Rapid Formation of the Textured (Bi,Pb)2(Sr,Ca)4Cu3Oy Superconductor by Multiple Pressing and Sintering Process

A superconducting (Bi, Pb)₂(Sr, Ca)₄Cu₃O₂ material has been prepared by tbe oxalate coprecipitation method. The high-Tc 110 K phase was effectively promoted by application of an intermediate grinding and pressing between the sintering heat treatments. The powder X-ray diffraction shows the existence of single high-Tc and high-textured microstructures with strong (001) reflections within a short sintering time ( 18 h). The morphology of the sintered samples was examined by scanning electron microscopy (SEM). Also, the kinetics of the formation of the high-Tc phase were investigated by the isothermal method. A possible mechanism of the formation of high-Tc 2223 phase was proposed.     

Carbon Species and Precise Elemental Analysis of Precursors for Superconducting (Bi,Pb)2Sr2Ca2Cu3Ox Tapes

 The chemical composition of BiPbSrCaCuO precursors prepared by different syntheses has to be checked analytically before further application to production of superconducting (Bi,Pb)₂Sr₂Ca₂Cu₃O_x tapes. Carbon species in concentrations below 0,1%(w/w) were observed to be possibly a source of gas evolving reactions during the heat treatment procedures for the superconducting phase formation. A method that allows the temperature controlled detection of CO₂ resulting from reactions of various carbon species was developed based on an commercial C/H₂O-analyser with IR gas detectors. By means of this method it is possible to relate the carbon content to the conditions of synthesis and technological steps of the tape production. The phase formation mechanism of the superconducting (Bi,Pb)2223 phase from a multiphase precursor strongly depends on its elemental composition. Titrimetric and ICP spectrometric methods that allow the determination of the content of the main components Bi, Pb, Ca, Sr, and Cu with high precision and accuracy were developed and their results were compared. The best results were obtained with a combined chemical-spectrometric procedure. The relative standard deviations (RSD) for all metallic elements do not exceed 1%. The analytical results of the main components and specific trace determinations are essential for the functioning of superconducting tapes.     

Efficient Synthesis of 2-(8-Quinolinoxy)-4H-imidazolin-4-ones

IntroductionMany N- heterocycles including 4H - imidazolin-4- ones show bactericidal and fungicidal activities,especially those with a 2 - alkoxyl substituent[1— 5] .The efforts to discover the new biologically activederivatives reflected by the still important numberof publications and patents have been devoted tothe subject[6— 11] .For example,some 2 - amino or 2 -alkylthio substituted 4H- imidazolin- 4- ones showsignificant antifungal and antibacterial activi-ties[7— 9] ,whereas others …     

YBa2Cu4O8/La2/3Ca1/3MnO3/YBa2Cu4O8异质结中的超导转变温度

采用对靶溅射技术制备了YBa2Cu4O8/La2/3Ca1/3MnO3/YBa2Cu4O8（Y-124/LCMO/Y-124）异质结, 研究了超导转变温度（TC）随LCMO层厚度（dL）的振荡行为. 当dL＞dLCR时, TC-dL曲线表现出清晰的非单调行为, 而金属-绝缘体转变温度（TMI）仅当dL＞dLCR时才能观测到. Y-124/LCMO/Y-124系统中所存在的这种对中间层的依赖关系, 显示了铁磁和超导耦合间强烈的相互作用.     

A New 2-((Z)-Thiosemicarbazidomethyl)- Quinolin-8-YL Acetate Ligand and its Cu(II) Complex: Syntheses,Structures, and Characterizations

Abstract

A new ligand, 2-((Z)-thiosemicarbazidomethyl)-quinolin-8-yl acetate (C₁₃H₁₂ N₄O₂S) (L) and its Cu(II) coordination complex, [Cu(L₁)] [HL₁ = (Z)-1-((8-hyd- roxyquinolin-2-yl)methylene)thiosemicarbazide], have been synthesized, and characterized by IR, elemental analysis, ¹H NMR, MS, and X-ray single-crystal diffraction. L shows a stable three-dimensional supramolecular structure through hydrogen bonds and π-π stacking interactions. [Cu(L₁)] shows a three-dimensional network structure formed only by hydrogen bonds. In addition, the fluorescence spectra of L were measured.     

