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

F. GENNARI; G. URRETAVIZCAYA; G. MEYER

Annecy, Francia

Simposio; International Symposium on Metal-Hydrogen Systems; 2002

D. Fruchart, Université de Grenoble

We investigate the mechanical alloying (MA) of the 2Mg-0.5Ni-0.5Ge mixture at room temperature under hydrogen atmosphere. The evolution of MA process and the thermal stability of the obtained hydrides were studied using XRD, DSC, DTA and TG. We observe the formation of MgH2 and Mg2NiH4 at short milling times. The presence of unreacted Ge reduces the desorption temperature of MgH2 in more than 100 °C [1]. 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 of c.a. 1 wt. % and is stable upon heating up to 410 °C. We present an alternative synthesis route for the Mg-Ge-Ni hydride that involves the MA of  the 2Mg-0.5Ni-0.5Ge mixture under argon and subsequent MA for shorter milling times under hydrogen. The experimental evidence showed that the Mg2Ni1.1Ge0.5 alloy, with Mg3MNi2-type cubic structure, is the precursor of the novel Mg-Ni-Ge hydride.   F. C. Gennari, F. J. Castro, G. Urretavizcaya and G. Meyer, J. Alloys Comp. 334 (2002) 2771.