Novel Mn1.5Co1.5O4 spinel cathodes for intermediate temperature solid oxide fuel cells

Mn(1.5)Co(1.5)O(4) spinel oxide as a cathode or one component of a composite cathode presents no visible reaction with an Y(2)O(3)-stabilized ZrO(2) electrolyte. The low electrode polarization resistances and good performance compared with traditional Sr-doped LaMnO(3)-YSZ composite cathodes imply promising application for the next generation of intermediate-temperature solid oxide fuel cells.     

Synthesis of GdBiTe1.5Se1.5 single crystals

GdBiTe_1.5Se_1.5has been synthesized in the Gd₂Te₃-Bi₂Se₃ system at a component ratio of 1: 1. The compound congruently melts at 800 K. GdBiTe_1.5Se_1.5 single crystals have been prepared by a gas-trans-port reaction. The compound crystallizes in a tetradymite-like rhombohedral structure. The unit cell parameters are a = 4.00 Å, c = 30.36 Å, space group $R\bar 3m$ ..     

Doping effects in single-layered La0.5Sr1.5MnO4 manganite

In this paper we report the results of the synthesis and structural, transport, and magnetic characterization of pure La(0.5)Sr(1.5)MnO(4) and B-site lightly doped samples, i.e. La(0.5)Sr(1.5)Mn(0.95)B(0.05)O(4), where B = Ru, Co, and Ni. The choice was made in order to probe the charge ordering/orbital ordering ground state of the monolayered La(0.5)Sr(1.5)MnO(4) manganite as a consequence of the cation doping. It is shown that even a light doping is successful in suppressing the charge and orbital order found in pure La(0.5)Sr(1.5)MnO(4). No long-range magnetic order has been detected in any of the doped samples but the setup of a spin-glass state with a common freezing temperature ( approximately 22 K). Structural parameters show an anisotropy in the lattice constant variation, with the tetragonal distortion increasing as the cell volume reduces, which may suggest a variation in the orbital character of the e(g) electrons along with the overall cation size.     

Crystal Structures and Electrochemical Properties of R1.5Ca1.5MgNi14(R=Nd,Gd and Er)Hydrogen Storage Alloys

Ca₃MgNi₁₄, Nd_1.5Ca_1.5MgNi₁₄, Gd_1.5Ca_1.5MgNi₁₄ and Er_1.5Ca_1.5MgNi₁₄ alloys were prepared by high frequency induction melting and sintering. Characterization and analysis were performed by X-ray diffraction/Rietveld full-spectrum fitting, gaseous P-C-T hydrogen storage test and electrochemical properties tests. It can be found that all alloys consist of Gd₂Co₇-type 3R phase and Ce₂Ni₇-type 2H phase. Although the hydrogen storage capacities of Nd_1.5Ca_1.5MgNi₁₄, Gd_1.5Ca_1.5MgNi₁₄ and Er_1.5Ca_1.5MgNi₁₄ decrease to some extent compared to that of Ca₃MgNi₁₄, their equilibrium pressures for absorption and desorption increase markedly. Moreover, R_1.5Ca_1.5MgNi₁₄ alloys have better cycling stabilities and high-rate discharge(HRD) properties as compared to Ca₃MgNi₁₄. The hydrogen diffusion in alloy electrodes is the main factor to influence the HRD performance.     

Structure and thermoelectric properties of the ordered skutterudite CoGe1.5Te1.5

The skutterudite-related material CoGe_1.5Te_1.5 has been synthesised and structurally characterised by powder neutron diffraction. Analysis of the high-resolution powder neutron diffraction data indicates that the structure of CoGe_1.5Te_1.5 retains the a⁺a⁺a⁺ tilt system of the ideal skutterudite structure, while the anions are ordered in layers perpendicular to the [111] direction of the skutterudite unit cell. This anion ordering results in a lowering of the symmetry from cubic to rhombohedral (space group , a=12.3270(5) and c=15.102(1) Å at 293 K). The electrical transport properties have been investigated using four-probe resistivity and Seebeck coefficient measurements. The temperature dependence of the electrical resistivity and the magnitude of the Seebeck coefficient indicate that CoGe_1.5Te_1.5 is an n-type semiconductor.     

