A novel non-stoichiometric medium-entropy carbide stabilized by anion vacancies

Peng, Chong; Tang, Hu; He, Ya‐Ling; Lu, Xiaoqian; Jia, Peng; Li, Guoying; Zhao, Yanqi

doi:10.1016/j.jmst.2020.02.049

Cited by 44 publications

(22 citation statements)

References 28 publications

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“…Among these HE ceramics, HE carbides should be possibly stable with some content of carbon vacancies similar to the singlecomponent carbides composed of the HE carbides. [34][35][36][37][38] In this work, we report a non-stoichiometric HE carbide ceramics with in-situ formed silicon carbide second phase prepared by reactive sintering based on the in-situ reaction between HE carbide and the added silicon. The addition content of silicon is 5 wt% in the present study and the theoretical content of carbon vacancy in the formed non-stoichiometric HE carbide based on the reaction ( 1) is x = 0.23.…”

Section: Introductionmentioning

confidence: 99%

Low‐temperature reactive sintering of carbon vacant high‐entropy carbide ceramics with in‐situ formed silicon carbide

et al. 2021

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It is thought that the sintering of high-entropy (HE) ceramics is generally more difficult when compared to that of the corresponding single-component ceramics. In this paper, we report a novel approach to densify the HE carbide ceramics at relatively low temperatures with a small amount of silicon. Reactive spark plasma sintering (SPS) was used to densify the ceramics using powders of HE carbide and silicon as starting materials. Dense ceramics can be obtained at 1600 -1700 • C. X-ray diffraction analysis reveals that only non-stoichiometric HE carbide phase with carbon vacancy and SiC phase exist in the obtained ceramics. The in-situ formed SiC phase inherits the morphology of the starting silicon powder owing to the slower diffusion of silicon atoms compared to that of the carbon atoms in HE carbide phase. The mechanical properties of the prepared ceramics were preliminarily studied.

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Section: Introductionmentioning

confidence: 99%

Low‐temperature reactive sintering of carbon vacant high‐entropy carbide ceramics with in‐situ formed silicon carbide

et al. 2021

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“…This work highlighted the use of nonstoichiometric boride TiB 1.5 as a raw material to prepare high‐entropy boride ceramics. In the ideal model, the configurational entropy of covalently bonded compounds can be calculated according to the following formula () 30 :

\begin{eqnarray} {S_{{\rm{mix}}}} = - R\left[ {{{\left( {\mathop \sum \limits_{i{\rm{\; = \;1}}}^N {x_i}\ln {x_i}} \right)}_{{\rm{cation}}}} + \left. {{{\left( {\mathop \sum \limits_{j\;{\rm{ = \;1}}}^M {x_j}\ln {x_j}} \right)}_{{\rm{anion}}}}} \right]} \right.\nonumber\\[-4pt] \end{eqnarray}

where x i and x j represent the mole fractions of elements present in the anions and cations in the compound, respectively, and R is the ideal gas constant.…”

Section: Resultsmentioning

confidence: 99%

Characterization and analysis of high‐entropy boride ceramics sintered at low temperature

Zou

et al. 2023

J Am Ceram Soc.

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Multicomponent transition metal boride composite–sintered bodies were prepared by spark plasma sintering, and the composite sintered bodies prepared at different sintering temperatures (1500–1900°C) were characterized. The experimental results showed that several other compounds diffused into the TiBx phase at lower sintering temperatures under the combined effect of temperature and pressure due to the nonstoichiometric ratio of TiB1.5 vacancies. When the temperature reached 1900°C, only the hexagonal phase remained. With the continuous increase of sintering temperature, the Vickers hardness and fracture toughness of the sintered bodies had a trend of increasing first and then decreasing, due to the continuous reduction of the porosity of the cross section of the sintered bodies and the growth of the grain size. The Vickers hardness and fracture toughness of sintered body obtained at 1800°C are the best, which are 24.4 ± 1.8 GPa and 5.9 ± 0.2 MPa m1/2. At 1900°C, the sintered body was a single‐phase hexagonal high‐entropy diboride. Its Vickers hardness and fracture toughness were 21.9 ± 1.5 GPa and 5.4 ± 0.2 MPa m1/2, respectively; it showed a clear downward trend.

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“…The hardness-load curve of B 4 C20 wt% TiH 2 is shown in Figure 9(a), revealing the obvious decrease in Vickers hardness (Hv) with increasing applied force, which was primarily attributed to the indentation size effect. An asymptotic Hv value of ~31.4 GPa was obtained when the applied load exceeded 5 N. It may be because the hardness of TiB 2 generated by the reaction is 34 GPa, and the hardness of C produced by the reaction is poor, which hardness is 1~2 GPa [32][33] , the hardness of B 4 C is 31 GPa, which hardness is between TiB 2 and C. However, the results indicate that due to very little C produced by the reaction, the hardness of B material, and C also can be used as an additive to produce high-toughness ceramic [34][35][36][37] , so the fracture toughness of B 4 C-TiB 2 composite ceramics are improved.…”

Section: Hardness and Fracture Toughnessmentioning

confidence: 96%

Properties of B₄C-TiB₂ ceramics prepared by spark plasma sintering*

et al. 2021

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By doping titanium hydride (TiH2) into boron carbide (B4C), a series of B4C + x wt% TiH2 (x = 0, 5, 10, 15, and 20) composite ceramics were obtained through spark plasma sintering (SPS). The effects of the sintering temperature and the amount of TiH2 additive on the microstructure, mechanical and electrical properties of the sintered B4C-TiB2 composite ceramics were investigated. Powder mixtures of B4C with 0–20 wt% TiH2 were heated from 1400 °C to 1800 °C for 20 min under 50 MPa. The results indicated that higher sintering temperatures contributed to greater ceramic density. With increasing TiH2 content, titanium diboride (TiB2) formed between the TiH2 and B4C matrix. This effectively improved Young’s modulus and fracture toughness of the composite ceramics, significantly improving their electrical properties: the electrical conductivity reached 114.9 S⋅cm−1 at 1800 °C when x = 20. Optimum mechanical properties were obtained for the B4C ceramics sintered with 20 wt% TiH2, which had a relative density of 99.9 ± 0.1%, Vickers hardness of 31.8 GPa, and fracture toughness of 8.5 MPa⋅m1 / 2. The results indicated that the doping of fine Ti particles into the B4C matrix increased the conductivity and the fracture toughness of B4C.

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A novel non-stoichiometric medium-entropy carbide stabilized by anion vacancies

Cited by 44 publications

References 28 publications

Low‐temperature reactive sintering of carbon vacant high‐entropy carbide ceramics with in‐situ formed silicon carbide

Low‐temperature reactive sintering of carbon vacant high‐entropy carbide ceramics with in‐situ formed silicon carbide

Characterization and analysis of high‐entropy boride ceramics sintered at low temperature

Properties of B₄C-TiB₂ ceramics prepared by spark plasma sintering*

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A novel non-stoichiometric medium-entropy carbide stabilized by anion vacancies

Cited by 44 publications

References 28 publications

Low‐temperature reactive sintering of carbon vacant high‐entropy carbide ceramics with in‐situ formed silicon carbide

Low‐temperature reactive sintering of carbon vacant high‐entropy carbide ceramics with in‐situ formed silicon carbide

Characterization and analysis of high‐entropy boride ceramics sintered at low temperature

Properties of B4C-TiB2 ceramics prepared by spark plasma sintering*

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Properties of B₄C-TiB₂ ceramics prepared by spark plasma sintering*