Ternary intermetallic compounds, Mg 2-xPr xNi 4 (0.6 ≤ x ≤ 1.4) were synthesized by induction melting and investigated with respect to hydrogenation properties and structural changes. These compounds have a cubic C15 b-type Laves structure (space group F-43m), where Mg and Pr have an ordered arrangement. The lattice parameters increased from a = 0.70101(3)nm to a = 0.71726(8)nm with increase of the Pr content. Mg 1.4Pr 0.6Ni 4 and Mg 1.2Pr 0.8Ni 4 absorbed and desorbed hydrogen up to ∼0.7 H/M reversibly through one plateau in the p-c isotherms. The stoichiometric MgPrNi 4 showed two plateaus and its maximum hydrogen content reached to ∼1.0 H/M at 35MPa. The enthalpy changes of hydrides formation of Mg 1.4Pr 0.6Ni 4 and Mg 1.2Pr 0.8Ni 4 were estimated to be -39.2 and -40.3 kJ/mol H 2 respectively. The enthalpy changes of hydrides formation of MgPrNi 4 at the lower and higher plateaus were estimated to be -42.4 and -19.6 kJ/mol H 2 respectively. The metal sublattice of hydrides Mg 1.4Pr 0.6Ni 4H ∼4 and Mg 1.2Pr 0.8Ni 4H ∼4 had cubic ordered C15 b-type Laves structure same as the crystal structure before hydrogenation while hydride at the lower plateau of the stoichiometric MgPrNi 4 had an orthorhombic structure. The hydrogenation of Mg 0.8Pr 1.2Ni 4 and Mg 0.6Pr 1.4Ni 4 led to amorphization.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering