Facile synthesis of nanostructured Ni-Co/ZnO material: An efficient and inexpensive catalyst for Heck reactions under ligand-free conditions

A simple, efficient and economically viable method for the Heck reaction has been accomplished in the absence of phosphine ligand. The Heck reaction was performed using nanostructured Ni-Co/ZnO material as a heterogeneous catalyst in a DMF/H₂O solvent system and in the presence of K₂CO₃, at 120 °C. The Ni-Co/ZnO nanostructures were prepared by the facile reduction-impregnation method. The structural and morphological properties of Ni-Co/ZnO nanostructure were investigated using various physico-chemical characterization techniques. Structural studies displayed the formation of hexagonal (wurtzite) ZnO. Electron microscopy imaging showed the presence of agglomerated clusters of Ni-Co nanoparticles over the surfaces of elliptical, flower bud-like and irregularly shaped sub-micron sized particle bundles of ZnO. The elemental composition analysis (EDX) confirmed the loading of Ni and Co nanoparticles over the nanocrystalline ZnO. The surface chemical state analysis of Ni-Co/ZnO material validated that Ni nanostructure exists in Ni²⁺ and Ni³⁺ species, whereas, Co nanostructure exists in Co²⁺ and Co³⁺ species. UV–Vis diffuse reflectance spectroscopy displays red shift in the light absorption edge of Ni-Co/ZnO catalyst compared to pure ZnO. The as-prepared Ni-Co bimetallic supported ZnO nanostructure showed better catalytic activity and stability for the Heck reactions under phosphine ligand-free conditions. Ni-Co/ZnO catalyzed Heck reactions afforded the corresponding cross-coupled products with moderate to good yields (up to 92%). Ni-Co/ZnO catalyst could be reused for five successive runs without significant loss of catalytic activity.     

Electrochemical synthesis,structure, and properties of nickel-tungsten-hydrogen ternary systems

The composition and structure of the electrochemically synthesized Ni-W-H alloys were studied. The co-deposition of nickel with tungsten mainly led to nickel solid solutions, and nanocrystalline alloys formed if the hydrogen content in them was at least 3 at %. The deposits included ∼2% of all evoluted hydrogen. The lattice constant of the solid solutions was 1.7–1.9% higher than the that of nickel. The tungsten solid solution phase found in a number of alloys was not nanocrystalline. The hardness of the alloys was several times higher than that of pure nickel.     

Ni-Co/RuO2复合电极的制备及其电催化析氢性能

采用快速凝固结合去合金化的方法制备纳米多孔Ni-Co合金,利用RuO_2对Ni-Co合金进行表面修饰,通过X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对多孔材料进行物相分析和形貌表征,并通过线性扫描伏安法、多电位阶跃法、交流阻抗法和恒电流电解法测试多孔电极的电催化析氢性能。结果表明,Ni-Co/RuO_2复合电极材料在50 mA·cm~(-2)电流密度下析氢过电位为180 mV,析氢过程由Volmer-Heyrovsky步骤控制,交换电流密度为4.42 mA·cm~(-2),经10 h恒电流电解后电位仅增加20 mV,表现出良好的析氢稳定性。     

Separating the strengthening phase in nickel–cobalt alloys doped with tantalum

The hardness values of monophasic (fcc solid solution) and biphasic (fcc solid solution and separated phase) nickel–cobalt alloys doped with tantalum are determined using the Vickers method. Based on the resulting data, a composition–structure–hardness diagram is devised for the Co–Ni–Ta system.     

Electrochemical characterization of Ni-Co and Ni-Co-Fe for oxidation of methyl alcohol fuel w ith high energetic catalytic surface*简

 Non Pt based metals and alloys as electrode materials for methyl alcohol fuel cells have been investigated with an aim of finding high electrocatalytic surface property for the faster electrode reactions. Electrodes were fabricated by electrodeposition on pure Al foil, from an electrolyte of Ni, Co, Fe salts. The optimum condition of electrodeposition were found out by a series of experiments, varying the chemistry of the electrolyte, pH valve, temperature, current and cell potential. Polarization study of the coated Ni-Co or Ni-Co-Fe alloy on pure Al was found to exhibit high exchange current density, indicating an improved electro catalytic surface with faster charge-discharge reactions at anode and cathode and low overvoltage. Electrochemical impedance studies on coated and uncoated surface clearly showed that the polarization resistance and impedance were decreased by Ni-Co or Ni-Co-Fe coating. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and atomic absorption spectroscopy (AAS) studies confirmed the presence of alloying elements and constituents of the alloy. The morphology of the deposits from scanning electron microscope (SEM) images indicated that the electrode surface was a three dimensional space which increased the effective surface area for the electrode reactions to take place.     

