Surfactant-free synthesis and electromagnetic properties of Co–Ni–B composite particles

The Co–Ni–B composite particles with different mol ratio of Co to Ni were composited of spheres, spheres in-pair, hierarchical assemblies of dentrites, which were surfactant-free synthesized by chemical reduction method in aqueous solution. The complex permeability of the Co–Ni–B composite particles indicated reverse resonant peak at the frequency range of 8–16 GHz, where the complex permittivity showed the positive resonant peak and the μ_r″ of particles showed negative values, caused by the transformation between electric and magnetic energy. The imaginary parts of relative permeability (μ_r″) of Co–Ni–B composite particles indicated one broad resonant peak over the 2–8 GHz range for the high effective anisotropy. A slight decrease in complex permittivity resulted in an excellent impedance matching property. The Co–Ni–B composite alloy particles with mol ratio of 7:3 exhibited reflection loss less than ?20 dB in frequency range of 4.0–14.5 GHz for the absorber thickness of 1.1–3.2 mm, and an optimal RL of ?32.4 dB was obtained at 12.8 GHz with thickness of 1.2 mm. The broadest bandwidth of reflection loss less than ?10 dB from 13.0 to 17.0 GHz, covering almost the whole Ku-band, was obtained for a thickness of 1.1 mm layer.     

A facile synthesis of graphene–metal (Pb, Zn, Cd, Mn) sulfide composites

We propose a general approach for the preparation of graphene-metal sulfide quantum dots (QDs) composites by π–π stacking of pyridine-capped metal sulfide QDs and chemically converted graphene (CCG) in aqueous solution. CCG sheets disperse stably in water without the assistance of dispersing agents, only by electrostatic repulsion. The aromatic structures of pyridine capped on metal sulfide QDs make these QDs dispersible in ethanol or water, and further introduce a π–π stacking interaction between CCG and QDs, and extend the conjugated structure of CCG. The structural details, formation mechanism, and textural properties of the resultant graphene-metal sulfide QDs composites are characterized by X-ray diffraction, UV–vis absorption, electron microscopy, and Raman scattering studies. The CCG–metal sulfide composites disperse stably in aqueous solution, allowing them to be potentially used in biological tissues and easy-to-form filtered films for further research and application.     

Sol–gel synthesis of Cu0.9Zn0.05M0.05O (M = Cr,Co, Cd) nanocrystals for removal of pollutant dyes and bacterial inactivation

Journal of Materials Science: Materials in Electronics - In this work, we focus on the synthesis of Cu0.95Zn0.05O and Cu0.9Zn0.05M0.05O (M?=?Cr, Co, Cd) nanocrystals by employing...     

Properties and microstructure of WC–TiC–Co and WC–TiC–MO2C–Co(Ni) cemented carbides

Abstract

The present study is an attempt to observe the changes in microstructure and properties of modified WC–10Co cemented carbides from the viewpoint of the distinctive role played by modified binder phase. Introduction of TiC into WC–10Co cemented carbide results in microstructural non-uniformity, i.e. a wide range of grain size distribution, which in turn gives rise to a drastic drop in values of transverse rupture strength and toughness. The modification of binder and carbide phases by incorporating, respectively, nickel and M02C improves the microstructural uniformity, which ensures better mechanical properties. The present findings have been interpreted in terms of various quantitative microstructural parameters, with particular attention being given to the wettability factor.

MST/1363     

The synthesis,characterization, and new optical property of M(Co and Fe)–phenylalanine complexes

In this paper, long flake-like Co(II)–phenylalanine and sphere-like Fe(II)–phenylalanine complexes were successfully synthesized by a refluxing method. The reaction time plays the key role during the whole process of the metal–phenylalanine complexes growth. The intensity of the peaks of metal–phenylalanine in photoluminscence spectra increased twice or more compared with that of pure phenylalanine. This synthesis approach is expected to become an appropriate method for preparation of other metal–organism complexes.     

A green route approach to the synthesis of Ni(II) and Zn(II) templated metal–organic frameworks

A new synthetic route involving mixing of solid reactants followed by heating has been developed for the preparation of two templated metal–organic frameworks (MOFs). [Ni(NO₃)₂(bipy)₂](pyrene)₂ (1) was obtained by mixing together Ni(NO₃)₂·6H₂O, 4,4-bipyridine and pyrene followed by heating at 85 °C for 4 h, while [Zn₂(fumarate)₂(bipy)] (2) was synthesized by mixing together Zn(O₂CCH₃)₂·2H₂O, fumaric acid and 4,4-bipyridine followed by heating at 160 °C for 16 h. The materials were characterized by elemental analysis, FT-IR spectroscopy and X-ray powder diffraction analysis (XRPD). Comparison of XRPD patterns of the materials with patterns simulated from the single crystal X-ray diffraction data, obtained from Cambridge Structural database, allowed identification of the products. Conversion of solid reactants to MOFs occurs spontaneously even when reactants are not mechanically stressed. Overall, the study suggests that MOFs can be synthesized in solid state simply by mixing together appropriate reactants without co-mill (ball-mill). Compared with traditional synthetic techniques such as solvothermal, ball-milling and solution-based, this method is environmentally friendly and highly efficient in the manufacture of these MOFs on a large scale.     

