Microstructure and hydrogen storage properties of magnesium–gallium binary alloys.

In this paper, gallium was used as alloying element to improve hydrogen storage properties of magnesium. Therefore, Mg– x wt% Ga (x = 5, 10, 25, 50) binary alloys were prepared by induction melting method. The microstructure and phase composition of Mg–Ga alloy were analyzed using X-ray diffractometer and scanning electron microscope. The results show that Mg–Ga binary alloys consist of Mg and Mg 5 Ga 2 phases. The Mg and Mg 5 Ga 2 react with H 2 to form Mg 2 Ga and MgH 2 during hydrogenation process. The hydrogen storage kinetics and thermodynamic properties of the alloys were tested using a Sieverts-type apparatus. It is found that the dehydrogenation rates of the samples increase with increasing gallium content, and they are all better than pure magnesium. Thermal analysis results indicate that increasing gallium content decreases dehydrogenation temperature of Mg–Ga alloy. The beneficial effects of adding gallium in magnesium is that interfaces and secondary phase resulted from alloying can promote the hydrogen desorption process of the alloy. The Mg–50 wt% Ga alloy has the lowest dehydrogenation activation energy. However, increasing gallium content inevitably reduces the hydrogen storage capacity of the Mg–Ga alloys. Furthermore, alloying with gallium does not change the thermomechanical properties of magnesium. [Display omitted] • Hydrogenation leads to the formation of Mg 2 Ga and MgH 2 in Mg–Ga alloy ingot powder. • Alloying Mg and Ga significantly reduces the hydrogen desorption temperature of MgH 2. • The hydrogen release kinetics of MgH 2 is greatly improved by increasing Ga content. • The dehydrogenation activation energy of the alloy decreases by increasing Ga content. • The E a of Mg–50 wt% Ga alloy is 116 kJ mol−1, which is 47 kJ mol−1 lower than MgH 2. [ABSTRACT FROM AUTHOR]