Na(1.5)Ag(1.5)MO3F3 (M = Mo, W): an ordered oxyfluoride derivative of the LiNbO3 structure

Na(1.5)Ag(1.5)MoO(3)F(3) and Na(1.5)Ag(1.5)WO(3)F(3) have been synthesized by solid state reactions and structurally characterized using synchrotron X-ray and neutron powder diffraction. Unlike the vast majority of salts containing [MO(3)F(3)](3-) anions (M = Mo, W) the oxyfluoride groups in Na(1.5)Ag(1.5)MoO(3)F(3) and Na(1.5)Ag(1.5)WO(3)F(3) are orientationally ordered, so that the Na(+) ions are coordinated by fluorine and the Ag(+) ions by oxygen. The resulting structure type, which has not previously been reported, is related to the LiNbO(3) structure, but the combination of Na/Ag ordering and orientational ordering of the [MO(3)F(3)](3-) anions produces a supercell that doubles the c-axis and changes the space group symmetry from R3 to R3. The use of hard (Na(+)) and soft (Ag(+)) cations to direct the orientational ordering of polar oxyfluoride building units provides a new approach to the design of polar materials.     

PVP and G1.5 PAMAM dendrimer co-mediated synthesis of silver nanoparticles

PVP and G1.5 PAMAM dendrimer co-mediated silver nanoparticles of smaller than 5 nm in diameter were prepared using H₂ as reducing agent. With the TEM micrograph, it was found that the molar ratios of PVP and G1.5 PAMAM dendrimer have significant effect in the morphology and size distribution of silver nanoparticles. The reaction rate (fitting a first-order equation) was strongly influenced by the molar ratios of PVP and G1.5 PAMAM dendrimer and the reaction temperature. From the UV-Vis spectra of an aqueous solution of silver nanoparticles, they could be stored for at least 2 months without coagulation at room temperature.     

Preparation of ultrafine Cu1.5Mn1.5O4 spinel nanoparticles and its application in p-nitrophenol reduction

In this work, ultrafine Cu_1.5Mn_1.5O₄ spinel nanoparticles were successfully synthesized by a sol–gel method combined with two complexing agents, which was firstly employed in the reductive transformation from p-nitrophenol into p-aminophenol. The effect of calcination temperature on the crystal phase and microstructure of Cu_1.5Mn_1.5O₄ nanoparticles was investigated in this article. It was found that Cu_1.5Mn_1.5O₄ nanoparticles with pure spinel phase can be obtained at 500 °C with the help of EDTA acid–citric acid complexing agents. Below 500 °C, there exists some Mn₂O₃ impure phase. SEM characterization indicated that the particle size of the spinel Cu_1.5Mn_1.5O₄ rapidly increases above 600 °C. The catalytic experimental results show that the Cu_1.5Mn_1.5O₄ nanoparticles prepared at 500 °C exhibit the highest catalytic activity which is even superior to some precious metal catalysts. With the calcination temperature increasing, the catalytic activity of Cu_1.5Mn_1.5O₄ spinel nanoparticles gradually degrades which can be ascribed to the particle size growth of Cu_1.5Mn_1.5O₄. It can also be observed that all the oxide samples, namely CuO, Mn₂O₃ and Cu_1.5Mn_1.5O₄, possess certain catalytic ability for the transformation from p-nitrophenol into p-aminophenol. However, the catalytic activity of Cu_1.5Mn_1.5O₄ spinel nanoparticles is obviously higher than CuO and Mn₂O₃. Especially, Mn₂O₃ alone has very poor catalytic activity in the reduction of p-nitrophenol.

