Advancing our understanding of the effect of Al/Mo substitution in the TiVNb alloy on the hydrogen storage properties
Résumé
The refractory body-centered cubic (bcc) high entropy alloys (HEAs) have shown large hydrogen uptake around 2.0 H/M, but challenges remain, the most important being the high stability of the hydrides, which requires high desorption temperatures. In this work, we reported an efficient hydride destabilization with the addition Al/Mo as non-hydride forming elements in the ternary TiVNb alloy. The alloys in the Alx(TiVNb)1-x-yMoy (x = 0-0.20; y = 0-0.25) system were successfully synthesized with a single-phase bcc structure and decreasing lattice parameters as Al/Mo content increases. Pressurecomposition isotherms curves reveals that the addition of Al/Mo destabilizes the hydride formation, and this could be attributed to multifactorial effects. The hydrogen uptake of the alloys is strongly associated with the amount of Al/Mo in the TiVNb, decreasing less drastically with Mo than with Al. The temperature of the phase transition during desorption strongly decreases with the Al/Mo content, in agreement with thermodynamic destabilization. Therefore, the present results demonstrate that the addition of Al/Mo to refractory HEAs can enhance the design of high-capacity alloys with tunable stability.