近期热点文章

正Metal-Free Dihydrogen Oxidation by a Borenium Cation:A Combined Electrochemical/Frustrated Lewis Pair Approach E.J.Lawrence,T.J.Herrington,A.E.Ashley,G.G.Wildgoose Angew.Chem.Int.Ed.DOI:10.1002/anie.201405721以一种含硼杂环分子为电子传递媒介,催化有机介质中的氢氧化反应(HOR).Exfoliation of Layered Double Hydroxides for Enhanced Oxygen Evolution Catalysis F.Song,X.Hu Nature Commun.DOI:10.1038/ncomms5477     

近期热点文章北大核心CSCD

关键词：Na＋活性·化学电源Operando研究方法Q. Li, Z. Liu, F. Zheng, R. Liu, J. Lee, G. Xu, G.Zhong, X. Hou, R. Fu, Z. Chen, K. Amine, J. Mi, S.Wu, C. P. Grey, Y. Yang. Identifying the Structural Evolution of the Na-Ion Battery Na2Fe PO4F Cathode,Angew. Chem. Int. Ed., 10.1002/anie.201805555.厦门大学杨勇教授和合作者采用原位高能XRD、固态NMR和DFT理论方法,研究了Na2FePO4F阴极材料循环过程中晶体结构的动态变化,发现存在两种Na＋晶格位点,但只有一种有电化学活性.化学电源中的Operando研究方法为揭示电极活性物质的构效关系和反应机理提供了有力工具.     

纳米晶Sb掺杂SnO2(ATO)粉体的合成与表征

以Sn粉和Sb₂O₃为原料.采用共沉淀法制备了纳米ATO粉.TG-DSC及FTIR结果表明.450℃以前前驱体已失去全部水分.并完全转化为氧化物.XRD测量结果表明.所得ATO粉具有四方金红石结构.500℃焙烧后粉体的粒径为12nm.随着焙烧温度的升高.粉体的粒径增加.TEM测定结果表明,粉体的分散性很好.团聚很少.粉体的烧结性能良好,950℃时烧结5h即达到理论密度的97.3％.用霍尔系数法测定粉体的导电行为.表明该粉体具有良好的导电性能.     

近期热点文章

<正>Size-Dependent Electrocatalytic Reduction of CO2 over Pd Nanoparticles D.Gao,H.Zhou,J.Wang,S.Miao,F.Yang,G.Wang,J.Wang,X.Bao J.Am.Chem.Soc.DOI:10.1021/jacs.5b00046CO2还原反应Pd纳米催化剂的粒度效应.发现3.7nm时CO产率可达91.2%.     

近期热点文章

<正>Graphene,Related Two-Dimensional Crystals,and Hybrid Systems for Energy Conversion and Storage F.Bonaccorso,L.Colombo,G.Yu,M.Stoller,V.Tozzini,A.C.Ferrari,R.S.Ruoff,V.Pellegrini Science DOI:10.1126/science.1246501关于石墨烯用于能量转化与储存的综述.引用了138篇参考文献.     

近期热点文章

正Size-Dependent Surface Phase Change of Lithium Iron Phosphate during Carbon Coating J.Wang,J.Yang,Y.Tang,J.Liu,Y.Zhang,G.Liang,M.Gauthier,Y.K.Chen-Wiegart,M.N.Banis,X.Li,R.Li,J.Wang,T.K.Sham,X.Sun Nature Commun.DOI:10.1038/ncomms4451发现LiFePO4包碳过程的界面相变与活性物质的粒径有关,纳米粒子的界面稳定性较高,而微米粒子在高温包碳过程中界面发生明显变化.     

近期热点文章

<正>Electrochemical Water-Splitting Based on Hypochlorite Oxidation K.M.Macounov觃,N.Simic,E.Ahlberg,P.Krtil J.Am.Chem.Soc.DOI:10.1021/jacs.5b02087碱性介质中ClO-在Pt电极表面氧化生成ClO·自由基,继而氧化H2O,产生O2和H2O2.间接实现水分解.     

近期热点文章

TiO2 Microboxes with Controlled Internal Porosity for High-Performance Lithium Storage X. Gao, G. Li, Y. Xu, Z. Hong, C. Liang, Z. Lin Angew. Chem. Int. Ed. DOI: 10.1002/anie.201506357 合成由TiO2纳米棒构成的纳米多孔结构,用作锂离子电池阳极材料,循环300周仍具有187 mAh?g-1的容量,且可20C高倍率放电. Highly Efficient Electrochemical Reduction of CO2 to CH4 in Ionic Liquid Using Metal-Organic Framework Cathode X. Kang, Q. Zhu, X. Sun, J. Hu, J. Zhang, Z. Liu, B. Han Chem. Sci. DOI: 10.1039/C5SC03291A 在碳纸表面沉积含Zn的金属有机框架（MOF）化合物,该电极可高效催化CO2电还原为CH4.     

