2024-03-28T15:15:26Zhttps://riubu.ubu.es/oai/requestoai:riubu.ubu.es:10259/58182023-03-31T11:46:20Zcom_10259_4759com_10259_2604col_10259_4760
Ultra high temperature high-entropy borides: effect of graphite addition on oxides removal and densification behaviour
Barbarossa, Simone
Orrù, Roberto
Garroni, Sebastiano
Licheri, Roberta
Cao, Giacomo
High-entropy metal borides
Oxide impurities
Spark plasma sintering
Self-propagating high-temperature synthesis
X-ray diffraction
Materiales
Materials
The introduction of 0.5–1.0 wt.% graphite to the powders prepared by Self-propagating High-temperature Synthesis (SHS) is found to be highly beneficial for the removal of oxide impurities (from 2.7-8.8 wt.% to 0.2–0.5 wt.%) during spark plasma sintering (1950°C/20 min, 20 MPa) of (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2 and (Hf0.2Mo0.2Ta0.2Zr0.2Ti0.2)B2 ceramics. Concurrently, the consolidation level achieved is enhanced from about 92.5% and 88%, respectively, to values exceeding 97%. While a further increase of graphite slightly improves samples densification, final products become progressively richer of the unreacted carbon.
It is assumed that graphite plays a double role during SPS, e.g. not only as a reactant during the carbothermal reduction of oxides contaminant, but also as lubricating agent for the powder particles. The latter phenomenon is likely the main responsible for the densification improvement when 3 wt.% or larger amounts of additive are used. Another positive effect is the crystallite size refinement of the high-entropy phases with the progressive abatement of oxides, to confirm that their presence promotes grain coarsening during the sintering process.
ARCHIMEDES project sponsored by Regione Autonoma della Sardegna (Italy) - Fondo di Sviluppo e Coesione (FSC) 2014–2020 (Cod. RAS: RASSR88309, Cod. CUP: F76C18000980002). One of the authors (S.B.) performed his activity in the framework of the International PhD in Innovation Sciences and Technologies at the University of Cagliari, Italy. One of us (G.C.) acknowledges the results obtained in this manuscript as quite important for the “Ithermal” and “Generazione E” projects, sponsored by Sardegna Ricerche, Italy (Cod. CUP: F21I18000130006) and by the Italian Ministry of Education, University and Research, Italy (Cod. CUP: B96G18000560005)
2021-06-28T11:37:21Z
2021-06-28T11:37:21Z
2021-03
info:eu-repo/semantics/article
info:eu-repo/semantics/acceptedVersion
0272-8842
http://hdl.handle.net/10259/5818
10.1016/j.ceramint.2020.10.200
eng
Ceramics International. 2021, V. 47, n. 5, p. 6220-6231
https://doi.org/10.1016/j.ceramint.2020.10.200
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
http://creativecommons.org/licenses/by-nc-nd/4.0/
info:eu-repo/semantics/openAccess
application/pdf
Elsevier