Counting electrons - A new approach to tailor the hydrogen sorption properties of high-entropy alloys
| Autor: | Dennis Karlsson, Bjørn C. Hauback, Magnus H. Sørby, Gustav Ek, Martin Sahlberg, Magnus Moe Nygård |
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| Rok vydání: | 2019 |
| Předmět: |
010302 applied physics
Thermogravimetric analysis Solid-state chemistry Materials science Polymers and Plastics Hydrogen Hydride High entropy alloys Metals and Alloys chemistry.chemical_element 02 engineering and technology Crystal structure 021001 nanoscience & nanotechnology 01 natural sciences Electronic Optical and Magnetic Materials Hydrogen storage Differential scanning calorimetry chemistry 0103 physical sciences Ceramics and Composites Physical chemistry 0210 nano-technology |
| Zdroj: | Acta Materialia. 175:121-129 |
| ISSN: | 1359-6454 |
| DOI: | 10.1016/j.actamat.2019.06.002 |
| Popis: | 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 o n s e t , 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 TiVCrNbH 8 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. |
| Databáze: | OpenAIRE |
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