Effect of substitution of titanium by zirconium in TiFe on hydrogenation properties

The influence of partial substitution of titanium by zirconium in the intermetallic compound TiFe on the hydrogenation characteristics was investigated. The compositions of the alloys correspond to the formula Ti^1-xZr_xFe with x = 0, 0.01, 0.04, 0.07, 0.1 and 0.2. X-ray analysis showed that the lattice parameters of the alloys increased with an increase in zirconium content. Activation properties were largely enhanced with an increase in zirconium content. It was found that the absorption of hydrogen by the zirconium-containing compounds reached saturation earlier than in the case of pure TiFe as the absorption-desorption cycle for activation was continued. The pressure-composition isotherms revealed that the thermodynamic properties of the alloys were different. The hydrogen storage capacity was drastically reduced and the γ phase disappeared. The plateau was inclined and the plateau pressure of the zirconium-containing compounds was lower than that of pure TiFe. The ΔH, ΔS, ΔG values were obtained from the plot of In P versus 1 T by the van't Hoff relation. The hysteresis energy loss was nearly constant with varying zirconium content.