Sol–gel synthesis and properties of YBa2(Cu1−xMx)4Oy (M=Co,Ni) and effects of additional replacement of yttrium by calcium

In this work the influence of replacing Cu by Ni or Co on the structural and superconducting properties of YBa₂Cu₄O₈ is studied by means of XRD, TGA, SEM, EDX and resistivity measurements. The samples are prepared by the acetate–tartrate sol–gel method, which has proved to be very appropriate for the synthesis of Y-124 at 1 atm with even very small amounts of dopants. It is demonstrated that the transition temperature drastically decreases upon Co or Ni substitution, and that superconductivity is lost at 3% Ni and 6% Co doping. XRD measurements show that Ni and Co produce different structural effects to the orthorhombic YBa₂Cu₄O₈ phase, possibly because they are introduced in different copper positions. Interesting results are obtained by additional substitution of Y by Ca in the Co- and Ni-doped samples: It is shown that the superconducting properties are enhanced in the samples with less than 3% Ni or 6% Co, and that superconductivity is even recovered in samples with more than 3% Ni or 6% Co.     

Investigation on diffusion bonding of functionally graded WC–Co/Ni composite and stainless steel

A functionally graded WC–Co/Ni composite (FGWC) and 410 stainless steel (410ss) were successfully bonded by diffusion bonding. With the bonding temperature or holding time increasing, the tensile strength of the joints increased firstly and then decreased. The maximum tensile strength of the FGWC/410ss joints was 195 MPa bonded at 950 °C for 80 min. A diffusion layer was formed between the Ni layer and the 410ss as a result of the interdiffusion of Ni and Fe. The Ni layer could release the residual stresses of the FGWC/410ss joints. The fracture of the FGWC/410ss joints occurred in the Ni layer by the way of ductile fracture.     

Single step hydrothermal based synthesis of M(II)Sb 2 O 6 (M = Cd and Zn) type antimonates and their photocatalytic properties

Experiments involving single step hydrothermal reactions of the divalent metal (Zn^2?+?, Cd^2?+?, Pb^2?+?, Cu^2?+?, Ni^2?+? and Mn^2?+?) salts with ilmenite NaSbO₃ yielded pure divalent antimonates in the case of CdSb₂O₆ crystallizing in the PbSb₂O₆ type structure and ZnSb₂O₆ crystallizing in the trirutile structure type. In the case of Pb^2?+?, Cu^2?+?, Ni^2?+? and Mn^2?+? divalent cations, phase pure product could not be obtained. The obtained powders were characterized by powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and UV-visible diffuse reflectance spectroscopy. The oxide powders obtained possessed lower crystallite size as compared to their solid-state synthesized counterparts. This was evident from the broadening of the powder X-ray diffraction peaks. The antimonates were photocatalytically active for the decomposition of methylene blue (MB) dye under UV light irradiation.     

One-step synthesis of Co–Ni ferrite/graphene nanocomposites with controllable magnetic and electrical properties

Co_1−xNi_xFe₂O₄/graphene nanocomposites were synthesized through a one-step solvothermal method. The as-synthesized products were characterized by X-ray powder diffraction, field emission scanning microscopy, transmission electron microscope, and high-resolution transmission electron microscope. The results show that the Co_1−xNi_xFe₂O₄ nanoparticles are uniformly dispersed on graphene sheets. The dependence of structure, magnetic and electrical properties of Co_1−xNi_xFe₂O₄/graphene nanocomposites on the Ni²⁺ concentration and the graphene content were also studied. The saturation magnetization and electrical conductivity of the as-prepared products reached 51.82 emu/g and 1.00 × 10² S/m, respectively.     

Determination of cadmium rich corner of Cd–Cu–Zn,Cd–Cu–Mg,and Cd–Cu–Pb phase diagrams

Abstract

The liquidus temperatures along the monovariant trough running from the Cd–Cu–Cd₃ eutectic in each of the systems Cd–Cu–Zn, Cd–Cu–Mg, and Cd–Cu–Pb were determined using thermal and microstructural analyses. The solidus temperatures in the Cd–Cu–Mg system were also determined using thermal analysis. Alloys of monovariant composition in the Cd–Cu–Zn and Cd–Cu–Mg systems were found to have higher liquidus temperatures than the binary eutectic, indicating that the monovariant trough in these systems slopes down towards the binary eutectic. In the Cd–Cu–Pb system the liquidus temperatures along the monovariant were found to be lower than that of the binary eutectic. For the Cd–Cu–Zn system the present results are at variance with an earlier investigation.