     

Progress of 1.5～1.6 μm Laser Crystals

Eye-safe 1.5～1.6 μm lasers have important applications in optical fiber communication, medicine, laser-range-finding, lidar, etc. Er^3＋ and Yb^3＋ co-doped crystal pumped by diode laser around 976 nm is an attractive method for obtaining 1.5～1.6 μm laser in compact device with high output beam quality. In this paper, the recent research and progress of several important Er^3＋ and Yb^3＋ co-doped laser crystals at 1.5～1.6 μm in authors’ lab are reported.     

水合肼对锂离子正极材料LiNi_(0.5)Mn_(1.5)O_4性能的影响

以NiSO4和MnSO4为原料,在用共沉淀法经二次干燥制备锂离子电池正极材料LiNi0.5Mn1.5O4的前驱体时,加入水合肼进行还原处理.实验结果发现:经还原处理的前驱体制备正极材料LiNi0.5Mn1.5O4的充放电比容量远远高于同样条件下不经水合肼还原处理的前驱体制备的正极材料的充放电比容量,而且处理前驱体制备的正极材料在高倍率放电条件下电化学行为更好.粉末X射线衍射(XRD)和扫描电镜(SEM)测试结果表明,用还原剂水合肼处理的前驱体合成的样品为单一的尖晶石结构,晶粒呈规则的八面体形貌,没有杂质相,而未处理前驱体合成的样品则含有少量的杂质相.这种杂质相是在前驱体的制备过程中由于Mn(OH)2被O2氧化而形成难溶Na0.55Mn2O4.1.5H2O化合物,最终转变为Na0.7MnO2.05.     

Amido-bridged Cu2N2 diamond cores that minimize structural reorganization and facilitate reversible redox behavior between a Cu1Cu1 and a class III delocalized Cu1.5Cu1.5 species

A novel Cu(2)N(2) diamond core structure supported by an [SNS](-) ligand (1) ([SNS](-) = bis(2-tert-butylsulfanylphenyl)amido) has been prepared. This dicopper system exhibits a fully reversible one-electron redox process between a reduced Cu(1)Cu(1) complex, [[SNS][Cu]](2) (2), and a class III delocalized Cu(1.5)Cu(1.5) state, [[[SNS][Cu]](2)][B(3,5-(CF(3))(2)C(6)H(3))(4)] (3). Structural snapshots of both redox forms have been obtained to reveal remarkably little overall structural reorganization. The Cu...Cu bond distance nonetheless undergoes an appreciable compression (approximately 0.13 A) upon oxidation, providing a Cu...Cu distance of 2.4724(4) A in the mixed-valence state that is virtually identical to the Cu...Cu distance observed in the reduced form of the Cu(A) site of thiolate-bridged cytochrome c oxidase. Despite the low structural reorganization evident between 2 and 3, the [SNS](-) ligand is quite flexible. For example, square-planar geometries can prevail for divalent copper ions supported by [SNS](-) as evident from the crystal structure of [SNS]CuCl (4). Physical characterization for the mixed valence complex 3 includes electrochemical, magnetic (SQUID), EPR, and optical data. The complex has also been examined by density functional methods. An attempt was made to measure the rate of electron self-exchange k(s) between the Cu(1)Cu(1) and the Cu(1.5)Cu(1.5) complexes 2 and 3 by NMR line-broadening analysis in dichloromethane solution. While the system is certainly in the fast-exchange regime, the exchange process is too fast to be accurately measured by this technique. The value for k(s) can be bracketed with a conservative lower boundary of > or =10(7) M(-1) s(-1), a value that appears to be larger than other low molecular weight copper model complexes for which similar data is available. The unusually large magnitude of k(s) likely reflects the minimal structural reorganization that accompanies Cu(1)Cu(1) <--> Cu(1.5)Cu(1.5) interchange.     

