Effect of the ZnNi y Mn2– y O4 (0 ≤ y ≤ 1) spinel composition on electrochemical lithium insertion

The electrochemical insertion of lithium in the spinel-type manganite with the formula ZnNi _y Mn_{2– y} O₄ has been studied. The galvanostatic discharge curves show that the best performance is obtained for y = 0.25, where a tetragonal to cubic structural transformation occurs. The thermodynamics and kinetics of the process of insertion of the lithium into the tetragonal spinel Li _x ZnNi_0.25Mn_1.75O₄ (x = 0.05–1.3) have been studied. The molar thermodynamic quantities, such as enthalpy, entropy and free energy determined by EMF-T measurements, varied with the lithium concentration in the oxide structure, and a major variation was observed around x = 0.8. The chemical diffusion coefficient of lithium in these spinels was also determined. Structural analysis, degree of oxidation and magnetic susceptibility measurements were carried out for the lithiated oxides in order to obtain the cationic distribution as a function of x. It has been possible to demonstrate that, upon lithium insertion, Mn⁴⁺ ions on B sites are reduced to Mn³⁺ and then to Mn²⁺. A cooperative Jahn-Teller effect is present in these spinel manganese-nickel oxides. Received: 4 February 1997 / Accepted: 11 April 1997     

Photophysical characterization of mixed micelles of n-butanol/SDS and n-hexanol/SDS. A study at low alcohol concentrations

 The effect of the addition of n-butanol (BuOH) and n-hexanol (HexOH) on the micellization of sodium dodecylsulfate (SDS) has been investigated using fluorescence quenching methods. The binding constants were calculated using an expression which relates the total concentration of alcohols and the micelle concentration. The values of K were 4.67 and 17.6 M^-1 for BuOH/SDS and HexOH/SDS, similar to values obtained by other methods. The cmc of SDS decreases on addition of alcohols and goes through a minimum for the BuOH/SDS system. Micellar aggregation numbers (N) were determined from linear plots of Ln (I ⁰/I) against [Quencher] at low alcohol concentrations. For 15 mM SDS, in the presence of BuOH the N values decrease on addition of alcohol up to 0.2 M. For HexOH, N can be assumed to be constant up to 4.8 mM, after which N decreases. The polarity of the micellar core containing alcohol was evaluated from the I ₁/I ₃ ratio of monomeric pyrene. The effect of addition of the alcohol causes a decrease in the I ₁/I ₃, which corresponds to a decrease in the polarity of the pyrene solubilization site. Received: 28 October 1996 Accepted: 10 January 1997     

双分布聚乙二醇接枝纳米二氧化硅的高效可控制备

在混合溶剂中通过"grafting to"的方法将2种分子量不同的聚乙二醇单甲醚(MPEG M_w=750,4000)接枝到氨基修饰的St?ber法二氧化硅(SiO_2-NH_2)表面,制备双分布纳米接枝复合物.采用二步法,先将带环氧端基的低分子量聚乙二醇单甲醚(MPEG-EO)与SiO_2-NH_2在甲苯溶剂中充分反应后,与高分子量的MPEG-EO在甲苯和正癸烷的混合溶剂中使用相同的反应条件和后处理方法,能便捷制备出具有双分布接枝的纳米复合物.在接枝反应体系中,分子链的链段尺寸和接枝密度之间存在着密切关系.一定的范围内,接枝密度随链段尺寸减小而增大.通过改变混合溶剂比例来调控接枝链段的尺寸,可以很好控制聚合物的接枝密度.在双分布接枝的纳米复合物中,低分子量的接枝密度为0.85 chains/nm~2,高分子量的接枝密度能达到0.40 chains/nm~2,体现出了简单、高效、可控的特点,与聚环氧乙烷(PEO)共混后分散良好,对于制备出均匀分散的纳米复合材料起到了一定的指导作用.     

