In situ pressure and temperature monitoring during the conversion of Mg into MgH2 by high-pressure reactive ball milling

We present a new and powerful method for the synthesis of hydrogen storage materials and monitoring of hydrogenation reactions by reactive ball milling under high hydrogen atmosphere. We have developed a synthesis technique, which involves high-energy ball milling in an especially designed vial, allowing in situ monitoring of temperature and, more importantly, of hydrogen pressure in the pressure range of 1–150 bar. In our study, Mg99Ni1 was chosen as a model system. The evolution of the hydrogenation reaction was studied as a function of applied pressure during milling and as a function of milling time. For comparison, undoped Mg was also investigated. Milling at high hydrogen pressures has proven to be very effective in promoting hydride formation, nanocrystallinity, monitoring and controlling the evolution of the reactions during milling as well as for enabling direct, i.e. one-step, synthesis.