Thermodynamic Evaluation for Formation of MgCu2 from MgH2 and Cu

Abstract

We proposed that there are competitive two kinds of pathways in the hydrogenation of Mg/Cu super-laminate composites; the one is that alloying (formation of MgCu2 from Mg and Cu) occurs in advance and Mg2Cu is hydrogenated to form MgH2 and MgCu2, and the other is that Mg is hydrogenated and then MgH2 and Cu reacts to form MgCu2 together with H2 gas, according to a hypothesis that the reaction of MgH2+2Cu -> MgCu2+H2 occurs. In order to confirm that the hypothesis is true, we investigated the conditions such as pressure and temperature at which the above-mentioned reaction proceeds. Well-mixed MgH2 and Cu powder was compacted to form pellet at 1.73GPa and then heated at various hydrogen pressures and temperatures. Experimental results at 673K indicated that the above-mentioned reaction occurs at pressures higher than 6.5MPa, approximately lower limit for the hydrogenation of Mg2Cu, whereas Mg2Cu is formed at 3.3MPa.