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Synthesis and mechanical treatment of the intermetallic hydrogen storage alloys by mechanical alloying method

Механохимический синтез и механическая активация интерметаллических соединений сплавов-накопителей водорода
Mechanical alloying (MA) is a method of solid-state synthesis of various equilibrium and non-equilibrium phases. Those phases have nanocrystalline substructure and wide concentration range as compared to known equilibrium diagrams. The noted peculiarities of MA are crucial for various applications, in particular for reversible hydrogen storage materials. Among hydride forming alloys considered as promising hydrogen storage media a special emphasis should be placed on TiFe intermetallic compound combining high hydrogen capacity with reduced cost. As for TiFe, conventional metallurgical method of TiFe production is comprised of melting of the components followed by prolonged high-temperature annealing: 1440 hours at 1073 K and then 240 hours at 1173 K. The alloy prepared in such a manner needs a hard activation to reach complete hydrogenation and reproducible hydrogen sorption properties. It was shown that intense grinding of the TiFe alloy and its transformation to the nanocrystalline state substantially simplified interaction with hydrogen. Optimization of the MA procedure to attain a high performance hydrogen absorbing material is an actual problem. Another one is related to practical application of fine powders in hydrogen storage systems. Pulverization of metallic alloys during hydrogenation-dehydrogenation cycles is their intrinsic feature. A promising solution of the problem is consisted in compacting the powder to prevent outpouring, to ensure good heat and gas transfer and to improve thus hydrogen absorption-desorption kinetics. This means that the bulk samples from hydrogen storage alloys must be like a sponge with high hydrogen permeability, thermal conductivity and durability at repeatable hydrogen absorption-desorption processes. As for TiFe intermetallic hydrogen sorption alloys, in the present work we demonstrated a possibility of direct solid-phase synthesis by MA of a nanostructured TiFe intermetallic compound from individual components Fe and Ti and to production of bulk samples from powders retaining nanoscale microstructure and hydrogen-sorption ability.

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Doctor of Science, professor
Ph.D., research associate
Ph.D., engineer
Ph.D., associated professor in Lomonosov Moscow State University

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