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In order to prepare high toughness (Ti,Zr,Nb,Ta,Mo)C ceramics at low temperatures while maintaining high hardness, a liquid-phase sintering process combined with Co-based liquid-phase extrusion strategy was adopted in this study. The densification temperature can be lowered to 1350 ℃, which is much lower than the solid-state sintering temperature (~2000 ℃) generally employed for high-entropy carbide ceramics. When sintered at 1550 ℃ and 30 MPa applied pressure, part of the Co-based liquid-phase was squeezed out of the graphite mold, such that only ~3.21 vol% of Co remained in the high-entropy ceramic. Compared to the Co-free solid-state sintered (Ti,Zr,Nb,Ta,Mo)C ceramics, prepared at 2000 ℃ and 35 MPa, the hardness was slightly decreased from 25.06±0.32 to 24.11±0.75 GPa, but the toughness was increased from 2.25±0.22 to 4.07±0.13 MPa·m1/2. This work provides a new strategy for low-temperature densification of high-entropy carbides with both high hardness and high toughness.
In order to prepare high toughness (Ti,Zr,Nb,Ta,Mo)C ceramics at low temperatures while maintaining high hardness, a liquid-phase sintering process combined with Co-based liquid-phase extrusion strategy was adopted in this study. The densification temperature can be lowered to 1350 ℃, which is much lower than the solid-state sintering temperature (~2000 ℃) generally employed for high-entropy carbide ceramics. When sintered at 1550 ℃ and 30 MPa applied pressure, part of the Co-based liquid-phase was squeezed out of the graphite mold, such that only ~3.21 vol% of Co remained in the high-entropy ceramic. Compared to the Co-free solid-state sintered (Ti,Zr,Nb,Ta,Mo)C ceramics, prepared at 2000 ℃ and 35 MPa, the hardness was slightly decreased from 25.06±0.32 to 24.11±0.75 GPa, but the toughness was increased from 2.25±0.22 to 4.07±0.13 MPa·m1/2. This work provides a new strategy for low-temperature densification of high-entropy carbides with both high hardness and high toughness.
This work was supported by the National Natural Science Foundation of China (Grant Nos. 51832002, 51402055, 51602060, and U1401247) and the Science and Technology Program of Guangzhou (Grant No. 201704030095).
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