Hydrogen sorption in the LaNi5-xAlx-H system (0 ≤ x ≤ 1) |
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| Affiliation: | 1. Department of Chemistry and NIS, University of Turin, Turin, Italy;2. ICAMS, Ruhr University, Bochum, Germany;1. School of Chemical Engineering, Northwest University, Xi’an 710069, PR China;2. The State Key Laboratory of Chemical Engineering, Dept. of Chemical Engineering, Tsinghua University, Beijing 100084, PR China;3. School of Chemical Engineering and Technology, Xi’an Jiaotong University, Xi’an 710049, PR China;1. Laboratory of Quantum and Statistical Physics, LR18ES18, Monastir University, Faculty of Sciences of Monastir, Tunisia;2. Laboratoire d’Etudes des Systèmes Thermiques et Energétiques (LESTE), ENIM, Route de Kairouan, 5019 Monastir, Tunisia;3. Laboratoire de Physique Appliquée, Faculté des Sciences, Université de Sfax, 3000 Sfax, Tunisia |
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| Abstract: | A thermodynamic assessment of hydrogen sorption in LaNi5-xAlx-H (0 ≤ x ≤ 1) alloys was performed combining experimental and theoretical investigations. The occurrence of sloped plateaux in Pressure Composition Isotherms (PCI) is discussed on the basis of compositional inhomogeneities and of possible re-distribution of metallic elements between the hydrogen rich and the hydrogen poor phases.In order to provide input for the thermodynamic assessment, literature data were reviewed and PCI experiments were performed at increasing temperatures on alloys with different Al contents. The presence of a compositional distribution was investigated using Rietveld refinement of X-Ray diffraction patterns, volumetric and calorimetric measurements, both on as received and annealed samples with LaNi4.8Al0.2 nominal composition. Moreover, ab initio energies of formation for LaNi5, LaAl5 and the respective hydrides were calculated. A full CALPHAD assessment of the Gibbs energy for LaNi5-xAlxHy (0 ≤ x ≤ 1, 0 ≤ y ≤ 7) phase was obtained, showing a good agreement between experimental and calculated results.The presence of sloped and flat plateaux has been related to the occurrence of ortho- and para-equilibrium conditions. |
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| Keywords: | B Hydrides B Hydrogen storage B Thermodynamic properties E Ab-initio calculations |
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