Modification of nano-eutectic structure and the relation on hydrogen storage properties: A novel Ti–V–Zr medium entropy alloy.

TiV-based alloys present desirable hydrogen storage properties owing to the formation of Body-centered cubic (BCC) solid solutions. However, the nanostructure that helps hydrogen absorption and desorption is hard to be designed and prepared in these alloys. In this study, Ti 40 Zr 60- x V x (x = 20, 25, 30) alloys with hyperfine nano-eutectic structures of 50–500 nm in lamellar space are prepared, and the nano-eutectic structures can be refined by increasing Zr content. Ti 40 Zr 60- x V x alloy powder exhibits excellent activation and hydrogenation properties. The phase separation and nano-eutectic structure are formed due to the differences of atomic size in Ti 40 Zr 60- x V x alloys. The highest total hydrogenation capacity of 2.4 wt% is obtained within 10 min at 200 °C under 1 MPa H 2 by Ti 40 V 35 Zr 25 alloy, surpassing that of Ti 40 Zr 40 V 20 and Ti 40 Zr 30 V 30 alloys of 2.2 wt% in 20min. Based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, lower energy is required for the hydrogenation of Ti 40 V 35 Zr 25 alloy. Due to the formation of some stable hydrides, the Ti 40 Zr 60- x V x alloys show lower reversible hydrogenation capacities. The spinodal decomposition in Ti 40 V 35 Zr 25 alloy facilitates the formation of reticular eutectics, which provide high-density phase interfaces and produce "synergistic effect". As a result, the hydrogenation kinetic and capacity are enhanced significantly. • Large atomic size differences of the Ti 40 Zr 60- x V x promote nano-eutectic structure. • Novel Ti 40 V 35 Zr 25 alloy form hyperfine nano-eutectic with lamellar space of 50–500 nm and spinodal decomposition structures. • The capacity of 2.4 wt% at 200 °C/1 MPa within 10 min is achieved by Ti 40 V 35 Zr 25 alloy. • The spinodal decomposition promote formation of eutectic phases with excellent hydrogenation absorption property. [ABSTRACT FROM AUTHOR]