La 0.9 M 0.1 Ga 0.8 Mg 0.2 O 3 -α的中温质子导电性及其在常压合成氨中的应用

采用水热沉淀法制备了La0.9M0.1Ga0.8Mg0.2O3-α (M＝Ca2＋, Sr2＋, Ba2＋)陶瓷样品的前驱体, 沉淀剂来自尿素在水热条件下的水解产物. 前驱体经煅烧和烧结后得到陶瓷样品. XRD显示样品具有单一的斜方晶LaGaO3钙钛矿结构. 同位素效应和氢的电化学透过(氢泵)实验证明陶瓷样品具有质子导电性. 用AC阻抗谱法测定了样品在300～600 ℃、氢气气氛中的质子电导率, 其大小取决于La位掺杂的碱土金属离子: σ(M＝Sr2＋)＞σ(M＝Ba2＋)＞σ(M＝Ca2＋). 以La0.9M0.1Ga0.8Mg0.2O3-α为固体电解质进行了常压合成氨, 最佳合成温度为520 ℃. 当施加的电流密度为1 mA•cm－2、合成温度为520 ℃时, 氨产率分别为: 1.63×10–9 mol•s－1•cm－2 (M＝Ca2＋), 2.53×10－9 mol•s－1•cm－2 (M＝Sr2＋)和2.04× 10－9 mol•s－1•cm－2 (M＝Ba2＋).     

Oxygen permeation and phase structure properties of partially A-site substituted BaCo_(0.7)Fe_(0.225)Ta_(0.075)O_(3-δ) perovskites

Ba0.9R0.1Co0.7Fe0.225Ta0.075O3-δ(BRCFT, R = Ca, La or Sr) membranes were synthesized by a solid-state reaction. Metal cation Ca2+,La3+or Sr2+doping on A-site partially substituted Ba2+in BaCo0.7Fe0.225Ta0.075O3-δoxides, and its subsequent effects on phase structure stability, oxygen permeability and oxygen desorption were systematically investigated by XRD, TG-DSC, H2-TPR, O2-TPD techniques and oxygen permeation experiments. The partial substitution with Ca2+, La3+or Sr2+, whose ionic radii are smaller than that of Ba2+, succeeded in stabilizing the cubic perovskite structure without formation of impurity phases, as revealed by XRD analysis. Oxygen-involving experiments showed that BRCFT with A-site fully occupied by Ba2+exhibited good oxygen permeation flux under He flow, reaching about 2.3mL min-1 cm-2at 900 ℃ with 1 mm thickness. Of all the membranes, BLCFT membrane showed better chemical stability in CO2, owing to the reduction in alkalinity of the mixed conductor oxide by La doping. In addition, we also found the stability of the perovskite structure under reducing atmospheres was strengthened by increasing the size of A-site cation(Ba2+La3+Sr2+Ca2+).     

香豆素/Betti碱主体合成及其对铷、钡离子的选择性响应(英文)

合成了一个新型香豆素/Betti碱主体化合物1,并对其进行了结构表征。在乙腈/水溶液中进行主体1和碱金属、碱土金属相关离子(Li+,Na+,K+,Rb+,Cs+,Be2+,Mg2+,Ca2+,Sr2+,Ba2+)的相互作用研究时,发现仅Rb+,Ba2+离子对主体1有敏感的紫外光谱及荧光光谱响应,而其它的碱金属、碱土金属离子无敏感性光响应。紫外光谱显示,Rb+,Ba2+离子使主体1产生明显的红移(ε=4.66×102L·(mol·cm)-1,Δ=91nm),肉眼可观察到明显的由浅黄向橙红色的颜色变化,并使主体1的荧光光谱发生一定程度的猝灭。     

锶掺杂对La_(1-x)Sr_xNbO_(4-σ)质子导体性能的影响

利用高温固相反应法制备了Sr掺杂LaNbO4质子导体La1-xSrxNbO4-σ(0≤x≤0.02),并且对其性能进行了表征。XRD分析表明,所有的样品具有单斜结构,晶胞体积随Sr掺杂量的增加而增大;La1-xSrxNbO4-σ样品在沸水中和二氧化碳气氛中具有很好的化学稳定性。SEM分析表明,La1-x Srx NbO4-σ粉体经1 500℃烧结8 h后均得到致密的、晶粒均匀的样品;Sr的掺杂抑制了陶瓷体裂缝的产生和晶粒的过度增长;随Sr的掺杂量增加,晶粒变小。交流阻抗谱分析表明,Sr掺杂改变了LaNbO4的电导率,其中样品La0.995Sr0.005NbO4-σ具有最高的电导率;样品在25℃水汽饱和的5%H2-Ar气氛下的电导率明显高于干燥空气气氛,在800℃时,La0.995Sr0.005NbO4-σ电导率达到0.003 S·cm-1,电导活化能为0.44 eV。     

