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Nanocrystalline high-entropy hexaboride ceramics enable remarkable performance as thermionic emission cathodes.
- Source :
-
Fundamental Research . Nov2023, Vol. 3 Issue 6, p979-987. 9p. - Publication Year :
- 2023
-
Abstract
- The development of high-entropy borides with combined structural and functional performance holds untold scientific and technological potential, yet relevant studies have been rarely reported. In this work, we report nanocrystalline (La0.25Ce0.25Nd0.25Eu0.25)B6 high-entropy rare-earth hexaboride (HEReB6-1) ceramics fabricated through the high-pressure sintering of self-synthesized nanopowders for the first time. The as-fabricated samples exhibited a highly dense (96.3%) nanocrystalline (94 nm) microstructure with major (001) fiber textures and good grain boundaries without any impurities, resulting in a remarkable mechanical, electrical, and thermionic emission performance. The results showed that the samples possessed outstanding comprehensive mechanical properties and a high electrical resistivity from room temperature to high temperatures; these were greater than the average values of corresponding binary rare-earth hexaborides, such as a Vickers hardness of 23.4 ± 0.6 GPa and a fracture toughness of 3.0 ± 0.4 MPa•m1/2 at room temperature. More importantly, they showed high emission current densities at elevated temperatures, which were higher than the average values of the corresponding binary rare-earth hexaborides. For instance, the maximum emission current density reached 48.3 A•cm−2 at 1873 K. Such superior performance makes the nanocrystalline HEReB6-1 ceramics highly suitable for potential applications in thermionic emission cathodes. [ABSTRACT FROM AUTHOR]
- Subjects :
- *BORIDES
*ENTROPY
*RARE earth borides
*LANTHANUM hexaboride
*THERMIONIC cathodes
Subjects
Details
- Language :
- English
- ISSN :
- 20969457
- Volume :
- 3
- Issue :
- 6
- Database :
- Academic Search Index
- Journal :
- Fundamental Research
- Publication Type :
- Academic Journal
- Accession number :
- 174154003
- Full Text :
- https://doi.org/10.1016/j.fmre.2022.04.010