Hydriding-dehydriding behavior of magnesium composites obtained by mechanical grinding with graphite carbon

Novel Mg/G composites were prepared by mechanical grinding of magnesium (Mg ) and graphite carbon (G) with cyclohexadiene, cyclohexene, cyclohexane, be nzene or tetrahydrofuran as an additive. The presence of organic additives during the grinding was very important in determining the composite structu res and hydriding-dehydriding properties. The composites prepared without a dditives [designated hereafter as (Mg/G)(none)] showed negligible activity for hydriding, whereas the use of additives led to drastic changes in compo site structures, leading to much improved hydriding and dehydriding behavio r. The effectiveness of organic additives in the initial hydriding was in t he order: cyclohexadiene approximate to tetrahydrofuran approximate to cycl ohexene > benzene > cyclohexane. In the course of the composite formation i n the presence of organic additives, the graphite was predominantly degrade d by cleavages along graphite layers, resulting in the occurrence of synerg etic interactions with magnesium. The graphite for (Mg/G)(none) was broken irregularly and disorderly to rapid amorphization with negligible interacti ons with magnesium. Various metal-doped Mg/G composites obtained by grindin g of magnesium and graphite with organometallic solutions (Al(C2H5)(3), Ti( OC3H7)(4), Fe(C5H5)(2), Ni(C5H5)(2) or Zn(C2H5)(2)) in benzene have been fu rther examined. Ti-doped Mg/G composites using Ti(OC3H7)(4) among others sh owed an excellent activity; the initial hydriding activity increased above 10-fold relative to that for the metal-free composites. (C) 2000 Internatio nal Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.