MST/579     

Influence of Ni concentration and deposition potential on the characterization of thin electrodeposited Zn–Ni–Co coatings

The electrodeposition of Zn–Ni–Co alloys from sulphate electrolytes was studied on steel rod. In order to elucidate the characteristics of the layer formation, a complementary approach was used based on the combination of various electrochemical techniques. The cyclic voltammetry and galvanostatic techniques for electrodeposition, while potentiodynamic polarization resistance and anodic linear sweeping voltammetry techniques were used for corrosion study. Under the examined conditions, electrochemical and surface analysis indicate that the deposition has taken place with the formation of three structures have a composition corresponding to pure Zn, γ-Ni₅Zn₂₁ and pure Co phases. The influence of nickel concentration as well as the effect of potential on the surface appearance and the deposits composition was examined. Under these experimental conditions the electrodeposition of the alloys is of anomalous type. The results indicate that the addition of Ni to the Zn–Co alloy, Zn–Ni–Co alloy formed which is more corrosion resistance than Zn–Co alloy. Also, the amount of γ-phase increased and the amount of pure Zn decreased with the increase of nickel concentration in the bath. The corrosion resistance of the zinc–nickel–cobalt alloy had been improved with the more concentration of nickel. The Ni content in the deposition layer had been increased at high deposition potential, whereas, pure Zn deposition had been decreased.     

Microstructural,Optical and Magnetic Study of Ni–Zn Nanoferrites

Journal of Superconductivity and Novel Magnetism - NixZn1-xFe2O4 (x?=?0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0) nanoferrites were synthesized using the citrate precursor method with...     

A nano-structured Ni(II)–chelidamic acid modified gold nanoparticle self-assembled electrode for electrocatalytic oxidation and determination of methanol

A nano-structured Ni(II)–chelidamic acid (2,6-dicarboxy-4-hydroxypyridine) film was electrodeposited on a gold nanoparticle–cysteine–gold electrode. The morphology of Ni(II)–chelidamic acid gold nanoparticle self‐assembled electrode was investigated by scanning electron microscopy (SEM). Electrocatalytic oxidation of methanol on the surface of modified electrode was studied by cyclic voltammetry and chronoamperometry methods. The hydrodynamic amperometry at a rotating modified electrode at constant potential versus reference electrode was used for detection of methanol. Under optimized conditions the calibration plots are linear in the concentration range 0–50 mM with a detection limit of 15 μM. The formed matrix in our work possessed a 3D porous network structure with a large effective surface area, high catalytic activity and behaved like microelectrode ensembles. The modified electrode indicated reproducible behavior and a high level stability during the experiments, making it particularly suitable for analytical purposes.     

Phase Formation in the Systems α(δ)-FeOOH–M(OH)2–H2O (M = Mn, Co, Zn)

The sequence of chemical transformations induced in the systems ()-FeOOH–M(OH)₂–H₂O (M = Mn, Co, Zn) by heat treatment in the range 125–200°C is studied. The results demonstrate that the kinetics of M(II) ferrite formation, the chemical and phase compositions of the product, and its particle size distribution depend on the heat-treatment temperature, the pH of the suspension (or NaOH concentration), the FeOOH polymorph used as a starting reagent, and the starting-mixture composition.     

Structural, Dielectric, and Magnetic Characterization of Nanocrystalline Ni–Co Ferrites

Spinel ferrites containing Nickel and Cobalt of composition with nominal formula Ni_(1?x)Co_(x)Fe₂O₄ (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) prepared by the coprecipitation method are reported. The single phase spinel formation of ferrites was confirmed by X-ray diffraction techniques. The lattice constants (a _th) were calculated based on the ionic radii of the constituents. The calculated lattice constants are smaller than the measured, because for calculations ideal ionic radii are used. The particle size calculated from the Scherrer formula varied within 15 to 33?nm. The dielectric constant and dielectric loss tangent measurement were carried out at room temperature as a function of frequency from 100 Hz to 3 MHz. Both the dielectric constant and dielectric loss tangent increased with increase in cobalt concentration. Ferrimagnetic transition temperature as a function of Co?concentration was measured with the low field ac susceptibility apparatus. The ferrimagnetic transition (T _c ) was observed in the temperature range 573 to 720?K. The T _c decreased with the addition of Co?concentration. The effect of Co?concentration on the magnetic properties was investigated using a vibrating sample magnetometer (VSM). It was found that both magnetic saturation (M _s ) and coercivity (H _c ) increase with Co?concentration.