(Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C high‐entropy ceramics with low thermal conductivity

Yan, Xueliang; Constantin, Loïc; Lu, Yongfeng; Silvain, Jean François; Nastasi, M.; Cui, Bai

doi:10.1111/jace.15779

Cited by 451 publications

(194 citation statements)

References 29 publications

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“…11b). Yan X et al 78 reported elastic (nanoindentation) and Vicker's hardness results for (Ti,Zr,Hf,Ta,Nb,Ta)C and found that they were comparable to those of the monocarbides reported in the literature. However, the HEC had a theoretical density of only 93%, which would have resulted in a relatively low Vicker's hardness.…”

Section: Mechanical Propertiesmentioning

confidence: 60%

“…Yan et al 78 2 )O the distortion from an ideal rocksalt structure occurs primarily through disorder of the anion sublattice, which was conrmed by an extended X-ray absorption ne structure (EXAFS) analysis. 64 It is worth mentioning that the carbon stoichiometry of the samples was not analysed, which has an effect on the thermal conductivity due to phonon scattering by carbon vacancies.…”

Section: Thermal Conductivitymentioning

confidence: 99%

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Review of high entropy ceramics: design, synthesis, structure and properties

2019

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Section: Mechanical Propertiesmentioning

confidence: 60%

Section: Thermal Conductivitymentioning

confidence: 99%

Review of high entropy ceramics: design, synthesis, structure and properties

2019

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“…The present authors [28] have previously developed and utilized an ab initio entropy descriptor to synthesize nine different five-metal carbides, six of which formed single-phase high entropy materials that demonstrated high hardness values. Recent work done by Castle et al [29,30] [32], which demonstrated low thermal conductivity and a high elastic modulus and hardness.…”

Section: Introductionmentioning

confidence: 99%

Phase stability and mechanical properties of novel high entropy transition metal carbides

et al. 2019

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Twelve different equiatomic five-metal carbides of group IVB, VB, and VIB refractory transition metals are synthesized via high-energy ball milling and spark plasma sintering. Implementation of a newly developed ab initio entropy descriptor aids in selection of candidate compositions for synthesis of high entropy and entropy stabilized carbides. Phase formation and composition uniformity are analyzed via XRD, EDS, S/TEM-EDS, and EXAFS. Nine of the twelve candidates form true single-phase materials with the rocksalt (B1) structure when sintered at 2473 K and can therefore be investigated as high entropy carbides (HECs). The composition (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 W 0.2)C is presented as a likely candidate for further investigation as an entropy stabilized carbide. Seven of the carbides are examined for mechanical properties via nanoindentation. The HECs show significantly enhanced hardness when compared to a rule of mixtures average of the constituent binary carbides and to the highest hardness of the binary constituents. The mechanical properties are correlated to the electronic structure of the solid solutions, offering a future route to tunability of the mechanical properties of carbide ceramics via exploration of a new complex composition space.

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“…Since 2015, high-entropy ceramics (HECs) have been made in bulk form, including various high-entropy oxides [6][7][8][9][10], borides [11,12], carbides [13][14][15], nitrides [16], and silicides [17,18]. Unlike metallic HEAs of simple FCC, BCC or HCP structures, HECs typically only have high-entropy mixing at one (or multiple) cation sublattice(s).…”

Section: Introductionmentioning

confidence: 99%

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

Wright

Wang

Huang

et al. 2020

Journal of the European Ceramic Society

201

125

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Using fluorite oxides as an example, this study broadens high-entropy ceramics (HECs) to compositionally-complex ceramics (CCCs) or multi-principal cation ceramics (MPCCs) to include medium-entropy and/or non-equimolar compositions. Nine compositions of compositionally-complex fluorite oxides (CCFOs) with the general formula of (Hf1/3Zr1/3Ce1/3)1x(Y1/2X1/2)xO2-δ (X = Yb, Ca, and Gd; x = 0.4, 0.148, and 0.058) are fabricated. The phase stability, mechanical properties, and thermal conductivities are measured. Compared with yttriastabilized zirconia, these CCFOs exhibit increased cubic phase stability and reduced thermal conductivity, while retaining high Young's modulus (~210 GPa) and nanohardness (~18 GPa).Moreover, the temperature-dependent thermal conductivity in the non-equimolar CCFOs shows an amorphous-like behavior. In comparison with their equimolar high-entropy counterparts, the medium-entropy non-equimolar CCFOs exhibit even lower thermal conductivity (k) while maintaining high modulus (E), thereby achieving higher E/k ratios. These results suggest a new direction to achieve thermally-insulative yet stiff CCCs (MPCCs) via exploring non-equimolar and/or medium-entropy compositions. Summary of Novel Conclusions:This study broadens "high-entropy ceramics" to "compositionally-complex ceramics". Using fluorite oxides as an example, we show that lower thermal conductivity and higher stiffness-toconductivity ratios are achieved in medium-entropy non-equimolar compositions. Highlights:• Nine compositionally-complex fluorite oxides (CCFOs) are made and investigated.• CCFOs exhibit reduced thermal conductivity and increased cubic phase stability.• Lower thermal conductivity is achieved in medium-entropy non-equimolar CCFOs.• High modulus and hardness retain in CCFOs with reduced thermal conductivity.• Non-equimolar CCFOs exhibit amorphous-like T-dependent thermal conductivity.

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(Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high‐entropy ceramics with low thermal conductivity

Cited by 451 publications

References 29 publications

Review of high entropy ceramics: design, synthesis, structure and properties

Review of high entropy ceramics: design, synthesis, structure and properties

Phase stability and mechanical properties of novel high entropy transition metal carbides

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

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