Fundamentals and properties of some Ti/Mn based Laves phase hydrides

Abstract For the application in hydrogen powered vehicles, the system of Ti/Mn based Laves phase hydrides has been investigated. Starting from simple empirical rules relating composition, structure and electron density to alloy- and hydride-formation the system has been optimized with respect to the intended use by modification of the components. The resulting alloy is Ti 0.98 Zr 0.02 V 0.43 Fe 0.09 Cr 0.05 Mn 1.5 . This alloy has particularly been investigated concerning different parameters necessary for technical utilization. The capacity loss after 2000 cycles is less than 5%. The sensitivity to the gaseous impurities CO, CO 2 , O 2 , H 2 O, N 2 and CH 4 are examined as well as the corresponding reactivation conditions. The kinetics of hydrogen absorption has been found to be so fast, that for technical application the heat transfer of the hydride bed is the only rate limiting parameter. The fast kinetics may be understood by the high bulk diffusion constant, measured with quasi-elastic neutron spectoscopy: D = 1.8(± 0.8) × 10 −4 (cm 2 s −1 ) exp (− 190 ± 30 meV/ k B T )