Synthesis and performance of carbon-modified LiFePO_4 using an in situ PVA pyrolysis procedure

LiFePOa/carbon composite cathode material was prepared by granulating and subsequent pyrolysis processing in N2 atmosphere with polyvinyl alcohol （PVA） as the carbon source. The influences of carbon content on the microstructure and battery performance were investigated. Single LiFePO4 phase and amorphous carbon can be found in the products. A special micro-morphology of the optimum sample was observed. The discharge capacity of the cell with the optimum cathode was 135 mAh.g^-1, close to the charge capacity of 153 mAh.g^-1 at 17 mA.g^-1. The influence of ambient temperature on the cell capacity was investigated. The temperature dependence of its electrochemical characteristic was evaluated by using AC impedance spectroscopy. A new equivalent circuit based on the charge and mass transfer control process in an electrode was proposed to fit the obtained AC impedance spectra. The tendency of every element in the equivalent circuit was used to interpret the temperature dependence of the capacity of the optimum cathode.

Preparation,Characterization and Applications of Titanate/Titania Nanocrystals

The present paper focused on the preparation of hydrogen titanate nanotubes and nanowires and their conversion into titania by heat treatments.The structural,morphology and optical properties of as-prepared nanostructured titanate and titania were investigated by transmission electron microscopy (TEM),X-ray diffraction (XRD) and diffusive reflectance spectra.The slim diameter of these nanostructured titanate and titania,the versatile crystal structure and special optical and electronic properties may make them find versatile applications in chemical sensors for multiple purposes.

Highly Active Rutile TiO_2 for Photocatalysis

Nanocrystalline titania was prepared by the homogeneous-precipitation method at temperature lower than 120℃. The properties of powders were identified by XRD,TEM and diffuse reflection spectra.The results showed that rutile titania formed at 70℃without calcination in air.Nanometer rutile TiO_2 had good crystalline and small particle size.The formation mechanism of rutile was also discussed.The photocatalytic activity of the prepared particles was tested for the degradation of methyl orange.The photocatalytic activity of rutile TiO_2 was higher than those obtained from Degussa P-25 TiO_2.The reasons for high photocatalytic activity of futile were discussed.

Fabrication and Characterization of GCO Electrolyte Films

Gd-doped Ceria (GCO:Gd_(0.1)Ce_(0.9)O_(1.95)) sensing films have been fabricated successfully on glasses and porous Al_2O_3 ceramic substrates by RF magnetron sputtering.Sputtering conditions such as power and temperature have been investigated and the sample was characterized in detail by XRD,SEM and AC impedance spectroscopy.The results show that the films grow preferentially along the (111) compact plane with a pure fluorite structure and the crystal grain grows more sufficiently with increasing of the annealing temperature.In addition,a high oxygen ion conductivity of 2.24×10^(-2) S.cm^(-1) is achieved at 800℃.

Hierarchical-structure anatase TiO2 with conductive network for high-rate and high-loading lithium-ion battery

Titanium dioxides have been extensively investigated as promising anodes for Lithium ion batteries(LIBs)because of the high–rate capacity and cyclability,as well as the improved safety over graphite anode(1,2)However,as a typical insertion–type anode,anatase TiO2 exhibits low conductivity(10–12S cm-1 for electron conductivity[3]and 10–17–10–10 cm2 s1 for Li+ion diffusion coefficient[4])and poor specific capacity(only accommodate<0.5 Li per bulk TiO2 unit[5]),severely limiting its practical applications.

Recent progress in Ti-based nanocomposite anodes for lithium ion batteries

Studying on the anode materials with high energy densities for next-generation lithium-ion batteries(LIBs) is the key for the wide application for electrochemical energy storage devices.Ti-based compounds as promising anode materials are known for their outstanding high-rate capacity and cycling stability as well as improved safety over graphite. However, Ti-based materials still suffer from the low capacity, thus largely limiting their commercialized application. Here, we present an overview of the recent development of Ti-based anode materials in LIBs, and special emphasis is placed on capacity enhancement by rational design of hybrid nanocomposites with conversion-/alloying-type anodes. This review is expected to provide a guidance for designing novel Ti-based materials for energy storage and conversion.

锂离子电池有机硅功能电解液

高安全高电压电解液的开发是锂离子电池电解液发展的重要方向。有机硅化合物由于具有独特的理化性能,使其成为锂离子电池电解液领域的研究热点之一。本文综述了有机硅电解液的研究进展,重点从功能分子设计的角度介绍含碳酸酯基、氨基甲酸酯基、腈基、离子液体、含氟类的有机硅功能电解液溶剂制备及电池性能表现;详细阐述具有结构多样性的有机硅化合物用作高电压添加剂、高安全添加剂、高/低温添加剂、储存/耐自放电添加剂、吸酸吸水添加剂及其在不同电池材料体系中的应用。最后,对有机硅电解液的研究趋势和应用前景进行了展望。

Nanowires-assembled WO3 nanomesh for fast detection of ppb-level NO2 at low temperature

Hierarchical WO3 nanomesh,assembled from single-crystalline WO3 nanowires,is prepared via a hydrothermal method using thiourea(Tu)as the morphology-controlling agent.Formation of the hierarchical architecture comprising of WO3 nanowires takes place via Ostwald ripening mechanism with the growth orientation.The sensor based on WO3 nanomesh has good electrical conductivity and is therefore suitable as NO2 sensing material.The WO3 nanomesh sensor exhibited high response,short response and recovery time,and excellent selectivity towards ppb-level NO2 at low temperature of 160℃.The superior gas performance of the sensor was attributed to the high-purity hexagonal WO3 with high specific surface area,which gives rise to enhanced surface adsorption sites for gas adsorption.The electron depletion theory was used for explaining the NO2-sensing mechanism by the gas adsorption/desorption and charge transfer happened on the surface of WO3 nanomesh.

Gas sensing capabilities of TiO_(2) porous nanoceramics prepared through premature sintering

Pure and noble metal(Pt,Pd,and Au)doped TiO_(2)nanoceramics have been prepared from TiO_(2)nanoparticles through traditional pressing and sintering.For those samples sintered at 550℃,a typical premature sintering occurred,which led to the formation of a highly porous microstructure with a Brunauer-Emmett-Teller(BET)specific surface area of 23 m^(2)/g.At room temperature,only Pt-doped samples showed obvious response to hydrogen,with sensitivities as high as~500 for 1000 ppm H_(2)in N_(2);at 300℃,all samples showed obvious responses to CO,while the responses of noble metal doped samples were much higher than that of the undoped ones.The mechanism for the observed sensing capabilities has been discussed,in which the catalytic effect of Pt for hydrogen is believed responsible for the room-temperature hydrogen sensing capabilities,and the absence of glass frit as commonly used in commercial thick-film metal oxide gas sensors is related to the high sensitivities.It is proposed that much attention should be paid to metal oxide porous nanoceramics in developing gas sensors with high sensitivities and low working temperatures.

香港离岸人民币市场利率与汇率联动效应研究

文章运用两区制门限协整模型对香港离岸市场利率与汇率的联动效应进行实证研究,发现香港离岸人民币市场利率与汇率的联动效应呈现非线性特征;在低利差区制,香港离岸人民币市场可以实现有效的自我调节,而在高利差区制,市场无法进行有效的自我调节,且随着远期汇率期限的增加,市场自我调节能力进一步降低。进一步分析香港离岸人民币市场利率与汇率的联动门限效应的影响因素发现,中美贸易摩擦、"811"汇改、央行货币政策等因素都会对离岸市场的状态造成差异化影响。因此,央行应根据区制的不同采取差异化政策,加快离岸市场基础设施建设,完善跨境资本流动管理和监察体制,推进利率和汇率市场化改革。

Contrasting room-temperature hydrogen sensing capabilities of Pt-SnO2 and Pt-TiO2 composite nanoceramics

Contrasting room-temperature hydrogen sensing behaviors have been revealed for Pt-TiO2 and Pt-SnO2 composite nanoceramics. In the case of the Pt-TiO2 nanoceramics, the ultrahigh hydrogen sensitivities are lost abruptly when the oxygen/hydrogen concentration ratio in ambient atmosphere reaches a critical value. However, in the case of the Pt-SnO2 nanoceramics, such a phenomenon does not occur, and the extraordinary room-temperature hydrogen sensing capabilities are observed in the presence of oxygen in air. Our combined experimental and theoretical investigations establish a unified mechanism for both the systems, which is rooted in hydrogen chemisorption on the surface and interstitial lattice sites of SnO2 and TiO2; the difference in stability of the chemisorbed hydrogen on SnO2 and TiO2 is considered responsible for the contrasting hydrogen sensing capabilities. The central findings are helpful in enriching our microscopic understanding of hydrogen interaction with various metal oxide semiconductors （MOSs） at room temperature in varying mixed gaseous concentrations, and they could be instrumental in developing reliable room-temperature hydrogen sensors based on bulk MOSs.

Efficient Synthesis of Isoquinolines by AgNO3-Catalyzed Sequential Imination-Annulation of 2-Alkynyl Aldehydes with Ammonium Bicarbonate

An operationally simple approach for the tandem synthesis of isoquinolines by the reaction of o-alkynylalde- hydes with ammonium bicarbonate via Ag-catalyzed 6-endo-dig ring closure is described. The reaction conditions and the scope of the reaction are examined, and a variety of substituted isoquinolines are prepared in moderate to excellent yields.

Recent progress in transition metal catalyzed cross coupling of nitroarenes

In this review,the recent development in transition metal catalyzed cross coupling of nitroarenes was highlighted.Firstly,development of transition metal catalyzed cross coupling was simply introduced.After presenting the advantages of nitroarenes,transition metal catalyzed cross coupling using nitroarenes as electrophilic coupling partners was classified and introduced in detail.Based on different chemical bonds such as C–O,C–S,C-C and C–N bonds constructed,different kinds cross coupling of nitroarenes would be highlighted and the plausible reaction mechanism would be presented if available.

DESs: Green solvents for transition metal catalyzed organic reactions

In this review,the recent development about using DESs as green solvents in transition metal catalyzed organic reactions was highlighted.Firstly,the development of DESs was simply introduced.After presenting the advantages of DESs,transition metals catalyzed organic reactions using DESs as green solvents were classified and introduced in detail.Different transition metals such as Au,metal impregnated on magnetite,Pd and Ru catalyzed organic reactions proceeded smoothly in DESs and gave corresponding products in good yields.And in some cases,the catalytic systems could be recycled up to several times without any decrease in activity.