Recent development of high-entropy transitional carbides: a review

Abstract

The high-entropy carbides (HECs) are reviewed in terms of the crystal structure, powder synthesis, densification, and mechanisms in this article. The inter-diffusion rate of binary carbide is mainly analyzed and predicted based on lattice parameters. During the solid solution formation progress, the densification methods usually adopted were hot pressing and spark plasma sintering. It was found that the distribution of metal atoms was more uniform in high-entropy powders derived from binary carbide raw materials. HECs displayed higher hardness, elastic modulus, and oxidation resistance, and meanwhile exhibited lower thermal conductivity compared to binary carbides. HECs are expected to be used as high-speed atmospheric re-entry vehicles.

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

“…The large R 2 ( H fitting is 0.82, E fitting is 0.87) and small error bar ( H fitting is ± 1 GPa, E fitting is ± 10 GPa) indicate that the calculated H and E match well with the collected experimental and theoretical results 7,16,36 . The H and E of (Zr 0.2 Hf 0.2 Ta 0.2 Ti 0.2 V 0.2 )C are 27.29 GPa and 442.48 GPa, respectively, which are the same as those of (Zr 0.2 Hf 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C. As shown in Table 2, these investigated HECs have high hardness and elastic modulus, which presents that they inherit the excellent mechanical properties of binary carbides 22 . It is noted that the predicted H and E of (Zr 0.2 Hf 0.2 Ta 0.2 Nb 0.2 V 0.2 )C are the lowest, which could be caused by the existence of V–C weak spots.…”

“…It is understood that the design of HECs approximately conforms the mixing rule. 22 Here, a, E 0 , V 0 , and even ΔH of (Zr 0.2 Hf 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C are approximately the average value of its corresponding component binary carbides, shown in Figure 2 and Table 1. However, the B 0 of three HECs is obviously lower than the average value of corresponding binary carbides.…”

“…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.…”

“…The lattice structures of them are all rock salt (NaCl) structure. Also, according to the atomic size misfit parameter δ < 10%, it can be inferred that they are more easily to form a single‐phase solid solution theoretically 22,24 . Moreover, their unique excellent physical and chemical properties can be further improved by the synthesis of HECs 23 .…”

Preparation of Single-phase High Entropy Carbides by a Modified Citric Acid Complexing Method

“…High entropy ceramics are multi-principal component solid solution materials in which the molar amounts of metal elements at the same lattice sites are equal or near equal, including carbides [1][2][3][4], borides [5][6][7][8], oxides [9][10][11][12][13], silicides [14,15], nitrides [16][17][18] and fluorides [19], etc. High entropy carbides (HEC) have become new candidates of ultra-high temperature ceramics used as structural components in aerospace propulsion and nuclear reactor systems, due to the excellent properties such as high hardness [20,21], low thermal conductivity [22][23][24], better oxidation resistance [25,26], excellent electrical conductivity [27] and so on.…”