Mg/AB₅, Mg/AB and Mg/C nanocomposites were synthesized by mechanical milling in planetary type ball mills. The milling conditions were varied with the aim to produce composites with different morphology and microstructure, characterized by electron microscopy and x-ray diffraction. Continuous milling results in grain size refinement and in some cases to amorphization of the material. Milling under hydrogen gas atmosphere results in substantially finer particle size of the Mg/AB₅ and Mg/AB composites compared to the materials milled under argon.

 The hydriding and dehydriding of the composites were carried out in a hydrogen gas phase as well as electrochemically. It was proved that the morphology and microstructure of the nanocomposites has an influence on their hydrogen capacity and hydriding/dehydriding kinetics. Finer particle and grain size improves markedly the kinetics of hydriding/dehydriding. Smaller nanocrystallites size generally results in an increase of the electrochemical capacity as well.

The hydrogen sorption kinetics of Mg/AB₅ and Mg/AB nanocomposites with different microstructure has been studied and the mechanism of the absorption process has been determined. A low-temperature (near room temperature) hydrogen absorption has been detected for the Mg/AB₅ nanocomposites. A small difference in the nanocrystalls size of the nanocomposites results also in noticeable difference in the electrochemical behavior (hydrogen capacity and stability at hydrogen charge/discharge cycling).

 The hydrogen capacity, hydrogen desorption temperature and absorption/desorption kinetics of MgH₂ mechanically milled with different carbon additives were found to be dependent on the amount of the additives as well as on the milling duration. Considerable decrease of the hydrogen desorption temperature has been obtained for the MgH₂/C nanocomposites. The electrochemical hydriding/dehydriding behavior of  Mg/C nanocomposites was also investigated.

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