熔融碱法制备三重价态钙钛矿锰氧化物

以MnO₂, Ca(OH)₂和La(OH)₃为反应原料, 在惰性气氛、 低温(500 ℃)熔融KOH体系中合成了具有菱形钙钛矿结构Ca, K共掺杂的La_0.64Ca_0.25K_0.11MnO₃纳米材料, 并对Mn的价态及磁学性能等进行了讨论. X射线光电子能谱(XPS)分析结果表明, La_0.64Ca_0.25K_0.11MnO₃纳米材料中的Mn具有三重混合价态, 其零场冷却低温磁化率曲线表现出顺磁-铁磁转变, 居里温度(T_c)为280 K.     

A New Stable Bubble Element for Incompressible Fluid Flow Based on a Mixed Petrov–Galerkin Finite Element Formulation

A new mixed Petrov–Galerkin formulation employing the MINI element with a non-confirming bubble function for an incompressible media governed by the Stokes equations, which is equivalent to the stabilized finite element by P ¹-P ¹ approximation, is proposed. The new formulation possesses better stability properties than the conventional Bubnov–Galerkin formulation employing the MINI element. In this aspect, the stabilizing effect of this formulation is evaluated by a stabilizing parameter determined by both shapes of the trial and the weighting bubble functions.     

Failure-tolerant control for small agile satellites using single-gimbal control moment gyros and magnetic torquers

This paper focuses on the attitude control problem of small agile satellites using single-gimbal control moment gyros(CMG) and magnetic torquers(MTQ).CMGs are regarded as effective torque generators for agile satellites because of their torque amplification capability.However,they are vulnerable to failure due to their complex inner mechanism.In this paper,different failure cases of CMGs are analyzed.A flexible failure-tolerant control strategy is developed by automatically redistributing the required control torque among the operating CMGs and MTQs,with a variable limiter to accommodate the actuator dynamics changes introduced by CMG failures.The performances of maneuvers about different directions under different failure cases are also discussed and examined.Numerical simulations demonstrate that the proposed strategy maintains certain agility in the cases of one or two CMGs failing.Moreover,a survival strategy with only one CMG left is also verified.Both sun-pointing stabilization and earth-pointing stabilization can be achieved in this case,which fulfill some basic mission requirements.     

Effect of mixed cations in synergizing the performance characteristics of PVA-based polymer electrolytes for novel category Zn/AgO polymer batteries—a preliminary study

Thin films of polymer electrolytes comprising of PVA and KOH (A) with and without the addition of zinc salts, viz., zinc acetate (B) and zinc triflate (C) as mixed cations were prepared via. solution casting method. The thermal stability and ionic conductivity of PVA–KOH solid polymer electrolyte (A) were improved by the partial substitution of KOH with zinc salts. Among the two salts, zinc triflate was found to improve both the physical as well as electrochemical properties of the PVA–KOH films more significantly than zinc acetate. An attempt to optimize the ratio of various components of polymer electrolytes, viz., polymer: KOH: zinc salt was also made, based on the dimensional stability and ionic conductivity values. Finally, the select category polymer film containing PVA–KOH–zinc triflate (C) in an optimum ratio of 40:35:25 was deployed in coin cell fabrication and subjected to charge–discharge studies with a view to demonstrate the possible electrochemical reversibility characteristics. Based on the encouraging results obtained from the cycling study, C type films [PVA–KOH–zinc triflate] qualify themselves as potential polymer electrolytes for use in rechargeable Zn/AgO polymer batteries.     

Hydrothermal Synthesis and Characterization of a Novel Two-dimensional Framework Materials Constructed from Polyoxometalate and Coordination Groups:[H2Mo5.5V10.5O40(PO4)][Cu(en)2]4·7H2O

A novel compound [H2Mo5.5V10.5O40(PO4)][Cu(en)2]4*7H2O(1) was synthesized from V2O5, MoO3, CuCl2*2H2O, en, H3PO4 and H2O in an aqueous solution via the hydrothermal method and characterized by means of single-crystal X-ray diffraction, elemental analyses, IR, EPR spectra and thermal analyses. C16H80Cu4Mo5.5N16O51PV10.5 crystallized in a triclinic system, the space group is P1 with M=2660.63, a=1.283590(10) nm, b=1.289910(10) nm, c=1.387870(10) nm, V=1.80942(2) nm3, Z=2, Dx=4.883 g/cm3, F(000)=2599, μ=6.956 mm-1, (Δ/σ)=0.000, S=1.089. The crystal structure was solved by the direct methods with the final R=0.0752 and wR=0.1988 for 6311 observed reflections with I≥2σ(I). The X-ray crystallography reveals that compound 1 is a novel two-dimensional framework material constructed from the mixed Mo/V polyoxometalate and coordination groups.     

