Effect of Magnetic Co–CoO Particles on the Carrier Transport in Monolayer Graphene

Physics of the Solid State - Electrodeposition of cobalt on monolayer graphene synthesized by chemical vapor deposition produces Co–CoO/graphene composite structures, which is accompanied by...     

Formation of alloys upon the simultaneous electrochemical deposition of gold and tin from ethylene glycol and aqueous electrolytes

An ethylene glycol (EG) solution containing Au(III) and Sn(IV) compounds, and conditions for the electrochemical deposition of Au–Sn alloy based on AuSn and Au₅Sn intermetallics with total tin content of 30–55 at % are proposed. Fundamental difficulties of the deposition of alloys with high tin content, (including eutectic Au–Sn alloy) from aqueous electrolytes are revealed. It is determined via voltammetry that the simultaneous deposition of gold and tin from aqueous and EG electrolytes proceeds with the depolarization effect of both Au(III) and Sn(IV) as a result of the formation of the alloy, the increase in the rate of tin cathodic reduction being more noticeable in case of EG solution. Formation of SnCl₂EG(H₂O)₂⁺ complex upon the dissolution of SnCl₄ · 5H₂O in glycol, the stability of the composition of tetracyanoaurate ions upon the dissolution of K[Au(CN)₄], and the weakening of intermolecular interactions in EG with small amounts of water were revealed via IR spectroscopy. It is suggested that the depolarization effect is due not only to alloy formation, but also to the formation of SnCl₂EG(H₂O)₂⁺ cations, their association with Au(CN)₄^- anions, and a change in the mechanism of Au(III) and Sn(IV) reduction.     

Discontinuous fission tracks on the surface of layered dielectrics

The structure of fission fragment tracks on the surface of dielectric layer crystals has been studied by electron microscopy methods. Single crystal of gypsum (CaSO₄·2H₂O), cadmium wolframate (CdWO₄) and muscovite mica (KAl₂(OH)₂Si₃AlO₁₀) have been chosen as objects of investigation. It has been found that a discontinuous change of the surface profile continues at abnormally large (30nm) penetrations of the ion from the surface into the bulk of the crystal. Formation mechanisms of separate segments in the track structure are discussed.     

Alloying during codeposition of copper and tin out of silicofluoride electrolytes

A technique for obtaining binary Cu-Sn alloys containing 20–35 mol % Sn is proposed. The technique—the electrochemical deposition out of silicofluoride electrolytes—ensures a high deposition rate of coatings (25–50 μm h^?1). The formation of intermetallic compound Cu₁₀Sn₃ is found to occur at a high current density, in conditions of the tin reduction depolarization and the copper reduction superpolarization. The alloys consist of submicron grains. Apart from crystalline Cu₁₀Sn₃, they include x-ray-amorphous tin (2–12 mol %) and tin oxides (≤1–3 mol %). The alloys feature high hardness (4200 MPa), corrosion resistance, and solderability.     

In‐line monitoring of immiscible polymer blends in a rheometer with a fiber‐optics‐assisted fluorescence detection system

In‐line studies of the initial stages of shear‐induced coalescence in two‐phase polymer blends were carried out with a home‐built device combining a cone and plate rheometer and a fiber‐optic‐assisted fluorescence detection system. A blend of 90 wt % poly(2‐ethylhexyl methacrylate) (PEHMA) and 10 wt % poly(butyl methacrylate) (PBMA) was prepared by the casting of films onto a solid substrate from mixed aqueous latex dispersions of the two polymers. The dispersions were prepared via emulsion polymerization under conditions in which both components were formed as spherical particles with a very narrow size distribution. By using a 14:1 particle ratio of PEHMA to PBMA, we obtained films in which 120‐nm PBMA particles were surrounded by a PEHMA matrix. The blend contained phenanthrene‐labeled PBMA particles and anthracene‐labeled PBMA particles in a ratio of 4:1, whereas the PEHMA matrix polymer was unlabeled. We monitored the anthracene‐to‐phenanthrene fluorescence intensity ratio (I₄₇₀/I₃₆₀) as a measure of direct nonradiative energy transfer from phenanthrene to anthracene, whereas the blend was sheared at different shear rates and temperatures. Under no‐shear conditions, the results of in‐line experiments were in good agreement with the results of off‐line measurements of energy transfer by conventional techniques. In blends under shear, the two sets of experiments, in‐line and off‐line, did not agree with each other. The cause of this disagreement was associated with normal forces in the blend under shear that affected the optical path length and the relative intensities of the fluorescence signals of the phenanthrene and anthracene groups in the blend. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2302–2316, 2001     

