Effect of Ni powder addition on the hydriding/dehydriding characters of Mg17Al12

The effect of 10% Ni (mass fraction) addition on the hydriding/dehydriding characters and structure of Mg17Al12 was studied by PCT and XRD measurements. The addition of 10% Ni powder improved the hydriding/dehydriding performances of Mg17Al12 center dot Mg17Al12 absorbs hydrogen fast at 423 K, and it shows the best hydrogen absorbing/desorbing performances at 523 K. The absorption capacity reaches 2.93wt% in 15 min, and the full absorbing capacity is 4.20% at 523 K. The platform pressure is 0.3 MPa, and the desorbing capacity is 3.45% at the same temperature. The enthalpy and entropy of the hydride are -68.37 kJ center dot mol(-1) H-2 and -121.42 J center dot(mol(-1)center dot K-1), respectively. After ball-milling with 10% Ni powder for I h, the main phase in the alloy is Mg17Al12 and a few Al-Ni metallic compounds, and after saturation hydriding, the phases are MgH2 Al and Al-Ni metallic compounds, respectively, while the main phase is Mg17Al12 after dehydriding. It is obvious that the hydriding /dehydriding of Mg17Al12 is reversible.