The influence of ball milling process on formation and electrochemical properties of amorphous MgNi hydrogen storage alloys

The present work investigated the influence of ball milling parameter, such as milling mode, milling velocity and milling time, and element addition on the microstructure and electrochemical properties of MgNi alloys prepared by mechanical alloying (MA). It has been found that partially amorphized MgNi (a-MgNi) alloy was obtained through an intermediate product of crystal (c-) Mg2Ni with continuous milling mode at a certain velocity. The fully amorphized MgNi alloy was gained by milling with intermittent mode, and the time required to form the amorphous phase is strongly affected by milling velocity and intermittent condition. The a-MgNi alloy can be prepared by continuous milling mode when nonmetallic elements, such as B and Si, are suitably added into powder mixture of Mg and Ni. The initial discharge capacities of a-MgNi hydrogen storage alloy changed in a zigzag trend with the prolonging of milling time. The maximal electrochemical capacity is the MgNi alloy with the structure of nearly full amorphous phase. (c) 2006 Elsevier B.V. All rights reserved.