Combustion synthesis of nickel ferrite powders: Effect of NaClO4 content on their characteristics and magnetic properties

Magnetic powders of nickel ferrite (NiFe₂O₄) were successfully synthesized by combustion synthesis in air using iron (Fe), iron oxide (Fe₂O₃), and nickel oxide (NiO) as reactants and sodium perchlorate (NaClO₄) as fuel (or oxidizing agent). The thermal behaviors were characterized using thermogravimetric analysis (TG) and differential thermal analysis (DSC). The as-combusted and final nickel ferrite powders were characterized in terms of chemical composition and morphology by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) coupled with energy dispersive X-Ray spectroscopy (EDX). In addition, magnetic properties were examined by vibrating sample magnetometer (VSM). The results of TG/DSC analysis indicated that increasing the content of NaClO₄ increased the exothermicity of combustion reaction. XRD indicated that the final nickel ferrite powders formed a single spinel NiFe₂O₄ phase when the amount of NaClO₄ used was 0.08 or 0.10 mol. SEM revealed roughly octahedron particles with sizes in a sub-micrometer range (∼500 nm). All final products exhibited soft magnetism and, synthesis that included 0.1 mol of NaClO₄ produced pure NiFe₂O₄ powders that had a saturation magnetization (M_s) of 58.93 emu/g, which is higher than the reported value (55 emu/g) for the bulk product.     

Synthesis and cationic ring‐opening polymerization of oxetane monomer containing five‐membered cyclic carbonate moiety via highly chemoselective addition of CO2

The bicyclic amidinium iodide effectively catalyzed the reaction of carbon dioxide and the epoxy‐containing oxetane under ordinary pressure and mild conditions with high chemoselectivity to give the corresponding oxetane monomer containing five‐membered cyclic carbonate quantitatively. The cationic ring‐opening polymerization of the obtained monomer by boron trifluoride diethyl ether proceeded to give linear polyoxetane bearing five‐membered cyclic carbonate pendant group in high yield. The molecular weight of the polyoxetane was higher than that of polyepoxide obtained by the cationic ring‐opening polymerization of epoxide monomer containing five‐membered cyclic carbonate. The cyclic carbonate functional crosslinked polyoxetanes were also synthesized by the cationic ring‐opening copolymerization of cyclic carbonate having oxetane and commercially available bisoxetane monomers. Analyses of the resulting polyoxetanes were performed by proton nuclear magnetic resonance, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2606–2615     

Convenient synthesis of cyclic carbonates from CO2 and epoxides by simple secondary and primary ammonium iodides as metal‐free catalysts under mild conditions and its application to synthesis of polymer bearing cyclic carbonate moiety

Hydroiodides of secondary and primary amines effectively catalyzed the reaction of carbon dioxide and epoxides under mild conditions such as ordinary pressure and ambient temperature, to obtain the corresponding five‐membered cyclic carbonates in moderate to high yields. Detailed investigation showed that the catalytic activity was highly affected by the counter anions of the ammonium salts; the iodides catalyzed efficiently the carbonate‐forming reactions, whereas the bromide and chloride counterparts exhibited almost no catalysis. We also revealed that two important factors on the amine moieties that affected the catalytic reactions. First, the catalytic activity increased with increasing bulkiness of the substituents on the ammonium nitrogen atoms. Second, the catalysis became more efficient as the parent amines become more basic. Dicyclohexylammonium iodide was the best catalyst among the ammonium salts investigated in this study. As an application of this reaction system, we synthesized homo‐ and copolymers bearing epoxide pendant groups as substrates, which were converted with high efficiency into the corresponding homo‐ and copolymers bearing cyclic carbonate pendant groups under 1 atm at 45 °C. All polymers were easily purified simply by precipitation in water, and were isolated in high yields (>95%). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Non‐isocyanate synthesis and application of telechelic polyurethanes via polycondensation of diurethanes obtained from ethylene carbonate and diamines

