Effect of compositional variations on hydrogen storage in ball-milled Fe-Ti

The hydrogen storage properties of nanocrystalline Fe40Ti60, Fe50Ti50, and amorphous Fe67Ti33 are presented. These materials were prepared by mechanical refinement of the intermetallic compound and by mechanical alloying of pure iron and titanium. Nanocrystalline Fe50Ti50 exhibits a narrower absorption plateau and a lower plateau pressure than coarse-grained FeTi. The non-equilibrium nature of ball milling allows the formation of metastable cubic Fe40Ti60 whose plateau pressure is decreased further. Amorphous Fe67Ti33 also absorbs hydrogen, unlike the Fe2Ti compound. Its storage behavior is typical of amorphous systems. The changes in storage properties induced by the crystallite size reduction and the compositional variations are analyzed in light of available models of the elastic interaction in hydrogen-metal systems.