In-situ neutron powder diffraction study of Mg–Zn alloys during hydrogen cycling

•First in-situ study of magnesium-zinc alloys.•First observation of a liquid magnesium-zinc phase at the temperatures required for reasonable hydrogen absorption kinetics.•The only hydride formed was hexagonal MgH2 and the Zn appeared not to play any part in the reaction.

An in-situ structural study of three Mg–Zn samples with nominal composition Mg0.9963Zn0.0037, Mg0.89Zn0.11 and Mg0.73Zn0.27 was performed using neutron diffraction to investigate what phases are formed during the hydrogen absorption process. It was found that at the temperatures needed for reasonable kinetics, a Mg–Zn liquid phase was present. This aspect of the reaction mechanism has not been revealed by previous ex-situ investigations in the literature. The only hydride formed was tetragonal MgH2. No Mg–Zn–H hydride phase was found and the Zn did not appear to play any part in the reaction.