近期热点文章

正A New Rechargeable Sodium Battery Utilizing Reversible Topotactic Oxygen Extraction/Insertion of CaFeOz(2.5≤z≤3)in An Organic Electrolyte M.Hibino,R.Harimoto,Y.Ogasawara,R.Kido,A.Sugahara,T.Kudo,E.Tochigi,N.Shibata,Y.Ikuhara,N.Mizuno J.Am.Chem.Soc.DOI:10.1021/ja411365z以CaFeO3为正极材料,充电时CaFeO3还原为CaFeO2.5,释放出来的O与Li+或Na+生成氧化物.     

近期热点文章

正Suppression of Lithium Dendrite Growth Using Cross-Linked Polyethylene/Poly(ethylene oxide)Electrolytes:A New Approach for Practical Lithium-Metal Polymer Batteries R.Khurana,J.L.Schaefer,L.A.Archer,G.W.Coates J.Am.Chem.Soc.DOI:10.1021/ja502133j将聚乙烯和聚氧乙烯的交联共聚物用作金属锂电池隔膜,不仅获得较高的离子电导率,还可抑制锂枝晶的生长.     

Contributions to the Chemistry of the Binary Compounds of the Transition Elements

Phase and structural relationships of the sulfur, selenium, and tellurium compounds of the 4d and 5d transition elements of groups IV to VII of the periodic system are discussed. Homologous elements behave very similarly with respect to the chalcogens, and this is particularly the case for niobium and tantalum, and for molybdenum and tungsten. However, zirconium, niobium, and molybdenum have a greater tendency towards formation of chalcogen-poor phases than their homologues hafnium, tantalum, and tungsten. Subchalcogenides are known only for zirconium and niobium. The number of phases and the tendency towards formation of solid solutions are considerably smaller among the tellurides than among the sulfides and selenides. The crystal structures of the telluride phases also differ from those of the sulfide and selenide phases of analogous composition. In addition, a review of the phase and structural relationships of the arsenic and antimony compounds of the 4d and 5d transition elements of groups V to VII is given.     

LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES MODIFIED BY ETHYLENE COPOLYMERS： EFFECTS OF FUNCTIONALIZED SEGMENTS ON MORPHOLOGY

Melt extrusion was used to prepare binary nanocomposites of ethylene copolymers and organoclay and trinary nanocomposites of low-density polyethylene （LDPE）, ethylene copolymer and organoclay. X-ray diffraction （XRD） and transmission electron microscopy （TEM） were used to analyze the structure of the clay phase and the morphology of the nanocomposites. Influences of the comonomer in the copolymer and the content of the copolymer on the morphology of the resulting nanocomposites were discussed. The binary and the trinary composites may form intercalated or exfoliated structures depending on the interaction between the copolymer and the clay layers and the content of the copolymer.     

多弧离子镀TiN与不同金属基材间的接触界面与表面特性

用多弧离子镀技术在不同金属基材上进行TiN镀膜实验,制备了TiN/Fe、 TiN/Cu和TiN/Cr/Cu复合膜.借助扫描电子显微镜(SEM)、 X射线衍射仪(XRD)和光电子能谱(XPS),研究了TiN与Fe、 Cu和Cr/Cu三种不同衬底接触界面的形貌、结构及其表面特性.SEM观察发现,在一定离子镀膜条件下, TiN涂层可与Fe、 Cu和Cr/Cu金属基材形成均匀平整的接触界面,在铜基上TiN界面清晰,在Fe与Cr/Cu界面有明显的层状晶界微结晶分布.XRD分析显示, Fe、 Cu和Cr/Cu表面生成的薄膜都包含TiN、 Ti2N等多晶相,在Cr/Cu界面还包含Ti-Cr的金属间化合物.XPS结果表明,表面除了TiN膜外,还生成TiO2和TiOxNy等氧化膜.Ar+刻蚀5 min后, TiO2消失, TiOxNy减少, TiN则呈增加趋势.TiN与Cr/Cu界面形成明显的Ti-Cr和Cr-Ni互扩散层,这有助于增强薄膜附着力,形成较牢固的TiN涂层.     

PROPERTIES AND MORPHOLOGY OF UNSATURATED POLYESTER/ACRYLATE-TERMINATED POLYURETHANE/ORGANOMONTMORILLONITE NANOCOMPOSITES

Unsaturated polyester resin （UPR）/acrylate-terminated polyurethane （ATPU）/organo-modified montmorillonite （OMMT） nanocomposites were prepared by the in situ intercalative polymerization method. Samples were prepared by the sequential mixing, i.e. mixture of the ATPU and styrene （S） and OMMT were prepared in the first step; UPR was then added to the pre-intercalates of ATPU/S/OMMT. Results indicate that the mechanical properties and thermal properties of UPR/ATPU/OMMT nanocomposites greatly depend on the amount of ATPU and OMMT. Results show that the addition of ATPU could increase the impact strength of UPR/ATPU composites, but the tensile strength, flexural strength and heat resistance of the materials are obviously decreased. When the weight ratio between UPR, ATPU and OMMT were 82：15：3, the impact strength and heat distortion-temperature of nanocomposite were greatly improved, meanwhile there was little change for other properties of the nanocomposites. The synergistic enhancement effects of ATPU and OMMT on the composites were observed. The structures and morphology of the composites were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.     

