Tuning the hydrogen storage properties of Ti-V-Nb-Cr alloys by controlling the Cr/(TiVNb) ratio

Abstract

This work presents an effective way to tune the thermodynamic properties of hydrogen absorption/desorption of body-centered multicomponent alloys (BCC-MCAs). A two-fold computational design was applied to screen the (TiVNb)100−xCrx system. First, the calculation of phase diagrams (CALPHAD) approach was used, aiming to BCC alloys. Secondly, a modeling was employed to predict the thermodynamics of the metal-hydrogen systems. The (TiVNb)100−xCrx alloys with x = 30, 35 and 40 were produced by arc-melting. The (TiVNb)70Cr30 and (TiVNb)65Cr35 alloys crystallize as a major BCC phase, while the (TiVNb)60Cr40 is composed mainly of a C15 Laves-type phase. The CALPHAD approach well predicted this tendency. The BCC (TiVNb)70Cr30 and (TiVNb)65Cr35 alloys absorb a large amount of hydrogen up to 2 H/M forming a dihydride. On the contrary, the (TiVNb)60Cr40 alloy displays a reduced capacity due to the low hydrogen uptake of the C15 phase. The thermodynamic of hydrogen absorption/desorption of BCC-MCAs was experimentally investigated via the acquisition of pressure-composition-temperature (PCT) diagrams. The experimental values are in good agreement with the modeling, confirming the accuracy of the computational approach. Moreover, it was demonstrated that increasing Cr content up to 35 at.% significantly impacts the thermodynamic properties, enabling reversible hydrogen absorption/desorption (for H/M ≈ 1) at room temperature.