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Nanocrystalline magnesium and its properties of hydrogen sorption

David E.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 20, nr 1-2

87-90

Purpose: The goal of this paper is to study the possibility of obtaining of magnesium and magnesium hydride in nanocrystalline form and then to activate these materials for to be used in efficient systems of hydrogen storage. Design/methodology/approach: The magnesium hydride (MgH2) was directly synthesized from mechanically grinded magnesium powder obtained through ball milling of Mg(BM), and hydrogen of high purity. The MgH2 was then chemical activation by surface modification of nanocrystalline Mg with nickel ultrafine particles addition. The hydrogen sorption properties of the nanocrystalline Mg were investigated by a conventional pressure-volume-temperature technique, X-ray diffraction, and scanning electron microscopy (SEM). Findings: We found that the mechanical activation improved significantly the kinetics of hydrogen absorption in nanocrystalline magnesium, increasing sorption rates by up to 2 orders of magnitude. A profound effect of the powder particle size on the hydrogen desorption characteristics has been also observed. It was also determined that the Mg2Ni compound absorbed hydrogen quickly and showed excellent hydrogen sorption properties at 300 degrees centigrade. Research limitations/implications: The reduction of the particle size of magnesium and the creation of fresh surfaces by mechanical ball milling help the kinetics but does not affect the thermodynamics. Practical implications: Further examination to obtain improved properties of hydrogen sorption process of magnesium based materials and investigations of achievement of new systems for hydrogen solid storage. Originality/value: This work contains new aspects, which show the conditions of obtaining of nanocrystalline metal clusters with size under 30nm and represents new approach of improvement of hydrogen sorption process in light metals, such as magnesium, that can provide promising results for hydrogen storage applications.