Crystal structure change in the dehydrogenation process of the Li-Mg-N-H system

T. Noritake; M. Aoki; M. Matsumoto; K. Miwa; S. Towata; H. W. Li; S. Orimo

doi:10.1016/j.jallcom.2011.04.079

Crystal structure change in the dehydrogenation process of the Li-Mg-N-H system

T. Noritake, M. Aoki, M. Matsumoto, K. Miwa, S. Towata, H. W. Li, S. Orimo

Advanced Institute for Materials Research (AIMR)

Research output: Contribution to journal › Article › peer-review

7 Citations (Scopus)

Abstract

The Li-Mg-N-H system has the property of reversible reaction with hydrogen between hydrogenation and dehydrogenation (Mg₃N₂ + 4Li₃N + 12H₂ ↔ 3Mg(NH₂)₂ + 12LiH). At the several dehydrogenation stages of p-c isotherm measurement at 523 K, the structural change was investigated using the synchrotron X-ray diffraction. There are two regions in p-c isotherm of the Li-Mg-N-H system, i.e. plateau and sloping region. In the plateau region, Mg(NH₂) ₂ and Li₃Mg₃(NH₂)(NH)₄ coexist. In the sloping region, the intermediate phase Li_3+3yMg ₃(NH₂)_1-y(NH)_4+2y changes continuously from Li₃Mg₃(NH₂)(NH)₄ to Li₂Mg(NH)₂. The chemical composition of the intermediate phase was estimated from the amount of desorbed hydrogen by p-c isotherm and the atomic ratio of Mg and N by Rietveld analysis. The crystal structure of the intermediate phase, Li_3+3yMg₃(NH ₂)_1-y(NH)_4+2y (space group: I222), was determined. Because all these intermediate structures are similar to anti-CaF₂-type, it is deduced that the dehydrogenation process are caused by the diffusion of Li⁺ to cation sites of Mg(NH ₂)₂. The analysis of structural change clarified the dehydrogenation process that is accomplished by the diffusion of Li⁺ and Mg²⁺ without N atom diffusion.

Original language	English
Pages (from-to)	7553-7558
Number of pages	6
Journal	Journal of Alloys and Compounds
Volume	509
Issue number	28
DOIs	https://doi.org/10.1016/j.jallcom.2011.04.079
Publication status	Published - 2011 Jun 1

Keywords

Complex hydride
Hydrogen storage materials
Synchrotron radiation
X-ray diffraction

ASJC Scopus subject areas

Mechanics of Materials
Mechanical Engineering
Metals and Alloys
Materials Chemistry

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@article{b9d9e507022a4f03bb7c50446e480be7,

title = "Crystal structure change in the dehydrogenation process of the Li-Mg-N-H system",

abstract = "The Li-Mg-N-H system has the property of reversible reaction with hydrogen between hydrogenation and dehydrogenation (Mg3N2 + 4Li3N + 12H2 ↔ 3Mg(NH2)2 + 12LiH). At the several dehydrogenation stages of p-c isotherm measurement at 523 K, the structural change was investigated using the synchrotron X-ray diffraction. There are two regions in p-c isotherm of the Li-Mg-N-H system, i.e. plateau and sloping region. In the plateau region, Mg(NH2) 2 and Li3Mg3(NH2)(NH)4 coexist. In the sloping region, the intermediate phase Li3+3yMg 3(NH2)1-y(NH)4+2y changes continuously from Li3Mg3(NH2)(NH)4 to Li2Mg(NH)2. The chemical composition of the intermediate phase was estimated from the amount of desorbed hydrogen by p-c isotherm and the atomic ratio of Mg and N by Rietveld analysis. The crystal structure of the intermediate phase, Li3+3yMg3(NH 2)1-y(NH)4+2y (space group: I222), was determined. Because all these intermediate structures are similar to anti-CaF2-type, it is deduced that the dehydrogenation process are caused by the diffusion of Li+ to cation sites of Mg(NH 2)2. The analysis of structural change clarified the dehydrogenation process that is accomplished by the diffusion of Li+ and Mg2+ without N atom diffusion.",

