Wednesday, December 23, 2009

Sharif University Researchers Demonstrate Hydrogen Storage in Metallic Nanohydride Mg-Ni/Nb2O5


The Iranian researchers at Sharif University of Technology took a great step in hydrogen storage by synthesis of a sort of metallic nanohydride which decreases adsorption and desorption temperatures of hydrogen by 150 to 200 degrees.

The storage of hydrogen in metallic and intermetallic compounds hydrides has attracted lots of attentions today, but operational temperature and pressure of these hydrides are high (350°C). So, a large number of attempts have been made to lower the mentioned temperature and pressure by compositing and alloying during recent years.

"Using nanostructured metallic hydrides might be a proper solution for hydrogen storage," Hamed Simchi, one of the researchers explained to the news service of  Iran Nanotechnology Initiative Council (INIC).

Elaborating on the procedure of magnesium nanohydride synthesis and hydrogen desorption kinetic improvement, Simchi reiterated, "Nanocrystalline nanocomposite of Mg-Ni/Nb2O5 were synthesized by means of mechanical milling. The effect of milling conditions along with addition of Ni and Nb2O5 on the structure and desorption kinetic of hydrogen was examined."

After these examinations, it was revealed that an increase in network strain caused by mechanical milling along with addition of appropriate amount of catalyst has a significant impact on the improvement of hydrogen desorption properties of MgH2.

High pressure phase of γ-MgH2 appeared in the structure after one hour of milling. Hydrogen desorption temperature dropped from 426 to 327 degrees of centigrade. It was also demonstrated that particle size doesn't have any considerable effect on hydrogen desorption kinetic within the size range of test particles (20-50μm).

Hydrogen desorption kinetic was improved remarkably by addition of Ni and Nb2O5 and hydrogen desorption temperature reduced by 50% compared to pure unmilled MgH2. These conditions caused about 100°C fall in nanocomposite hydrogen desorption temperature in proportion to milled pure MgH2 so hydrogen desorption temperature reduced to the range of 200°C to 230°C.

According to the researcher, synthesized powder hydrogen desorption temperature is about 200°C less than pure magnesium hydride. Under optimum conditions, hydrogen desorption temperature dropped from 426°C to the range of 200°C to 230°C.

You could find more details at International Journal of Hydrogen Energy, volume 34, pages 7724 to 7730, 2009.

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