Tunis, Tunisia
Tunis, Tunisia

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Boussami S.,LMMP | Khaldi C.,LMMP | Lamloumi J.,LMMP | Mathlouthi H.,LMMP | And 2 more authors.
Journal of Physics and Chemistry of Solids | Year: 2013

The electrochemical impedance responses of the LaY2Ni 9 alloy electrode after activation at different states of charge (SOC), immersion time in 7 M KOH and room temperature was studied. Electrochemical impedance spectrum of the metal hydride electrode obtained was interpreted by an equivalent circuit modeling including the different electrochemical processes taking place on the interface between the MH electrode and the electrolyte. The results indicate that the electrochemical reaction activity of hydride electrode was markedly enhanced with increasing state of charge. The hydrogen diffuses in the bulk of the alloy and this process is not the limiting step for the hydrogen absorption. During a long immersion time a continuous nanocrystalline corrosion scale appears and the modification of passive film toward more organized structure is concluded. © 2013 Elsevier Ltd.

Boussami S.,LMMP | Khaldi C.,LMMP | Lamloumi J.,LMMP | Mathlouthi H.,LMMP | Takenouti H.,University Pierre and Marie Curie
Electrochimica Acta | Year: 2012

Cobalt-free AB5-type hydrogen storage alloys have been examined for the purpose of lowering metal hydride raw material costs. For this purpose, the electrochemical behaviour of cobalt-free LaNi 3.55Mn 0.4Al 0.3Fe 0.75 alloy was investigated using chronopotentiometry and electrochemical impedance spectroscopy. It was shown that the discharge capacity decreases by 50% after fifty cycles. To investigate the capacity decrease, the impedance measurements were conducted during charging at different stages of life cycle. The experimental impedance spectroscopy reveals that the metal hydride electrode exhibits a porous behaviour. The results were then analyzed on the basis of equivalent circuit model involving the porous electrode behaviour according to de Levie's model, i.e. equivalent cylindrical pores connected in parallel. The pore texture of electrode material was then estimated namely by the pore number, mean values of cylinder radius and effective length. The loss of discharge capacity is due to that of the reactivity of the electrode material and not the collapsing of pore texture. © 2012 Elsevier Ltd.

Rousse D.R.,École de Technologie Supérieure of Montreal | Asllanaj F.,University of Lorraine | Salah N.B.,LMMP | Lassue S.,University of Artois
Numerical Heat Transfer, Part B: Fundamentals | Year: 2011

This article presents selected problems used to assess the validity and usefulness of a first-order skew, positive coefficient, upwind scheme (SPCUS) applied to radiative transfer. This particular procedure could be incorporated in several discretization methods such as finite-volume, finite-element, or control-volume finite-element methods for the prediction of radiative transfer in participating media. The suggested scheme has been validated by application to several basic two-dimensional test problems, acknowledged by the radiative heat transfer community, and its performance has proven to be good. 2011 02 03. Copyright © Taylor & Francis Group, LLC.

Sidhom N.,LMMP | Sidhom H.,LMMP | Braham C.,CNRS Process and Engineering in Mechanics and Materials Laboratory | Ledion J.,CNRS Process and Engineering in Mechanics and Materials Laboratory
Materials Science Forum | Year: 2011

Mechanical brushing of machined AA5083H11 surface, performed in optimized conditions of brush wire hammering, generates distributions of compressive residual stresses. These distributions are controlled by the process parameters such as the pressure of the brush wires on the surface, the speed of rotation or the number of passes. X-ray diffraction (XRD) measurements relative to different surface preparations show that the stresses due to brushing are less deep and that the maximal values in compression are the same as the ones from shallow shot-peening treatment (without defects). Moreover, the bushing provides high quality surface at a microscopic scale (low roughness) and integrity state of the treated surfaces, better for cyclic stability of compressive stresses. The stabilized state of residual stresses resulting from brushing and shot-peening is determined by finite element analysis. These analyses are experimentally validated by XRD using the psi-tilt method on tested fatigue specimens. Fatigue results show that the good surface topography generated by the wire brushing process compensates the reduction of the amplitude and the depth of the compressive residual stress profiles compared to shot-peening so that it could provide an equivalent fatigue improvement rate (20 to 30% of σ D 2.10 6 cycles) of the AA5083H11.

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