oxidation on the leaching process is primarily determined by the phase change; oxidation at 600 and 700℃ slightly increased the rate of iron leaching because the ilmenite was transformed into hematite, while the oxidation at 900-1000℃ significantly reduced the rate of iron leaching because a pseudobrookite phase formed. The reduction effect was subsequently investigated; the as-oxidized ilmenite was reduced under H2 at 750 ℃ for 30 min. The reduction significantly accelerated the rate of subsequent iron leaching such that nearly all of the iron had dissolved after leaching for 2 h in 20% HCl at 105 ℃. This enhanced iron-leaching rate is mainly attributed to the cracks and holes that formed during the reduction process.

关键词： llmenite Oxidation Reduction Hydrochloric acid leaching

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Erratum to: “engineering molecular dynamics simulation in chemical engineering” [Chem. Eng. Sci. 121 (2015) 200–216]

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Chemical engineering Science 2015年 123卷 674-675页

作者： Ji Xu Xiaoxia Li Chaofeng Hou Limin Wang Guangzheng Zhou Wei Ge Jinghai Li The EMMS Group State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 People׳s Republic of China

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