ON THE HYDROGEN STORAGE BEHAVIOUR OF ALLOYS La_2Mg_(17) AND La_2Mg_(16)Ni

The hydrogen storage behaviour of the Mg-rich rare earth alloys, La_2Mg_(17) and La_2Mg_(16)Ni, has been investigated. Two plateaus related to the reactions Mg2Ni+2H_2(?)Mg_2NiH_4 and Mg+H_2(?)MgH_2 respectively exhibit in the pressurecomposition isotherm of La_2Mg_(16)Ni alloy. Partial substitution of Mg by Ni in La_2Mg_(17) gives a two-phase mixture: the major is La_2Mg_(17) type phase and the minor, Mg_2Ni type one. Hydriding of the La_2Mg_(16)Ni alloy leads to the formation of MgH_2, La hydride and Mg_2NiH_4. An experiment was also carried out on the hydrogen absorption by the alloys under either normal temperature and lower pressure or normal pressure and elevated temperature. It was found that La_2Mg_(17) and La_2Mg_(16)Ni seem to be the considerable hydrogen storage materials.