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arXiv · 2002.09756

Dual-Phase High-Entropy Ultra-High Temperature Ceramics

Mingde Qin·Joshua Gild·Chongze Hu·Haoren Wang·Md Shafkat Bin Hoque·Jeffrey L. Braun·Tyler J. Harrington·Patrick E. Hopkins·Kenneth S. Vecchio·Jian Luo
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Abstract

A series of dual-phase high-entropy ultrahigh temperature ceramics (DPHE-UHTCs) are fabricated starting from N binary borides and (5-N) binary carbides powders. >~99% relative densities have been achieved with virtually no native oxides. These DPHE-UHTCs consist of a hexagonal high-entropy boride (HEB) phase and a cubic high-entropy carbide (HEC) phase. A thermodynamic relation that governs the compositions of the HEB and HEC phases in equilibrium is discovered and a thermodynamic model is proposed. These DPHE-UHTCs exhibit tunable grain size, Vickers microhardness, Young' and shear moduli, and thermal conductivity. The DPHE-UHTCs have higher hardness than the weighted linear average of the two single-phase HEB and HEC, which are already harder than the rule-of-mixture averages of individual binary borides and carbides. This study extends the state of the art by introducing dual-phase high-entropy ceramics (DPHECs), which provide a new platform to tailor various properties via changing the phase fraction and microstructure.

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Mingde Qin, Joshua Gild, Chongze Hu, Haoren Wang, Md Shafkat Bin Hoque, Jeffrey L. Braun, Tyler J. Harrington, Patrick E. Hopkins, Kenneth S. Vecchio, Jian Luo. 2020-02-22. Dual-Phase High-Entropy Ultra-High Temperature Ceramics. https://doi.org/10.1016/j.jeurceramsoc.2020.05.040

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