Tuesday, April 1, 2008 - 10:30 PM

Highly Improved Hydrogen Absorption Kinetics of Magnesium-based Nanocomposites Using Carbon Nanotubes

Jie-Ren Ku, Pei-Shan Yen, Ming-Shan Jeng, Fanghei Tsau, and Yi-Yie Yan. Industrial Technology Research Institute

The system hydrogen capacity for vehicle application is targeted on 6.0wt.% by 2010. Moreover, the hydrogen refilling time should be limited within 3 minutes for practical purpose. Magnesium has a high hydrogen storage capacity of 7.6 wt.%, which shows a great potential in hydrogen storage. However, the high reaction temperature (~573 K) and the slow kinetics of hydrogen absorption limit the practical application of Magnesium. Recently, there are lots of methods have been reported to improve hydrogen absorption temperature and kinetics of magnesium, such as adding transition elements into magnesium. Our recent results show the hydrogen absorption kinetics of magnesium-based hydrogen storage materials have been enormously improved by adding carbon nanotubes (CNTs). The as-prepared magnesium-based composite absorbed 4.05wt.% hydrogen at 423 K within 2 minutes, which is even more rapid absorption kinetics than the magnesium-based composites reported by Yao (J. Phys. Chem. B 2006, 110, 11697-11703). Balling milling of Mg, FeTi, and CNTs was used to make the magnesium-based nanocomposite powders (Mg-FeTi-CNTs). Transmittance electromicroscopy (TEM) and X-ray diffraction (XRD) was conducted to analyze the grain size of the materials. The Sieverts-type apparatus was used to examine the kinetics of the materials. The TEM images show the grain size of the magnesium-based composite with CNTs is ~40 nm which is smaller than that of the magnesium-based composite without CNTs. The absorption kinetics of the magnesium-based composite with CNTs is faster than that of the magnesium-based composite without CNTs. We conclude that the adding CNTs has effects on reducing the grain size and improves the kinetics of hydrogen absorption of magnesium-based composite .

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