The influence of the partial substitution of iron by aluminium in TiFe on the hydrogen absorption properties was systematically investigated. The pressure-composition isotherms were determined to establish differences in the thermodynamic properties. When aluminium was added to the TiFe compound, the hydrogen storage capacity decreased markedly and the γ phase was not formed. The plateau pressure was sloping and was higher for TiFe0.98Al0.02 and TiFe0.96Al0.04 and lower for TiFe0.94Al0.06 and TiFe0.90Al0.10 than for pure TiFe. These results are explained by the difference between the number of valence electrons present in aluminium and iron. The ΔHo, ΔSo and ΔGo values were obtained from plots of In P versus 1 T using the van't Hoff relation. The hysteresis energy loss decreased with increasing aluminium content.
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