The new ternary intermetallic NdNiMg5: Hydrogen sorption properties and more

The hydrogen sorption properties of the new compound NdNiMg5 have been investigated. The compound starts to absorb hydrogen at 573 K under a pressure of 1 MPa. The absorption leads to the decomposition into two binary hydrides MgH2 and NdH2.6, and a ternary hydride Mg2NiH4. The maximum hydrogen sorption capacity reached is 3.2 wt.% and the cycling properties of the mixture decreases quickly due to grain growth. The activation energies for absorption and desorption are estimated to be equal to 14(3) kJ/mol H2 and 110(9) kJ/mol H2, respectively. Preliminary studies of the mechanical properties were also performed. Despite the high content in magnesium, NdNiMg5 exhibits an average microhardness of 210 Hv and a reduced Young Modulus of 9(1) GPa.