Vanadium-based BCC alloys: phase-structural characteristics and hydrogen sorption properties

This work was focused on the studies of vanadium-based “low-temperature” bcc alloys as H storage materials. Both as cast and annealed at 1100 ° C quaternary alloys V92.5−x−yZr7.5Ti7.5+x−yMy (M = Cr, Mn, Fe, Co, Ni; x=0, 10; y=0, 7.5) were studied. They were characterised by XRD, PCT hydrogen absorption–desorption measurements (T=30 –120 ° C) and thermal desorption spectroscopy studies of H desorption from the saturated hydrides (T=−100to800° C). The thermodynamics of the VH∼2↔ VH∼1 transition and hydrogen sorption capacities (1.55,…,1.80 H/M) were found to be significantly influenced by the substituting M-element. The reversible hydrogen storage capacity (T<100° C, P>0.1 bar) reaches 50–60% of its overall value. Complete hydrogen desorption proceeds in vacuum at T<300° C. The major future challenge of the work is in increasing of the easy-reversible part of the H storage capacity corresponding to transformation VH∼2↔ VH∼1 by reducing the content of H in the monohydride.