Thermal stability and hydrogen storage property of Mg 1.9Cu 0.1Ni x ( x = 1.8, 1.9, 2.0 and 2.1) alloys

Abstract

Amorphous Mg 1.9Cu 0.1Ni x ( x = 1.8, 1.9, 2.0, 2.1) alloys were synthesized through high energy ball milling. Thermal stability and the hydrogen storage properties of the alloys held at 200, 250 and 300 °C in 5 atm hydrogen for 20 min were investigated. It was found that the nickel content in the alloys significantly affects the crystallization and the hydrogenation–desorption temperatures. With an increase of nickel content, the crystallization temperature increases, the hydride content is reduced and the desorption temperature decreases. The observations were successfully interpreted in terms of the formation enthalpy of a nickel monovacancy in the magnesium and nickel based alloys during heating. The calculated values of the formation enthalpy of the nickel monovacancy are 61.5, 62.6, 63.8 and 64.9 kJ/mol corresponding to nickel content x = 1.8, 1.9, 2.0 and 2.1, which demonstrates that the thermal stability of the as-prepared alloys, the hydrogenation potential, and the desorption kinetics are closely related to the nickel content.