Methane Combustion Over Fe, Co and Ni Modified Manganese Oxide Catalysts

Fe-Mn, Co-Mn and Ni-Mn composite oxide catalysts based on high specific surface area MnO₂ precursor were prepared and applied to catalytic combustion of CH₄. Results were compared with that of unmodified MnOx and 1wt.% Pd/-Al₂O₃. Below 450°C, manganese oxide catalysts show higher activity than Pd/-Al₂O₃, while the modified manganese oxide catalysts exhibit higher activity than the unmodified one below 420°C. All catalysts were characterized by means of N₂-BET, XRD, TG-DTA and H₂-TPR. Due to the interaction between Fe, Co or Ni oxides and manganese oxide, the activity of the oxygen species of the modified catalysts is improved, which leads to the increase of their CH₄ combustion activity.     

低钴AB5型稀土系贮氢电极合金的研究

为了进一步降低AB5型混合稀土系贮氢合金的成本,采用Cr,Si,Cu替代Co和调节化学计量比的方法制备低钴AB5型贮氢合金。结果表明:3种取代元素在寿命方面的效果依次为Si>Cr>Cu,在放电容量和活化性能方面依次是Cu>Cr>Si。Cr,Cu,Si只有少量的替代才可能发挥其有利影响;通过非化学计量比的调节,低钴混合稀土系贮氢电极合金的放电容量、活化性能及倍率放电能力都能较好地达到实用要求,但是循环寿命有待提高。     

Impedance study of Ni–Co electro-deposition on Fe powder particles in fluidised bed systems

The electrochemical impedance method was applied during the electrochemical deposition of a binary Ni–Co coating on iron powder in a fluidised bed electrode system. The influence of the suspension density on the charge transfer in the course of the electro-deposition process was studied. At a potential of −900 mV (vs. Ag/AgCl/3 M KCl), when the binary Ni–Co layer was formed, the impedance data were characterised by two semicircles with the semicircle at high frequencies being larger in magnitude. A contribution of the diffusion process to the overall current was observed. The optimal suspension density for the charge transfer in the bed was 10×10⁻³–15×10⁻³ (i.e., 4–6 g of iron powder in 50 ml of electrolyte). The most probable mechanism of the charge transfer for the studied concentrations of powder particles is the convective mechanism. The iron particles dispersed in the electrolyte were considered to act as either a depolariser or an additional working electrode depending on the applied electrode potential and on the suspension density.     

Hydrothermal Synthesis,Crystal Structure and Thermal Analyses of Pyrazine-2,3-dicarboxylic Acid Bridged Co(II) Coordination Polymer of _∞~2[Co(phen)(μ-L)_(3/3)]·H_2O (H_2L = Pyrazine-2,3-dicarboxylic Acid)

1 INTRODUCTION Molecular assembly and supramolecular che-mistry are young and rapidly growing subjects andhave attracted great attention. Microporous materialsbuilt up by organic ligands and metal ions have po-tential applications in catalysis, chemical absorption,magnetism and electronic conductivity[1～3]. Multi-dentate organic ligands are good building blocks,such as 1,2,4,5-benzene tetracarboxylic acid (BT-CA), 1,3,5-benzene tricarboxylic acid, terephthalicacid, 1,10-phenanthrol…     

The Reactivity of Cr‐Te Superlattice Reactants and of Co‐deposited Cr‐Te Films: Studies with in‐situ X‐ray Diffractometry

The reactivity of a Cr‐Te multilayer film consisting of 326 Cr/Te double‐layers with about 88(3) at% Te was investigated with in‐situ X‐ray diffraction. The occurrence of a superstructure reflection caused by the multilayer system is observed. During the annealing procedure between 80 and 90 °C the layer‐by‐layer arrangement is destroyed and elemental Te crystallizes. After 6 h isothermal annealing at 140 °C CrTe₃ starts to crystallize. The amount and the crystal size of CrTe₃ increase with raising temperature and Te is consumed during the growth process. At 220 °C the formation of crystalline Cr₂Te₃ is observed and between 220 and 260 °C CrTe₃ is completely decomposed into Cr₂Te₃. The two Cr tellurides grow as highly textured materials. The size of CrTe₃ crystals is significantly larger than that of Cr₂Te₃. For a co‐deposited Cr‐Te film with composition 77(3) at% Te the tri‐telluride and elemental Te crystallize simultaneously. The texture of CrTe₃ is less pronounced and different reflections of the tri‐telluride occur besides the (h00)‐reflections. Up to 160 °C a pronounced increase of the crystallite size is observed and the crystals are significantly larger than those obtained with the multifilm sample. At 130 °C the crystallization kinetics seem to be controlled by nucleation.     