KIO3-KI-KBrO3-KBr混合体系中各组分含量的测定

利用沉淀分离、氧化-还原、萃取和分光光度法测定KIO3-KI-KBrO3-KBr混合体系中各组分含量.实验设计方案对实验综合设计以及复杂体系中各组分测定具有参考价值.     

Characterisation of mixed lithium dodecyl sulphate/lithium perfluorooctanesulphonate pseudo‐stationary phases in MEKC

Lipophilicity and methylene selectivity of mixed pseudo‐stationary phases (PSPs) (containing lithium dodecyl sulphate (LDS) and lithium perfluorooctanesulphonate (LiPFOS) in different molar ratios) applied in MEKC have been investigated. Micellar proportion (t_prop,mic, a quantity expressing that how much time is spent by the analyte in the micellar phase related to its whole migration time), CLOGP₅₀ value (showing the value of hydrophobicity of a molecule spending exactly 50% of its migration time in the PSP) and methylene selectivity have been determined for different LDS/LiPFOS mixed phases. Values of the above‐mentioned parameters have been determined for analytes with different chemical structures (alkylbenzene and alkylphenone homologous series, alcohols). Good linear correlation was obtained between either the micellar proportion, CLOGP₅₀, or methylene selectivity and the phase composition for the mixed phases. Lipophilicity and methylene selectivity of the mixed LDS/LiPFOS PSPs can be calculated and can continuously be changed by mixing the two single phases (LDS and LiPFOS) in the appropriate (and calculable) portion.     

两个金属铜配位聚合物Cu3(2,2′-bipy)2(C8H4O4)2(C8H5O4)2和Cu(Ⅰ)Cu(Ⅱ)(4,4′-bipy)1.5(C8H4O4)(C8H5O4)混合溶剂热合成及结构与性能研究

在中温混合溶剂热条件下合成了两个金属铜配位聚合物Cu3(2,2′-bipy)2(C8H4O4)2(C8H5O4)2和Cu(Ⅰ)Cu(Ⅱ)(4,4′-bipy)1.5(C8H4O4)(C8H5O4)(bipy=联吡啶,C8H4O4=1,3-间苯二甲酸),并对其进行了单晶结构解析及相关性能表征.配合物Cu3(2,2′-bipy)2(C8H4O4)2(C8H5O4)2(1)晶体属三斜晶系,P1空间群,a=1.03314(4)nm,b=1.08350(3)nm,c=1.15826(4)nm,α=83.104(2)°,β=84.609(2)°,γ=66.125(2)°,Z=1.配合物Cu(Ⅰ)Cu(Ⅱ)(4,4′-bipy)1.5(C8H4O4)(C8H5O4)(2)晶体属三斜晶系,P1空间群,a=1.06979(3)nm,b=1.09209(3)nm,c=1.47887(3)nm,α=91.795(2)°,β=93.2460(10)°,γ=118.6170(10)°,Z=2.通过使用不同的有机碱配体(2,2′-联吡啶和4,4′-联吡啶),并调节不同有机碱配体的用量,得到了结构不同的两个目标晶体产物相.产物均可稳定到3...     

