RT info:eu-repo/semantics/article
T1 Ultra high temperature high-entropy borides: effect of graphite addition on oxides removal and densification behaviour
A1 Barbarossa, Simone
A1 Orrù, Roberto
A1 Garroni, Sebastiano
A1 Licheri, Roberta
A1 Cao, Giacomo
K1 High-entropy metal borides
K1 Oxide impurities
K1 Spark plasma sintering
K1 Self-propagating high-temperature synthesis
K1 X-ray diffraction
K1 Materiales
K1 Materials
AB 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.
PB Elsevier
SN 0272-8842
YR 2021
FD 2021-03
LK http://hdl.handle.net/10259/5818
UL http://hdl.handle.net/10259/5818
LA eng
NO 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)
DS Repositorio Institucional de la Universidad de Burgos
RD 24-dic-2024