Improvement on the kinetic and thermodynamic characteristics of Zr1-xNbxCo (x = 0–0.2) alloys for hydrogen isotope storage and delivery

Abstract

Abstract In order to promote the application of ZrCo alloy in storage and delivery system of hydrogen isotope, Zr1-xNbxCo (x\u202f=\u202f0–0.2) alloys were prepared by induction levitation melting method under argon atmosphere. The effects of Nb substitution for Zr on the microstructure, initial activation behavior, dehydrogenation thermodynamics, disproportionation behavior and cycling stability of Zr1-xNbxCo (x\u202f=\u202f0–0.2) alloys were systematically investigated. The results show that all alloys contain a ZrCo main phase and a little secondary phase of ZrCo2. With the content of Nb increasing, the lattice parameters of ZrCo main phase decrease and the distribution of ZrCo2 secondary phase is more uniform. It is found that the initial activation period is remarkably reduced from 87.79\u202fh for ZrCo to 8.08\u202fh for Zr0.8Nb0.2Co. Meanwhile, the equilibrium pressure of hydrogen desorption is enhanced from 0.197 (x\u202f=\u202f0) to 0.85\u202fbar (x\u202f=\u202f0.2) at 350\u202f°C, which is beneficial to delivery of hydrogen isotope. Further experiments exhibit that the anti-disproportionation performance and cycling stability have been greatly improved after Nb partial substitution, which could be explained by the enlargement of the apparent activation energy from 147.8\u202fkJ/mol (ZrCo) to 182.1\u202fkJ/mol (Zr0.85Nb0.15Co) for disproportionation reaction.