metal based
Phase Transition in Nanocomposites LixCuySnz as Anode Material in Recharcheable Lithium Batteries
M. Mladenov(a), P. Zlatilova(a), D. Kovacheva(b), K. Belov(c), I. Dragieva(a)
a: Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences, Acad. G.Bonchev str., Block 10, 1113 Sofia, Bulgaria
b: Institute of Inorganic and General Chemistry, Bulgarian Academy of Sciences, Acad. G.Bonchev str., Block 11, 1113 Sofia, Bulgaria
c: Central Laboratory of Mechatronics and Instrumentation, Bulgarian Academy of Sciences, Acad. G.Bonchev str., Block 1, 1113 Sofia, Bulgaria
Abstract
This investigation summarizes work on preparing of CuySnz alloys in the micron-size particle range and its changes as electrochemical active material in Li-ion cells. The nanoparticles were obtained by low-temperature synthesis from corresponding metal salts using boron hydride as a reducing agent. By means of microprobe analyses the Cu:Sn atomic ratio of the obtained nanosized materials was found to vary from 1.1 to 1.57 depending on the synthesis conditions. XRD analyses were performed in order to determine the phase composition of the materials and the changes at different consecutive stages of the electrochemical lithiation process. The progressive phase transformation from hexagonal phase Cu6Sn5 (hcp type) into the cubic face-centered structure (fcc type) of the Li2CuSn and further to lithium rich amorphous phase of type Li4.4-xSn and Cu was observed. The mechanism of the lithiation process and electrochemical anode performances was discussed. In the cycling setup a novel data collection and experiment control methods are tested which utilize contextual information connected with the experiment.
categories
metal basedSynthesis and Characterization of Cobalt Nanoparticles, Nanowires and their Composites
I. Markova – Deneva(a), K. Alexandrova, I. Dragieva
a: University of Chemical Technology and Metallurgy, Institute of Electrochemistry and Energy Systems-Bulgarian Academy of Sciences, Sofia, Bulgaria
Abstract
Cobalt (Co) nanoparticles and nanowires were synthesized at room temperature and atmospheric pressure by chemical reduction in aqueous solutions of Co salts with NaBH4. Two types of reactors were used ensuring various hydrodynamic conditions of mixing for both solutions (CoSO4.7H2O solution and NaBH4 solution). Co nanoparticles in amorphous state were synthesized using an ideal mixing conditions reactor (T-method), as well as Co nanoparticles with a crystalline structure in a reactor with an ideal displacement regime (A–method) were synthesized too. From the synthesized Co nanoparticles and micronized AlN powder (10-30 mass %) were prepared composites by pressing and sintering in the temperature range from 550 o to 750 oC for a potential application as getters or catalysts. Co nanowires were synthesized also by reduction in the presence of SiO2, SiMCM и AlMCM supports. The content of B, H2, and O2 by elemental analysis of nanoparticles and their specific surface area by the BET method were determined. Some physical-mechanical properties such as density and electro conductivity of samples of sintered amorphous and crystalline nanoparticles and their composites with micronized AlN powder heat treated in 200 o to 850 oC range were measured. IR spectroscopic studies of Co nanoparticles and their AlN composites were carried out by FTIR in 4000 to 400 cm-1 frequency range, as well as SEM micrographs of the Co nanowires were made which allow determining their diameters.
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