Faculty of Technology and Metallurgy
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Item type:Publication, Active/Passive Transition of Niobium in Strong Acid and Alkaline Solutions(Sociedade Portuguesa de Electroquímica, 2006); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Thin Layers of Polyaniline/TiO2 Nano-particles Using Electrochemical Deposition(World Scientific and Engineering Academy and Society Press, 2007); Arsov, LjubomirBy 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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Electrochemical behavior of tantalum in potassium hydroxide solutions(International Association of Physical Chemists (IAPC), 2018-08-31)The electrochemical behavior of tantalum in various concentrations of KOH solutions (0.1 M -10 M), was investigated using the evolution of the open circuit potentialin time, cyclic voltammetry and ellipsometricmeasurements. Depending on KOH concentrations, the open circuit potential measurements have shown three distinct behaviors concerning oxide film formation on the electrode surface and its dissolution. The cyclic voltammetry measurements were performed in various potential ranges, from -1.4 to 8 V, different concentrations of KOH solutions (0.110 M) and sweep rates ranging from 0.005 V/s to 1 V/s. In the passive region, very stable passive films were formed, which reduction has not been possible during cathodic polarization even at highly concentrated KOH solutions. In the trans-passive region, the very strong peak at 1.65 V was monitored, which nature and chemical composition is still not well known. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Active/Passive Transition of Niobium in Strong Acid and Alkaline Solutions(Portugaliae Electrochimica Acta, 2006-05-29)Mickova, Irena; Abdurauf, Prusi; Grcev, Toma; Arsov, LjubomirBy 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.