Hydrogen desorption kinetics of melt-spun and hydrogenated Mg90Ni10 and Mg80Ni10Y10 using in-situ synchrotron X-ray diffraction and thermogravimetry

Two nanocrystalline magnesium-rich alloys, Mg90Ni10 and Mg80Ni10Y10, were produced by meltspinning. After hydrogenation they consist of a MgH2 matrix with finely dispersed Mg2NiH4 grains of about 2m in size. In the case of Mg80Ni10Y10, nanocrystalline YH3 grains are found, additionally. The desorption kinetics of hydrogenated Mg90Ni10 and Mg80Ni10Y10 was investigated by thermogravimetry at different temperatures in the range from 150°C to 250°C. It was observed that Mg80Ni10Y10 exhibits a much faster desorption kinetics in comparison toMg90Ni10 of up to 1.3 wt.%H2/min. Differential scanning calorimetry indicates that these alloys undergo a two-step desorption process. The corresponding phase transformations were investigated in detail by in situ synchrotron X-ray diffraction, thus, the different hydrogen desorption kinetics can be explained.