H2 absorption in amorphous and nanostructured Zr-based alloys under milling

We report on the mechanical hydriding of amorphous and nanostructured Zr-based alloys. The absorption process induces a demixing of the crystalline ZrH1.66 from the amorphous matrix with the concurrent formation of a less stable amorphous hydride. This phase releases the absorbed hydrogen at lower temperatures. No phase separation was observed in the nanostructured powders, which absorb hydrogen more quickly with respect to the amorphous structure through high diffusivity paths such as grain boundaries and free surfaces. Irrespective of the structural characteristics and the composition of the starting alloys, the absorption kinetics follows in both cases a well-defined sigmoidal trend. The conversion rate increases with the intensity of the milling treatment.