| dc.date.accessioned | 2024-02-28T14:00:27Z | |
| dc.date.available | 2024-02-28T14:00:27Z | |
| dc.date.issued | 2024 | |
| dc.identifier.uri | http://hdl.handle.net/10852/108732 | |
| dc.description.abstract | Magnetic refrigeration is being explored as a promising alternative to current cooling methods, but existing magnetocaloric materials face challenges for mass production. This thesis investigates two types of materials: high entropy alloys (HEAs) and MnNiSi-based compounds. By changing their compositions, it is possible to tailor their magnetic properties for efficient room temperature refrigeration. By a combination of microscopy techniques, powder diffraction (X-rays and neutrons), caloric and magnetic measurements, a thorough evaluation of the compounds and the magnetic transitions was performed.
The studied V1-xFeCoNiAl1+x and V1-xFeCoNiCu1+x HEAs were ferromagnetic, but had less effective magnetocaloric properties compared to other materials. In contrast, MnNiSi-based compounds exhibited abrupt magnetic transitions due to a structural change. Compositions such as Mn1-xNi1-xFe2xSi0.95Al0.05 with x between 0.31 and 0.32 showed better magnetocaloric performance than the HEAs. Despite internal disorder affecting their magnetocaloric effect in HEAs and MnNiSi compounds, post-synthesis processing was found to improve the MnNiSi-based materials even more, offering a pathway towards competitive MnNiSi-based magnetocaloric materials using abundant elements (Mn, Ni, Si, Fe, and Al). | en_US |
| dc.language.iso | en | en_US |
| dc.relation.haspart | Paper I. Bruno G. F. Eggert, Erna K. Delczeg-Czirjak, Fernando Maccari, Susmit Kumar, Oliver Gutfleisch, Helmer Fjellvåg, Bjørn C. Hauback, Christoph Frommen. ‘Exploring V-Fe-Co-Ni-Al and V-Fe-Co-Ni-Cu high entropy alloys for magnetocaloric applications’. In: Journal of Alloys and Compounds. Volume 921, (2022). DOI: 10.1016/j.jallcom.2022.166040. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.jallcom.2022.166040 | |
| dc.relation.haspart | Paper II. Bruno G. F. Eggert, Erna K. Delczeg-Czirjak, Bjørn C. Hauback, Christoph Frommen. ‘Magnetic transitions in V-Fe-Co-Ni-Cu-based high entropy alloys’. In: Materials Today Physics. Volume 35, (2022). DOI: 10.1016/j.mtphys.2023.101116. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.mtphys.2023.101116 | |
| dc.relation.haspart | Paper III. Bruno G. F. Eggert, João Horta Belo, João P. Araújo, Bjørn C. Hauback, Christoph Frommen. ‘Structural transitions and magnetocaloric properties of low-cost MnNiSi-based intermetallics’ In: Intermetallics. Volume 154, (2022). DOI: 10.1016/j.intermet.2023.107823. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.intermet.2023.107823 | |
| dc.relation.haspart | Paper IV. Bruno G. F. Eggert, Erna K. Delczeg-Czirjak, Øystein S. Fjellvåg, Bjørn C. Hauback, Christoph Frommen. ‘Structure and Magnetism of Fe-substituted MnNiSi0.95Al0.05’. To be submitted. The paper is not available in DUO awaiting publishing. | |
| dc.relation.haspart | Paper V. Bruno G. F. Eggert, Kun Wang, Sina Jafarzadeh, Christian R. Bahl, Bjørn C. Hauback, Christoph Frommen. ‘Study of the magnetostructural transition in critical-element free Mn1−xNi1−xFe2xSi0.95Al0.05’ In: API Advances. Volume 13, (2023). DOI: 10.1063/9.0000511. The article is included in the thesis. Also available at: https://doi.org/10.1063/9.0000511 | |
| dc.relation.uri | https://doi.org/10.1016/j.jallcom.2022.166040 | |
| dc.relation.uri | https://doi.org/10.1016/j.mtphys.2023.101116 | |
| dc.relation.uri | https://doi.org/10.1016/j.intermet.2023.107823 | |
| dc.relation.uri | https://doi.org/10.1063/9.0000511 | |
| dc.title | Composition tuning microstructure and magnetic properties of High Entropy Alloys and MnNiSi-based compounds | en_US |
| dc.type | Doctoral thesis | en_US |
| dc.creator.author | Eggert, Bruno G. F. | |
| dc.type.document | Doktoravhandling | en_US |