Browsing by Author "Milanova M."

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    Glass formation and structure of glasses in the ZnO-WO3-La2O3-Al2O3 system
    (2015-01-01) Ataalla M.; Milanova M.; Aleksandrov L.; Iordanova R.; Staneva A.; Dimitriev Y.
    The glass formation region in the section 90(xZnO.yWO3.zLa2O3).10Al2O3 of a constant Al2O3 content of 10 mol % and varying amounts of WO3, ZnO and Nd2O3 from ZnO-WO3-La2O3-Al2O3 system is determined by the melt quenching technique (with cooling rates of 10 Ks-1 - 102 Ks-1). The glasses are obtained from compositions of a high WO3 content (60 mol % - 75 mol %). The amorphous state of the samples is verified by X-ray diffraction (XRD). The thermal parameters of the investigated glasses are obtained by differential thermal analysis (DTA). The glass transition temperature (Tx) is in the range 440°C - 510°C, while the crystallization temperature (Tg) varies from 520°C to 650°C. The glasses are characterized by a good thermal stability in respect to crystallization. ΔT varies in the range of 60°C - 135°C (ΔT = Tx-Tg). The glasses structure is studied by IR spectroscopy. It is established that the amorphous network is built up mainly by WO6 octahedra connected through W-O-W bridges.
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    Structure and Electrochemical Performance of Glasses in the Li2O-B2O3-V2O5-MoO3 System
    (2025-09-01) Milanova M.; Yang X.; Vargas P.; Rosero-Navarro N.C.; Harizanova R.; Jivov B.; Aleksandrov L.; Iordanova R.; Shopska M.; Koleva S.
    Applying the melt quenching method (cooling rate 101–102 K/s), new multicomponent vanadate glasses were synthesized, containing different amounts of MoO3 at the expense of B2O3 with the composition 20Li2O:(30 − x)B2O3:50V2O5:xMoO3, x = 10, 20 mol%. The obtained samples were characterized by X-ray diffraction, infrared spectroscopy, differential scanning calorimetry and impedance spectroscopy. The density of the glasses was measured by the Archimedes method, on the basis of which the physicochemical parameters molar volume, oxygen molar volume and oxygen packing density were calculated. It was found that the replacement of B2O3 with MoO3 leads to changes in electrical conductivity, which are a consequence of the increase in non-bridging oxygen atoms in the amorphous structure. The electrochemical characterization of the 20Li2O:(30 − x)B2O3:50V2O5:20MoO3 glass obtained was performed by assembling an all-solid-state cell, employing 20Li2O:(30 − x)B2O3:50V2O5:20MoO3 glass as a cathode active material. The obtained results show that the studied glass compositions are interesting in view of their potential application as cathode materials in all-solid-state lithium-ion batteries.