The formation of superconducting oxide phases in the (Bi,Pb)−Sr−Ca−Cu−O System

The crystallization mechanism of superconducting phases in the (Bi,Pb)?Sr?Ca?Cu?O system was determined on the basis of the results of DTA, DTG and TG studies, supplemented by X-ray examination of ceramic powders obtained by the sol-gel method. It has been demonstrated that the factor determining the formation of superconducting phases: Bi₂Sr₂CaCu₂O_x (low-T _c ) and Bi₂Sr₂Ca₂Cu₃O_x (high-T _c ) is the kinetics of reaction of calcium and strontium carbonates with molten CuBi₂O₄. As a result of the reaction of the bimetallic compound CuBi₂O₄ with SrCO₃ in the liquid phase the compound Bi₂Sr₂CuO₆ is formed. This compound, reacting with calcium and copper oxides, yields superconducting phases: the low-T _c and the high-T _c phase. It has been also observed that an increase in the volume fraction of high-T _c phase in powder subjected to thermal treatment takes place probably due to the repeated disproportionation of low-T _c phase and its repeated synthesis from Bi₂Sr₂CuO₆, CuO and CaO.     

Thermal properties,texture, second-order stress,and magnetic susceptibility of the Bi1.8Pb0.3Sr2Ca2Cu3.3Ox

Mono-phase high critical temperature (Bi,Pb)-2223 superconductor from the off-stoichiometric Bi_1.8Pb_0.3Sr₂Ca₂Cu_3.3O_x belonging to the tetragonal system, has been obtained. We studied the crystalline structure, the stress of second order, and the texture of the surface pellet, in the framework of XRD diffractometry. Results of the thermal measurements made in the nitrogen, with a heating rate of 10 K min^?1, from room temperature (RT) to 1273.15 K, show a slow mass decrease of 1.25 % from RT to 1003.15 K probably due to the elimination of water, oxygen, and of the other gases accumulated on the crystallite surface through chemical adsorption. Two endothermic processes were evidenced on DSC, and DTG curves: the first in the range of 1135.15–1193.15 K (melting and slow decomposition), and another after 1217.45 K (decomposition). The contribution of crystal lattice to the estimated specific heat capacity was in conformity with the Einstein model, giving for the Einstein temperature a value of 1297.5 K. In conformity with the Müller critical state model, we found linear dependences for intragrain critical transition temperature, T _g, and intergrain coupling temperature, T _p, versus the amplitude of the external AC magnetic fields. There was evidenced that intergrain critical currents are five orders smaller than the intragrain critical currents.     

Synthesis of light-emmting materials bis-[2′-2″-(9H-fluoren-2-yl)-vinyl-8-hydroxyquinoline] zinc(II) and bis-[2′-4″-(4,5-diphenyl-1H-imidazol-2-yl)styryl-8-hydroxyquinoline] zinc(II)

Two novel light-emitting materials bis-[2′-2″-(9H-fluoren-2-yl)-vinyl-8-hydroxyquinoline] zinc(II) (3) and bis-[2′-4″-(4,5-diphenyl-1H-imidazol-2-yl)styryl-8-hydroxyquinoline] zinc(II) (4) containting 8-hydroxyquinoline and fluorene or imidazole moieties have been synthesized. The optical properties of these complexes were influenced by the styryl substituents, and exhibited orange-emission. They have higher fluorescence quantum yields than Alq₃, and good stabilities with thermal decomposition temperatures 395 °C and 435 °C. The single-layer OLED fabricated by 3 emitted lemon-yellow, and exhibited good device performance with a maximum luminance of 489 cd m⁻², and luminance efficiency of up to 0.41 cd A⁻¹. The single-layer OLED fabricated by 4 emitted yellow-green, and exhibited good device performance with a maximum luminance of 323 cd m⁻², and luminance efficiency of up to 0.54 cd A⁻¹.     

Ba2Cu3O5+δ as an intermediate phase during the synthesis of YBa2Cu4O8

We propose a reaction model for the synthesis of YBa₂Cu₄O₈ under normal pressure conditions, which contains 4 partial reaction steps. In a first step bariumnitrate and copperoxide react to Ba₂Cu₃O_5+δ. This substance will be formed for each mixtures Ba:Cu=2∶3...3∶2. The following two partial reaction steps are connected to Ba₂Cu₃O_5+δ, which reacts with Y₂O₃ and CuO to YBa₂Cu₄O₈ or decomposes to BaCuO₂ and CuO. In a last step parts of BaCuO₂ reacts with Y₂O₃ and CuO to YBa₂Cu₄O₈.     

