Synthesis and Phase Stability of the High-Entropy Carbide (Ti_0.2Zr_0.2Nb_0.2Ta_0.2Mo_0.2)C under Extreme Conditions

Abstract

As a novel ultrahigh temperature ceramic, the stability of a high-entropy transition metal carbide under extreme conditions is of great concern to its application. Despite the intense research, the available high-pressure experimental results are few so far. Here, we synthesized the nanocrystalline (Ti 0.2 Zr 0.2 Nb 0.2 Ta 0.2 Mo 0.2 )C by a highpressure solid-state reaction successfully. Meanwhile, synchrotron radiation X-ray diffraction experiments were carried out to explore the phase stability and mechanical response under high pressure. The single cubic B1 phase structure of the high-entropy carbide is retained under extreme hydrostatic pressure. An abnormal cubic-to-cubic phase transition was observed unexpectedly under nonhydrostatic compression. This result reflects the effect of the severe lattice distortion of the initial B1 phase highentropy carbide and the shear strain caused by deviatoric stress under high nonhydrostatic pressure. The physical mechanism about electronic/magnetic characteristics behind findings is an interesting issue for future studies.

High‐entropy carbide‐based ceramic cutting tools

“…Generally, the grain size of high‐entropy carbides is microlevel due to the high sintering temperature 22–24 . Preparing a sub‐microlevel grain size needs to adopt high‐pressure sintering route 25,26 . In this study, a sub‐microlevel grain size (0.60 ± 0.15 μm) of (Ti 0.2 Zr 0.2 Nb 0.2 Ta 0.2 Mo 0.2 )C 0.8 phase could be obtained at 1450°C and a uniaxial pressure of 4.3 MPa by the introduction of cobalt as liquid‐phase sintering aid.…”

“…[22][23][24] Preparing a sub-microlevel grain size needs to adopt high-pressure sintering route. 25,26 In this study, a sub-microlevel grain size (0.60 ± 0.15 µm) of (Ti 0.2 Zr 0.2 Nb 0.2 Ta 0.2 Mo 0.2 )C 0.8 phase could be obtained at 1450 • C and a uniaxial pressure of 4.3 MPa by the introduction of cobalt as liquid-phase sintering aid. The cobalt content within the HEC3 sample was ∼7.7 vol%.…”

Achieving Dislocation Strengthening in Hafnium Carbide through High Pressure and High Temperature

“…The results below demonstrate that our strategy is successful with HfC ceramics. On the one hand, the HPHT technique greatly reduces the sintering temperature of HfC; on the other hand, it also effectively improves the density of HfC by promoting the deformations of the crystal grains to produce a certain degree of defects, which is widely used in the synthesis of many refractory materials, such as diamond, cBN, and other transition metal carbides (ReB 2 , WC, and TaC). − In the present work, we consolidated a series of HfC ceramics by HPHT. The samples were characterized in terms of their density, microstructure, deformation behavior, mechanical properties, and oxidation resistance.…”

Local orders, lattice distortions, and electronic structure dominated mechanical properties of (ZrHfTaM1M2)C (M = Nb, Ti, V)

“…Among the current reported bulk HECs, 20–23 transition metal carbides of IVB (TiC, ZrC, HfC) and VB (VC, NbC, TaC) groups are the main constituents. The lattice structures of them are all rock salt (NaCl) structure.…”

“…1 In particular, high-entropy carbides (HECs) present excellent mechanical properties, 10 low thermal conductivity, 11,12 good thermal expansion, 12 high oxidation resistance, [13][14][15] high corrosion resistance, 16 and high irradiation resistance, 17 which play a significant role in aerospace, nuclear energy, machinery, metallurgy, and other extreme environment fields. 11,18,19 Among the current reported bulk HECs, [20][21][22][23] transition metal carbides of IVB (TiC, ZrC, HfC) and VB (VC, NbC, TaC) groups are the main constituents. The lattice structures of them are all rock salt (NaCl) structure.…”