Faculty of Technology and Metallurgy

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Start date: 2000End date: 2009

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    Raman spectra of anodized valve metal electrodes
    (First Regional Symposium on Electrochemistry of South-East Europe, 2008)
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    Arsov, Ljubomir
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    Optical properties of electrochemically polished and anodized niobium surfaces
    (First Regional Symposium on Electrochemistry of South-East Europe, 2008)
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    Electrochemical passivation of niobium in KOH solutions
    (CROATIAN CHEMICAL SOC, 2006-12)
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    Prusi, Abdurauf
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    Grcev, Toma
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    Arsov, Ljubomir
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    Electrochemical characterization of the passive films formed on niobium surfaces in H2SO4 solutions
    (National Library of Serbia, 2006)
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    Prusi, Abdurauf
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    Grcev, Toma
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    Arsov, Ljubomir
    The electrochemical formation and characteristics of passive films on niobium surfaces in aqueous H2SO4 solutions were studied using open circuit potential and cyclic voltammetry. In the potential region between -1.0 and 1.2 V(NHE), the cyclic voltammetry data showed that the active/passive transition involves slow metal dissolution followed by the formation of semiconducting passive oxide films. The possible electrochemical reactions and the change of the oxidation steps of some niobium oxides occurring in the passive film during the polarization are proposed. A strong influence of the natural air-formed oxide film on the chemical composition of the passive film was shown. This influence makes chemical structure of thin passive films more complicated than that of thick anodic films. It is shown that the passive films consists of more or less stable oxides, such as NbO, NbO2 and Nb2O5. The Raman spectra revealed that the thin passive films were amorphous, while the films formed at higher voltages consist, primarily, of well-crystallized Nb2O5.
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    Active/Passive Transition of Niobium in Strong Acid and Alkaline Solutions
    (Sociedade Portuguesa de Electroquímica, 2006)
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    Abdurauf, Prusi
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    Grcev, Toma
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    Arsov,Ljubomir
    By cyclic voltammetry the active/passive transition of Nb electrode has been investigated in concentration range from 0.1 M to 10 M aqueous solutions of H2SO4 and KOH. Results indicate the strong influence of the concentration and electrolyte nature to the active/passive transitions and stability of passive films. Depending on electrolyte concentrations, at potential of 1 V the calculated thickness of passive films varied from 2.2 nm to 3.2 nm. For the same concentrations of H2SO4 and KOH the formed passive films in KOH are thicker than in H2SO4. By multiple cycle sequences in which the final anodic potential is gradually enlarged, the barrier properties of passive films on Nb electrode were confirmed. In the first positive scan after the active/passive transition, no cathodic or reactivation peaks for both 1 M H2SO4 and KOH were observed. Only for higher concentrations of KOH (> 2 M) the small reactivation process was recorded. In concentration of 5 M and 10 M KOH, if after the passive film formation the Nb electrodes were maintained for 15 min at cathodic potential of -1.55 (SHE), the cyclic voltammograms indicated the complete dissolution of passive films. The voltammetric data have confirmed that the Nb electrode is more resistant in concentrated H2SO4 than in concentrated KOH solutions.
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    Thin Layers of Polyaniline/TiO2 Nano-particles Using Electrochemical Deposition
    (World Scientific and Engineering Academy and Society Press, 2007)
    Arsov, Martin
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    Arsov, Ljubomir
    By cycling voltammetry the thin layers of polyaniline on mechanically polished Nb electrode from sulfuric aqueous solutions with aniline added were deposited. During the repetitive voltammetric scans, by simultaneous in-situ Raman spectroscopical measurements, the redox reactions and formation of degradation production in polymer film were investigated. It was found that the new monitored voltammetric waves appear only when the polyaniline reaches an over-oxidized state. The comparative measurements on Pt electrode in sulfuric aqueous solutions with aniline and TiO2 nano-particles added were also performed. It was shown that the TiO2 nano-particles inhibits the formation of degradation products.
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    Electrochemical formation of semi-conducting oxides for solar energy conversion
    (WORLD SCIENTIFIC AND ENGINEERING ACAD AND SOC, 2007)
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    Prusi, Abdurauf
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    Arsov, Ljubomir
    The formation of anodic oxide films on Nb electrodes in 1 M H2SO4 and 1 M KOH, for potential region from 0 to 90 V SCE, have been investigated. The film thickness growth, refractive indices and dielectric constants of formed films, depending of applied potential and time of anodization, have been determined using ellipsometric method. By Raman spectroscopical measurements the amorphous structure of anodic oxide films, up to 10 V SCE and progressive evolution of crystallization from 10 to 90 V has been shown. The semi-conducting properties (n or p tip semi-conductor, energy gap and flat bend potentials) has been determined using photocurrent measurements.
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    Barrier Properties of Anodically Formed Nb2O5
    (Faculty of Technology and Metallurgy Belgrade, Serbia and Montenegro, 2005)
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    Prusi, Abdurauf
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    Ellipsometric Investigation of Anodic ZrO2 Films Formed in H3PO4
    (Faculty of Technology and Metallurgy Belgrade, Serbia and Montenegro, 2005-09)
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    Arsov, Ljubomir
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    Electrochemical formation of anodic oxide films on Nb surfaces: ellipsometric and Raman spectroscopical studies
    (SPRINGER, 2007-02)
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    Arsov, Ljubomir
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    Hebestreit, Niels
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    Anders, Andreas
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    Plieth, Waldfried
    Electrochemical formation of anodic oxide films on niobium (Nb) surfaces in 1 M H2SO4 solutions was studied using ellipsometry and Raman spectroscopy. By in situ ellipsometric measurements, the coefficient of film thickness growth and the complex index of refraction of anodic oxide films in the voltage range between 0 and 100 V were determined. The Raman spectra reveal that the thin passive films are amorphous. In the beginning of crystallization, the anodic oxide films consist of mixtures of NbO2 and Nb2O5, while NbO2 is completely transformed to Nb2O5 for thicker and well-crystallized films.