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Link visio: https://orsay.bbb.cnrs.fr/b/mar-o8z-dar-0mk
The defence will be in French.
Abstract: Multiple principal element alloys (MPEAs) are an interesting new class of alloys for hydrogen storage. Unlike a conventional alloy in which 1 or 2 elements are added in small quantities to a high-concentration element, here at least 4 elements are mixed in almost equal proportions. Depending on the composition, the increase in mixing entropy can lead to the formation of a single-phase solid solution (mainly cubic or hexagonal in structure). Equilibrium pressure is generally less than 1 bar, which means that the hydride is thermodynamically stable. This low equilibrium pressure is not suitable for storage applications, as the dehydridation reaction requires a significant amount of energy to occur. In order to improve the first equilibrium pressure plateau, new compositions are designed on the basis of the AB type classification, with A a stable hydride-forming element and B an unstable hydride-forming element. This thesis deals with the synthesis, microstructural and structural studies and sorption properties of four-element alloys, mainly transition elements.
