Magnesium alloy-graphite composites with tailored heat conduction properties for hydrogen storage applications

Melt spun magnesium alloys that contain catalytically active constituents have become attractive hydrogen storage materials due to their ultra fine and homogeneous micro structure and their excellent (de)hydrogenation characteristics However their heat conduction properties have to be improved for practical applications For this purpose composites of melt spun magnesium alloys and expanded natural graphite (ENG) were examined in this work Melt spun flakes were mixed with different amounts of up to 25 5 wt % ENG These mixtures were compacted to cylindrical pellets using compaction pressures up to 600 MPa For comparison, pellets of pure magnesium hydride and ENG were equally processed All sets of specimens were investigated regarding their thermal conductivities in radial and axial direction, their microstructure and phase fractions It was found that the heat transfer characteristics can be tailored in a wide range e g the thermal conductivity of magnesium alloy ENG compacts were tuned from 1 up to 47 W m(-1) K-1 For the system MgH2 ENG the thermal conductivity can be adjusted from 1 up to 43 W m(-1) K-1 Therefore a hydrogen storage material with homogeneous heat transfer properties can be anticipated which only slightly depend on the hydrogenated fraction (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved