Modification of Nano-Eutectic Structure and the Relation on Hydrogen Storage Properties: A Novel Ti-V-Zr Medium Entropy Alloy

Abstract

TiV-based alloys present desired hydrogen storage properties owing to the formation of BCC solid solutions. However, nanostructure is scarce in these alloys though it can facilitate hydrogen absorption and desorption. In this study, Ti₄₀Zr_60-xV_x (x = 20, 25, 30) alloys are prepared, and hyperfine nano-eutectic structures with lamellar space of 50–500 nm are formed, which can be refined by increasing Zr content. The Ti₄₀Zr_60-xV_x alloys exhibit excellent activation and hydrogenation properties with high hydrogen storage capacities. The atomic size differences in the Ti₄₀Zr_60-xV_x (x = 20, 25, 30) alloys can cause phase separation and nano-eutectic structure. Ti₄₀V₃₅Zr₂₅ alloy achieves the fastest activation rate without incubation period, and the largest hydrogenation capacity of 2.4 wt.% is obtained within 10 min at 200°C under 1 MPa H₂. The spinodal decomposition in Ti₄₀V₃₅Zr₂₅ alloy facilitate the formation of an interconnected net-work eutectic phases, which can provide high-density phase interfaces and play a role of 'synergistic effect'. As a result, the hydrogenation kinetics and capacity are significantly enhanced.

Keywords: Medium entropy alloy, BCC structure, Nano-eutectic phase, Hydrogen storage