M_2RSbO_6:R′~(3+)(M=Ba,Sr,Ca;R=La,Gd,Y,Bi;R′=Sm,Eu,Dy,Ho,Er,Tm)复合氧化物的合成,组成,结构和荧光性质

本文按文献的方法合成了Ba-2BiSbO_6,Ba_2GdSbO_6、M_2RSbO_6(M=Ba,Sr,Ca,R=La,Y),以M_2RSbO_6为基质掺Sm~(3+)、En~(3+)、Dy~(3+)、Ho~(3+)、Er~(3+)、Tm~(3+)、Bi~(3+)研究它们的化学组成,晶体结构与发光性能的关系及规律,Bi~(3+)的荧光及敏化作用,同时研究了它们     

SrGaF_5中Eu~(2+)的荧光光谱结构

Hewes 和Hoffman首次报道了 MAIF,(M=Ca,Sr,Ba)中Eu~(2+)的光谱特性,发现当M=Sr或Ba时,Eu~(2+)可以产生4f~7(~6P_(7/2))→df~7(~8S_(7/2))跃迁锐线发射(简称f→f跃迁发射),峰值位于 360nm附近。随后,Blasse和Fouassier先后对Eu~(2+)产生f→f     

A Quinoline Derivated Chemosensor for Cu^2＋ Recognition

A quinoline derivative N-(2-hydroxyl-naphthylmethyl)-N-(quinol-8-yl)amine(2) was synthesized and characterized, which can selectively recognize Cu2+ over other metal ions such as Zn2+, Cd2+, Sn2+, Pb2+, Hg2+, Ni2+, Mg2+, Cr3+, Mn2+, Sr2+, K+, Ca2+, Na+, Ba2+ in acetonitrile/water(volume ratio 99:1). Cu2+ induced a new absorption peak at 464 nm in the absorption spectrum(ε=4.66×102 L·mol-1·cm-1) and quenched the fluorescence emission of quinoline derivative 2. The binding of quinoline derivative 2 to Cu2+ wa...     

Ce~(3+)在硫化物中的配位环境与其发光行为的相关性研究

应用CS_2气、固相反应合成了MLn_2S_4:Ce、MAl_2S_4:Ce和Ln_2S_3:Ce(M=Ca、Sr、Ba;Ln=La、Gd、Lu、Y)发光体。将Ce~(3+)在硫配位化物中的最大发射峰位与配位体的成键性质、Ce~(3+)可能取代格位的点群对称性及基质阳离子的电负性与半径之比X/R相关联,得到一些有意义的结果。BaLu_2S_4:Ce和SrAl_2S_4:Ce的荧光寿命分别为37和28ns。     

Eu2+/Mn2+激活的M3MgSi2O8-M2SiO4(M=Ba,Ca)荧光粉的发光特性

采用高温固相法制备了Eu2+/Mn2+单激活和共激活的M3MgSi2O8-M2SiO4(M=Ba,Ca)两相荧光粉.通过X射线衍射(XRD)和荧光光谱(PL)对样品材料的晶体结构和光谱性能进行了表征.XRD测试结果表明所合成的样品具有M3MgSi2O8和M2SiO4两种晶相结构.PL测试显示,Eu2+在Ba3MgSi2O8-Ba2SiO4体系中发射442和502nm两个波带的光;而Eu2+在Ca2+部分取代Ba2+的BaCa2MgSi2O8-Ba1.31Ca0.69SiO4体系中发射420～520nm的连续波带,并且激发光谱向长波扩展,更加适用于被InGaN芯片(395 nm)激发.通过改变Mn2+的掺杂量可制得颜色可调的BaCa2MgSi2O8-Ba1.31Ca0.69SiO4:Eu2+,Mn2+白光荧光粉.     

碱土金属锡酸盐掺铕体系荧光粉合成和荧光性质研究

本文报道了MSnO_3∶Eu~(3+)和M_2SnO_4∶Eu~(3+)(M=Ca,Sr,Ba)体系荧光粉的合成和荧光性质。产品经X射线确证CaSnO_3∶Eu~(3+)和Ca_2SnO_4∶Eu~(3+)为正交晶系,SrSnO_3∶Eu~(3+)和BaSnO_2∶Eu~(3+)为立方晶系,而Sr_2SnO_4∶Eu~(3+)和Ba_2SnO_4∶Eu~(3+)为四方晶系。激发光谱表明,随Ba—Sr—Ca离子半径减小,Eu~(3+)的电荷迁移能量紫移,而Eu~(3+)的f-f跃迁红移。发射光谱表明,CaSnO_3∶Eu~(3+)和Ca_2SnO_4∶Eu~(3+)以电偶极跃迁为主,而其它4种化合物不存在电偶极跃迁。     

Photoelectrochemical Currents at Gold Electrode at Negative Potentials

Photoelectrochemical and electrochemical processes at ground, polished, and etched surfaces of gold in a 0.5 M NaClO₄ solution are studied.     