Nanocrystalline structure and soft magnetic properties of nickel–molybdenum alloy thin films electrodeposited from acidic and alkaline aqueous solutions

Nanocrystalline nickel–molybdenum (Ni–Mo) alloy thin films were electrochemically synthesized in acidic and alkaline aqueous solutions. Transmission electron microscope bright-field images and electron diffraction patterns of the electrodeposits made it obvious that pure Ni consists of a submicron crystalline phase with the grain diameter of several hundred nanometers, while Ni–20 %Mo alloy was composed of a nanocrystalline phase with the grain diameter of a few nanometers. It was estimated that the nanocrystalline phase of electrodeposited Ni–Mo alloy thin films was introduced by the formation of supersaturated Ni–Mo solid solution phase with Mo content in the deposit more than 20 %. Submicron crystalline pure Ni thin films were hardly magnetized in perpendicular direction to the film plane while the nanocrystalline Ni–20 %Mo alloy thin films were isotropically magnetized. It was suggested that the isotropical magnetization behavior was caused by decreasing the demagnetizing field and the magneto crystalline anisotropy with a decrease in the magnetic moment and the average crystal grain size. Coercive force of a submicron crystalline pure Ni thin film electrodeposited from an acidic aqueous solution was ca. 100 Oe while that of a nanocrystalline Ni–20 %Mo alloy thin film electrodeposited from an alkaline aqueous solution was only 1～2 Oe. Soft magnetic properties of Ni–Mo alloy thin films electrodeposited from an alkaline aqueous solution were better than that from an acidic aqueous solution and it was improved with an increase in Mo content in the deposit. It was estimated that the electrodeposited Ni–Mo alloy catalysts could be easily recovered with magnetic field less than 1 kOe.     

Effect of nano-Al2O3 particles and of the Co concentration on the corrosion behavior of electrodeposited Ni–Co alloys

Incorporation of nano-Al₂O₃ particles into a Ni–Co alloy by electrodeposition influences the corrosion properties, morphology, and structure of the layers. The resistance against corrosion of Ni–Co/Al₂O₃ composite films deposited on stainless steel was investigated in a 0.1-M NaCl solution by potentiodynamic polarization. The presence of nanoparticles improves the corrosion resistance of Ni–Co/nano-Al₂O₃ deposits when compared to pure Ni–Co alloy. Moreover, by increasing the pH of the electrodeposition bath and the content of Co in the alloy, the resistance against corrosion is furthermore improved. The morphology of the deposits before and after their corrosion was analyzed by scanning electron microscopy. The presence of the embedded alumina particles in the Ni–Co alloys was one of the key factors that limited further propagation of corrosion on the metallic surface. Preferential corrosion attack, in the form of a pitting corrosion, was located mainly at the grain boundaries.     

花球状镁铝复合氧化物负载Ni⁃Co催化剂的合成及正十二烷水蒸气重整制氢

采用水热晶化的方法制备了花球状镁铝层状水滑石材料,经过高温焙烧和氢气还原成功制备了镁铝复合氧化物负载的Ni?Co合金催化剂。通过扫描电子显微镜、透射电子显微镜、氮气吸附-脱附测试、粉末X射线衍射、程序升温还原等技术表征了所制备催化剂的物理化学性质,并且测试了所制备催化剂催化正十二烷水蒸气重整制氢性能。实验结果表明:水热晶化后催化剂的前驱体是花球状层状水滑石结构,焙烧后催化剂以复合氧化物的结构存在,且存在非常丰富的介孔和大孔。通过调控Co的加入量,可以调控金属载体相互作用的强度及金属颗粒尺寸。还原后,Ni和Co形成合金且均匀地分布在层状薄片镁铝复合氧化物上面。所制备的催化剂用于正十二烷水蒸气重整制氢,结果显示,相比于Ni单金属催化剂,形成Ni?Co合金的催化剂的活性及产氢率均有较大程度的提升,且抗积碳性能大幅度提高。这归因于Ni?Co协同的合金状态和较小的金属纳米颗粒尺寸。     

