Correlation between hydrogen storage properties and structural characteristics in mechanically milled magnesium hydride MgH2

In this work, we clarified the correlation between hydrogen storage and crystallographic properties in nanostructural magnesium hydride MgH2 prepared by mechanical milling under hydrogen gaseous atmosphere. At the early stage within 2 h milling, the amount of desorbed hydrogen decreases #~16% from 7...

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Bibliographic Details
Published in:Journal of alloys and compounds 2004-03, Vol.366 (1-2), p.269-273
Main Authors: HANADA, Nobuko, ICHIKAWA, Takayuki, ORIMO, Shin-Ichi, FUJII, Hironobu
Format: Article
Language:English
Subjects:
Applied sciences
Condensed matter: structure, mechanical and thermal properties
Energy
Energy. Thermal use of fuels
Equations of state, phase equilibria, and phase transitions
Exact sciences and technology
Materials and auxiliary equipments used in energy engineering
Physics
Solubility, segregation, and mixing
phase separation
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Summary:In this work, we clarified the correlation between hydrogen storage and crystallographic properties in nanostructural magnesium hydride MgH2 prepared by mechanical milling under hydrogen gaseous atmosphere. At the early stage within 2 h milling, the amount of desorbed hydrogen decreases #~16% from 7.3 to 6.1 wt.% and the onset temperature of dehydrogenation decreases by 70 K from 670 K, while both the powder size and the crystallite size in powder decrease with increasing the milling time down to 1 *mm and 15 nm, respectively, and the lattice strain of 0.3% is rapidly introduced. At the middle stage with longer milling time than 2 h, however, the crystallite size hardly change, but the lattice strain is once released at 2-5 h milling and again increases for longer milling time than 5 h. On the other hand, the amount of desorbed hydrogen suddenly increases from 2 to 5 h, and again decreases with a little increase of lattice strain during 5-80 h milling. At the final stage, the hydrogen capacity and desorption temperature reach to saturation of, respectively, 6.5 wt.% and 600 K, whereas the crystallite size and lattice strain reach to saturation of #~7 nm and 0.2%, respectively. The results obtained indicate that the reduction of crystallite size as well as the introduction of lattice strain in MgH2 during milling gives rise to the decrease in hydrogen storage capacity.
ISSN:0925-8388
1873-4669
DOI:10.1016/s0925-8388(03)00734-5