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

Abstract

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 O 2 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.

Influence of near-surface oxide layers on TiFe hydrogenation: mechanistic insights and implications for hydrogen storage applications

“…The (110) surface forms with the lowest energy and has an area fraction of 57.2%, suggesting that it is the most preferred orientation for the TiFe IMC. This is in agreement with a previous theoretical study, 72 the (110) peak intensification observed in X-ray diffraction (XRD), 16,73,74 and the transmission electron microscopy (TEM) analysis of TiFe lattice planes. 16,73,75 Therefore, in the following we focused on the (110) orientation as the most representative surface of TiFe.…”

“…This is in agreement with a previous theoretical study, 72 the (110) peak intensification observed in X-ray diffraction (XRD), 16,73,74 and the transmission electron microscopy (TEM) analysis of TiFe lattice planes. 16,73,75 Therefore, in the following we focused on the (110) orientation as the most representative surface of TiFe. As passivating oxide films are almost always present under actual operating conditions of the material, we discuss oxide layer formation, stability energetics and dynamics based on the TiFe (110) surface in the following subsections.…”

Microstructure and Hydrogen Storage Performance of Ball-Milled MgH2 Catalyzed by FeTi

“…Doping FeTi by Zr, Mn or Y additives promotes the activation of hydrogen uptake at room temperature, however, with a sluggish kinetics [40][41][42]. When FeTi alloy is subjected to SPD by different processing routes, such as HEBM, high-pressure torsion and groove or cold rolling, the formation of cracks and subgrain boundaries positively influence the activation of hydrogenation [43][44][45][46].…”

Synergetic Effect of FeTi in Enhancing the Hydrogen-Storage Kinetics of Nanocrystalline MgH2

“…Several investigations have pointed out that the Fe-Ti system is capable of absorbing and desorbing hydrogen [56,57]; however, the Fe-Ti alloys must be activated at relatively high temperatures (400-450 • C) [56]. Nevertheless, the activation of hydrogenation of Fe-Ti is positively influenced when the alloy is subjected to SPD by different processing routes, such as HEBM, high-pressure torsion and groove or cold rolling via the formation of cracks and subgrain boundaries [58][59][60][61].…”