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Graphene/metal oxide composites have generated interest for a variety of applications, such as energy storage, catalysts, and electronics, etc. However, one of the primary technical barriers to real applications has been the lack of practical and environmentally benign synthesis methods for producing homogenous graphene/metal oxide nanocomposites on a wide scale. Therefore, a simple, efficient, and environmentally friendly approach to the synthesis of graphene (reduced graphene oxide: rGO)/metal oxide (MO) nanocomposites was developed with the chemical reaction of graphene oxide (GO) and various metal oxide powders under mild temperature conditions. In this study, the GO was synthesized from graphite powder using modified Hummer’s technique initially. Later, using ascorbic acid (AA) as a reducing agent, various binary nanocomposites such as rGO/ZnO, rGO/CuO, rGO/TiO2, and rGO/Ag2O were synthesized by in situ approach. The structural and surface properties of the synthesized binary nanocomposites were extensively examined by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDX), and Raman spectroscopy techniques. The XRD analysis of the synthesized binary rGO/MO nanocomposites confirmed the nanocrystalline nature. However, the FESEM and EDX analysis substantiated the MO nanoparticles were uniformly distributed onto the rGO layers anchoring of MO onto rGO particles and interacted with the rGO residual functional groups. Raman spectroscopy analysis indicated the increased number of defects because of the interfacial interaction between rGO and MO and the formation of binary rGO/MO nanocomposites.

A rapid and easy synthesis of pure neodymium hexaboride, NdB6 nanocrystals was developed, without applying heat treatments at high temperatures. The mechanochemical synthesis of NdB6 powders was performed at room temperature inside a planetary ball mill. The Nd, B2O3 and Mg starting blends were mixed, and subsequently mechanically alloyed to constitute NdB6-MgO as final products. The effect of milling duration on the NdB6 formation mechanism and metallothermic reduction was investigated. Following mechanochemical synthesis, MgO was removed from the system by leaching the powders with CH3COOH solution. The formation of NdB6 phase was monitored by the X-ray diffraction (XRD) analysis. Microstructure and morphology of the synthesized nanocrystals were characterised by using scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS), and high resolution transmission electron microscopy (HRTEM) techniques. Pure NdB6 nanocrystals with a crystallite size of 18.2 ± 2.0 nm were obtained after 15 h of milling. Microscopic investigations revealed the irregular shape and morphology of NdB6 nanocrystal structures. Rietveld refinements confirm the cubic structure (space group Pm-3m) with a lattice constant of 4.1254 (2) Å and 92 ± 8 nm particle size of NdB6 phase. The Raman active phonons of Pm-3m symmetry were characterised by Raman spectroscopy. © 2019 Elsevier B.V.

In this work, nanocrystalline Co65Ti25W5B5 (at.%) powders were prepared by mechanical alloying (MA) of the elemental powder mixture under argon gas atmosphere. The powders were milled during different periods (2.5, 5, 10, 20 and 30 h) using a planetary ball-mill (Retsch PM100 CM) at 400 rpm. The structural, morphological, thermal and magnetic properties of the nanocrystalline Co65Ti25W5B5 powders were studied by means of X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX), differential thermal analysis (DTA) and vibrating sample magnetometer (VSM) techniques. Because of its high melting point, hardness and low solubility in the alloy components, a small amount of tungsten remained in the amorphous matrix during MA. By using the Williamson-Hall method, the crystallite size and lattice strain of the tungsten phase were calculated as about 25 nm and 0.48% respectively, for 30 h of milling. The DTA curves of the milled powders demonstrated an exothermic peak at about 600 °C, indicating the crystallization of the amorphous phase. The apparent mean activation energy, 303.5 ± 7 kJ/mol for 20 h milled powders was determined by Kissenger and Ozawa methods. The saturation magnetization (Ms), the coercivity (Hc) and the remanence-to-saturation ratio (Mr/Ms), values were of about 66 emu/g, 11 Oe and 0.012 respectively, after 30 h of milling. © 2015 Elsevier B.V.

In this work, ZnO and boron doped ZnO (ZnO:B) thin films were produced by chemical spray pyrolysis method. ZnO and ZnO:B films were obtained onto glass substrates at 450°C by spray pyrolysis method and the physical properties of those films were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible spectrometer (UV) and four probe technique. XRD measurements show that all films have hexagonal wurtzite structure and all films grow preferentially along (002) direction. Morphologies of the films were examined by using a scanning electron microscopy and it was observed that almost all films were quite intense with a regular structure. Optical measurements showed that the band gap energies of the films increased with boron concentrations. The resistances of the B-doped ZnO films were measured by four probe method and resistances of films initially decreased to its minimum 1 at% boron doping and then it increased again with increasing B concentration. It was also observed that that boron doping increased the activation energies of the films. © 2015, Pleiades Publishing, Inc.