Aliphatic polyurethanes could be obtained in high yield via a non‐isocyanate method based on the self‐polycondensation of dihydroxyurethanes obtained by the reaction of diamines and ethylene carbonate. The polycondensation under a N₂ atmosphere yielded [6,2]polyurethane with a M_n value of 5300 in 87% yield. Two‐step polycondensation, consisting of the polycondensation under a N₂ atmosphere followed by that under reduced pressure, was effective to improve the yield and the molecular weight up to 90% and 10,000, respectively. Although the second polycondensation step at 180 °C was accompanied by formation of urea groups, this side reaction was relatively suppressed at 150 °C. The resulting polyurethane having hydroxyl groups at both of the end groups was converted to polyurethane methacrylate via a reaction with glycidyl methacrylate, and the polyurethane methacrylate served as a crosslinker for radical polymerization of methyl acrylate. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Hetero‐ and homo‐leptic Ru(II) catalyzed synthesis of cyclic carbonates from CO2; Synthesis,spectroscopic characterization and electrochemical properties

Based on the a ligand BDPPZ [(9a,13a‐dihydro‐4,5,9,14‐tetraaza‐benzo[b]triphenylene‐11‐yl)‐phenyl‐methanone] (1) and its polypyridyl hetero‐ and homoleptic Ru(II) metal complexes, [Ru(bpy)₂L](PF₆)₂ (2), [Ru(phen)₂L](PF₆)₂ (3), [Ru(dafo)₂L](PF₆)₂ (4), [Ru(dcbpy)₂L](PF₆)₂ (5) and [RuL₃](PF₆)₂ (6) (where, L = ligand, bpy = 2,2′‐bipyridine, phen = 1,10‐phenantroline, dafo = 4,5‐diazafluoren‐9‐one and dcbpy = 3,3′‐dicarboxy‐2,2′‐bipyridine), have been synthesized and characterized by elemental analysis, UV–vis, FT‐IR, ¹H and ¹³C‐NMR spectra (for ligand), molar conductivity measurements and X‐ray powder techniques. The electrochemical parameters of the substituted ligand and its polypyridyl hetero‐ and homoleptic Ru(II) metal complexes are reported by cyclic voltammetry. UV–vis spectroscopy is used to compare the differences between the conjugated π systems in this ligand and its Ru(II) metal complexes. The polypyridyl hetero‐ and homoleptic Ru(II) metal complexes also tested as catalysts for the formation of cyclic organic carbonates from carbon dioxide and liquid epoxides which served as both reactant and solvent. The results showed that the [Ru(L)₃](PF₆)₂ (6) complex is more efficient than the other Ru(II) complexes for the formation of cyclic organic carbonates from carbon dioxide. Copyright © 2010 John Wiley & Sons, Ltd.     

端视电感耦合等离子体发射光谱测定保温材料中钠和钾的研究

本文利用端视电感耦合等离子体发射光谱建立了一种钠和钾的分析测定方法,优化了分析测试条件,方法对钠和钾氧化物的检出限分别为0.005和0.002μg/mL,将该方法用于保温材料中和钠的分析测定,获得了令人较为满意的结果.     

