• J Datta

      Articles written in Bulletin of Materials Science

    • Influence of Cl, Br, NO$^{−}_{3}$ and SO$^{2−}_{4}$ ions on the corrosion behaviour of 6061 Al alloy

      J Datta C Bhattacharya S Bandyopadhyay

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      The effects of anions like Cl, Br, NO$^{–}_{3}$ and SO$^{2-}_{4}$ on the anodic dissolution of the monolithic Al 6061 alloy have been investigated at neutral pH through immersion testing and electrochemical techniques like potentiodynamic polarization and a.c. impedance spectroscopy. Scanning electron microscopy was employed to characterize the corroded surface and to observe the extent of pitting in different media. From the evaluated corrosion parameters it was found that the dissolution of the matrix was extensively reduced in presence of aqueous solutions containing Br, NO$^{–}_{3}$ and SO$^{2-}_{4}$ ions while Cl ions aggravated corrosion by penetrating into the barrier oxide film on the surface of the material. Pronounced effect of pitting was observed in presence of Cl and the level of pitting in NO$^{–}_{3}$ and Br were mild. In presence of SO$^{2-}_{4}$ ions passivity was extended over a wide potential range and breakdown of passivity occurs when the material was polarized beyond pitting potential. The departure of capacitive behaviour towards resistive behaviour was clearly observed through impedance measurements when investigations were conducted in Cl media and in presence of the other electrolytes. Corrosion rates were, however, controlled during prolonged exposure in the electrolytic media, specially in case of chloride media, due to the predominance of film repair kinetics.

    • A comprehensive study on the effect of Ru addition to Pt electrodes for direct ethanol fuel cell

      J Datta S Singh S Das N R Bandyopadhyay

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      The electro-oxidation of ethanol was studied over nanosized Pt and different compositions of PtRu catalysts synthesized by the borohydride reduction method. Physicochemical characterizations of the catalyst material were made by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDX analysis and transmission electron microscopy (TEM). XRD patterns showed that Ru induces a contraction of the Pt lattice. EDX provided the composition of binary catalysts while TEM images indicated uniform distribution of discrete nanoparticle of the catalysts with narrow range. The electro-catalytic activities of the materials towards ethanol oxidation were investigated through electrochemical techniques, viz. cyclic voltammetry (CV), potentiodynamic polarization, chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) at room temperature. The onset potential of ethanol electro-oxidation is lowered on bimetallic PtRu catalysts compared to that on Pt alone. Of the investigated catalyst compositions the one with the highest electrocatalytic activity was found to be Pt82Ru18. This enhancement towards ethanol oxidation is explained on the basis of a structural effect and modified bi-functional mechanism.

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