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Dry mechanochemical synthesis of alane from LiH and AlCl3

TitleDry mechanochemical synthesis of alane from LiH and AlCl3
Publication TypeJournal Article
Year of Publication2014
AuthorsHlova, IZ, Gupta, S, Goldston, JF, Kobayashi, T, Pruski, M, Pecharsky, VK
JournalFaraday Discussions
Volume170
Pagination137-153
Date Published12
Type of ArticleArticle
ISBN Number1359-6640
Accession NumberWOS:000345208300010
Keywordsalh3, aluminum-hydride, complex metal-hydrides, lialh4, sodium, thermal-decomposition, transformations
Abstract

wder X-ray diffraction, solid-state Al-27 NMR spectroscopy, and temperature programmed desorption analysis of the as-milled mixtures. We show that excess LiH in the starting mixture (with an optimal ratio of 9LiH : 1AlCl(3)) is essential for the formation and stability of Al-H bonds, initially in the form of alanates and, eventually, as alane. Further processing of this mixture, gradually adding AlCl3 to reach the ideal 3LiH : 1AlCl(3) stoichiometry, appears to restrict the local accumulation of AlCl3 during the ball-milling process, thereby preventing the formation of unstable intermediates that decompose to metallic Al and molecular hydrogen. We also demonstrate that under the milling conditions used, a moderate hydrogen pressure of ca. 300 bar is required to suppress competing reactions that lead to the formation of metallic Al at room temperature. The identification of the reaction intermediates at each stage of the synthesis provides significant insight into the mechanism of this solid-state reaction, which may potentially afford a more rational approach toward the production of AlH3 in a simple solvent-free process.

DOI10.1039/c3fd00161j
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Complex Hydrides