Characterization of high-temperature superconductors by electron microprobe analysis

In order to optimize the physical properties of HTSC small single crystals grown from a melt for basic studies of their physical properties the influence of the environment on their impurity content was investigated by EPMA. This requires quantitative analysis of all elements being present in the crystals. The accuracy of results was affected by problems with the choice and quality of standards, by contamination but also by malfunction of microprobe electronics. The HTSC materials were found to react with mills, milling balls, crucibles and the atmosphere. These problems are being discussed and some reactions being studied for Y₁Ba₂Cu₃O_6+x (0 < x < 1) HTSC in A1₂O₃ and ZrO₂ crucibles. The crystals grown contain reproducible amounts of impurities depending on boundary conditions and exhibit a zone structure in composition particularly for Y and Ba within their range of homogeneity.     

On the calculation of expectation values and transition matrix elements by coupled cluster method

Summary Finite order expressions are derived for expectation values and transition matrix elements within the framework of the coupled cluster method.     

Imidazole Coordinated Sandwich-type Antimony Polyoxotungstates Na9[ {Na（H=O2}3{M（C3H4N2）}3（ Sb W9O33）2]·xH=O（M=Ni^Ⅱ, Co^Ⅱ, Zn^Ⅱ, Mn^Ⅱ）

The imidazole covalently coordinated sandwich-type heteropolymngstates Na9[ {Na（H=O2}3{M（C3H4N2）}3（ Sb W9O33）2]·xH=O（M=Ni^Ⅱ, Co^Ⅱ, Zn^Ⅱ, Mn^Ⅱ） were obtained by the reaction of Na2WO4·2H2O, SbCl3·6H2O, NiCl2·6H2O [MnSO4·H2O, Co（NO3）2·6H2O, ZnSO4·7H2O] and imidazole at pH≈7.5. The structure of Na9[{Na（H2O）2}3{Ni（C3H4N2）}3（SbW9O33）2]·32H2O was determined by single crystal X-ray diffraction. Polyanion [{Na（H2O）2}3{Ni（C3H4N2）}3（SbW9O33）2}3]^9- has approximate C3v symmetry, imidazole coordinated six-nuclear duster [{Na（H2O）2}3{Ni（C3H4N2）}3]^9＋ is encapsulated between two （α-SbW9O33）^9-, the three rings of imidazole in the polyanion are perpendicular to the horizontal plane formed by six metals （Na-Ni-Na-Ni-Na-Ni） in the central belt, and x-stacking interactions exist between imidazoles of neighboring polyanions with dihedral angel of 60%. The compounds were also characterized by IR, UV-Vis spectra, TG and DSC, and the thermal decomposition mechanism of the four compounds was suggested by TG curves.     

Silica-Based and Transition Metal-Based Inorganic-Organic Hybrid Materials—A Comparison

Organically substituted metal alkoxides can be prepared by reaction of the parent alkoxides with complexing organic compounds. The chemical and structural consequences of such substitutions are discussed in this article. Examples are given showing how functional organic moieties, such as polymerizable groups, can be incorporated into sol-gel materials via the complexing ligands. Major structural differences between silica-based and metal-based hybrid materials originate from the different charge/coordination number ratios of silicon and most metals. This results in a high tendency for the molecular building blocks to aggregate. In many cases, metal oxide clusters are formed which are capped by the organic ligands. Such surface-modified clusters are themselves very valuable condensed matter units for materials syntheses.     

催化燃烧去除VOCs污染物的最新进展

催化燃烧是目前最有效的处理挥发性有机物(VOCs)技术之一. 本文从催化剂活性组分、催化剂载体、有效组分颗粒大小、水蒸汽的影响及催化燃烧反应中的积碳等几个方面, 对近年来催化燃烧处理VOCs的研究进行了总结. 分析表明: 贵金属催化剂的研究主要着重于选择有效的载体和双组分贵金属催化剂; 非贵金属催化剂的研究主要集中在高活性的过渡金属复合氧化物、钙钛矿和尖晶石型等催化剂的研制, 还有这些活性组分粒径大小及载体对催化燃烧VOCs反应活性的影响;此外, 在实际应用中,水蒸汽和催化剂积碳失活等问题对催化燃烧VOCs的反应也有很大影响. 本文的评述将为选择合适的催化燃烧技术处理VOCs污染物提供一定参考.     

