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Counting electrons - A new approach to tailor the hydrogen sorption properties of high-entropy alloys
Inst Energy Technol, Dept Neutron Mat Characterizat, POB 40, NO-2027 Kjeller, Norway.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Inst Energy Technol, Dept Neutron Mat Characterizat, POB 40, NO-2027 Kjeller, Norway.
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2019 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 175, p. 121-129Article in journal (Refereed) Published
Abstract [en]

We have investigated the structure and hydrogen storage properties of a series of quaternary and quintary high-entropy alloys related to the ternary system TiVNb with powder X-ray diffraction (PXD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and manometric measurements in a Sieverts apparatus. The alloys have body-centred cubic (bcc) crystal structures and form face-centred cubic (fcc) metal hydrides with hydrogen-to-metal ratios close to 2 by hydrogenation. The onset temperature for hydrogen desorption, T-onset, decreases linearly with the valence-electron concentration, VEC. Moreover, the volumetric expansion per metal atom from the bcc alloys to the fcc hydrides, [(V/Z)(fcc) - (V/Z)(bcc)]/(V/Z)(bcc), increases linearly with the VEC. Therefore, it seems that a larger expansion of the lattice destabilizes the metal hydrides and that this effect can be tuned by altering the VEC. Kissinger analyses performed on the DSC measurements indicate that the destabilization is a thermodynamic rather than kinetic effect. Based upon these insights we have identified TiVCrNbH8 as a material with suitable thermodynamics for hydrogen storage in the solid state. This HEA-based hydride has a reversible hydrogen storage capacity of 1.96 wt% H at room temperature and moderate H-2-pressures. Moreover, it is not dependent on any elaborate activation procedure to absorb hydrogen.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD , 2019. Vol. 175, p. 121-129
Keywords [en]
Metal hydrides, Hydrogen storage, High-entropy alloys, HEAs
National Category
Metallurgy and Metallic Materials Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-393330DOI: 10.1016/j.actamat.2019.06.002ISI: 000479023600011OAI: oai:DiVA.org:uu-393330DiVA, id: diva2:1355363
Funder
Swedish Foundation for Strategic Research , GMT14-0048NordForsk, 81942Available from: 2019-09-27 Created: 2019-09-27 Last updated: 2019-09-27Bibliographically approved

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Ek, GustavKarlsson, DennisSahlberg, Martin

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