Hydrogen Absorption/Desorption Behavior of a Cold-Rolled TiFe Intermetallic Compound

The (de)hydrogenation properties of a TiFe intermetallic compound (IMC) alloy activated by cold rolling inside a glovebox at ambient temperature were investigated by kinetic measurements, x-ray powder diffraction (XRD), and transmission electron microscopy (TEM). Rate-limiting steps were identified by testing kinetic models on hydrogen absorption and desorption curves. To prevent surface poisoning during air exposure, the TiFe IMC was also cold rolled with polytetrafluoroethylene (PTFE) and ultra-high molecular weight polyethylene (UHMWPE). The addition of either PTFE or UHMWPE to nanostructured TiFe by cold rolling did not produce a polymer-metal composite with O2 poisoning resistance, regardless of the polymer-mixing way adopted. This occurred because large surfaces of the particles were not adequately coated with polymer. The results identify challenges to the TiFe IMC polymer-covered material that must be overcome before a methodology can significantly contribute to the formation of nanostructured TiFe-polymer composites with enhanced hydrogen storage properties. The diffusion-controlled reactions in the cold-rolled TiFe IMC without polymer were prevalent in all cases, as predicted by the Jander three-dimensional diffusion model. The main contribution of this work regards estimation of the amount of hydrogen released, which was 0.60% after 6 min and reproducible for the three subsequent cycles.