Objective
It is believed that the metal hydrides, that are capable reversibly outputting hydrogen, offer a cost-effective, safe and efficient basis for the development of alternative hydrogen power engineering. Recent developments in advanced fuel cell technologies have enhanced their economic attractivity, including that of the most commonly used hydrogen-oxygen fuel cells. Their specific energy is a function of hydrogen storage density, both volume and weight. Up to now, the full-scale usage of hydrogen as a fuel requires to improve parameters of hydrogen storage materials, reduce the costs of technology, its incorporation into available technical systems. Recent intensive studies of new hydrogen storage materials are aimed to large extent on hydrogen-absorbing alloys based on magnesium, which can reversibly store ~7.7 wt.% hydrogen. Mg2Ni-based alloys also offer very high capacity (>4 wt.% H2 , >900 mAh/g). This storage capacity, coupled with a low price, suggests that Mg and Mg-based alloys could be advantageous for use in Ni-MH battery electrodes and gaseous-hydrogen storage systems. However, the cycle life of these alloys, corrosion resistance and operational characteristics at mild temperature conditions are still not satisfactory. The further studies and progress in the development of these materials could be qualified as extraordinary significant. That is why Mg-based materials will be in the focus of our studies in the frame of this project. The main objectives of this project are the synthesis of novel Mg-based alloys with high H-capacity, including those prepared in nano-, amorphous or controlled micro-gradient states; synthesis of the Mg-based intermetallics stabilised by light interstitial elements (O,N,C); Mg-composites with Ti(Zr)-based suboxides (Ti4Ni2O, Zr3NiO). Gas hydrogen absorption-desorption properties will be studied for all prepared materials. The modified Mg-based alloys, composites and their related hydrides will be prepared either by conventional methods or by high energy ball milling and reactive mechanical alloying. These materials are expected to possess the hydrogen capacity above 4.0 wt.%, enhanced hydrogen kinetics and long cycling behaviour under mild conditions. R- (Rare earth) and Ti/Zr-based alloys will be also involved in our research program to establish new possibilities to enhance their hydrogen storage operational characteristics. The partial substitution in R-M binary intermetallic compounds by light Mg component, which can lead to changes of structure and increase of H-capacity, will be studied. High pressure hydrogenation will be used for selected alloys (modified R- and Ti/Zr-based compounds) and novel Mg-based composite materials to achieve larger capacities. The correlation between composition, structure, hydrogenation capacity (gas & electrochemical) and cyclic stability for the studied materials will be in the focus of our attention also in order to formulate the general rules of their relationships.
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THIAIS
France