钼钨铌磷杂多化合物的研究（Ⅰ）：杂多酸的合成和表征

提出了分步酸化一分步加料合成[PNb_2Mo_xW_(10-x)O_(40)]~(5-)(x=0,2,4,6)系列杂多酸的方法,给出了最佳配料比和生成反应的pH值,并进行了红外、紫外、极谱、电位滴定及热稳定性研究。     

Neue Alkalioxoarsenate(V): NaLi2[AsO4] — ein neuer Formeltyp [1]

New Alkali Oxoarsenates(V): NaLi₂[AsO₄] — A New Type of Formula [1] . By heating of well ground mixtures of the binary oxides As₂O₃, Na₂O, and Li₂O₂, molar ratio As:Na:Li = 1.0:1.0:2.0, in a well closed Ni tube (650°C, 21 d) colourless single crystals of NaLi₂[AsO₄] were obtained for the first time. The new orthoarsenate(V) crystallizes orthorhombic (space group P mn2₁-C, No. 31) with Z = 2. The structure determination showed that it is isostructural to β_II-Li₃[VO₄] and that means the Li₃[PO₄]-type. The lattice constants a = 702.9(2) pm, b = 520.5(1) pm, c = 505.4(2) pm were taken from Guinier-Simon powder data. The structure was determined by four-circle diffractometer data [Philips PW 1 100, AgKα , 679 independent out of 2 373 I_o(hkl), R = 3.03%, R_w = 2.29%; parameter see text]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these calculated via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

计算机差谱法测定混合稀土元素

报道了在自装光电二极管阵列电感耦合等离子体原子发射光谱仪上采用计算机差谱法进行混合稀土元素分析。该法能有效而简便地消除光谱干扰，结果准确可靠。     

丙酮肟与某些芳烃相互作用的~1H核磁共振研究

Hatton和Richards通过对酰胺分子的~1H NMR谱溶剂效应的研究,提出了DMF与苯生成分子络合物的模型.如果络合物按1:1生成,那么将出现一个“饱和点”,在这点上甲基的芳香溶剂诱导位移(ASIS)的变化趋势或程度将出现一个明显的变化,事实上随着苯的摩尔分数从0到1逐渐增加时,化学位移总是有规则的逐渐移向高场.这就显示了分子络合物观点的局限性.它能被一些研究者所支持和接受,是因为它能够解释两个甲基共振峰先重合而后又分离的现象.     

双（十二烷基亚磺酰）乙烷溶剂萃取钯及其机理的研究

本文研究用双（十二烷基亚磺酰）乙烷萃取钯的性能，在ＫＩ存在下从７ｍｏｌ／Ｌ盐酸介质中用含有ＢＤＳＥ的氯仿能定量萃取钯，有机的钯可被硫脲或氨溶液反萃继之用ＴＭＫ－ＴｒｉｔｏｎＸ－１００光度法测定，研究了萃取的最佳条件及干扰情况，斜率法测得萃合物组成为Ｐｄ：Ｉ：ＢＤＳＥ＝１：２：１，红外光谱证实萃合物中ＢＤＳＥ的二个亚砜以硫原子与钯配位，萃合物为异位体络合物，提出了选择性萃取分离钯的新方法。     

Untersuchung der Phasenbeziehungen in quaternären Systemen Bi2O3/Bi2Ch/Bi2Ch (Ch = S,Se, Te)

Investigations of the Phase Relations in the Quaternary Systems Bi₂O₃/Bi₂Ch /Bi₂Ch (Ch = S, Se, Te) The stability ranges in the pseudobinary systems Bi₂O₂S/Bi₂O₂Se, Bi₂O₂S/Bi₂O₂Te and Bi₂O₂Se/Bi₂O₂Te have been studied by solid state and chemical transport reactions. A complete mixed crystal Bi₂O₂(Te_xSe_1–x), 0 ≤ x ≤ 1 exists between the ternary compounds Bi₂O₂Te and Bi₂O₂Se. The thermal behaviour of the mixed crystal and the coexistence ranges have been determined by x‐ray and thermal analysis.     

Markov chain model of mixed surfactant systems

A new model of mixed surfactant systems have been developed in the work presented. It includes two parameters only connected directly with the Gibbs free energy of the surfactant aggregation. They can be determined using both the aggregation equilibrium constant values or the phase composition data. It has been shown also the relation between these new parameters and the same of the regular solution approximation and the alternative models. The possibility to describe the available experimental information about the micelle composition as a function of the singly dispersed surfactant mixture composition better than by the other models has been shown also.