AMORPHIZATION AND ELECTROCHEMICAL HYDROGEN STORAGE PROPERTIES OF MECHANICALLY ALLOYED MG-NI

Several mechanically alloyed (MA) Mg-Ni based amorphous alloys have be en found to have the properties to absorb and desorb electrochemically large amounts of hydrogen at room temperature. In the present work, m echanically alloying MgXNi100-x, alloys over the composition range x=1 0 similar to 90, including the extent of amorphous region were studied and their electrochemical properties were investigated. XRD and TEM o bservation 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 tempera ture. At a current density of 100 mA g(-1) all amorphous MgXNi100-X al loys with x=40 similar to 60 reached their maximum discharge capacitie s 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 c ontent was increased the discharge capacity decreased while the cyclin g stability increased, although the cycling stability of MA amorphous Mg-Ni alloys was poor.