RT info:eu-repo/semantics/article T1 High-entropy transition metal diborides by reactive and non-reactive spark plasma sintering: A comparative investigation A1 Tallarita, Giovanna A1 Licheri, Roberta A1 Garroni, Sebastiano A1 Barbarossa, Simone A1 Orrù, Roberto A1 Cao, Giacomo K1 High-entropy ceramics K1 Borides K1 Spark plasma sintering K1 Self-propagating high-temperature synthesis K1 Resistance to oxidation K1 Materiales K1 Materials AB The direct synthesis and consolidation by SPS (1950 °C, 20 min, 20 MPa) of high-entropy (Hf0.2Mo0.2Zr0.2Nb0.2Ti0.2)B2 from elemental powders resulted in a multiphase product. An increase of the heating rate determined a change of the mechanism governing the synthesis reaction from gradual solid-state diffusion to rapid combustion regime, while the final conversion degree was 67 wt.%. The sintered product displayed a non-uniform microstructure with the presence of 10–15 μm sized pores, due to volatilization phenomena occurring during the combustion synthesis reaction. In contrast, when the SPS process was preceded by powder synthesis via SHS, a homogeneous single-phase ceramic was obtained. Clear benefits are derived by the use of SHS, able to provide very shortly powders with elemental species very well intermixed, so that the obtainment of (Hf0.2Mo0.2Zr0.2Nb0.2Ti0.2)B2 during the subsequent SPS stage is strongly promoted. The resulting 92.5% dense product shows superior oxidation resistance with respect to individual borides prepared with the same method. PB Elsevier SN 0955-2219 YR 2020 FD 2020-04 LK http://hdl.handle.net/10259/5594 UL http://hdl.handle.net/10259/5594 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 (G.T.) performed her 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), respectively DS Repositorio Institucional de la Universidad de Burgos RD 23-nov-2024