Browsing by Author "Zamfirova G."

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    IR-SPECTROSCOPY, THERMOPHYSICAL AND MECHANICAL PROPERTIES OF GLASSES IN THE SYSTEM Na2O/BaO/TiO2/B2O3/SiO2/Al2O3
    (2023-01-01) Harizanova R.; Gaydarov V.; Gugov I.; Zamfirova G.; Mihailova I.; Pernikov M.; Rüssel C.
    Glasses with the compositions (23.1-x)Na2O/23.1BaO/23TiO2/9.8B2O3/21SiO2/xAl2O3 x = 3, 7, 11 and 15 mol% were melted using a traditional melt-quenching technique. The thermophysical properties of the obtained glasses, i.e., glass transition temperature, Tg, and crystallization peak maximum temperature, Tc, were determined by differential scanning calorimetry and showed that the increasing alumina concentration leads to an increase of both the Tg and Tc values, while the difference Tg-Tc, used as a glass stability criterium, changes in the opposite manner, being highest for the glass with 3 mol % Al2O3 and smallest for the composition with 15 mol % Al2O3. The structure of the prepared series of glasses was studied by infrared spectroscopy and showed that the main structural units present are isolated and interconnected SiO4 tetrahedra. Both BO4 and BO3 structural units, which number initially increases with the increasing alumina concentration and then starts to decrease, are also present. The conducted depth-sensing indentation on the obtained glasses allowed to determine mechanical properties such as universal (HMV) and indentation (Hit) hardness, elastic modulus and elastic part of indentation work. The change of the Na2O/Al2O3 ratio resulted in increasing HMV and Hit up to 11 mol% Al2O3 and then a slight decrease of the respective parameters was observed.