High-entropy carbide: A novel class of multicomponent ceramics

Zhou, Jieyang; Zhang, Jinyong; Zhang, Fan; Niu, Bo; Lei, Liwen; Wang, Weimin

doi:10.1016/j.ceramint.2018.08.100

Cited by 353 publications

(161 citation statements)

References 26 publications

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“…In general, densification of UHTCs can be promoted by reducing the particle size of the starting powders because finer particles have higher surface energies, thus providing a higher driving force for densification at lower temperatures . The synthesis of high‐entropy carbide (HEC) powders with fine particle sizes have rarely been reported in previous studies . Zhou et al reported that (Hf, Zr, Ti, Ta, Nb)C powders synthesized at 1950°C using commercial carbide mixtures had an average particle size of approximately 2 µm .…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6] Recently, single-phase high-entropy carbide ceramics (HECCs) have attracted attention due to notable properties such as high hardness, chemical stability, and oxidation resistance. [7][8][9][10] Heretofore, HECCs have been produced by hot pressing (HP) a mixture of four or more transition-metal carbides, which have been hypothesized to be more thermodynamically stable at elevated temperatures due to the contribution of configurational entropy to the overall Gibbs free energy. 11,12 Temperatures of 2200°C or higher are typically required for densification of HECCs due to their strong bonding and low self-diffusion coefficients.…”

Section: Introductionmentioning

confidence: 99%

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Low‐temperature sintering of single‐phase, high‐entropy carbide ceramics

Fahrenholtz

2019

J Am Ceram Soc

159

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Dense (Hf, Zr, Ti, Ta, Nb)C high‐entropy ceramics were produced by hot pressing (HP) of carbide powders synthesized by carbothermal reduction (CTR). The relative density increased from 95% to 99.3% as the HP temperature increased from 1750°C to 1900°C. Nominally phase pure ceramics with the rock salt structure had grain sizes ranging from 0.6 µm to 1.2 µm. The mixed carbide powders were synthesized by high‐energy ball milling (HEBM) followed by CTR at 1600°C, which resulted in an average particle size of ~100 nm and an oxygen content of 0.8 wt%. Low sintering temperature, high relative densities, and fine grain sizes were achieved through the use of synthesized powders. These are the first reported results for low‐temperature densification and fine microstructure of high‐entropy carbide ceramics.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Low‐temperature sintering of single‐phase, high‐entropy carbide ceramics

Fahrenholtz

2019

J Am Ceram Soc

159

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“…HEOs are a class of materials where a large number of different (incorporated) elements increases the configurational entropy, leading to entropy stabilization . The concept of entropy stabilization was first applied to metallic alloy systems and later transferred to ionic and covalently‐bonded structures . For high‐entropy materials, a single‐phase crystal structure can be achieved when the Gibbs free energy is negative or, in other words, when the entropy term is greater than the enthalpy of mixing .…”

Section: Introductionmentioning

confidence: 99%

“…[18][19][20][21] The concept of entropy stabilization was first applied to metallic alloy systems and later transferred to ionic and covalently-bonded structures. [22][23][24][25][26] For high-entropy materials, a single-phase crystal structure can be achieved when the Gibbs free energy is negative or, in other words, when the entropy term is greater than the enthalpy of mixing. [27] The configurational entropy is determined by the number of different elements on the same sublattice (configurational entropy, S config ) and can be calculated according to Equation S1.…”

Section: Introductionmentioning

confidence: 99%

Gassing Behavior of High‐Entropy Oxide Anode and Oxyfluoride Cathode Probed Using Differential Electrochemical Mass Spectrometry

Breitung

Schiele

Tripković

et al. 2020

Batteries & Supercaps

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Multicomponent materials may exhibit favorable Li‐storage properties because of entropy stabilization. While the first examples of high‐entropy oxides and oxyfluorides show good cycling performance, they suffer from various problems. Here, we report on side reactions leading to gas evolution in Li‐ion cells using rock‐salt (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O (HEO) or Li(Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)OF (Li(HEO)F). Differential electrochemical mass spectrometry indicates that a robust solid‐electrolyte interphase layer is formed on the HEO anode, even when using an additive‐free electrolyte. For the Li(HEO)F cathode, the cumulative amount of gases is found by pressure measurements to depend strongly on the upper cutoff potential used during cycling. Cells charged to 5.0 V versus Li+/Li show the evolution of O2, H2, CO2, CO and POF3, with the latter species being indirectly due to lattice O2 release as confirmed by electron energy loss spectroscopy. This result attests to the negative effect that lattice instability at high potentials has on the gassing.

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“…To date, only two methods have been developed to synthesize high‐entropy metal carbide powders. For example, Zhou et al synthesized the high‐entropy (Hf, Zr, Ta, Nb, Ti)C powders by spark plasma sintering at 2223 K using metal carbides as the starting materials, but the expensive starting materials limit the extensive applications of high‐entropy metal carbides. Recently, Feng et al prepared the high‐entropy (Hf, Zr, Ta, Nb, Ti)C powders via a two‐step synthesis process consisting of carbothermal reduction at 1873 K followed by solid‐solution formation at 2273 K using low‐cost metal oxides and graphite as the starting materials .…”

Section: Introductionmentioning

confidence: 99%

One‐step synthesis of coral‐like high‐entropy metal carbide powders

Ning

Liu

et al. 2019

J Am Ceram Soc

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The synthesis of high‐entropy metal carbide powders is critical for implementing their extensive applications. However, the one‐step synthesis of high‐entropy metal carbide powders is rarely studied. Herein, the synthesis possibility of high‐entropy metal carbide powders, namely (Zr0.25Ta0.25Nb0.25Ti0.25)C (ZTNTC), via one‐step carbothermal reduction was first investigated theoretically by analyzing chemical thermodynamics and lattice size difference based on the first‐principle calculations, and then the ZTNTC powders with particle size of 0.5‐2 μm were successfully synthesized experimentally. The as‐synthesized powders not only had a single rock‐salt crystal structure of metal carbides, but also possessed high‐compositional uniformity from nanoscale to microscale. More interestingly, they exhibited the distinguished coral‐like morphology with the hexagonal step surface, whose growth was governed by a classical screw dislocation growth mechanism.

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High-entropy carbide: A novel class of multicomponent ceramics

Cited by 353 publications

References 26 publications

Low‐temperature sintering of single‐phase, high‐entropy carbide ceramics

Low‐temperature sintering of single‐phase, high‐entropy carbide ceramics

Gassing Behavior of High‐Entropy Oxide Anode and Oxyfluoride Cathode Probed Using Differential Electrochemical Mass Spectrometry

One‐step synthesis of coral‐like high‐entropy metal carbide powders

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