Hydrogen storage and thermal transport properties of pelletized porous Mg-2 wt.% multiwall carbon nanotubes and Mg-2 wt.% graphite composites L. Popilevsky a,b , V.M. Skripnyuk a , M. Beregovsky a , M. Sezen c , Y. Amouyal a , E. Rabkin a,* a Department of Materials Science and Engineering, TechnionIsrael Institute of Technology, 32000 Haifa, Israel b Grand Technion Energy Program (GTEP), TechnionIsrael Institute of Technology, 32000 Haifa, Israel c Nanotechnology Research and Application Center (SUNUM), Sabanci University, Orhanli, Tuzla, 34956 Istanbul, Turkey article info Article history: Received 3 December 2015 Received in revised form 16 February 2016 Accepted 1 March 2016 Available online xxx Keywords: Magnesium hydride Multiwall carbon nanotubes High energy ball milling Porous metal matrix composites abstract We synthesized pelletized porous composites of Mg admixed with 2 wt.% of either multiwall carbon nanotubes or graphite. The composites were prepared by high energy ball-milling of Mg powder with carbonaceous additives, followed by uniaxial compression and sintering in hydrogen environment under mechanical constraint. The correlations between ball-milling conditions, composite microstructure, hydrogenation kinetics, and thermal conductivity of the pellets were established. The presence and condition of carbon additives controls the morphology of Mg particles and, consequently, the mechanical stability of the pellet upon hydrogenation cycling. The best combination of hydrogen desorption kinetics, thermal conductivity, and mechanical stability was obtained for the pellets synthesized from the mixture of Mg with 2 wt.% of carbon nanotubes processed by 4 h of co-milling. The milling transformed carbon nanotubes into carbon nano-particles/ nano-onions. These carbonaceous species promote metal nucleation from the hydride phase and allow formation of Mg-Mg bonds between the Mg particles contributing to mechanical stability of the pellet. Copyright © 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Introduction Magnesium is considered as one of the most attractive ma- terials for hydrogen storage because of its high hydrogen storage capacity and abundance. However, its main draw- backs are slow hydrogenation kinetics and high formation enthalpy of MgH 2 hydride. Ball-milling of Mg powders was shown to reduce crystallite and particle size, break the surface oxide layer, introduce defects and activate the surface for hydrogen absorption [1]. As a result, the hydrogenation ki- netics of Mg-based powders can be accelerated. In materials with high hydride formation enthalpy, hydrogen absorption reaction is highly exothermic. For the hydrogenation reaction to proceed, the heat should be quickly removed, while for the * Corresponding author. Tel.: þ972 4 829 4579; fax: þ972 4 8295677. E-mail address: erabkin@tx.technion.ac.il (E. Rabkin). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2016) 1 e14 http://dx.doi.org/10.1016/j.ijhydene.2016.03.014 0360-3199/Copyright © 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Popilevsky L, et al., Hydrogen storage and thermal transport properties of pelletized porous Mg-2 wt.% multiwall carbon nanotubes and Mg-2 wt.% graphite composites, International Journal of Hydrogen Energy (2016), http://dx.doi.org/ 10.1016/j.ijhydene.2016.03.014