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NMR and X-ray Diffraction Studies of Phases in the Destabilized LiH-Si System

Published online by Cambridge University Press:  01 February 2011

R. C. Bowman Jr
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, U.S.A.
S.-J. Hwang
Affiliation:
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, U.S.A.
C. C. Ahn
Affiliation:
Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, U.S.A.
J. J. Vajo
Affiliation:
HRL Laboratories, LLC, Malibu, CA 90265, U.S.A.
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Abstract

Hydrogen absorption and desorption isotherms have been measured on ballmilled mixtures of LiH+Si powders to evaluate the thermodynamic parameters of these reversible reactions. The phase compositions at the various stages of reaction have been examined by Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) of the 7Li, 1H, and 29Si nuclei and powder x-ray diffraction (XRD). The initial mixtures of LiH and Si were found to convert into known Li-Si silicide intermetallics (i.e., Li12Si7, Li7Si3, and Li13Si4) as well as providing evidence for a previously unknown ternary Li-Si-H phase as hydrogen was first desorbed and then absorbed. While the absorption reactions are reversible over portions of the Li-Si-H composition range, incomplete recovery of the original LiH + Si phases was also observed under some test conditions.

Type
Research Article
Copyright
Copyright © Materials Research Society 2005

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References

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