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Olu P.-Y.,Joseph Fourier University | Olu P.-Y.,University of Liege | Gilles B.,Science et Ingenierie des MAteriaux et Procede s SIMAP | Job N.,University of Liege | And 2 more authors.
Electrochemistry Communications | Year: 2014

In this study, we show that the platinum electrode preparation procedure influences its behavior towards the borohydride electrooxidation reaction (BOR) mechanism. Cycling a smooth polycrystalline Pt electrode in alkaline electrolyte within the water stability domain prior to the BOR characterization radically changes the shape of the BOR voltammogram obtained in hydrodynamic conditions using the rotating disk electrode (RDE) setup, compared to the "classical" one measured on a smooth polycrystalline Pt electrode just polished before the BOR RDE study. This particular BOR voltammogram is reversibly brought back to the "classical" one after voltammetric cycling in borohydride alkaline media. These changes in the BOR voltammogram highlight the sensitivity of the BOR mechanism towards the Pt surface morphology. A first comparison of the Pt electrode surface before and after the voltammetric cycling in alkaline media using tapping mode atomic force microscopy (AFM) shows no morphological differences between the two surfaces within the AFM observation range, suggesting a very fine atomic structure disordering of the Pt surface. Such strong dependence of the BOR mechanism on Pt regarding the electrode atomic structuring opens the way to future studies focusing on the BOR on well-defined Pt single crystals. © 2014 Elsevier B.V.

Pascal C.,Science et Ingenierie des MAteriaux et Procede s SIMAP | Thomazic A.,Science et Ingenierie des MAteriaux et Procede s SIMAP | Antoni-Zdziobek A.,Science et Ingenierie des MAteriaux et Procede s SIMAP | Chaix J.-M.,Science et Ingenierie des MAteriaux et Procede s SIMAP
Powder Metallurgy | Year: 2012

This study aims at understanding the physicochemical phenomena which take place during pressureless cosintering of Hadfield steel (X120Mn12) and cemented carbide (WC cemented by an Fe rich binder). The experimental approach consists in studying the sintering behaviour of single materials (dimensional changes and weight losses during sintering, microstructure and hardness after sintering) before studying cosintering. Two bimaterial architectures are investigated: one consists of a two layer bimaterial and the other consists of cemented carbide inclusions in steel matrix. For both architectures, when the contact between materials is achieved, a multiphase intermediate layer appears between the two materials. This intermediate layer consists of a M 6C continuous matrix with remaining WC grains at the cemented carbide side and with Fe rich islands at the steel side. M 6C formation is the result of WC dissolution and asymmetric diffusion of W and C in the steel layer. © 2012 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute.

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