Solid solutions of perovskite in the LaO1.5-BaO-ScO1.5-ZrO2 system at 1600 °C

A partial pseudoternary phase diagram of the LaO_1.5-BaO-ScO_1.5 system was established at 1600 °C. According to the phase diagram, the solubility of barium into the cubic perovskite phase (LaScO₃) at 1600 °C is 0.24 in a mole fraction of barium oxide (X_BaO) on the composition line where the mole fraction of scandium oxide is 0.50. Another cubic perovskite phase (BaZrO₃) in the BaO-ZrO₂-ScO_1.5 system is also known. We investigated the phase relationships between the two cubic perovskites in the pseudoquaternary phase diagram of the LaO_1.5-BaO-ScO_1.5-ZrO₂ system. As a result, we found the existence of a wide solid solution region between the cubic perovskites at 1600 °C. The region was determined by X-ray diffraction (XRD) analysis and energy dispersive X-ray (EDX) microanalysis of samples with various compositions, and established the partial pseudoquaternary phase diagram.     

熔盐法合成LiNi0.5Mn1.5O4及电化学性能

以一定比例的LiCl-LiNO_3为低熔点共混物,采用熔盐法合成了电化学性能良好的LiNi_(0.5)Mn_(1.5)O_4,XRD表征结果显示产物为单一尖晶石相,SEM表征显示出材料良好的晶形,充放电测试结果显示出材料在4.7V平台附近有较大的可逆容量,在4.1V平台附近仅有较少的可逆容量。文章讨论了影响产物晶形和性能的各种因素,建议通过退火、改变合成气氛来消除4.1V平台的产生;研究结果还显示,容量的损失主要发生在第一次放电过程中在高电位区时的电解液的氧化分解.建议通过更换适合在高电位条件下工作的电解液来克服此问题;同时,通过调整低熔点共混物的配比、气氛、反应时间等条件可以实现对产物的结晶形态和大小进行适当的控制,显示了该方法在制备LiNi_(0.5)Mn_(1.5)O_4材料中的应用前景.     

Structural snapshots of a flexible Cu2P2 core that accommodates the oxidation states Cu(I)Cu(I), Cu1.5Cu1.5, and Cu(II)Cu(II)

The phosphido-bridged dicopper(I) complex {(PPP)Cu}2 has been synthesized and structurally characterized ([PPP]- = bis(2-di-iso-propylphosphinophenyl)phosphide). Cyclic voltammetry of {(PPP)Cu}2 in THF shows fully reversible oxidations at -1.02 V (Cu1.5Cu1.5/CuICuI) and -0.423 V (CuIICuII/Cu1.5Cu1.5). Chemical oxidation of {(PPP)Cu}2 by one electron yields the class III mixed-valence species [{(PPP)Cu}2]+ (EPR, UV-vis). Structural data establish an unexpectedly large change (0.538 A) in the Cu...Cu distance upon oxidation state. Oxidation of {(PPP)Cu}2 by two electrons yields the dication [{(PPP)Cu}2]2+, an antiferromagnetically coupled dicopper(II) complex. Maintenance of a pseudotetrahedral geometry that is midway between a square plane and an ideal tetrahedron at the copper centers, along with a high degree of flexibility at the phosphide hinges, allows for efficient access to CuICuI, Cu1.5Cu1.5, and CuIICuII redox states without the need for ligand exchange, substitution, or redistribution processes.     

Synthesis and characterization of the new pyrochlore Bi1.5Sb1.5−xNbxMnO7 solid solution

The solid solution with formula Bi_1.5Sb_1.5−xNb_xMnO₇ has been synthesized using the ceramic method at 1000 °C. This solid solution was crystallized in the pyrohlore structure in cubic lattice with Fd-3 m space group. The cell parameter increases linearly with increase in the niobium concentration. The magnetic susceptibility measurements achieved between 4 and 300 K show a paramagnetic behaviour with an effective moment 5.84 μ_β for Bi_1.5Sb_1.5MnO₇ compound (x = 0) and 5.61 μ_B for Bi_1.5Nb_1.5MnO₇ compound (x = 1.5) indicating “ + 2” oxidation state for manganese ion. The electric conductivity measured using the complex impedance spectroscopy method put in evidence an increase of the electric conductivity with the temperature, and the antimony compound is slightly more conductor than the niobium compound; results indicate electronic conductivity with semi-conducting behaviour.     

