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Published October 31, 2007 | public
Journal Article

NMR studies of the aluminum hydride phases and their stabilities

Abstract

Multinuclear and multidimensional solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH_3 samples. At least three distinct polymorphic AlH_3 phases have been prepared by desolvating the alane etherate product from its organometallic synthesis. MAS-NMR spectra for the ^(1)H and ^(27)Al nuclei have been obtained on a variety of AlH_3 samples that include the β- and γ-phases as well as the α-phase. ^(27)Al MAS NMR was found to respond with high sensitivity for showing differences in spatial arrangements of AlH_6 octahedra in the three polymorphs studied. Based on the characteristic NMR signatures determined, phase transition of the γ-AlH_3 to the α-AlH_3 was studied at room and high temperatures. Direct decomposition of the γ-AlH_3 to aluminum metal at room temperature was also unambiguously confirmed by NMR studies.

Additional Information

© 2007 Elsevier. Received 27 October 2006; received in revised form 11 January 2007; accepted 11 January 2007; Available online 28 January 2007. This research was partially performed at the Jet Propulsion Laboratory, which is operated by the California Institute of Technology under contract with the NASA. This work was partially supported by DOE through Award Number DE-AI-01-05EE11105. The NMR facility at Caltech was supported by the National Science Foundation (NSF) under Grant Number 9724240 and partially supported by the MRSEC Program of the NSF under Award Number DMR-0080065. This work was supported at BNL by the DOE under contract DEA-AC0298CH100886. Financial support received from the Office of Hydrogen, Fuel Cells and Infrastructure Technologies of US Department of Energy is gratefully acknowledged. We thank J.G. Kulleck (JPL) for his X-ray diffraction measurements and Dr. X. Tang from the United Technologies Research Center for providing the Russian made α-AlH3 material labeled UTRC. Finally, the authors are very grateful to Drs. H. Brinks and V.A. Yartys for providing their detailed crystal structure results to us prior to publication.

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023