keywords = "Complex hydride, Hydrogen storage materials, Synchrotron radiation, X-ray diffraction",

author = "T. Noritake and M. Aoki and M. Matsumoto and K. Miwa and S. Towata and Li, {H. W.} and S. Orimo",

year = "2011",

month = jun,

day = "1",

doi = "10.1016/j.jallcom.2011.04.079",

language = "English",

volume = "509",

pages = "7553--7558",

journal = "Journal of Alloys and Compounds",

issn = "0925-8388",

publisher = "Elsevier BV",

number = "28",

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TY - JOUR

T1 - Crystal structure change in the dehydrogenation process of the Li-Mg-N-H system

AU - Noritake, T.

AU - Aoki, M.

AU - Matsumoto, M.

AU - Miwa, K.

AU - Towata, S.

AU - Li, H. W.

AU - Orimo, S.

PY - 2011/6/1

Y1 - 2011/6/1

N2 - The Li-Mg-N-H system has the property of reversible reaction with hydrogen between hydrogenation and dehydrogenation (Mg3N2 + 4Li3N + 12H2 ↔ 3Mg(NH2)2 + 12LiH). At the several dehydrogenation stages of p-c isotherm measurement at 523 K, the structural change was investigated using the synchrotron X-ray diffraction. There are two regions in p-c isotherm of the Li-Mg-N-H system, i.e. plateau and sloping region. In the plateau region, Mg(NH2) 2 and Li3Mg3(NH2)(NH)4 coexist. In the sloping region, the intermediate phase Li3+3yMg 3(NH2)1-y(NH)4+2y changes continuously from Li3Mg3(NH2)(NH)4 to Li2Mg(NH)2. The chemical composition of the intermediate phase was estimated from the amount of desorbed hydrogen by p-c isotherm and the atomic ratio of Mg and N by Rietveld analysis. The crystal structure of the intermediate phase, Li3+3yMg3(NH 2)1-y(NH)4+2y (space group: I222), was determined. Because all these intermediate structures are similar to anti-CaF2-type, it is deduced that the dehydrogenation process are caused by the diffusion of Li+ to cation sites of Mg(NH 2)2. The analysis of structural change clarified the dehydrogenation process that is accomplished by the diffusion of Li+ and Mg2+ without N atom diffusion.

AB - The Li-Mg-N-H system has the property of reversible reaction with hydrogen between hydrogenation and dehydrogenation (Mg3N2 + 4Li3N + 12H2 ↔ 3Mg(NH2)2 + 12LiH). At the several dehydrogenation stages of p-c isotherm measurement at 523 K, the structural change was investigated using the synchrotron X-ray diffraction. There are two regions in p-c isotherm of the Li-Mg-N-H system, i.e. plateau and sloping region. In the plateau region, Mg(NH2) 2 and Li3Mg3(NH2)(NH)4 coexist. In the sloping region, the intermediate phase Li3+3yMg 3(NH2)1-y(NH)4+2y changes continuously from Li3Mg3(NH2)(NH)4 to Li2Mg(NH)2. The chemical composition of the intermediate phase was estimated from the amount of desorbed hydrogen by p-c isotherm and the atomic ratio of Mg and N by Rietveld analysis. The crystal structure of the intermediate phase, Li3+3yMg3(NH 2)1-y(NH)4+2y (space group: I222), was determined. Because all these intermediate structures are similar to anti-CaF2-type, it is deduced that the dehydrogenation process are caused by the diffusion of Li+ to cation sites of Mg(NH 2)2. The analysis of structural change clarified the dehydrogenation process that is accomplished by the diffusion of Li+ and Mg2+ without N atom diffusion.

KW - Complex hydride

KW - Hydrogen storage materials

KW - Synchrotron radiation

KW - X-ray diffraction

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U2 - 10.1016/j.jallcom.2011.04.079

DO - 10.1016/j.jallcom.2011.04.079

M3 - Article

AN - SCOPUS:79958191486

VL - 509

SP - 7553

EP - 7558

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

SN - 0925-8388

IS - 28

ER -