NiB和NiP超细非晶合金的退火晶化行为及催化性能

 采用X射线吸收精细结构（XAFS）,X射线衍射（XRD）和差热分析（DTA）等方法研究了以化学还原法制备的NiB和NiP超细非晶态合金催化剂在退火过程中的结构变化．XRD结果表明,在300℃下退火时,NiB超细非晶态合金晶化生成纳米晶Ni3B亚稳物相,NiP超细非晶态合金则主要晶化生成金属Ni和部分晶态Ni3P的混合物相;在500℃退火且近于完全晶化的条件下,大部分超细非晶态合金都晶化为金属Ni．XAFS结果定量地说明,对于NiB和NiP初始样品,第一近邻Ni－Ni配位的平均键长Rj分别为0.274和0.271nm,其结构无序度σS很大,分别为0.033和0.028nm,其热无序度σT分别为0.0069和0.0060nm．300℃退火后,晶化生成的Ni3B的Ni－Ni配位的σS降低到初始样品的33％,仅为0.011nm．500℃退火后,NiB样品的结构参数与金属Ni基本一致,但NiP样品的Ni－Ni配位的σS还远大于σT,仍为0.0125nm,表明NiB和NiP超细非晶态合金的退火晶化行为有很大的差别．纳米晶Ni3B催化苯加氢反应的转化率比超细Ni－B非晶态合金或多晶金属Ni更高,表明纳米晶Ni3B中的Ni与B原子组成了苯加氢催化反应的活性中心．     

退火晶化过程中Ni-B纳米非晶态合金的结构

采用XAFS和XRD两种方法研究化学还原法制备的Ni B纳米非晶态合金在退火过程中的结构变化.我们发现,在573 K左右的退火温度下, Ni B纳米非晶态合金生成亚稳的纳米晶Ni和Ni3B.在773 K或更高的退火温度下, Ni B纳米非晶态合金大部分晶化为晶态金属Ni.     

纳米晶Ni-Mo-Co合金镀层的结构与析氢行为

电沉积;结构;纳米晶Ni-Mo-Co合金镀层的结构与析氢行为     

High electrocatalytic activity of non-noble Ni-Co/graphene catalyst for direct ethanol fuel cells

The electrocatalytic oxidation of ethanol is studied on the non-noble catalysts Ni-Co/graphene and Ni/graphene supported on glass carbon electrode (GCE) in alkaline medium. The synthesized materials are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning transmission electron microscopy. The elements of Ni-Co/graphene and Ni/graphene catalysts are characterized using energy-dispersive X-ray spectroscopy. The electrocatalytic properties of Ni-Co/graphene and Ni/graphene for ethanol oxidation are investigated by cyclic voltammetry, chronoamperometry, and Tafel plot. Compared with Ni/graphene catalyst, Ni-Co/graphene has the higher electroactivity and better stability for ethanol oxidation. The rate constant (k _s) and charge-transfer coefficient (α) are calculated for the electron exchange reaction of the modified GCE. The results indicate that Co addition could promote the oxidation reaction at the Ni/graphene catalyst. Our study demonstrates that the low-cost electrocatalyst Ni-Co/graphene has a great potential for real direct ethanol fuel cells’ application.     

Ni含量对Co_(1-x)Ni_xB催化水解放氢性能的影响(英文)

采用化学还原法以乙醇为溶剂在冰水浴中合成了一系列Co1-xNixB合金催化剂,研究了该系列合金不同Ni含量对NaBH4水解放氢性能的影响.X射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)显示Co1-xNixB合金是纳米非晶态颗粒.放氢测试表明Co1-xNixB具有很高的催化活性.放氢速率先随着Ni含量的增加而增大,并在x=0.15时放氢速率达到最大值,然后随x值的增加而减小.298K时Co0.85Ni0.15B合金催化碱性硼氢化钠水解的最大放氢速率可达4228mL·min-1·g-1,CoB和Co0.85Ni0.15B合金催化放氢的活化能分别为34.25和31.87kJ·mol-1.因此以乙醇为溶剂合成的Co1-xNixB合金具有较高的催化活性.     

