Effects of Si addition on the microstructure and the hydrogen storage properties of Ti26.5V45Fe8.5Cr20Ce0.5 BCC solid solution alloys

The microstructure and the hydrogen storage properties of Ti-26.5(V0.45Fe0.085)(100-x)Cr20Ce0.5Six. (x=0 and 1) have been investigated by EPMA, XRD, in situ temperature XRD, neutron diffraction and P-C isotherm Si addition results in the precipitation of a TiFe2-type Laves phase and produces chemical heterogeneity in the BCC phase As a consequence, SI-added alloy exhibits a lower hydrogen capacity and both a higher plateau pressure and slope factor as compared to Si-free alloy Si enters in both Laves and BCC phases with a higher preference for the former phase. For both alloys, all metal atoms (Ti, V, Fe and Cr) are supposed to be randomly distributed in the 2a sites of the BCC phase and deuterium atoms occupy the 8c sites on fully charged deuterides Si has no significant influence on the hydrogen occupation Two hydrides are observed during the desorption process for Ti-26.5(V0.45Fe0.085)(100)Cr20Ce0.5 alloy, a hydrogen rich one with distorted FCC structure (space group P4/mmm) and a hydrogen poor one with BCT structure (space group 14/mmm). (C) 2009 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved.