Browsing by Author "Milanova V.L."

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    AN EFFECT OF THE ELEMENTAL COMPOSITION ON THE ELECTROCHEMICAL BEHAVIOR OF ALLOYED (Co-Sn, Ni-Sn) NANOPOWDERS IN A Li-ION BATTERY
    (2020-01-01) Markova-Deneva I.; Petrov T.I.; Piskin M.B.; Zahariev I.Z.; Milanova V.L.
    Alloyed Co-Sn and Ni-Sn nanopowders are synthesized at a room temperature through a borohydride reduction with NaBH4 in a mixture of aqueous solutions of the relevant chloride salts (CoCl2.6H2O, NiCl2.6H2O and SnCl2.2H2O) at mass ratios of the metallic components chosen in accordance with the corresponding binary systems phase diagrams (Co:Sn = 35:65, Ni:Sn = 45:65). Intermetallic Co-Sn and Ni-Sn nanoparticles are obtained applying a template technique which involves the use of a carbon support such as graphite (CF) and a carbon powder (CP). As a result, carbon nanocomposites are prepared in-situ. The samples obtained are electrochemically tested as anodes in a three-electrode half cell (a Li-ion battery). Their electrochemical characteristics such as specific capacity, cyclability, and efficiency are evaluated. The investigated electrode materials based on the synthesized intermetallic Co-Sn and Ni-Sn nanoparticles and their carbon nanocomposites exhibit a different electrochemical behavior depending on their morphology, microstructure, their elemental and phase composition. Based on the capacity, the cyclability, and the efficiency observed it can be concluded that Co-Sn (Co:Sn = 35:65) and Ni-Sn (Ni:Sn = 45:55) nanoparticle’s powders and their carbon composites are promising electrode materials. CF and CP used as carriers in a template synthesis of intermetallic nanoparticles are suitable matrices for the preparation of nanocomposite electrode materials of improved electrochemical parameters. The resulting carbon nanocomposite materials based on Co-Sn and Ni-Sn nanoparticles exhibit more stable electrochemical characteristics compared to those of the synthesized Co-Sn and Ni-Sn alloys. They are characterized by a higher initial discharge capacity and better cycling stability after the 10th cycle and are suitable alternative of the graphite anodes in the Li-ion batteries. The investigation carried out verifies the effect of the elemental composition on the electrochemical behavior of the investigated intermetallic (Co-Sn, Ni-Sn) nanopowders.
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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.