Anodic behavior of nickel-based alloys in the electrolytic production of NF3

The Ni-based alloys, such as Ni-Co, Ni-Mn, Ni-Ag, Ni-Cu, Ni-Al and Ni-Si, prepared by hot isostatic pressing (HIP) at 1000 °C under 2 × 10⁸ Pa for 2 h were employed as the anodes for electrolytic production of NF₃. The current efficiencies for NF₃ formation were 42-38, 52-40, 52-47, 63-62, 50 and 41% for Ni-Co, Ni-Mn, Ni-Ag, Ni-Cu, Ni-Al and Ni-Si alloys, respectively. The current efficiencies only on Ni-Cu alloys with Cu concentrations lower than 10 mol% were almost the same as those on Ni sheet and HIPed Ni anodes, whereas those on the other alloys used in this study were smaller compared with those on both Ni anodes. On the other hand, the current losses caused by anodic dissolution of Ni-Co, Ni-Mn, Ni-Ag, Ni-Cu, Ni-Al and Ni-Si alloy electrodes were 7.95-4.42, 6.40-7.02, 5.60-6.30, 3.34-6.33, 5.10 and 0.18%, respectively. The anode consumptions of Ni-5 mol% Cu and Ni-5 mol% Si alloys were almost the same or smaller compared with those of Ni sheet and HIPed Ni electrodes, though those of other alloys used were large compared with those of both Ni anodes. Consequently, addition of Cu to the nickel matrix is available for a cheaper cost of anode with keeping a same current efficiency as that on the Ni anode and addition of Si to the nickel matrix is effective for decreasing anode consumption largely. A Ni sheet electrode containing a trace of impurities, such as Co, Mn, Ag and Al, is also favorable as the anode for electrolytic production of NF₃.     

Ni-Zr alloys: relationship between surface characteristics and electrocatalytic behavior

A relationship between electrocatalytic activity for the hydrogen evolution reaction and the surface composition of the electrode was established for Ni-Zr crystalline and amorphous alloys by means of secondary ion mass spectrometry (SIMS). Electrocatalytic activity was tested by means of cathodic polarization in 1 M KOH at 25 degrees C and the resulting exchange current density has been taken as a measure of catalytic efficiency. Surface activation treatment involved chemical etching in HF solutions; the consequent morphological and compositional surface changes were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of the pure elements (Ni and Zr) was also considered for comparison. All samples submitted to chemical etching in HF solutions showed an increase in electrocatalytic activity, particularly the alloy with the highest Ni content. The beneficial effect of chemical etching is due to dissolution of the zirconium oxide layer and to the formation of nanocrystalline Ni on the surfaces.     

Ultrasound technique as a tool for high-rate incorporation of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> in NiCo layers

NiCo–Al₂O₃ composite coatings were prepared by electrodeposition in a sulfamate plating bath containing Al₂O₃ particles to be co-deposited under sonication. For reliable determination of the microstructure, detailed studies on composite cross-sections were carried out by energy-dispersive spectrometer (matrix composition, particle content) and FE-SEM/electron backscattered diffraction data (particle distribution, grain size), accompanied by XRD analyses concerning texture, lattice parameter, grain size, and residual stress. The NiCo matrix with a Co/Co + Ni ratio up to 0.4 is a face-centered cubic solid solution with <100> and <110> fiber textures. The distribution of the particles (size 250 nm) was well-dispersed and enhanced up to 15 wt.% by ultrasound application during plating. Vickers hardness increased up to 50% by dispersion hardening. First-order residual stress in the matrix increased with rising Co content, thus decreasing wear resistance and revealing the complex of composite properties with partially opposite effects.     

