Abstract
We have been proposing that there are competitive two kinds of pathways in the hydrogenation of Mg/Cu super-laminate composites. The one is that Mg reacts with Cu to form Mg2Cu and then Mg2Cu is hydrogenated to form MgH2 and MgCu2. 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 the present study, the reaction conditions such as pressure and temperature were investigated in order to confirm that the hypothesis is true. Well-mixed MgH2 and Cu powder was compressed to a pellet at 1.73 GPa and then heated at various hydrogen pressures and temperatures. Following results were obtained from the experiments at 673 K. The above-mentioned alloying accompanied by H2 emission occurs at pressures higher than 6.6 MPa of H2 pressure, which is higher than lower limit for the hydrogenation of Mg2Cu. On the other hand, Mg2Cu is formed at 3.3 MPa which is lower than the limit. The reaction of MgH2 with Cu also occurs at 573 K in 3.3 MPa H2. But it requires very long time such as 691.2 ks, although the existence of MgCu2 is confirmed in 86.1 ks of heating time in the case of Mg/Cu super-laminate composites.
