Nanocrystalline TiC Powers For Improving The Hydrogenation/Dehydrogenation Behaviors of MgH2

INTRODUCTION Owing to the dramatic growing global demands for energy and the huge consumption of the finite resources of fossil fuels, coupled with drastic global environmental changes caused by the carbon dioxide emissions,... [ view full abstract ]

INTRODUCTION

Owing to the dramatic growing global demands for energy and the huge consumption of the finite resources of fossil fuels, coupled with drastic global environmental changes caused by the carbon dioxide emissions, developing alternate and renewable energy sources become necessary for a sustainable future. Hydrogen is an energy carrier, which holds tremendous promise as a new renewable and clean energy option.  However, hydrogen can be stored in its gaseous or liquids states, the real applications of these methods have shown many technical difficulties due to the high cost and safety issues. The worldwide interest in MgH₂ storage system is attributed to its pioneering coupling a light weight and a high storage capacity,cost effective,reversibility,and cyclability of Mg metal. 

EXPERIMENTAL

Certain amount (5 g) of hcp-Mg the powder was balanced inside a helium gas atmosphere-glove box and then sealed together with forty hardened steel balls into a hardened steel vial . The vial was then filled with 50 bar of H₂ gas and mounted on a high-energy ball mill operated at 250 rpm. The as-synthesized MgH₂ powders obtained after 200 h of milling time was then doped with 5 wt.% TiC nanocrystalline powders and then ball-milled for 50 h under hydrogen gas atmosphere. The samples obtained after selected ball milling time were characterized by means of XRD, FE-HRTEM/STEM, and FE-SEM. The thermal stability of the milled powders were investigated by DSC with different heating rates.  

RESULTS AND DISCUSSION

Figures 1(a) and 1(b) displays the temperature effect on the hydrogenation absorption for nanocomposite MgH₂/5wt.% TiC powders obtained after 50h of milling time.

The synthesized nanocomposite powders showed excellent absorbing kinetics with short time at temperature ranging from 50^oC up to 275^oC as shown in Fig. 1(a). The maximum H₂ contents and the corresponding absorption time of the samples examined at 275, 250 and 150^oC were 5.50wt.%/6.95 min, 5.28wt.%/ 19 min, and 4.18 wt.%/37.17 min, respectively. (a). The desorption behaviors at 275^oC showed fast kinetics, indexed by the short time (10 min) required to release about 5.50 wt.% of hydrogen, as shown in Fig.1(c).