Hydrogen-Induced Phase Transformations in Mg-Ni Alloys

Hydrogen is suggested as a promising fuel of the near future for the utilization in automotive and mobile applications. Therefore, safe and effective hydrogen storage systems need to be developed. One of the possibilities, suitable especially for mobile applications, is the storage of hydrogen in the form of light-metal hydrides. In this work we studied microstructure and hydrogen absorption and desorption kinetics in selected Mg-Ni alloys. Hydrogen saturation was carried out by the cathodic polarization in alkaline water-based solution. It was confirmed that hydrogen could be stored in the Mg2Ni intermetallic phase forming Mg2NiH0.3 phase using this technology. MgH2 hydride is also formed when the temperature of 90 °C is applied. The total content of hydrogen in the material after saturation is approx. 0.7 wt. % according to the thermogravimetry analysis. This low value is caused probably by the surface oxidation, blocking further hydrogen diffusion. Thermal hydrogen desorption tests showed that the Mg2NiH0.3 phase is able to release hydrogen even at temperatures lower than 100 °C.