Hydriding properties of magnesium-salt mechanical alloys

Mechanical alloying of magnesium with inorganic salt addition has been demonstrated to promote metal powdering and modify the metal surface. This leads to an acceleration of the hydriding and dehydriding reactions of obtained materials and to quite high hydrogen capacities (about 5.5-6 wt.%). The investigated salts (NaF, NaCl, MgF2 or CrCl3) had a different influence on the metal surface properties, which was reflected in reaction kinetics, in particular at first hydriding. MgF2 and NaCl peel off of the oxide layer from magnesium surface facilitating hydride nucleation. CrCl3 may additionally act as catalysis for hydrogen chemisorption. The formation of NaMgF3 ternary fluoride has been observed at the initial stages of hydriding of Mg-NaF mechanical alloys. This ternary fluoride was found to play an active role in the hydriding process.