Microstructure Characteristics and Hydrogen Storage Kinetics of Mg(77+x)Ni(20−x)La(3) (x = 0, 5, 10, 15) Alloys

Mg(77+x)Ni(20−x)La(3) (x = 0, 5, 10, 15) alloys were successfully prepared by the vacuum induction melting method. The structural characterizations of the alloys were performed by using X-ray diffraction and scanning electron microscope. The effects of nickel content on the microstructure and hydrogen storage kinetic of the as-cast alloys were investigated. The results showed that the alloys are composed of a primary phase of Mg(2)Ni, lamella eutectic composites of Mg + Mg(2)Ni, and some amount of LaMg(12) and La(2)Mg(17). Nickel addition significantly improved the hydrogen-absorption kinetic performance of the alloy. At 683 K, Mg(77)Ni(20)La(3) alloy and Mg(82)Ni(15)La(3) alloy underwent hydrogen absorption and desorption reactions for 2 h, respectively, and their hydrogen absorption and desorption capacities were 4.16 wt.% and 4.1 wt.%, and 4.92 wt.% and 4.69 wt.%, respectively. Using the Kissinger equation, it was calculated that the activation energy values of Mg(77)Ni(20)La(3), Mg(82)Ni(15)La(3), Mg(87)Ni(10)La(3) and Mg(92)Ni(5)La(3) alloys were in the range of 68.5~75.2 kJ/mol, much lower than 150~160 kJ/mol of MgH(2).