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Metallographic and numerical characterization of MgH2-Mg system

Published online by Cambridge University Press:  15 March 2011

Annalisa Aurora
Affiliation:
ENEA - C.R. Casaccia, Via Anguillarese 301, 00123 S. Maria di Galeria (Rome), Italy
Massimo Celino
Affiliation:
ENEA - C.R. Casaccia, Via Anguillarese 301, 00123 S. Maria di Galeria (Rome), Italy
Fabrizio Cleri
Affiliation:
IEMN - CNRS (UMR-8520), Université des Sciences et Technologies de Lille, F-59652 Villeneuve d'Ascq cedex, France
Daniele Mirabile Gattia
Affiliation:
ENEA - C.R. Casaccia, Via Anguillarese 301, 00123 S. Maria di Galeria (Rome), Italy
Simone Giusepponi
Affiliation:
ENEA - C.R. Casaccia, Via Anguillarese 301, 00123 S. Maria di Galeria (Rome), Italy
Amelia Montone
Affiliation:
ENEA - C.R. Casaccia, Via Anguillarese 301, 00123 S. Maria di Galeria (Rome), Italy
Marco Vittori Antisari
Affiliation:
ENEA - C.R. Casaccia, Via Anguillarese 301, 00123 S. Maria di Galeria (Rome), Italy
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Abstract

The remarkable ability of magnesium to store significant quantities of hydrogen has fostered intense research efforts in the last years in view of its future applications where light and safe hydrogen-storage media are needed. Magnesium material, characterized by light weight and low cost of production, can reversibly store about 7.7 wt% hydrogen. However, further research is needed since Mg has a high operation temperature and slow absorption kinetics that prevent the use in practical applications. For these reasons a detailed study of the interface between Mg and MgH2 is needed. Further insights are gained by characterizing the Mg-MgH2 system from both the experimental and the numerical point of view.

The study of the MgH2-Mg phase transformation in powder samples has been performed to gain detailed metallographic information. A method for studying this phase transformation by cross sectional samples scanning electron microscopy observation of partially transformed material has been developed. This method exploits the peculiar features of this system where the MgH2 phase is insulating and the Mg is a metallic conducting phase. This difference can induce a contrast between the two phases owing to the different secondary emission yield. Further insights are gained by characterizing Mg-MgH2 interfaces by means of accurate first-principle molecular dynamics simulations based on the density-functional theory. Extensive electronic structure calculations are used to characterize the equilibrium properties and the behavior of the surfaces in terms of total energy considerations and atomic diffusion.

Type
Research Article
Copyright
Copyright © Materials Research Society 2009

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References

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