New processing routes by high-pressure torsion of different nature of magnesium based powders for improved hydrogen storage applications

Abstract : The present work mainly focuses on the effects of severe plastic deformation through high-pressure torsion (HPT) of different nature of magnesium based powders on improving the hydrogen sorption properties of Mg. The different nature of powders was obtained by either a gas-atomization process or an arc-plasma evaporation/condensation method. These powders were consolidated into bulk products by a two-step HPT process. Among the studied powder composites, the Mg/graphene based powder demonstrated excellent hydrogen sorption properties representing faster activation kinetics. A significant advantage of the HPT processing was to break the impervious MgO oxide layers, and to disperse them uniformly along with catalytic additives within the Mg domains. Through the introduction of structural defects and microstructural refinement, the HPT processing has allowed significant improvements in the first hydrogenation kinetics for the consolidated Mg products compared to their initial powder precursors while it was reverse for the C-doped HPT products. Another significant impact of the HPT processing was to reduce the hysteresis between the absorption and desorption plateau pressures during the pressure-composition-temperature (PCT) experiments. Moreover, it was revealed that the HPT processing has drastically reduced the hydrogen desorption temperatures for all the powder combinations while the rate of dehydrogenation was slightly diminished for their consolidated products. Nevertheless, the major drawback of the HPT processing, irrespective of the nature of studied composites, was that it always impaired the maximum hydrogen storage capacity of the starting powder precursors.
Document type :
Theses
File URL :
http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2018_0337_PANDA.pdf
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https://hal.univ-lorraine.fr/tel-02346615
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Submitted on : Tuesday, November 5, 2019 - 9:46:26 AM
Last modification on : Thursday, November 7, 2019 - 1:31:24 AM

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  • HAL Id : tel-02346615, version 1

Citation

Subrata Panda. New processing routes by high-pressure torsion of different nature of magnesium based powders for improved hydrogen storage applications. Materials Science [cond-mat.mtrl-sci]. Université de Lorraine, 2018. English. ⟨NNT : 2018LORR0337⟩. ⟨tel-02346615⟩

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