氢化燃烧法合成La1.5Ni0.5Mg17的工艺优化

采用正交实验设计方法安排实验，运用L9(3^4)优化氢化燃烧法合成La1.5Ni0.5Mg17的工艺，考察了施压制饼时间、合成保温时间、合成起始氢气压力、保温温度4个因素对储氢材料的储放氢容量和速率的影响，通过直观分析和方差分析得出优化的工艺为：保温温度903K，制饼施压时间40min，合成起始氢气压力为1MPa，合成保温时间1800min。此条件下合成储氢材料La1.5M0.5Mg17在573K的储放氢容量分别为：5．40和5．15％H(质量分数)；储放氢速率分别为：0．734和0.681％H／min。用XRD分析了材料吸氢和脱氢后的物相结构发现：用Ni适量取代La2Mg17中的La没有导致结构变化，存在的LaNi5，LaH3和La改善了材料的吸放氢速率。     

Structure and electrical transport properties of the ordered skutterudites MGe1.5S1.5 (M=Co, Rh, Ir)

High-resolution powder neutron diffraction data collected for the skutterudites MGe_1.5S_1.5 (M=Co, Rh, Ir) reveal that these materials adopt an ordered skutterudite structure (space group R3¯), in which the anions are ordered in layers perpendicular to the [111] direction. In this ordered structure, the anions form two-crystallographically distinct four-membered rings, with stoichiometry Ge₂S₂, in which the Ge and S atoms are trans to each other. The transport properties of these materials, which are p-type semiconductors, are discussed in the light of the structural results. The effect of iron substitution in CoGe_1.5S_1.5 has been investigated. While doping of CoGe_1.5S_1.5 has a marked effect on both the electrical resistivity and the Seebeck coefficient, these ternary skutterudites exhibit significantly higher electrical resistivities than their binary counterparts.     

Chromatographic behaviour and purification of N1.5-glycosyl enkephalins

Summary N ^1.5-Glycosyl enkephalins are potent analgesics. Two enkephalin-related glycosyl peptides: [DMet², Pro⁵] enkephalin (N ^1.5 -glucopyranosyl] amide and [DMet², Pro⁵] enkephalin [N ^1.5 -galactosyl] amide have been prepared following the liquid phase procedure. The chromatographic behavior of both the final glycosyl enkephalins and their synthetic intermediates on reversed-phase columns has been tested. Semipreparative, reversed-phase, HPLC conditions have been developed in order to obtain a simple and rapid procedure for the purification of the two synthetic pentapeptides. Thus, using isocratic elution, injections of 10mg of crude material after gel filtration gave homogeneous (99.9%) glycosyl enkephalins.     

Rapid phosphine exchange on 1.5-nm gold nanoparticles

Triphenylphosphine-cappped, 1.5-nm gold nanoparticles "Au(101)(PPh(3))(21)Cl(5)" prepared following Hutchison's procedure (Weare, W. W.; Reed, S. M.; Warner, M. G.; Hutchison, J. E. J. Am. Chem. Soc. 2000, 122, 12890) undergo rapid exchange of capping ligand phosphine with dissociated and added phosphine in dichloromethane solvent at 298 K. Remarkably, while the (1)H NMR spectrum resonances of the attached phosphine are broad, characteristic of a range of incompletely averaged environments, the (31)P NMR spectrum (observable only at 213 K and below) exhibits a single, narrow resonance indicating that all of the phosphorus atoms are magnetically equivalent.