Hydrogen absorption properties of Ti–V–Fe alloys: Effect of Cr substitution

Hydrogen absorption properties of Ti1-xVFexTi1-xVFex (x=0.0,0.1,0.15,0.2x=0.0,0.1,0.15,0.2 and 0.4) alloys have been investigated in detail. The samples have been characterized by X-ray diffraction and pressure-composition isotherms are studied at different temperatures. With increasing Fe content the hydrogen storage capacity of the Ti–V–Fe alloys increases up to x=0.15x=0.15 after which it decreases drastically. Among the various Fe substituted alloys studied here, the composition Ti0.85VFe0.15Ti0.85VFe0.15 shows the maximum hydrogen storage capacity of 3.7 wt%. The ease of activation is found to improve with increasing Fe content. Further, the compositions Ti0.85VFe0.15Ti0.85VFe0.15 and Ti0.80VFe0.20Ti0.80VFe0.20 are modified by chromium substitution (60 at%) in place of V in order to see the effect of Cr on the activation performance. We find that the chromium-substituted alloy, Ti0.8V0.4Fe0.2Cr0.6Ti0.8V0.4Fe0.2Cr0.6, absorbs 1.51 wt% hydrogen without any thermal treatment during the activation procedure. Thermal desorption studies on the hydrides as well as deuterides of selected compositions have been carried out to compare the relative stability of the hydrides vis-à-vis the deuterides.