The first hydrogenation of most metal hydrides is a lengthy process that usually requires high pressure and temperature. This, in turn, significantly increases the production cost of metal hydrides. In this paper, the low temperature hydride-forming LaNi5 was selected to investigate the mechanism of first hydrogenation. For the first time, the effect of particle size, temperature and pressure on the incubation time were studied. We found that the first hydrogenation of LaNi₅ follows an Arrhenius process, with an activation energy of E_A = 78 ± 4 kJ/mol H₂. We also found that the pre-exponential factor depends on the applied pressure.

The effect of the substitution of Nb by V on the microstructure and hydrogen storage properties of TiHfZrNb_1−xV_1+x alloys (x = 0.1, 0.2, 0.4, 0.6 and 1) was investigated. For x = 0, the alloy was pure BCC and upon the substitution of niobium by vanadium, the BCC was progressively replaced by HCP and FCC phases. For x = 0.6, a C15 phase was also present and becomes the main phase for x = 1. The substitution greatly enhanced the first hydrogenation and makes it possible at room temperature under 20 bars of hydrogen. The capacity of all substituted alloys was around 2 wt.%.

The effect of adding Zr on microstructure and hydrogen storage properties of BCC Ti₁V_0.9Cr_1.1 synthesized by arc melting was studied. The microstructures of samples with Zr were multiphase with a main BCC phase and secondary Laves phases C15 and C14. The abundance of secondary phases increased with increasing amount of zirconium. We found that addition of Zr greatly enhanced the first hydrogenation kinetics. The addition of 4 wt % of Zr produced fast kinetics and high hydrogen storage capacity. Addition of higher amount of Zr had for effect of decreasing the hydrogen capacity. The reduction in hydrogen capacity might be due to the increased secondary phase abundance. The effect of air exposure was also studied. It was found that, for the sample with 12 wt % of Zr, exposure to the air resulted in appearance of an incubation time in the first hydrogenation and a slight reduction of hydrogen capacity.

The hydrogen storage properties of a multi-component alloy of composition Ti_0.3V_0.3Mn_0.2Fe_0.1Ni_0.1 were investigated. The alloy was synthesized by arc melting and mechanical alloying, resulting in different microstructures. It was found that the as-cast alloy is multiphase, with a main C14 Laves phase matrix along with a BCC phase and a small amount of Ti₂Fe-type phase. The maximum hydrogen storage capacity of the alloy was 1.6 wt.%. We found that the air-exposed samples had the same capacity as the as-cast sample but with a longer incubation time. Synthesis by mechanical alloying for five hours resulted in an alloy with only BCC structure. The hydrogen capacity of the milled alloy was 1.2 wt.%, lower than the as-cast one. The effect of ball milling of the as-cast alloy was also studied. Ball milling for five hours produced a BCC structure similar to the one obtained by milling the raw materials for the same time.

In this study, we evaluated the effects of a mechanical treatment by cold rolling (CR) and ball milling (BM) on the first hydrogenation of Ti₁V_0.9Cr_1.1 alloy. The as-cast alloy has a body-centered cubic (BCC) crystal structure, and the first hydrogenation at room temperature under 20 bars of hydrogen is practically impossible. However, the samples mechanically activated by CR or BM readily absorbed hydrogen. The sample cold-rolled for one pass exhibited faster kinetics than the sample ball-milled for five minutes, but both samples reached the same storage capacity of 3.6 wt % hydrogen. Increasing the amount of rolling or the milling time decreased the hydrogen capacity. CR is considered the best and most efficient method for the activation of Ti₁V_0.9Cr_1.1 alloy.