The “Facilitated Transition” hypothesis as an explanation for the gemdialkyl effect

A new technique of searching the conformational space of transition states was used to explore the cause of the rate acceleration in the gem-dialkyl effect in intramolecular cyclization reactions. Several previous hypotheses were discarded and a new hypothesis was advanced based on this new data. This hypothesis, the “Facilitated Transition” hypothesis, states that increased steric hindrance reduces the overall activation energy by facilitating rotation through the transition state. The older “Reactive Rotamer” hypothesis was eliminated by generating all conformations of the starting materials using the and computer programs and demonstrating that no relationship is found between rate increase and a change in the concentration of “reactive rotamers”.     

笼形聚偕胺肟树脂的研究HX／ACAO树脂吸附贵金属

氢卤酸、硝酸、硫酸、磷酸和硼酸处理的笼形聚偕胺肟树脂（ＨＸ／Ａ－ＣＡＯ）对Ａｇ＋和等贵金属离子的吸附能力按如下顺序：ＰｄＣｌ４２－：Ｈ３ＢＯ３／ＡＣＡＯ＞ＢＣＡＯ＞Ｈ３ＰＯ４／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ＞ＨＣｌ／ＡＣＡＯ＞ＨＮＯ３／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ．ＩｒＣｌ６２－：ＢＣＡＯ＞Ｈ３ＰＯ４／ＡＣＡＯ＞Ｈ３ＢＯ３／ＡＣＡＯ＞ＨＣｌ／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ≥ＨＮＯ３／ＡＣＡＯ．ＰｔＣｌ６２：ＢＣＡＯ＞Ｈ３ＢＯ３／ＡＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ＞ＨＮＯ３／ＡＣＡＯ＞ＨＣｌ／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ＞Ｈ３ＰＯ４／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ．Ａｇ＋：ＢＣＡＯ＞Ｈ３ＢＯ３／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ＞ＨＣｌ／ＡＣＡＯ＞Ｈ３ＰＯ４／ＡＣＡＯ＞ＨＮＯ３／ＡＣＡＯ．ＡｕＣｌ４－：ＢＣＡＯ＞Ｈ３ＢＯ３＞Ｈ３ＰＯ４／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ＞ＨＣｌ／Ａ－ＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ＞ＨＮＯ３／Ａ－ＣＡＯ．研究了Ｈ３ＢＯ３／ＡＣＡＯ树脂对Ａｇ＋和离子的吸附动力学，讨论了吸附机理．     

强冲击加载条件下的钨合金的界面研究

借助定量金相、扫描电子显微镜、透射电子显微镜等微观分析手段对钨质量分数为９３％的钨合金在１５～５０ＧＰａ冲击压力下微观结构响应性态进行了考察，发现了一些钨合金所特有的现象，即钨颗粒与粘结相交界处出现成分迁移，新相析出；并结合断口分析，探讨了钨合金在冲击作用下发生断裂的微观特征与韧脆转化间的关系及其物理本质。     

OClO与OH反应机理的理论研究

用密度泛函B3LYP/-311+G~(* *)和级电子相关倒映 合簇CCSD(T)/6-311+G~(* *)方法研究了OClO与OH反应的微观机理，研究结果表明：该反应经过缔合、H转移 和离解等复杂过程，最终得到四种产物，分别为HOCl+O_2，HCl+O_3,ClO+HO_2和 HOClO_2,从能量上看，形成HOCl+O_2和HCl+O_3的通道更容易进行，而形成 ClO+HO_2的通首在动力学上是最不利的。     

Reduced parabolic model for radical addition reactions

The transition state of addition of free radicals and atoms to multiple bonds is considered as a result of intersecting of two parabolic potential curves. One of them characterizes the stretching vibration of the attacked multiple bond, and another curve characterizes the stretching vibration of the bond formed in the transition state. The force constant of the latter is calculated by an empirical equation that correlates the force constant with the bond dissociation energy. In the framework of this model, the thermally neutral activation energy (E _e0) and the elongation of the attacked and formed bonds (r _e) in the transition state were calculated from the experimental data (activation energy (E _e) and enthalpy of reaction (H _e)) for the addition of an H atom and methyl, alkoxyl, aminyl, triethylsilyl, and peroxyl radicals to the C=C bond and the addition of H and CH₃ to the C=O and CC bonds. Analysis of the data obtained showed that E _e0 depends linearly on the |H _e| + E_e sum, i.e., E_e0/kJ mol^–1 = 14.2 + 0.61 · (E_e – H _e), and the bond elongation in the transition state for addition of the most part of radicals to ethylene and acetylene vary within (0.65–0.87)·10_–10 m. The factors affecting the activation energy of the radical addition reactions are discussed.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1542–August, 2004.