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Correlation between microstructural and mechanical behavior of nanostructured MgH2 upon hydrogen cycling

Abstract : Reversible hydrogen storage in magnesium hydride is the most suitable solution for stationary applications, which require large-scale storage systems with an expected lifetime exceeding 5000 hydrogen cycles. Highly reactive nanostructured powders are produced on a large scale by co-milling of MgH2 with transition metals. These powders present a very stable weight capacity upon cycling. However, the MgH2 grains tend to recrystallize and to induce a progressive swelling of the compacted disks. The purpose of this study was to quantify and understand this irreversible phenomenon, through correlations with microstructural evolutions. In-situ dilatometry measurements were performed on samples prepared with different additives. The irreversible phenomenon increases progressively up to about 50 cycles where a stabilisation is achieved. Granulometry measurements show a bi-modal distribution of the as-milled powders. Upon cycling, we observe the coalescence of the “small” MgH2 particles, which tend to create large agglomerates and results - again after about 50 cycles - in mono-disperse powders. This evolution induces an increase in porosity, which explain the progressive swelling of the composites. The maximum of deformation strongly depends of the additive. A relaxation of the maximum strain is observed after 50 cycles for Vanadium whereas it remains constant for Ti-V-Cr. This could be correlated to the ability of the fine additive particles to prevent the motion of the grain boundaries, then to limit the agglomeration of MgH2 particles.
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https://hal.archives-ouvertes.fr/hal-02000463
Contributor : Patricia de Rango Connect in order to contact the contributor
Submitted on : Wednesday, January 30, 2019 - 3:53:57 PM
Last modification on : Wednesday, October 20, 2021 - 12:58:15 AM

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  • HAL Id : hal-02000463, version 1

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UGA | CNRS | NEEL

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Patricia de Rango, Simeon Nachev, Daniel Fruchart, Nataliya Skryabina, Philippe Marty. Correlation between microstructural and mechanical behavior of nanostructured MgH2 upon hydrogen cycling. International Symposium on Metal Hydrogen Systems (MH2014), Jul 2014, Manchester, United Kingdom. ⟨hal-02000463⟩

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