甲醇气相氧化羰基化合成碳酸二甲酯的研究 Ⅱ助剂对催化性能的影响

考察了碱金属助剂对ＰｄＣｌ２－ＣｕＣｌ２ＡＣ催化剂上甲醇气相氧化羰基化直接合成碳酸二甲酯反应性能的影响及助剂的作用。结果表明：采用不同碱金属助剂时的碳酸二甲酯收率顺序为Ｋ＞Ｎａ＞Ｌｉ；ＫＯＡｃ助剂的主要作用是与ＰｄＣｌ２、ＣｕＣｌ２发生化学反应，促进催化活性位的形成；ＫＯＡｃ为助剂母体的效果明显好于ＫＣｌ母体；Ｋ助剂的最佳含量为２～３ｗ％；在反应温度Ｔ＝１５２℃，进料气体空速和液体空速分别为１４８３ｈ－１和４ｈ－１，进料ＣＯＯ２比为２８３时，对于Ｐｄ＝０６１ｗ％，原子比为ＰｄＣｕＫ＝１１４１４的ＰｄＣｌ２－ＣｕＣｌ２－ＫＯＡｃＡＣ催化剂，在６ｈ的运转时间内碳酸二甲酯的时空收率可达到３１７～３６１ｇＬ－ｃａｔｈ，甲醇的单程转化率为１４８～１６９％     

新型石墨烯-壳聚糖/二茂铁衍生物/细胞色素c修饰电极的制备及其用于亚硝酸钠的检测研究

具有共轭结构的分子导线是构筑分子电子器件的重要组成单元,而含有二茂铁单元的该类化合物具有良好的电化学性质,被广泛研究。基于此,本实验通过Sonogashira交叉偶联等反应合成了一种新型二茂铁乙炔衍生物( Fc-NH2),并经红外( IR)、核磁共振(1 H NMR和13 C NMR)、质谱( MS)和循环伏安( CV)等方法表征。利用Fc-NH2与石墨烯-壳聚糖( GH-CS)之间的相互作用制备了GH-CS/Fc-NH2复合物,并成功用于细胞色素c(Cytc)的固定,得到GH-CS/Fc-NH2/Cytc修饰电极。研究表明,GH-CS/Fc-NH2/Cytc/GCE在-0.2 V附近出现一对峰,对应于Cytc的可逆氧化还原峰。此电极对NaNO2有良好的电催化作用,在1×10-7~1.5×10-4 mol/L范围内,NaNO2浓度与氧化峰电流呈良好的线性关系,检测限低至4×10-8mol/L。此修饰电极不但可以实现细胞色素c的直接电化学,也可以用于定量检测NaNO2。     

Solution Preparation of Li(Co,Fe)O2 Coatings for Molten Carbonate Fuel Cell Components

An aqueous solution process has been used for dip coating onto substrates of 316L stainless steel. Coatings of LiCoO₂, Li(Co_0.5Fe_0.5)O₂ and LiFeO₂ were applied and heat treated to 650°C for 3 hrs. Thermal analysis, X-ray diffraction analysis, and SEM analysis were carried out to characterize the microstructure of the coatings. Results showed that the coatings transformed from a gel to a porous, crystalline layer between 270 and 350°C. Microhardness measurements at low load (50 g) were used as an indication of the surface coverage. Samples subjected to 10 thermal cycles at 10°C/min to 650°C and back to ambient, to simulate use in a molten carbonate fuel cell, showed no decrease in microhardness.     

Mathematical modeling of kinetic behavior of the hydrogen electrode in carbonate melts under non-steady-state conditions: An analysis of various reaction schemes

An extended analysis of the kinetic behavior exhibited by the hydrogen electrode in a molten carbonate electrolyte is performed by a method of mathematical modeling of relaxation processes as applied to chronoamperometric and coulostatic experiments. A set of differential equations with corresponding initial and boundary conditions, which fixes the balance of charge and substance at the electrode/electrolyte interface, is presented for several particular versions of reaction schemes and the method used for bringing the system out of equilibrium. Numerical calculations are performed and their results are compared with the experimental time dependences of the current and overvoltage obtained in chronoamperometric and coulostatic conditions, respectively. As a result, possible intervals of variations in the kinetic, adsorption, and transport parameters of the system are evaluated. The deviations of their values when using different investigation procedures and different electrode materials (gold, nickel) are discussed. To differentiate assorted reaction schemes as applied to a real electrode process of the anodic oxidation of hydrogen in a carbonate electrolyte it is necessary to expand the base of experimental material to be analyzed and the circle of procedures to be used for investigation.