Effects of Co addition on the microstructure and the hydrogen absorption properties of Zr–V–Fe-based alloys

Abstract

This work investigates the influence of minute additions of cobalt (Co) on the hydrogen absorption characteristics, phase composition, binding energy, and adsorption energy of the Zr₇₀V_24.6Fe_5.4−xCo_x (wt%) (x = 0 ~ 2.0) alloys. The research revealed that the Zr₇₀V_24.6Fe_4.4Co_1.0 alloy exhibits the peak hydrogen absorption capacity. In comparison with the Zr₇₀V_24.6Fe_5.4 (wt%) alloy, the hydrogen absorption properties increase from 80196.34 Pa cm³ g⁻¹ (x = 0) to 133364.79 Pa cm³ g⁻¹ (x = 1.0 wt%), representing a 66.30% improvement in performance. The enhancements in performance can be attributed to: an increase in lattice volume due to the addition of Co, which promotes the diffusion of hydrogen atoms within the lattice; a phase transition of the AB₂ phase from Zr(V_0.75Fe_0.25)₂ to Zr(V_0.91Co_0.09)₂, and a significant decrease in the binding energy of Zr from 182.99 eV (x = 0) to 182.30 eV (x = 1.0 wt%), V in the alloy from 530.91 eV (x = 0) to 530.35 eV (x = 1.0 wt%), thereby enhancing the alloy’s reactivity; according to the density functional theory calculations, the weighted adsorption energy of the alloy for H₂ is increased from 35.11 to 38.14 eV. These research findings offer valuable guidance for the development of getters, and besides, expected to help promote further application of getters in high-tech fields such as military and medical.