Issue 16, 2019

A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite

Abstract

A multicomponent composite of refractory carbides, B4C, HfC, Mo2C, TaC, TiC and SiC, of rhombohedral, face-centered cubic (FCC) and hexagonal crystal structures is reported to form a single phase B4(HfMo2TaTi)C ceramic with SiC. The independent diffusion of the metal and nonmetal atoms led to a unique hexagonal lattice structure of the B4(HfMo2TaTi)C ceramic with alternating layers of metal atoms and C/B atoms. In addition, the classical differences in the crystal structures and lattice parameters among the utilized carbides were overcome. Electron microscopy, X-ray diffraction and calculations using density functional theory (DFT) confirmed the formation of a single phase B4(HfMo2TaTi)C ceramic with a hexagonal close-packed (HCP) crystal structure. The DFT based crystal structure prediction suggests that the metal atoms of Hf, Mo, Ta and Ti are distributed on the (0001) plane in the HCP lattice, while the carbon/boron atoms form hexagonal 2D grids on the (0002) plane in the HCP unit cell. The nanoindentation of the high-entropy phase showed hardness values of 35 GPa compared to the theoretical hardness value estimated based on the rule of mixtures (23 GPa). The higher hardness was contributed by the solid solution strengthening effect in the multicomponent hexagonal structure. The addition of SiC as the secondary phase in the sintered material tailored the microstructure of the composite and offered oxidation resistance to the high-entropy ceramic composite at high temperatures.

Graphical abstract: A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite

Associated articles

Supplementary files

Article information

Article type
Communication
Submitted
16 Nov 2018
Accepted
07 Feb 2019
First published
08 Feb 2019
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2019,48, 5161-5167

A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite

H. Zhang, D. Hedman, P. Feng, G. Han and F. Akhtar, Dalton Trans., 2019, 48, 5161 DOI: 10.1039/C8DT04555K

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