Ein alternativer Weg zur Darstellung von Bi2Sr2CaCu2Ox,YBa2Cu3O7−δ, und YBa2Cu3−xMxO7−δ (M  Ni,Ag und x ≤ 33 Mol%)

An Alternative Method for Preparation of Bi₂Sr₂CaCu₃O_x, YBa₂Cu₃O_7?δ, and YBa₂Cu_3?xM_xO_7?δ (M ? Ni, Ag and x ≤ 33 Mol%) Oxidation of quenched melts of metals in a well defined argon/oxygen atmosphere has been found as an alternative method to prepare hight purity samples of Bi₂Sr₂CaCu₂O_x without Pb-stabilization. A special equipment for the oxidation of powder samples will be described. By our new method it is also possible to prepare YBa₂Cu₃O_7?δ and derivatives of this compound, where Cu is substituted by high amounts of Ni or Ag.     

Structure and Luminescence Characteristics of Europium Activated Strontium Silicates Sr（Eu ,Bi）SiO3 and Sr（Eu ,Bi）2SiO4

Sr2SiO4 ： Eu^3 , Bi^3 and SrSiO3 ：Eu^3 , Bi^3 samples were synthesized at high temperature and high pressure. The effect of high pressure on the structure and luminescence properties of the samples were stud-ied. As a comparison, the samples were also prepared by the method of sol-gel at high temperature and atmo-spheric pressure. The SrSiO3 ： Eu^3 , Bi^3 prepared at atmosphere has a hexagonal phase structure; in the pressure range of 2. 34—4. 10 GPa, it is transformed into a pseudo-orthorhombic structure (monoclinic), and in the pressure range of 4. 10—4. 15 GPa, the structure change of Sr2SiO4 ： Eu^3 , Bi^3 has not been ob-served, it maintains the monoclinic structure of the samples synthesized at an atmospheric pressure. High pressure makes the luminescence properties of the samples changed obviously. The intensity and the relative quantum luminescent efficiency decrease, the half-width increases obviously and the red shift occurs. The changes of the luminescence properties result from the pressure-induced changes of the crystal structures.     

Transformations de la phase supraconductrice a hauteT c (Bi,Pb)2Sr2CaCu2O8+x

DTA-DTG systematic study of highT _c superconducting phase (Bi,Pb)₂Sr₂CaCu₂O_8+x, with and without lead, shows a quantitatively opposite variation of oxygen stoechiometry on heating and cooling. Multiplate sample container, designed for the study, allowed to dissociated PbO loss from oxygen variations. Phases transformations have been studied under severalP _O2 by scanning DTA and DTG. Oxygen variations evolution has been evaluated by isothermal TG. The results proved that phase diagram representation must take into consideration theP _O2 coordinate.     

Synthesis,crystal structure,and photophysical properties of a double open cubane-like Cd(II) complex based on 2-substituted-8-hydroxyquinoline

A 2-substituted-8-hydroxyquinoline (E)-2-[2-(3-thienyl)ethenyl]-8-quinolinol (HL) was synthesized and characterized by ESI-MS, NMR spectroscopy, and elemental analysis. Using solvothermal method, a tetranuclear complex [Cd₄L₆Br₂]·6DMF (1) was fabricated by assembly of Cd(II) with HL. X-ray structural analysis shows that 1 exhibits a double open cubane-like core structure, which is bridged by six 8-hydroxyquinolinate-based ligands. The supramolecular structure of 1 features a 3-D porous solid constructed by aromatic stacking interactions, C–H···π interactions and C–H···O hydrogen bonds. The assembly of cadmium salts and HL in solution was investigated by UV–vis and photoluminescence. We also studied the thermal stability and photophysical properties (fluorescent emission, lifetime, and quantum yield) of 1. The results show that 1 emits yellow luminescence in the solid state.     

钼掺杂磷酸钒锂正极材料的制备及其电化学性能研究

以Li2CO3,NH4H2PO4,V2O5和MoO3为原料,柠檬酸为络合剂和碳源,采用溶胶凝胶法制备了锂离子正极材料Li3MoxV2-x(PO4)3/C (x = 0.01, 0.02和0.03). X射线衍射（XRD）表明,合成的材料具有单一的单斜晶系结构,空间群为P21/n. 扫描电镜（SEM）显示Li3Mo0.02V1.98(PO4)3/C具有均一的表面形貌。恒流充放电测试表明,当x = 0.02时,掺杂后的Li3Mo0.02V1.98(PO4)3具有最佳的电化学性能. 在1C倍率下,3.0 ~ 4.3 V电位区间,Li3Mo0.02V1.98(PO4)3/C的首次放电比容量达到122.3 mAh?g-1,循环50周之后,容量没有衰减的迹象;而当x = 0, 0.01和0.03时,首次放电比容量仅分别为117.1 mAh?g-1,115.1 mAh?g-1和116.0 mAh?g-1. 在3C和5C倍率下,样品Li3Mo0.02V1.98 (PO4)3/C仍能保持优异的循环稳定性.     

