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
   233   234   235   236   237   238   239   240   241   242   243