Synthesis and electrode characteristics of the new composite alloys Mg2Ni-xwt%Ti2Ni

A new composite alloy Mg2Ni-xwt.%Ti2Ni has been successfully synthesised using a 'particle inlaying' method. Scanning electron microscopy and energy dispersive spectroscopy revealed that very fine Ti2Ni particles were inlaid onto the surface of Mg2Ni particles by mechanical treatment and sintering. XRD showed the composite alloys were composed of primary alloys Mg2Ni, Ti2Ni and new phases TiNi, Ti-Mg formed in the composite procedure. The electrode characteristics of Mg2Ni-xwt.%Ti2Ni alloys in an alkaline solution have been investigated and compared with those of Mg2Ni. The discharge capacity of the alloy electrode was effectively improved from 8 mA h g(-1) of Mg2Ni to 165 mA h g(-1) of Mg2Ni-40wt.%Ti2Ni at ambient temperature, which is almost comparable with that of Ti2Ni electrode (170 mA h g(-1)). It is believed that the fine Ti2Ni particles inlaid on the surface of Mg2Ni particles play a two-fold role: firstly, they hydride-dehydride as hydrogen storage materials themselves; secondly, they provide active sites and pathways for Mg2Ni hydriding-dehydriding. This is supported by analysis of discharge behaviour and electrochemical impedance spectra studies.