Amorphization and electrochemical hydrogen storage properties of mechanically alloyed Mg-Ni

Several mechanically alloyed (MA) Mg-Ni based amorphous alloys have been found to have the properties to absorb and desorb electrochemically large amounts of hydrogen at room temperature. In the present work, mechanically alloying MgXNi100-x, alloys over the composition range x=10 similar to 90, including the extent of amorphous region were studied and their electrochemical properties were investigated. XRD and TEM observation showed that the range of the amorphous phase for MAMg(X)Ni(100-X) alloys extends from x=30 to 60 when pure elemental powders were milled together for 120 h with a ball to powder weight ratio of 15:1. Electrochemical measurement indicated that only the amorphous alloys could electrochemically absorb and desorb hydrogen at the room temperature. At a current density of 100 mA g(-1) all amorphous MgXNi100-X alloys with x=40 similar to 60 reached their maximum discharge capacities at the first charge/discharge cycle. and all amorphous alloy in the region x=45 similar to 50 exhibited a favourable capacity of over 350 mA h g(-1) at room temperature. In the amorphous region, when the Ni content was increased the discharge capacity decreased while the cycling stability increased, although the cycling stability of MA amorphous Mg-Ni alloys was poor.