Page 238 - Academic Press Encyclopedia of Physical Science and Technology 3rd InOrganic Chemistry
P. 238
P1: FJU/FFV P2: FJU Final Pages Qu: 00, 00, 00, 00
Encyclopedia of Physical Science and Technology EN009A-426 July 6, 2001 20:44
Metal Hydrides
Holger Kohlmann
University of Geneva
I. Introduction
II. Preparation and Characterization
III. Crystal Structures and Properties
IV. Applications
V. Conclusion and Outlook
GLOSSARY Solid solution Homogeneous solid phase with variable
composition, e.g., Cu 1−x Au x , also called mixed crys-
Alloy Mixture of metals, intermetallic compounds and/or tal. In general boundary phases have isotypical crystal
nonmetals. structures, similar atomic radii, electronegativity, and
Cu type Crystal structure isotypic to Cu, space group Fm valence electron concentration.
3m,Cuin4a 0, 0, 0; in the literature also called fcc W type Crystal structure isotypic to W, space group Im
(face centered cubic) or ccp (cubic closest packed). 3m, W in 2a 0, 0, 0; in the literature also called bcc
M Metallic element. (body centered cubic).
Metal deuteride Metal hydride containing hydrogen in
an isotopic purity >99% D.
Metal hydride Chemical compound of one or more met- HYDROGEN reacts with most of the metals to form
als with hydrogen (H); generally H consists of the chemical compounds—metal hydrides. Their properties,
1
natural isotopic mixture of 99.985% H (protium) + crystal structures and chemical bonding cover a wide
2
0.015% H (deuterium, D); the term metal hydride is range, including features of typical ionic, covalent, metal-
also used as a collective name for hydrogen compounds lic and complex compounds. Metal hydrides are particu-
of all isotopes, i.e., protides, deuterides, and tritides. larly useful for reversible storage of hydrogen in applica-
Mg type Crystal structure isotypic to Mg, space group tions as an energy carrier.
P6 3 /mmc,Mgin2c 1/3, 2/3, 1/4; in the literature
also called hcp (hexagonal closest packed). I. INTRODUCTION
Intermetallic compound Chemical compound from two
or more different metals with a stoichiometric or close The first report on the reaction of hydrogen with a metal
tostoichiometriccompositionandingeneralanordered dates from 1866, when Graham observed the absorption
crystal structure. of hydrogen by palladium up to 935 times its own volume.
441