THERMODYNAMIC REASSESSMENT OF THE LA-MG-NI SYSTEM AND ITS APPLICATION FOR HYDROGEN STORAGE

摘要

Phase equilibria at the Mg-Ni side of the La-Mg-Ni ternary system were thermodynamically reassessed with the consideration of the(La,Mg)_5Ni_(19)phase, which is a promising alloy for hydrogen storage materials. LaMg_2Ni phase was treated as stoichiometric compound,(La,Mg)_2Ni_7,(La,Mg)_5Ni_(19), La_2(Mg,Ni)_(17)and(La,Mg)Ni_3 phases were described by compound energy formalism". The mixing enthalpy of liquid, the vertical sections along 75 wt.% Mg, Mg_2Ni-La_2Mg_(17)and Mg_2Ni-Lao.6Mgo.4 and the isothermal sections at 773 K, 973 K and 1173 K were thermodynamically optimized and a set of self-consistent thermodynamic description of the La-Mg-Ni system was obtained, which showed a good agreement with the experimental data. With the thermodynamic description, the vertical section of LaNis-Mg was calculated, and the solidifications of LaNi_(5-y)Mg(y = 80 wt.% and 50 wt.%)alloys were simulated, which were used to analyze the microstructure of LaNi_(5-y)Mg(y = 80 wt.% and 50 wt.%)prepared by sintering method.