Synthesis of hydrides by mechanical alloying in the Mg-Ni-Ge system

We investigated the mechanical alloying (MA) of 2Mg-0.5Ni-0.5Ge mixture at room temperature under hydrogen atmosphere. The evolution of the phases during MA process and the thermal stability of the obtained hydrides were studied using XRD, DSC, DTA and TG. Formation of MgH2 and Mg2NiH4 was observed at short milling times. Unreacted Ge in the product reduces the desorption temperature of MgH2 in more than 100degreesC. As the milling time increases, the MA leads to the formation of a new Mg-based hydride in the Mg-Ni-Ge system. This novel hydride has a hydrogen content higher than 1 wt.% and is stable upon heating up to 410degreesC. We present an alternative synthesis route for the Mg-Ni-Ge hydride that involves the MA of the 2Mg-0.5Ni-0.5Ge mixture under argon followed by short milling times under hydrogen atmosphere. Our results show that the ternary alloy obtained by milling of the 2Mg-0.5Ni-0.5Ge mixture under argon, with Mg3MNi2-type cubic structure, is the precursor of the novel Mg-Ni-Ge hydride. (C) 2003 Elsevier B.V. All rights reserved.