High-entropy carbide-nitrides with enhanced toughness and sinterability

Abstract

High-entropy ceramics (HECs) have attracted much attention due to their huge composition space, unique microstructure, and desirable properties. In contrast to previous studies, which have primarily focused on HECs with one anion, herein, we report a new family of ceramics with both multi-cationic and-anionic structures, i.e., high-entropy carbide-nitrides (Ti 0.33 Zr 0.33 Hf 0.33)(C 0.5 N 0.5), (Ti 0.25 Zr 0.25 Hf 0.25-Nb 0.25)(C 0.5 N 0.5) and (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)(C 0.5 N 0.5). These as-synthesized HECs are mainly comprised of a face-centered cubic solid-solution phase accompanied by minor inevitable oxide phases. The formation mechanism of the solid-solution phase is discussed in terms of the lattice size difference and thermodynamic competition between configurational entropy and mixing enthalpy. It is found that the increment in the configurational entropy can effectively lower the sintering temperature and increase the fracture toughness. Particularly, the newly developed (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)(C 0.5 N 0.5) exhibits a decent fracture toughness of 8.4 MPa m 1/2 and a low sintering temperature of 1750°C, making it promising for ultra-high temperature applications. Our work not only enriches knowledge regarding the HECs categories, but also opens a new pathway for developing HECs with multi-cationic and-anionic structures.

Effects of Ta2O5 content on mechanical properties and high‐temperature performance of Zr6Ta2O17 thermal barrier coatings

“…Figure 7 shows the typical images of Vickers indentation on the surface of the Zr‐12Ta specimen at 78.4 N. It is found that cracks appear in the four indentation corners, and obvious crack deflection occurs. During the crack propagation process, the crack deflection would consume more energy, which hinders the further propagation of cracks 31–33 . This phenomenon can partially explain why the Zr 6 Ta 2 O 17 coating has relatively high fracture toughness.…”

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

“…Refractory transition metal carbides are widely used in extreme environment fields, such as supersonic vehicle and engine inlet leading edge, high speed missile rudder, and cutting tool, due to their high melting point, extreme hardness, excellent mechanical properties, and physicochemical stability 1–6 . To meet the requirements of material performance under extreme conditions, the multi‐component ultra‐high temperature ceramics are attracting wide attentions and becoming one of the promising candidates for the final applications 7–9 . Correspondingly, various kinds of high‐entropy ceramics have been developed rapidly 1 .…”

“…[1][2][3][4][5][6] To meet the requirements of material performance under extreme conditions, the multi-component ultra-high temperature ceramics are attracting wide attentions and becoming one of the promising candidates for the final applications. [7][8][9] Correspondingly, various kinds of high-entropy ceramics have been developed rapidly. 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.…”

The new complex high‐entropy metal boron carbonitride: Microstructure and mechanical properties

“…16 Recently, on the basis of single-anion HECs, researchers broke the limitation of single-anion HECs and prepared binary or ternary-anion HECs. [31][32][33][34][35][36][37] Wen et al 31 synthesized a single rock-salt structure of metal nitridecarbides ceramic (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )(N 0.5 C 0.5 ) at 1773 K by hot-pressing sintering. It showed that a high microhardness of 19.5 ± 0.3 GPa and a nanohardness of 33.4 ± 0.5 GPa simultaneously possessed a Bulk modulus of 258 GPa, Young's modulus of 429 GPa, Shear modulus of 176 GPa, and elastic modulus of 572 ± 7 GPa.…”

“…Recently, on the basis of single‐anion HECs, researchers broke the limitation of single‐anion HECs and prepared binary or ternary‐anion HECs 31–37 . Wen et al 31 .…”