Hydrogen storage properties of compacts of melt-spun Mg 90Ni 10 flakes and expanded natural graphite

Abstract

In recent years, melt-spun magnesium alloys have attracted a lot of attention due to their excellent (de-)hydrogenation characteristics resulting from their nanoscale crystal structure and the homogeneous distribution of minor catalyst phases. Besides reaction kinetics, the heat conductivity of the storage material is important to transfer the reaction enthalpies in a controlled manner. Due to the inferior heat conduction properties of magnesium hydride, composites containing melt-spun Mg 90Ni 10 flakes and expanded natural graphite (ENG) up to 25.5 wt.% have been examined. Mixtures of those starting materials were compacted to cylindrical pellets using compaction pressures up to 600 MPa. Investigations of thermal conductivities in radial and axial directions, microstructure and phase fractions were carried out upon all sets of specimens. The heat transfer characteristics were tuned in a wide range from 1 up to 47 W m −1 K −1. Furthermore, cyclic (de-)hydrogenation was carried out upon the compacts showing a hydrogen uptake of up to 4 wt.%-H 2 within 10 min. During the hydrogen loading process, the Mg 90Ni 10–ENG pellets remained mechanically stable.