Browsing by Author "Hristoforou E."

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    Influence of the support on the morphology of Co-Sn, Ni-Sn, Co-Ni nanoparticles synthesized through a borohydride reduction method applying a template technique
    (2018-01-01) Markova I.N.; Piskin M.B.; Zahariev I.Z.; Hristoforou E.; Milanova V.L.; Ivanova D.I.; Fachikov L.B.
    Intermetallic (Co-Sn, Ni-Sn, Co-Ni) nanoparticles have been synthesized through a borohydride reduction with NaBH4 in aqueous solutions of the chloride salts of Co, Ni, Sn at room temperature using a template technique with a carbon support. As a result nanocomposite materials have been obtained in situ. The ratio of the metallic components has been chosen according the phase diagrams of the relevant binary (Co-Sn, Ni-Sn, Co-Ni) systems: Co:Sn=35:65, Ni:Sn=45:55, Co:Ni=50:50. As carbon supports have been used graphite and carbon powder. To avoid the nanoparticle's aggregation β-cyclodextrin has been added to the reaction solutions. To study the influence of the supports used on the morphology, specific surface area, elemental and phase composition of the synthesized intermetallic nanoparticles and their carbon nanocomposites SEM, EDS, BET, and XRD investigation techniques have been used. The particle's morphology varies with the different supports, but in the all cases it is typical for alloyed materials. The nanoparticles are different in shape and size and exhibit a tendency to aggregate. The last-one is due to the unsaturated nanoparticle's surface and the existing magnetic forces. Regardless of the elemental composition, the nanosized particles are characterized by a relatively high specific surface area (SSA). The Ni-Sn nanoparticle have the largest SSA (80 m2/g), while the Co-Sn particles have the lowest SSA (69 m2/g). The use of a carrier modifies the SSA of the resulting nanocomposites differently depending on the size and shape of the carrier's particles. The studies conducted on the intermetallic nanoparticles synthesized with various carriers demonstrate that the particle's morphology, size, and specific surface area for the different supports are suitable for use as catalysts, electrode materials in Li-ion batteries and as magnetic materials for biomedical applications.
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    Influence of the support on the morphology of Co-Sn, Ni-Sn, Co-Ni nanoparticles synthesized through a borohydride reduction method applying a template technique
    (2018-01-01) Markova I.N.; Piskin M.B.; Zahariev I.Z.; Hristoforou E.; Milanova V.L.; Ivanova D.I.; Fachikov L.B.
    Intermetallic (Co-Sn, Ni-Sn, Co-Ni) nanoparticles have been synthesized through a borohydride reduction with NaBH4 in aqueous solutions of the chloride salts of Co, Ni, Sn at room temperature using a template technique with a carbon support. As a result nanocomposite materials have been obtained in situ. The ratio of the metallic components has been chosen according the phase diagrams of the relevant binary (Co-Sn, Ni-Sn, Co-Ni) systems: Co:Sn=35:65, Ni:Sn=45:55, Co:Ni=50:50. As carbon supports have been used graphite and carbon powder. To avoid the nanoparticle's aggregation β-cyclodextrin has been added to the reaction solutions. To study the influence of the supports used on the morphology, specific surface area, elemental and phase composition of the synthesized intermetallic nanoparticles and their carbon nanocomposites SEM, EDS, BET, and XRD investigation techniques have been used. The particle's morphology varies with the different supports, but in the all cases it is typical for alloyed materials. The nanoparticles are different in shape and size and exhibit a tendency to aggregate. The last-one is due to the unsaturated nanoparticle's surface and the existing magnetic forces. Regardless of the elemental composition, the nanosized particles are characterized by a relatively high specific surface area (SSA). The Ni-Sn nanoparticle have the largest SSA (80 m2/g), while the Co-Sn particles have the lowest SSA (69 m2/g). The use of a carrier modifies the SSA of the resulting nanocomposites differently depending on the size and shape of the carrier's particles. The studies conducted on the intermetallic nanoparticles synthesized with various carriers demonstrate that the particle's morphology, size, and specific surface area for the different supports are suitable for use as catalysts, electrode materials in Li-ion batteries and as magnetic materials for biomedical applications.
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    Template synthesis and study of Co-Ni core/carbon shell nanoparticles
    (2017-01-01) Zahariev I.; Hristoforou E.; Markova I.
    Co-Ni core/carbon-based shell nanoparticles are synthesized at room temperature by the help of a template technique, using a carbon-containing support through a chemical reduction with 0.2 M NaBH4 in a mixture of aqueous solutions of 0.1 M CoCl2.6H2O and 0.1 M NiCl2.6H2O at a ratio Co:Ni=1:1. As a support of fluorinated graphite (CF) in the presence of β-cyclodextrine (β-CDx), or respectively N-Methyl-2-pyrrolidone (NMP) and N-acetyl-Dglucosamine (NAG), is used during the reduction process. Both Scanning electron microscopy (SEM) and Energy dispersitive spectroscopy (EDS) analyses are carried out to determine the morphology and surface elemental composition. The SEM images show that the synthesized core/shell nanoparticles are too small, but definitely spherical in shape. The particles are spheroidal assemblies, because of magnetic interaction forces. It is observed that the nanoparticles are deposited among the graphite grains and surrounded with the β-CDx, NMP and NAG molecules, respectively. The ratio Co:Ni = 1:1, set in the reaction solution, is exactly reproduced in the Co-Ni nanoparticles. The prepared hybrid core/shell nanoparticles are also investigated with X-ray diffraction (XRD) and Infrared spectroscopy with Fourier transformation (FTIR) in the mid-Infrared region (4000-400 cm-1). XRD analysis proves the formation of amorphous Co-Ni nanoparticles. FTIR spectra establish the existence of different chemical bonds such as O-H, C-O, C-H, C-N, B-O, B-H, Co-O, Ni-O in the corresponding atom groups situated on the nanoparticle surface.