Oligoethyleneoxide spacer groups in polymerizable surfactants

Cationic and zwitterionic polymerizable surfactants bearing tri- and tetraethyleneglycol spacer groups between the polymerizable moiety and the surfactant structure were prepared and polymerized. Monomers and polymers were investigated with respect to their aggregation behavior in aqueous systems and compared to analogous monomers and polymers lacking spacer groups. In the case of the monomeric surfactants, the spacer groups depress both the Kraffttemperature and the critical micelle concentration. the area occupied per molecule at the air-water interface is substantially enlarged by the spacers, whereas the depression of surface tension is nearly constant. Although the monomers with and without spacers are true surfactants, all the polymers are water-insoluble, but form monomolecular layers at the air-water interface. In analogy to the monomer behavior, the incorporation of the spacer groups increases the area occupied per repeat unit at the air-water interface substantially, but hardly affects the surface activity.     

纳米粒子的精准组装

纳米材料由于其独特的光、电、磁、力学等性质,成为了构建功能材料与器件的理想基元。实现纳米粒子的精确组装,是探究粒子之间的耦合聚集性质和制备宏观功能器件的基础。但是由于纳米粒子的小尺寸以及在溶液中运动的随机性与复杂性,精准控制纳米粒子组装体的形貌以及在空间中的相对位置仍存在巨大挑战。为了将纳米粒子组装成理想的有序结构,许多控制粒子组装的策略与方法得到发展。本文首先概述了纳米粒子自组装的控制方法与典型形貌,着重分析了影响粒子精准排布的因素与控制方法,并对纳米粒子及其组装体的光学性质与器件应用的最新研究进展进行了讨论,最后对目前纳米粒子精准组装所面临的挑战以及未来发展的方向进行了展望。     

电流变液中悬浮颗粒的体积与形状的变化

基于偶极近似,运用电极化方法,定量研究了电流变液中悬浮颗粒在外电场作用下其体积和形状的变化,并计算了其体积和形状的相对变化率.研究结果表明:悬浮颗粒的体积和形状的相对变化率均与电场强度的平方成正比,并与ER本身的性质有关.一般情况下,颗粒的体积和形状的相对变化率分别为8.4%和12.5%,对总体积变化率的贡献为1.68%.这种变化对于ER系统的电涨和电热都作出了贡献,仅当将颗粒当作刚性球时,其自由能才与电场强度的平方成正比.     

引入PNA、1, 2-PG对聚氨酯胶粘剂微相形态及性能的影响

引入PNA、1; 2-PG对聚氨酯胶粘剂微相形态及性能的影响;聚氨酯胶粘剂;结晶;微相分离;软段;硬段     

花生酸与铈β-二酮络合物混合单分子膜的成膜特性

将铈β-二酮络合物(Ce(tmhd)4)的氯仿溶液与花生酸(AA)的氯仿溶液以不同摩尔比混合并铺展在纯水亚相上,得到其与AA的混合单分子膜.对混合单分子膜的成膜特性(π-A等温线和体系超额自由能)进行了探讨,发现混合单分子膜的超额自由能为负值,混合过程为热力学自发过程,且在配比为1∶ 2时其绝对值最大,体系最稳定,并进一步讨论了混合单分子膜可能的凝聚态结构.在配比为1∶ 2时,研究了混合单分子膜的静态弹性和动态弹性.     

Spectrophotometric determination of the dissociation constants of crown ethers with grafted acridone unit in methanol based on Benesi-Hildebrand evaluation

As potential chromo- and fluorophores for optical sensors a number of acridone grafted crown ethers containing NO2 group(s) and/or Br or Cl atom(s) in the aromatic rings (compounds) were studied by spectrophotometric method. In the first step of this work the acid-base and complexing properties of these compounds as well as those of the acridone, thioacridone and 4,5-dinitroacridone were investigated. Compounds proved to be very week acids and therefore the conventional spectrophotometric method based on the measurement of the ratio of the protonated/deprotonated forms of the compounds was not applicable for the determination of the dissociation constants (pKa values). Thus, a new spectrophotometric approach was elaborated for the pKa determination of these compounds, which is based on spectrophotometric titration in methanol with strong base and the titration results were evaluated by the Benesi-Hildebrand method. (In the studies with TEAOH, TMAOH and LiOMe, the complex formation between the ionophores and the cations of the bases could be excluded.) As it was expected, the experimentally determined pKa values depended on the nature of the substituents of the acridone moiety and pKa values ranged between 12.6 and 14.9. The lower pKa value of thioacridone compared to the acridone can be explained by the larger size of the sulfur atom. The outstandingly larger pKa value for 4,5-dinitroacridone can be attributed to the formation of intramolecular hydrogen-bonds between the ortho-position nitro group and the NH proton. As a trend, the strong electron withdrawing nitro substituents decreased considerably the pKa values of compounds and compared to that of the halogen (Cl and Br) atoms (for example compounds and) of weaker withdrawing effect.