Amorphous Mg61Cu24Y15 ribbons were manufactured by melt-spinning at wheel speeds in the range 5–20 ms−1. The crystallization behavior of amorphous ribbons was investigated by a combination of differential scanning calorimetry (DSC) and X-ray diffractometry. DSC measurements showed that the amorphous ribbons exhibit distinct glass transition temperature and wide supercooled liquid region before crystallization. During continuous heating three exothermic peaks and two endothermic peaks were observed. The characteristic thermodynamic parameters such as T g, T x , ΔT x , and T rg are around 432–439, 478–485, 46–54 K, and 0.55–0.56, respectively. Isothermal annealing DSC traces for this amorphous alloy, the first crystallization peak showed a clear incubation period and Avrami exponent was found to be 2.30–2.74, which indicate that the transformation reaction involved nucleation and three-dimensional diffusion controlled growth. Mechanical properties of the as-quenched and subsequently annealed ribbons were examined by Vickers microhardness (HV) measurements. Results showed that microhardness of the as-quenched ribbons were about 309 HV. However, the results also showed that microhardness of the rapidly solidified ribbons increases with the increasing temperature.

Quasicrystalline phase formation during heat treatment in the mechanically alloyed Al65Cu20Fe15 powders was studied by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mechanical alloying was performed at speed of 300 rev min–1 for times up to 70 h. It was found that mechanical alloying of the Al65Cu20Fe15 powders did not result in the quasicrystalline (QC) icosahedral phase (i-phase) formation. The long time milling resulted in the formation of a cubic Al (Cu,Fe) solid solution phase (β-phase). The cubic Al (Cu,Fe) solid solution identified as β-phase was observed to be present as one of the major phases in the Al65Cu20Fe15 alloy. The formation of the quasicrystalline icosahedral phase (i-phase) was only observed for short time milled powders after additional annealing at temperature above 500°C. The present investigation also showed that a tetragonal Al2Cu phase (θ-phase) forms with short time milling. The tetragonal Al7Cu2Fe1 phase (w-phase) was observed after heat treat...

The present research aimed to characterize the microstructure of icosahedral quasicrystalline phase (i-phase) in different chemical compositions of Al–Cu–Fe alloys. The ternary alloys with the nominal compositions of Al70Cu20Fe10, Al65Cu20Fe15 and Al63Cu25Fe12 (at%) were rapidly solidified by melt-spinning technique. The melt-spun ribbons were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). According to the XRD results, diffraction patterns of Al70Cu20Fe10 alloy showed the presence of the i-phase together with tetragonal θ-Al2Cu phase. However, XRD pattern of the melt-spun Al63Cu25Fe12 alloy showed the formation of i-phase together with a small amount of β-phase. The single quasicrystalline phase was observed only in the rapidly solidified Al65Cu20Fe15 alloy. The SEM examinations showed that the melt-spun Al70Cu20Fe10 and Al63Cu25Fe12 alloys composed of i-phase with an average grain size of 1–5 μm. However, for the Al65Cu20Fe15 alloy, the quasicrystalline particles in the star-shape dendritic formations were observed. The melting point of i-phase was determined as 890 °C by DTA examinations.

WOS: 000347660000001, Cobalt(II) and copper(II) complexes of a novel Schiff base ligand containing two -N=N- chromophore groups, derived from the condensation of 2-hydroxy-5-[(E)-phenyldiazenyl]benzaldehyde with p-aminoazobenzene were synthesized and characterized by analytical and spectroscopic methods. The X-ray powder diffraction analysis was used to determine the unit cell parameters of the synthesized ligand and its metal complexes. Self-isomerization via intramolecular proton transfer was investigated by UV-Vis and theoretical calculations. The effect of solvent polarity on UV-Vis was examined. The electronic structures of compounds were also predicted with computational chemistry methods. Theoretical vibrational and electronic spectra of the metal complexes were obtained from these structures. Binding energies of the metal complexes were obtained by quantum chemical calculations. Upon irradiation the ligands and their metal complexes gave blue light. The (1a) azo-aldehyde and (2a) azo-azomethine ligands revealed quantum yields of 35 and 41% and their excited-state lifetimes were 326 and 3.86 ns, respectively. Decreases in photoluminescence intensity and quantum yield upon complexation with metal ions were noted. The thermal behavior to include activation energy (E), entropy (Delta S*), enthalpy (Delta H*) and Gibbs free energy change (Delta G*), using Coats-Redfern (CR) and Horowitz-Metzger (HM) methods, were examined. (C) 2014 Elsevier B.V. All rights reserved.