Preparation and properties of Ni–Co–P/nano‐sized Si3N4 electroless composite coatings

Ni–Co–P/nano‐sized Si₃N₄ composite coating was successfully fabricated on aluminum alloys by electroless plating in this work. The surface and cross‐sectional morphologies, composition, microstructure, microhardness, friction and wear behavior of deposits were investigated with SEM, EDS, XRD, Vickers hardness and high‐speed reciprocating friction, respectively. It was found that a Ni–Co–P/nano‐sized Si₃N₄ composite coating on aluminum alloy substrate is uniform and compact. The existence of nano‐sized Si₃N₄ particles in the Ni–Co–P alloy matrix causes a rougher surface with a granular appearance, and increases the microhardness but decreases the friction coefficients and wear rate of electroless coatings. Meanwhile, the effects of heat treatment at 200, 300, 400 and 500 °C for 1 h on the hardness and tribological properties were researched. It is revealed that both of the microhardness and tribological properties of Ni–Co–P coatings and Ni–Co–P/Si₃N₄ composite coatings increase with the increase of heating temperature in the range of 200–400 °C, but show different behavior for the two coatings after annealing at 500 °C. Copyright © 2011 John Wiley & Sons, Ltd.     

Petrographic, chemical and microprobe analysis of an oxidized iron nodule from Dahr Safra, NW Syria: Is it an iron ore, or a meteorite called shale-ball?

The iron nodule DS-S revealed the concentrations of Ni, Co, Ga, Ge, As, Sb, P, S, many trace and rare earth elements, Fe (> 93 wt.%), and 2 wt.% silicates. The plotting of Ga, Ge, Cr, Cu, As, Au, W, and Ir-concentrations vs. Ni/Co in the classes (groups) IIAB, IIIAB, IVA, ungrouped (ung), NBS 809B steel (st), and DS-S, confirmed the meteoritic origin for DS-S. Magnetite-hematite resulted from oxidation during the melting/solidification process of the original meteorite across the atmosphere. The silicates suggested the presence of Ca-rich plagioclase, and traces of opx, cpx, and/or olivine which explained the low concentrations of Ni-Co. The plotting of Ga/Ge vs. Ni/Co; Ni/Co, Ga vs. P; and Ni/Co, Ga/Ge vs. As revealed the affinity of the DS-S nodule with the ungrouped Bellsbank trio. The compositional homogeneity in the DS-S nodule was probably due to O-fugacity. The conformable REE-graphs, for chondrite and DS-S, and the presence of silicates with the same phases suggested a mesosideritic origin for DS-S.     

Thermal analysis of Fe(Co,Ni) based alloys prepared by mechanical alloying

In this work several Fe(Co,Ni) based nanocrystalline alloys were obtained by mechanical alloying. Thermal study was performed by differential scanning calorimetry and thermogravimetry. After 80 h milling, all DSC scans show several reactions on heating. At low temperature, about 400 K, the exothermal process detected is associated to structural relaxation. In all alloys, the main crystallization process begins over 700 K and has apparent activation energy values between 3.7 and 3.1 eV at^–1. The Co content increases the thermal stability of this process. Furthermore, thermomagnetic measurements confirm the Co solid solution into Fe. The ferromagnetic–paramagnetic transition occurs at about 900 K.     

Surface analysis and corrosion resistance of new nickel base thin film alloys

Electroless Zn–Ni–P thin films were deposited on low carbon steel from an alkaline non‐cyanide aqueous electrolyte. The newly developed ternary alloys structure and microstructure investigations were carried out via X‐ray diffraction and SEM. Chemical composition of the coatings was investigated via energy dispersive spectroscopy. Polarization tests were used to study the corrosion properties of the coatings in a 3.5 wt.% NaCl solution. The results confirmed the high corrosion resistance of Zn–Ni–P alloy plated steel sheet. The surface analysis of the thin film samples before and after corrosion was performed by XPS. The incorporation of Zn in Ni–P thin film is proven for all initial samples to be as a mixture of zinc and zinc oxide, while nickel exists in +2 and +3 oxidized states. A passive film of a mixture of oxide and hydroxide of zinc and nickel forms on the surface and prevents the Zn–Ni–P thin films from corrosion. Copyright © 2014 John Wiley & Sons, Ltd.