Crystals 2012, 2(2), 159-175; doi:10.3390/cryst2020159
Article

Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites

1 Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Ave. W., N2L 3G1, Waterloo, Ontario, Canada 2 Wroclaw Research Centre EIT+, Stablowicka 147, 54-066 Wroclaw, Poland
* Author to whom correspondence should be addressed.
Received: 13 January 2012; in revised form: 21 February 2012 / Accepted: 22 March 2012 / Published: 2 April 2012
(This article belongs to the Special Issue Hydrogen Storage Alloys)
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Abstract: Hydrogen storage properties of the (nLiAlH4 + LiNH2) hydride composite where n = 1, 3, 11.5 and 30, synthesized by high energy ball milling have been investigated. The composite with the molar ratio n = 1 releases large quantities of H2 (up to ~5 wt.%) during ball milling up to 100–150 min. The quantity of released H2 rapidly decreases for the molar ratio n = 3 and is not observed for n = 11.5 and 30. The XRD studies indicate that the H2 release is a result of a solid state decomposition of LiAlH4 into (1/3)Li3AlH6 + (2/3)Al + H2 and subsequently decomposition of (1/3)Li3AlH6 into LiH + (1/3)Al + 0.5H2. Apparently, LiAlH4 is profoundly destabilized during ball milling by the presence of a large quantity of LiNH2 (37.7 wt.%) in the n = 1 composite. The rate of dehydrogenation at 100–170 °C (at 1 bar H2) is adversely affected by insufficient microstructural refinement, as observed for the n = 1 composite, which was milled for only 2 min to avoid H2 discharge during milling. XRD studies show that isothermal dehydrogenation of (nLiAlH4 + LiNH2) occurs by the same LiAlH4 decomposition reactions as those found during ball milling. The ball milled n = 1 composite stored under Ar at 80 °C slowly discharges large quantities of H2 approaching 3.5 wt.% after 8 days of storage.
Keywords: solid state hydrogen storage; lithium alanate; lithium amide; ball milling; mechanical and thermal dehydrogenation

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MDPI and ACS Style

Varin, R.A.; Zbroniec, L. Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites. Crystals 2012, 2, 159-175.

AMA Style

Varin RA, Zbroniec L. Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites. Crystals. 2012; 2(2):159-175.

Chicago/Turabian Style

Varin, Robert A.; Zbroniec, Leszek. 2012. "Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites." Crystals 2, no. 2: 159-175.

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