Hydrogen Storage Properties of Graphite-Modified Mg-Ni-Ce Composites Prepared by Mechanical Milling Followed by Microwav
- PDF / 1,115,857 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 45 Downloads / 214 Views
I.
INTRODUCTION
MAGNESIUM has great potential in the areas of high-energy batteries and hydrogen storage[1–3] because of its high capacity among the metal-based hydrogen storage materials. However, its high reaction temperature and poor hydriding/dehydriding (H/D) kinetic properties limit its practical application. Various additives[4–8] were used to destabilize magnesium hydride and significantly improve its kinetics. Wang et al.[8] published that the Mg-Ce/Ni composite prepared by induction melting and subsequent ball milling (BM) could absorb 2.92 wt pct H2 at 393 K (120 C) and could desorb 2.12 wt pct H2 at 453 K (180 C) under 0.1 MPa H2. Milanese et al.[9] prepared the ternary Mg-Nb2O5-graphitic C mixtures (mol ratio pct = 97.5:0.5:2.0) by high-energy BM and found that the absorption/desorption rates of the mixture milled for 1 hour were 64/4.5 times faster than those of a pure Mg sample ball milled for the same time. Spassov et al.[10] synthesized MgH2 75 at. pct-C 25 at. pct composite by BM using different kinds of carbon additives and found that the composite containing nanodiamonds strongly decreases the MgH2 decomposition temperature above 100 K (–173 C). Milanese et al.[11] also prepared the Mg-Ni-C (graphite from 5 to 15 wt pct) by high-energy JIE MENG, Staff Member, and KUO-CHIH CHOU, Professor, are with the Shanghai Key Laboratory of Modern Metallurgy & Materials Processing, Shanghai University, Shanghai 200072, People’s Republic of China. XUN-LI WANG, Distingished Research Staff Member, is with the Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831. QIAN LI, Distinguished Visiting Scientist and Faculty Member, Neutron Scattering Science Division, Oak Ridge National Laboratory, is Professor, Shanghai Key Laboratory of Modern Metallurgy & Materials Processing, Shanghai University. Contact e-mail: [email protected] Manuscript submitted March 25, 2012. Article published online September 19, 2012 58—VOLUME 44A, JANUARY 2013
BM in Ar for 2 hours and found that the 5 wt pct C-containing sample charged up to 5 wt pct H2. Additionally, they thought that the C did not lead to variation in the sorption enthalpies of the Mg-Ni system. Recent advances in the enhancement of metal hydrides were made by incorporating carbon nanotubes as a catalyst for the H/D reaction.[12] In addition to additives, preparation methods can influence the microstructure, morphology, and properties of the hydrogen storage material. Mechanical alloying (MA) by high-energy BM was found to be a promising method to synthesize Mg-based hydrogen storage materials.[13] Mechanical milling generally involves the reduction of crystallite size and the formation of various defects, such as grain boundaries, point defects, and plane defects, which shorten the diffusion length and increase the number of active sites for hydrogenation.[14] Furthermore, Mg-Ni-C composites[15] and LaMg11Ni alloys[16] can be destabilized by mechanical grinding, resulting in a remarkable decrease in dehydriding temperature. Additional
Data Loading...
