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Contribution à l'étude des propriétés thermodynamiques et électroniques d'hydrures de composés de Haucke substitués

Abstract : This manuscript presents a combined experimental and theoretical contribution to the study of the substituted Haucke phase AB5. These compounds can reversibly absorb hydrogen under conditions of pressure and temperature satisfactory for many technological applications including hydrogen storage.

The thermodynamic characterization of the solid-gas reaction was carried out for mono and polysubstituted compounds. In the respect of good conditions of growth (decomposition) of the hydride phase, we sought to determine the thermodynamic trajectories allowed during some various transformations. The experimental results showed that the rate of transformation and the hierarchy of the return-points memory are the only parameters allowing to draw a general law related to the irreversible character of hysteresis. These systems evolve in "static" mode, independent of the time and whatever the nature of host materials.

Moreover, the effect of substitution elements on electronic properties has been studied using ab initio band structure calculations for the ANi5 (A=La, Y, Ca) and LaNi5-xMx compounds, where M is an element of the type s-p (Al, Si, Ge, Sn), of type s (Cu), or a transition metal (Mn, Fe, Co). While dissociating the structural effects, the role of the chemical interaction with hydrogen was analyzed. These results made it possible to identify the factors which control the stability of the hydrides and their maximum absorption capacity. The bulk moduli of these materials were calculated and their variation was discussed in relation to the properties of hydrogen absorption..
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https://tel.archives-ouvertes.fr/tel-00010686
Contributor : Jean-Claude Crivello <>
Submitted on : Wednesday, October 19, 2005 - 11:24:56 AM
Last modification on : Tuesday, October 22, 2019 - 5:02:10 PM
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Jean-Claude Crivello. Contribution à l'étude des propriétés thermodynamiques et électroniques d'hydrures de composés de Haucke substitués. Matériaux. Université Paris Sud - Paris XI, 2005. Français. ⟨tel-00010686⟩

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