Structural features, nonstoichiometry and high-temperature transport in SrFe1−xMoxO3−δ

The oxide solid solutions SrFe_1−xMo_xO_3−δ, where x=0.05, 0.1 and 0.2, are studied in this work. It is shown that substitution of iron for molybdenum results in stabilization of a cubic quasi-perovskite locally inhomogeneous structure, which is evidenced by HREM and Mössbauer spectroscopy. The coulometric titration is used in order to determine changes of oxygen nonstoichiometry in the obtained solutions with temperature and ambient oxygen partial pressure. Partial molar thermodynamic functions of the labile oxygen are calculated from the measured data. The variations of partial molar entropy with oxygen content follow the ideal gas model reasonably well thus demonstrating approximately random distribution of oxygen vacancies in the doped ferrite at high temperatures. The partial molar enthalpy is found to increase with doping, which is indicative of a progressive decrease in average values of the bonding energy of labile oxygen ions. The measurements of total conductivity are used in order to determine partial contributions of charge carriers. The oxygen ion component is shown to increase at small level of doping, x=0.05 while further increase in molybdenum content is accompanied with the decline in the ion conductivity. The electron contribution in reducing conditions tends to increase with molybdenum content, which is interpreted as a manifestation of involvement of Mo⁵⁺ cations in electron transport. Concentration and mobility of electron carriers are calculated. Some increase in mobility of electron holes at small doping is explained as related to the filling of oxygen vacancies.     

Crystal and solution structures of di-n-butyltin(IV) complexes of 5-[(E)-2-(4-methoxyphenyl)-1-diazenyl]quinolin-8-ol and benzoic acid derivatives: En route to elegant self-assembly via modulation of the tin coordination geometry

Reactions of ⁿBu₂SnCl(L¹) (1), where L¹ = acid residue of 5-[(E)-2-(4-methoxyphenyl)-1-diazenyl]quinolin-8-ol, with various substituted benzoic acids in refluxing toluene, in the presence of triethylamine, yielded dimeric mixed ligand di-n-butyltin(IV) complexes of composition [ⁿBu₂Sn(L¹)(L^2-6)]₂ where L² = benzene carboxylate (2), L³ = 2-[(E)-2-(2-hydroxy-5-methylphenyl)-1-diazenyl]benzoate (3), L⁴ = 5-[(E)-2-(4-methylphenyl)-1-diazenyl]-2-hydroxybenzoate (4), L⁵ = 2-{(E)-4-hydroxy-3-[(E)-4-chlorophenyliminomethyl]-phenyldiazenyl}benzoate (5) and L⁶ = 2-[(E)-(3-formyl-4-hydroxyphenyl)-diazenyl]benzoate (6). All complexes (1-6) have been characterized by elemental analyses, IR, ¹H, ¹³C and ¹¹⁷Sn NMR and ¹¹⁹Sn Mössbauer spectroscopy and their structures were determined by X-ray crystallography, complemented by ¹¹⁷Sn CP-MAS NMR spectroscopy studies in the solid state. The crystal structure of 1 reveals a distorted trigonal bipyramidal coordination geometry around the Sn-atom where the Cl- and N-atoms of ligand L¹ occupy the axial positions. In complexes 2-5, the molecules are centrosymmetric dimers in which the Sn-atoms are connected by asymmetric μ-O bridges through the quinoline O-atom to give an Sn₂O₂ core. The differences in the Sn-O bond lengths within the bridge range from 0.28 to 0.48 Å, with the longer of the Sn-O distances being in the range 2.56-2.68 Å and the most symmetrical bridge being in 5. The carboxylate group is almost symmetrically bidentate coordinated to the tin atom in 5 (Sn-O distances of 2.327(2) and 2.441(2) Å), unlike the other complexes in which the distance of the carboxylate carbonyl O-atom from the tin atom is in the range 2.92-3.03 Å. The structure of 5 displays a more regular pentagonal bipyramidal coordination geometry about each tin atom than in 2-4. In contrast, the centrosymmetric dimeric structure of 6 involves asymmetric carboxylate bridges, resulting in a different Sn₂C₂O₄ motif. The Sn-O bond lengths in the bridge differ by about 0.6 Å, with the longer distance involving the carboxylate carbonyl O-atom (2.683(2) and 2.798(2) Å for two molecules in the asymmetric unit). The carboxylate carbonyl O-atom has a second, even longer intramolecular contact to the Sn-atom to which the carboxylate group is primarily coordinated, with these Sn?O distances being as high as 3.085(2) and 2.898(2) Å. If the secondary interactions are considered, all the di-n-butyltin(IV) complexes (2-6) display a distorted pentagonal bipyramidal arrangement about each tin atom in which the n-butyl groups occupy the axial positions.