Microstructure and hydrogen storage properties of Ti10+xV80-xFe6Zr4 (x=0~15) alloys.

The microstructure and hydrogen storage properties of Ti 10+ x V 80- x Fe 6 Zr 4 (x = 0, 5, 10, 15) alloys have been studied. XRD and SEM analyses show that all alloys consist of a BCC main phase and a small fraction of C14 Laves secondary phase, in which the latter precipitates along the grain boundary of the former becoming network structure. With increasing Ti content in the alloy, the lattice parameter and cell volume of the BCC main phase of the alloy increase. The chemical composition of each phase is analysed by EDS, from which the lattice parameters of BCC phase have a good linear relationship with their average atomic radii. All bulk alloys have good activation behaviors and hydriding kinetics. With the increase of Ti content, the incubation time for activation decreases first and then increases under an initial hydrogen pressure of 4 MPa at 298 K. The incubation time of Ti 15 V 75 Fe 6 Zr 4 alloy is only 12 s. It is one of the shortest incubation time in V-based solid solution alloys as far as we know, which may be related to the existence of C14 Laves phase. All the alloys have relatively high hydrogen absorption capacities of above 3 wt%, which increase first and then decrease as the Ti content increases, achieving the maximum capacity of 3.61 wt% at x = 10 at 298 K. With increasing x , the equilibrium plateau pressure of dehydrogenation of the samples at 353 K decreases owing to the expansion of unit cell of main phase, which is far below 0.1 MPa for x = 10 and 15. The maximum desorption capacity of 1.94 wt% (desorbed to 0.001 MPa) is obtained at x = 5, compared to that of 1.6 wt% (desorbed to 0.1 MPa) achieved at x = 0. • Bulk Ti 10+ x V 80- x Fe 6 Zr 4 (x = 0, 5, 10, 15) are directly used into the activation. • The incubation time for activation for Ti 15 V 75 Fe 6 Zr 4 is only 12 s. • The substitution of Ti for V within 10 at.% enhances the absorption capacity. [ABSTRACT FROM AUTHOR]