Novel polymeric metal complexes as dye sensitizers for Dye-sensitized solar cells based on poly thiophene containing complexes of 8-hydroxyquinoline with Zn(II),Cu(II) and Eu(III) in the side chain

Novel polymeric metal complexes as dye sensitizer for dye-sensitized solar cells (DSSCs) based on poly thiophene containing complexes of 8-hydroxyquinoline with Zn(II),Cu(II), and Eu(III) in the side chain have been synthesized according to the Stille coupling method and characterized by FTIR, GPC, and Elemental analysis. The UV-vis absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, and the applications in dye-sensitized solar cells (DSSCs) are also determined and studied. The DSSCs fabricated by PZn(Q)₂-co-3MT, PCu(Q)₂-co-3MT, and PEu(Q)₃-co-3MT exhibit good device performance with a power conversion efficiency of up to 0.56%, 0.78%, and 1.16%, respectively, under simulated AM 1.5 G solar irradiation (100 mW/cm²). They possess excellent stabilities and their thermal decomposition temperatures are 340 °C, 400 °C, and 540 °C, respectively, indicating polymeric metal complexes are suitable for the fabrication processes of optoelectronic devices.     

(Li,Ca,A)_2SiO_4:Eu,Bi发光体的合成和发光性能的研究(A=Al,Y,La,Gd)

为了寻找新的发光基质材料,用高温固相反应合成了(Li,Ca,A)_2SiO_4:Eu,Bi系列发光体(A=Al,Y,La,Gd).通过激发光谱和发射光谱的测试.首次在碱土金属硅酸盐体系中研究了Al,Y,La,Gd等三价金属离子对Bi~(3+)、Eu~(3+)发光特性和Bi~(3+)敏化Eu~(3+)发光性能的影响,得到了良好的基质组成.实验结果表明.基质中适当含量的Gd~(3+)可大幅度提高Eu~(3+)的发光强度,使~5D_0-~7F_2发射强度增加6倍.Bi~(3+)对Eu~(3+)有很好的敏化作用,以A=Gd或Al时较好,对~5D_0-~7F_1辐射跃迁的敏化效果尤为突出.     

高锰酸钾-鲁米诺反应体系中碱土金属离子Mg2+,Ca2+,Sr2+,Ba2+化学发光行为研究

将被认为没有化学发光活性的第二主族(碱土金属)离子Mg^2 ,Ca^2 ,Sr^2 ,Ba^2 溶液注入到已充分反应的高锰酸钾与鲁米诺混合液中时,又发生了新的化学发光反应,并检测到强的化学发光信号．在对有关反应的动力学性质、化学发光光谱、紫外可见光谱及其它一系列实验研究的基础上,提出了可能的化学发光反应机理．同时,优化了反应条件,评价了这一反应用于Mg^2 ,Ca^2 ,Sr^2 ,Ba^2 分析的可行性．     

Mechanism of formation of YBa2Cu4O8 superconductor in the sol-gel synthesis

It was shown that a single phase YBa₂Cu₄O₈ (124-phase) could be formed from gels at 1 atm oxygen pressure, and the mechanism of its formation was elucidated. It was found that there are two key routes for the sol-gel formation of the 124-phase, one involving the tetragonal YBa₂Cu₃O _y with a low concentration of oxygen defects (tetra-I phase) and the other involving the Ba₂Cu₃O_5.9 as important intermediates of the 124-phase. The rapid formation of these intermediate compounds from the gel was attributed to the small particle size of the oxides and carbonates precipitating at the initial stage of heating. It was thought that the small particles characteristic of sol-gel processing lead to the rapid formation of the intermediate compounds and subsequent precipitation of the 124-phase.     

一种新型对苯乙炔基苯衍生物：荧光行为与传感应用

设计合成了一种以8-羟基喹啉(8-HQ)为捕获基团,胆固醇(Chol)为辅助结构的新型光化学稳定的对苯乙炔基苯(BPEB)衍生物(OPBMQ)。研究表明,该化合物荧光光谱由8-HQ的荧光发射和BPEB的荧光发射组成,且其荧光发射对沙林毒气模拟物(DCP)的存在极为敏感。计算检出限可达1 × 10⁻⁹ mol·L^-1以下。此外,其它相关神经毒剂模拟物、有机磷农药,甚至它们的混合物的存在均不显著干扰化合物对DCP的传感。更为重要的是,无论是以高纯水、自来水,还是海水作为介质,均对测定结果没有显著影响。需要指出的是,对沙林毒气模拟物的灵敏、高选择性测定也可以在滤纸片上以目视法进行。基于这些结果,发展了一种概念性沙林毒气模拟物检测仪器。