四溴代邻苯二甲酸根桥联的双核钴（Ⅱ）配合物的合成和表征

合成和表征了４种以四溴代邻苯二甲酸根阴离子（４Ｂｒ－ＰＨＴＨ）桥联、以１，１０－菲咯啉（ｐｈｅｎ），５－硝基－１，１０－菲咯啉（ＮＯ_２－ｐｈｅｎ），２，２′－联吡啶（ｂｐｙ）和４，４′－二甲基－２，２′－联吡啶（Ｍｅ_２ｂｐｙ）端接的双核钴（Ⅱ）配合物［Ｃｏ_２（４Ｂｒ－ＰＨＴＨ）（Ｌ）_４］（ＣｌＯ_４）（Ｌ＝ｐｈｅｎ（ｌ），ＮＯ_２－ｐｈｅｎ（２），ｂｐｙ（３），Ｍｅ_２ｂｐｙ（４））。基于ＩＲ光谱、元素分析、电导测量等方法推定配合物具有四溴代邻苯二甲酸根桥联结构和Ｃｏ（Ⅱ）离子具有畸变的八面体配位环境。进行了配合物变温磁化率（７５～３００Ｋ）的测定，其数据已用从自旋哈密顿符导出的磁方程拟合，求得交换参数Ｊ＝－０．８７ｃｍ~（－１）（１），－０．８４ｃｍ~（－１）（２），－０．８２ｃｍ~（－１）（３），－０．８５ｃｍ~（－１）（４），表明金属离子间有弱的反铁磁性自旋交换相互作用。     

Fe和Co催化的碳-碳偶联反应的最新进展

作为廉价而且低毒的金属, Fe和Co是发展催化剂的理想元素. 同时由于Fe和Co有着多种氧化还原价态, 它们的催化化学应该具有极其丰富的内容. 然而由于种种原因, Fe和Co的催化剂很少得到有机化学家的关注. 直到最近几年, 人们才发现Fe和Co的催化剂可以很好地催化碳-碳偶联反应. 综述了Fe和Co催化碳-碳偶联反应的条件、产率和选择性; 探讨了这些新奇反应的可能机理; 并介绍了这些反应在复杂化合物合成中的应用.     

室温以上磁制冷材料La(Fe1-xCox)11.7Al1.3化合物的研究

通过X射线衍射分析和超导量子干涉磁强计（SQUID）磁性测量,研究了Co替代Fe含量对居里温度在室温以上的磁制冷材料La（Fe1-xCox）11.7Al1.3（x=0.072,0.081）磁结构和磁性能的影响。La（Fe1-xCox）11.7Al1.3材料的居里温度随Co的含量增加而增加,La（Fe0.919Co0.081）11.7Al1.3的居里温度为311 K。当外场变化为1.9 T时磁熵变达到3.6 J·kg^-1·K^-1,RCP值为168.6 J·kg^-1,虽然它的磁熵变小于具有巨磁熵变的磁制冷材料,但是它在磁场为1.9 T时的制冷能力与这些材料相当。     

Poly(ethylene glycol) as Impregnator for Silica Gel in Salting-Out Thin-Layer Chromatography of Some Co(III) Complexes

Silica gel impregnated with poly(ethylene glycol) of different molecular mass (400, 1000, 1540, 4000, and 5500) was investigated for salting-out thin-layer chromatography of 15 mixed aminocarboxylato Co(III) complexes using eight ammonium sulphate solutions as mobile phases. Regularities established earlier for non-impregnated adsorbents are also valid in this work. Poly(ethylene glycol) of high molecular mass increases the hydrophobicity of the adsorbent. Positive linear dependence of R_M values and of salting-out efficiency on average poly(ethylene glycol) molecular mass was usually observed. In contrast with non-impregnated silica gel, separation was achieved between complexes with the smallest hydrocarbon groups.     

Determination of nickel in standard rocks and glasses by photon activation analysis with 30-MeV bremsstrahlung

The determination of nickel in various silicate rocks and glasses by photon activation analysis with a linear electron accelerator is described. Simultaneous irradiation of the sample and comparative standards produces the ⁵⁸Ni(γ, n)⁵⁷Ni reaction, and a post-irradiation chemical separation is used in conjunction with Ge(Li) γ-spectrometry. Nickel abundances for ten standard silicate rocks and two elementally doped glasses are presented and compared with the data previously published. The method is quite simple and gives good reproducible results for nickel down to sub-p.p.m. levels.