Confocal microscopy studies of shear‐induced coalescence in blends of poly(butyl methacrylate) and poly(2‐ethylhexyl methacrylate)

This article reports the results of confocal fluorescence microscopy studies of shear‐induced coalescence in binary blends of poly(2‐ethylhexyl methacrylate) (PEHMA; 90 wt %) and poly(butyl methacrylate) (PBMA; 10 wt %). We prepared the blends by casting a mixture of latex dispersions of the components onto a substrate and allowing the film to dry under ambient conditions. The initial morphology of the film was a dispersion of 120‐nm PBMA spheres in a continuous PEHMA matrix. One‐fifth of the PBMA particles were labeled with anthracene, the emission of which we observed with confocal microscopy. The blends were sheared in a parallel‐plate rheometer at 80 and 100 °C for 1 and 10 h. Careful image analysis allowed us to estimate the mean size of the dispersed phase and the width of the size distribution. The results were compared with the theoretical limits of Wu and Taylor. After 10 h of shearing, the mean particle size decreased and the particle distribution became narrower in comparison with the results obtained after 1 h of shearing. We explain this result by inferring that before the sample reached steady‐state morphology, its rate of coalescence was greater than the rate of particle breakup. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2317–2332, 2001     

Synthesis and crystal structure of the pyridinium acid nitrate [(PyH)2(NO3)][H2(NO3)3] containing a dihydrogen trinitrate anion

1. Download : Download high-res image (91KB)
2. Download : Download full-size image

     

Interphase synthesis and some characteristics of aqueous nickel dispersions

The facilities of one-step preparation method of nickel nanoparticles by the interphase reduction of nickel oleate using sodium borohydride at room temperature without soluble polymer as a protective agent were studied. Nickel obtained by such technique was concentrated in aqueous phase as a black dispersion. The composition and morphology of the colloid's dispersive phase were investigated by transmission electron microscopy, XRD and IR-spectroscopy. The dispersive phase of the prepared colloidal solution represents crystalline spherical nickel nanoparticles with some admixture of nickel boride. Their average size varies between 2 and 6 nm. In accordance with the IR-spectroscopy results the stability of the nickel colloidal dispersions was provided by the surfactant produced through the interphase reaction.     

One-dimensional magnet basic copper(ii) dihydroxoborate Cu2{BO(OH)2}(OH)3: synthesis and properties

Russian Chemical Bulletin - Basic copper(ii) dihydroxoborate Cu2{BO(OH)2}(OH)3 contains infinite chains consisting of [CuO4] squares that are linked together by sharing opposite edges, due to which...     

Optical and electrophysical properties of nanocomposites based on PEDOT: PSS and gold/silver nanoparticles

The absorption spectra in the visible region and current-voltage characteristics in a wide range of electric fields have been investigated at the macroscopic level (planar structures) and at the microscopic level (using a conductive atomic force microscope) in films based on the electroactive polymer PEDOT: PSS and gold/silver nanoparticles (PEDOT: PSS + Au/AgNP). It has been shown that the behavior of the current-voltage characteristics of the nanocomposite films depends significantly on the electric field strength. It has been found that the introduction of gold nanoparticles into PEDOT: PSS in weak electric fields leads to an increase in the bulk conductance by almost two orders of magnitude (due to donor-acceptor interactions), a 50% decrease in the conduction activation energy, and an increase in the sensitivity to adsorbed oxygen. It has been demonstrated that electrical conduction of PEDOT: PSS + AuNP films is provided by hopping charge transfer both in the system of intrinsic localized states and in the system of impurity states of adsorbed oxygen. In strong electric fields, the current-voltage characteristics exhibit a different behavior in the forward and reverse scanning modes.