Hydriding combustion synthesis of Mg-CaNi5 composites

The composites of Mg-x wt.% CaNi5 (x = 20, 30 and 50) were prepared by hydriding combustion synthesis (HCS) and the phase evolution during HCS as well as the hydriding properties of the products were investigated. It was found that Mg reacted with CaNi5 forming Mg2Ni and Ca during the heating period of HCS. Afterwards, the resultant Mg2Ni and Ca as well as the remnant Mg reacted with hydrogen during the cooling period. The lower platform in the P-C isotherms corresponds to the hydriding of Mg, and the higher one corresponds to Mg2Ni. With the increase of the content of CaNi5 from 20 to 50 wt.%, the hydrogen content of the HCS products increases at first and then decreases. The Mg-30 wt.% CaNi5 composite has the maximum hydrogen capacity of 4.74 wt.%, and it can absorb 3.51 wt.% of hydrogen in the first hydriding process without activation.