Browsing by Author "Denev I."

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    Nanocomposites based on intermetallic nanoparticles template synthesized using different supports
    (2013-12-17) Milanova V.; Petrov T.; Denev I.; Markova I.
    A template synthesis of intermetallic (Cu-Sn, Ni-Sn) nanoparticles has been carried out using different supports through a borohydride reduction with NaBH4 in a mixture of aqueous solutions of CuCl2.2H2O, SnCl2.2H2O, NiCl2.6H2O, respectively, at mass ratio Cu:Sn (Ni:Sn) = 40:60 at room temperature and atmospheric pressure. The obtained nanocomposites are of a type - inert matrix/Cu-Sn (Ni-Sn) nanoparticles. Porous carbon (C-foam), carbon powder (C-powder) and AlN-powder (commercial products) have been used as supports. The influence of the quantity of citric acid as a surfactant on the morphology of the Cu-Sn nanoparticles deposited on and inside the C-foam pores has been studied. A physico-chemical investigation of the prepared nanocomposites based on Cu-Sn (Ni-Sn) nanoparticles is carried out with SEM/EDS, and XRD analyses.
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    Synthesis and study of carbon-based nanocomposites with Co-Sn nanoparticles for electrode materials
    (2015-01-01) Milanova V.; Markova I.; Piskin M.; Stankulov T.; Petrov T.; Denev I.
    Intermetallic Co-Sn nanoparticles have been synthesized through a template borohydride reduction with NaBH4, using a carbon-containing support in a mixture of aqueous solutions of the corresponding chloride salts (CoCl2.6H2O and SnCl2.2H2O) at mass ratio Co:Sn = 35:65. The ratio is chosen in accordance with the Co-Sn binary system phase diagram. The ``template`` technique involves reductive precipitation of intermetallic nanoparticles on a support. Fluorinated graphite (CF) and graphite/β-cyclodextrin (Dx) hydrate have been used as supports. Subsequently, carbon polymer-based nanocomposites with Co-Sn nanoparticles have been obtained. The content of the polymer in the obtained nanocomposites varies between the samples. The reductive precipitation was carried out at room temperature and atmospheric pressure. Samples were studied by physic-chemical and electrochemical analyses. The morphology, structure, phase composition and surface element content of the prepared nanocomposites have been investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. The nanocomposite morphology is typical for the alloy materials. CoSn2 and CoSn phases are formed according to the Co-Sn binary system phase diagram. The surface element composition has proven the existence of Co and Sn. Electrochemical study of these nanocomposite materials has been carried out by a cycling voltammetry. The samples are assembled in argon filled glove box and are electrochemically tested as electrode materials (anodes) in a Li-ion battery. The charge-discharge tests have shown that these nanocomposite materials, containing a CoSn2 phase, are characterized by a stable specific capacity after the 20 cycles, better cyclicibility and higher efficiency, as compared to the Co-Sn alloy. Their measured capacity is a reason to be an alternative replacement of the graphite electrodes in Li-ion batteries.