Ultra high temperature high-entropy borides: Effect of graphite addition on oxides removal and densification behaviour
نویسندگان
چکیده
The introduction of 0.5–1.0 wt.% graphite to the powders prepared by Self-propagating High-temperature Synthesis (SHS) is found be highly beneficial for removal oxide impurities (from 2.7-8.8 0.2–0.5 wt.%) during spark plasma sintering (1950°C/20 min, 20 MPa) (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2 and (Hf0.2Mo0.2Ta0.2Zr0.2Ti0.2)B2 ceramics. Concurrently, consolidation level achieved enhanced from about 92.5% 88%, respectively, values exceeding 97%. While a further increase slightly improves samples densification, final products become progressively richer unreacted carbon. It assumed that plays double role SPS, e.g. not only as reactant carbothermal reduction oxides contaminant, but also lubricating agent powder particles. latter phenomenon likely main responsible densification improvement when 3 or larger amounts additive are used. Another positive effect crystallite size refinement high-entropy phases with progressive abatement oxides, confirm their presence promotes grain coarsening process.
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ژورنال
عنوان ژورنال: Ceramics International
سال: 2021
ISSN: ['0272-8842', '1873-3956']
DOI: https://doi.org/10.1016/j.ceramint.2020.10.200