Hydriding Reaction of L a N i 5 : Correlations between Thermodynamic States and Sorption Kinetics during ActivationReport as inadecuate




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Research Letters in Physical ChemistryVolume 2008 2008, Article ID 346545, 4 pages

Research Letter

Institut de Chimie Moléculaire et des Matériaux, CNRS UMR 8182, Université Paris Sud, 15 rue Georges Clémenceau, 91405 Orsay Cedex, France

Laboratoire d'Electrochimie et de Physicochimie des Matériaux et des Interfaces, CNRS UMR 5631-INPG-UJF, ENSEEG, 1130 rue de la piscine, 38402 Saint Martin d'Hères, France

Received 25 October 2007; Accepted 11 March 2008

Academic Editor: Vasudevanpillai Biju

Copyright © 2008 P. Millet et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This research work concerns the hydriding reaction of L a N i 5 during the first hydriding cycles activation process. Step-by-step sorption isotherms Δ H - M ≈ 0 . 0 3 were measured at 298 K, in the composition range 0 < H - M < 2 . 0 , at the beginning first hydriding cycle, where hysteresis is maximum and at the end tenth hydriding cycle, where hysteresis is minimum of the activation process, offering the possibility to correlate thermodynamic states pressure-composition data points to sorption kinetics. Using pneumatochemical impedance spectroscopy PIS, experimental impedance diagrams were obtained for each data point of the isotherms. Microscopic rate parameters such as surface resistance and hydrogen diffusion coefficient were obtained as a function of composition, by fitting appropriate model equations to experimental impedances. It is found that the high-frequency pneumatochemical resistance significantly decreases during activation. This is correlated with the surface increase of the solid-gas interface area. The hydrogen diffusion coefficient is found to be larger at the beginning of the activation process and lower on a fully activated sample.





Author: P. Millet, C. Lebouin, R. Ngameni, A. Ranjbari, and M. Guymont

Source: https://www.hindawi.com/



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