Tuning the hydrogen storage properties of Ti-V-Nb-Cr alloys by controlling the Cr/(TiVNb) ratio
Résumé
This work presents an effective way to tune the thermodynamic properties of hydrogen absorption/desorption of body-centered multicomponent alloys (BCC-MCAs). A twofold 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, thermodynamic modeling was employed to predict the thermodynamics of the metal-hydrogen systems. (TiVNb)100-xCrx alloys with x = 30, 35 and 40 alloys 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 thermodynamics 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. 2 Moreover, it was demonstrated that increasing Cr content up to 35 % significantly impacts the thermodynamic properties, enabling reversible hydrogen absorption/desorption (for H/M ≈ 1) at room temperature.
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