Browsing by Author "Gegova R."

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    Combustion gel method for synthesis of nanosized ZnO/TiO2 powders
    (2013-05-21) Gegova R.; Dimitriev Y.; Bachvarova-Nedelcheva A.; Iordanova R.; Loukanov A.; Iliev T.
    Nanosized powders in the ZnO-TiO2 system were synthesized by combustion gel method using different precursors: Zn(NO3)2.6H2O, Ti(OC2H5)4 and Ti(OC4H9)4. During the combustion process only one phase, ZnO was obtained. The phase formation and structural transformation at every step of routes for the synthesis were followed by XRD and IR analysis. Our previous investigation in the same system, applying the hydrolytic sol-gel method showed that the type of precursor and the order of adding the components influenced on the microstructure of the final product in the ZnO-TiO2 system, which was proved also in this study. The obtained powders possess photocatalytical activity against organic dye (Malachite green) in the UV and Vis region.
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    Photocatalytic properties of ZnO/TiO2 powders obtained via combustion gel method
    (2013-03-01) Bachvarova-Nedelcheva A.; Iordanova R.; Stoyanova A.; Gegova R.; Dimitriev Y.; Loukanov A.
    The present study is a continuation of our previous investigations on the ZnO-TiO2 system. By applying different sol-gel methods we proved that the type of precursor and the order of adding the components influence the microstructure of the final product. This study focuses on the combustion sol-gel synthesis and photocatalytic properties of nanosized (∼7-20 nm) ZnO-TiO2 powders. The photocatalytic tests were performed toward two model organic dyes, Malachite Green and Reactive Black 5, in the UV and Vis region. For synthesis of ZnO/TiO2 powders, different precursors such as Zn(NO3)2·6H2O, Zn(CH 3COO)2·2H2O, Ti(OC2H 5)4 and Ti(OC4H9)4 were used. During the combustion process various phases (ZnO, TiO2 - anatase and rutile, ZnTiO3) were obtained. The structure and morphology of the resulting particles were characterized by XRD and SEM analysis. All samples exhibited a good photocatalytic activity in both UV and Vis regions. © 2012 Versita Warsaw and Springer-Verlag Wien.
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    Photocatalytic properties of ZnO/TiO2 powders obtained via combustion gel method
    (2013-03-01) Bachvarova-Nedelcheva A.; Iordanova R.; Stoyanova A.; Gegova R.; Dimitriev Y.; Loukanov A.
    The present study is a continuation of our previous investigations on the ZnO-TiO2 system. By applying different sol-gel methods we proved that the type of precursor and the order of adding the components influence the microstructure of the final product. This study focuses on the combustion sol-gel synthesis and photocatalytic properties of nanosized (∼7-20 nm) ZnO-TiO2 powders. The photocatalytic tests were performed toward two model organic dyes, Malachite Green and Reactive Black 5, in the UV and Vis region. For synthesis of ZnO/TiO2 powders, different precursors such as Zn(NO3)2·6H2O, Zn(CH 3COO)2·2H2O, Ti(OC2H 5)4 and Ti(OC4H9)4 were used. During the combustion process various phases (ZnO, TiO2 - anatase and rutile, ZnTiO3) were obtained. The structure and morphology of the resulting particles were characterized by XRD and SEM analysis. All samples exhibited a good photocatalytic activity in both UV and Vis regions. © 2012 Versita Warsaw and Springer-Verlag Wien.
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    Synthesis, structure and optical properties of TiO2/TeO2/MnOm (M = Zn, B) gels: A comparison
    (2015-01-01) Gegova R.; Iordanova R.; Bachvarova-Nedelcheva A.; Dimitriev Y.
    We report in this study the preparation of gels of a nominal composition 50TiO2-25TeO2-25MnOm (M = Zn, B) and our attempt to verify the oxide components behaviour using Ti butoxide, Te (VI) acid, Zn acetate and boric acid as precursors. The phase and structural transformations of the prepared gels upon heat treatment in the temperature range of 200 °C - 700°C are thoroughly studied. The powdered samples still contain organics at 200°C as verified by XRD. Composites containing an amorphous phase along with different crystalline phases (elementary Te, α-TeO2, TiO2 (anatase), ZnTeO3 and TiTe3O8) are formed with temperature increase (above 300°C). The IR results obtained show that the amorphous phases (300 °C - 400°C) of the composite materials consist of TiO6, TeO4, ZnO4, BO3 and BO4 units in different ratio depending on the composition. The UV-Vis spectra of the gels prepared exhibit a red shift of the cut-off compared to pure Ti butoxide gel behavior.