Effect of addition of rare earth element La on the hydrogen storage properties of TiFe alloy synthesized by mechanical alloying

In this paper, we report the effect of adding the rare earth element lanthanum on the hydrogen storage properties of TiFe synthesized by mechanical alloying (MA). A remarkable improvement was observed in the first hydrogenation (activation) of La-added TiFe. Milling led to the refinement of the crystallite size of the TiFe alloy leading to nanocrystallinity. The formation of a stable hydride phase LaH3 facilitated heterogeneous nucleation and acted as a gateway for the hydrogenation of the TiFe phase. No change in thermodynamics was observed for the rare earth-added TiFe compared to pure TiFe reported in the literature. The microstructure revealed a uniform distribution of the elements. However, La was completely immiscible with the TiFe alloy-a conclusion drawn from the thermodynamics study of the sample. Also investigated was pure TiFe synthesized by MA and arc melting to compare these two synthesis methods.