SYNTHESIS AND PROPERTIES OF USEFUL METAL HYDRIDES

Publisher Summary This chapter discusses the synthesis and properties of useful metal hydrides. The properties of intermetallic hydrides have found to be of interest for convenient and economic storage of hydrogen. It is rather difficult to predict a priori whether an intermetallic compound will react with hydrogen or as to which reaction path will be followed and what products will form. However, some empirical predictive theories have been developed, of which the most notable is the theory of reversed stability. This theory has been quite useful in systems involving AB5 alloys, but it has enjoyed only limited success in those involving first row transition intermetallic compounds. It is found, however, that intermetallic-hydrogen systems, without exception, will obey three rather simple rules: (1) in order for an intermetallic compound to react directly and reversibly with hydrogen to form a distinct hydride phase, it is necessary that at least one of the metal components be capable of reacting directly and reversibly with hydrogen to form a stable binary hydride, (2) if a reaction takes place at a temperature at which the metal atoms are mobile, the system will assume its most favored thermodynamic configuration, and (3) if the metal atoms are not mobile, only hydride phases can result that are structurally very similar to the starting intermetallic compound.