Meisenheimer complexes bonded at carbon and at oxygen

The carbon-bonded gas-phase Meisenheimer complex of 2,4,6-trinitrotoluene (TNT) and the nitromethyl carbanion CH(2)NO(2)(-) (m/z 60) is generated for the first time by chemical ionization using nitromethane as the reagent gas. Collision-induced dissociation (CID) of the Meisenheimer complex furnishes deprotonated TNT, a result of the higher gas-phase acidity of TNT than nitromethane. The formation of Meisenheimer complexes with CH(2)NO(2)(-) in the gas phase is selective to highly electron-deficient compounds such as dinitrobenzene and trinitrobenzene and does not occur with organic molecules with lower electron-affinity such as methanol, methylamine, propionaldehyde, acetone, ethyl acetate, chloroform, toluene, m-methoxytoluene, and even nitrobenzene and p-fluoronitrobenzene. As such, the reaction allows selective detection of TNT in mixtures. Meisenheimer complexes between CH(2)NO(2)(-) and the three dinitrobenzene isomers display distinctive fragmentations. The oxygen-bonded sigma-complex of TNT with the deprotonated hemiacetal anion CH(3)OCH(2)O(-) (m/z 61), represents a different type of Meisenheimer complex. It displays characteristic fragmentation involving loss of HNO(2) upon CID. The combination of a selective ion/molecule reaction (Meisenheimer complex formation) followed by a characteristic CID process provides a second novel and highly selective approach to the detection of TNT and closely related compounds in mixtures. The assay is readily implemented using neutral loss scans in a triple quadrupole mass spectrometer. Gas-phase reactions of denitrosylated TNT with benzaldehyde produce the corresponding dihydrofuran in an aldol condensation, a result that parallels the corresponding condensed-phase reaction.     

Nuclear forensics education at the University of Texas at Austin

Nuclear forensics continues to be an integral part of the Domestic Nuclear Detection Office, the Defense Threat Reduction Agency and the National Nuclear Security Administration. As with our previous three-year Nuclear Forensics Education Award Program we will continue to offer a comprehensive educational program and closely collaborate with national laboratories to pursue common research. Our research will primarily focus on analysis of radioactive debris following a nuclear or radiological dispersive device event or the investigation of the pedigree of nuclear materials in nonproliferation. This research will include using Compton suppression and gamma coincidence low-level gamma ray counting, investigation of nuclear fuel cycles for nonproliferation, on-site inspection within the context of the Comprehensive Nuclear-Test-Ban Treaty and radioxenon detection physics. We also offer a graduate program in nuclear robotics, an interdisciplinary program in the automation of handling special nuclear materials. To better equip our students who are entering the workforce at the national laboratories and government agencies we are also proposing the development of several new laboratory modules for non-destructive identification of fission products in environmental samples and irradiated uranium specimens at various enrichments and characterizing naturally occurring radioactive material. Collaboration with Florida Memorial University a Historically Black Colleges and Universities will continue for training and collaborative research.     

Polyvinylamine at last

A sustained effort to develop and commercialize a practical radical addition route to amine functional polymers (AFPs) resulted, after almost 20 years, in the successful completion of a world scale monomer plant to produce N‐vinylformamide (NVF). NVF is readily polymerized and its polymers are easily hydrolyzed to reactive and atom economical polyvinylamine (PVAm) or its salts. This highlight touches on work by many companies, but focuses on efforts at Air Products and Chemicals, tracing the origins, rational, challenges, technical and commercial advances, and failures. Practical routes to new AFPs, copolymers, and derivatives across the entire molecular weight range (MW < 10³ to >10⁶) were achieved. NVF offers access to multiple water soluble, water dispersible, and nonwater soluble polymer markets, including papermaking additives and coatings, water treatment polymers, enhanced oil recovery polymers, radiation cure monomers, stabilizers, dispersing agents, surfactants, and crosslinkers. Lessons learned along the road to commercializing major new chemical technologies are also highlighted. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2257–2283, 2010     

Constraining molecules at the closest approach: chemistry at high pressure

The purpose of this tutorial review is to illustrate the effects that the application of high pressures can have on chemical reactions involving highly compressible molecular materials. The essentials of the high-pressure technology (generation and in situ control of high pressures) are described with particular attention to the versatile diamond anvil cell (DAC) apparatus. The general effects of pressure on chemical equilibrium, reaction rate and reaction mechanism are discussed. The motivation for application of high-pressure methods (in the 1-300 MPa range) to chemical synthesis and in biochemistry are illustrated focusing the attention on environmental effects and with an excursus on developing biotechnological applications. The peculiarities and the unexpected outcomes of chemical reactions occurring at very high pressures (>or=300 MPa) are discussed considering the extraordinary results obtained in polymerization and amorphization of simple molecules and of unsaturated hydrocarbons. The possible connection of the high temperature-high pressure thresholds for chemical reactions with microscopic counterparts (intermolecular distances, molecular orientations) is also discussed.