First-principles investigation of intrinsic defects and self-diffusion in ordered phases of V<sub>2</sub>C

Demaske, Brian; Chernatynskiy, Aleksandr V.

doi:10.1088/1361-648x/aa7031

Cited by 22 publications

(11 citation statements)

References 53 publications

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“…By contrast, metal self-diffusion can only occur upon the formation of a nearest neighbour metal vacancy; and hence depends on both the vacancy formation energy and the energy for migration. As such, measured C self-diffusion coefficients tend to be several orders of magnitude higher than metal self-diffusion coefficients in carbides 22 .…”

Section: Resultsmentioning

confidence: 93%

Processing and Properties of High-Entropy Ultra-High Temperature Carbides

Castle

Csanádi

Grasso

et al. 2018

Sci Rep

642

361

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Bulk equiatomic (Hf-Ta-Zr-Ti)C and (Hf-Ta-Zr-Nb)C high entropy Ultra-High Temperature Ceramic (UHTC) carbide compositions were fabricated by ball milling and Spark Plasma Sintering (SPS). It was found that the lattice parameter mismatch of the component monocarbides is a key factor for predicting single phase solid solution formation. The processing route was further optimised for the (Hf-Ta-Zr-Nb)C composition to produce a high purity, single phase, homogeneous, bulk high entropy material (99% density); revealing a vast new compositional space for the exploration of new UHTCs. One sample was observed to chemically decompose; indicating the presence of a miscibility gap. While this suggests the system is not thermodynamically stable to room temperature, it does reveal further potential for the development of new in situ formed UHTC nanocomposites. The optimised material was subjected to nanoindentation testing and directly compared to the constituent mono/binary carbides, revealing a significantly enhanced hardness (36.1 ± 1.6 GPa,) compared to the hardest monocarbide (HfC, 31.5 ± 1.3 GPa) and the binary (Hf-Ta)C (32.9 ± 1.8 GPa).

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Section: Resultsmentioning

confidence: 93%

Processing and Properties of High-Entropy Ultra-High Temperature Carbides

Castle

Csanádi

Grasso

et al. 2018

Sci Rep

642

361

View full text Add to dashboard Cite

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“…In UHTC carbides, the metal self‐diffusion is independent of the C self‐diffusion 31 . The measured C self‐diffusion coefficient is several orders of magnitude higher than metal self‐diffusion coefficients in carbides 32 . Hence, in the TaC‐HfC system, the self and interdiffusion rates of component metal would be the main limiting factor for the diffusion bonding.…”

Section: Resultsmentioning

confidence: 90%

“…31 The measured C self-diffusion coefficient is several orders of magnitude higher than metal self-diffusion coefficients in carbides. 32 Hence, in the TaC-HfC system, the self and interdiffusion rates of component metal would be the main limiting factor for the diffusion bonding. Ta has lower vacancy formation energy (3.5 eV) when compared to Hf (9.3 eV).…”

Section: Tac-hfc Jointmentioning

confidence: 99%

Electric field assisted solid‐state interfacial joining of TaC‐HfC ceramics without filler

et al. 2021

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The application of ultra‐high‐temperature ceramics (UHTCs) demands effective ways of joining in overcoming the problems associated with the fabrication of complex‐shaped components. In this study, we choose to investigate a new method of rapidly joining pre‐sintered TaC and HfC ceramics without any filler material using the spark plasma sintering (SPS) technique. A well‐bonded TaC–HfC interface was observed with no apparent cracking and porosity at the joint. The joining mechanisms were predominantly driven by solid‐state diffusion and localized plastic deformation. The nanomechanical properties of the TaC‐HfC joint are better than the HfC while comparable to that of the TaC. High‐load indentation (up to 200 N) results suggest that the TaC–HfC interface is stronger than the parent UHTCs with no crack propagating at the interface. Upon comparison with the parent UHTCs, the damaged area and the average crack length at the interface, reduced up to ~94% and ~56%, respectively. This study shows that the SPS technique can also apply to joining other UHTCs without any filler, resulting in the new field of developing complex components for the thermal protection system (TPS).

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“…[46][47][48][49] In addition, for C atoms, with a much smaller radius than the metal atoms, the self-diffusion coefficient was supposed to be much higher than the self-diffusion coefficients of metal atoms in carbides. [50] In the (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25 )C system, four metal carbides showed a similar fcc structure, i.e., similar distribution and composition of carbon atoms in the structure. Thus, C self-diffusion would not be the dominate factor determining the lattice parameter of the new phase ((Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25 )C).…”

Section: Resultsmentioning

confidence: 94%

Preparation of High-Entropy (Zr0.25Hf0.25Ta0.25Ti0.25)C-Ni-Co Composite by Spark Plasma Sintering

Liu

Xiong

Guo

et al. 2020

Metall Mater Trans A

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In the present work, the thermodynamic formation possibility and stability of high-entropy (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25)C ceramic single phase were theoretically calculated by first principles, and a novel (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25)C high-entropy ceramic-Ni-Co composite was successfully prepared by spark plasma sintering (SPS). The first principles calculation indicated the atomic size difference d for (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25)C was 3.23 pct, which was < 6.6 pct, and solid solution would possibly happen. The calculated DFT formation enthalpy of the (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25)C system was À 1.78 eV. The negative formation enthalpy indicated that (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25)C was thermodynamically stable. The experimental results showed a new fcc (Fm-3m) single rock salt crystal structure ceramic phase was formed after SPS sintering. Two phases (ceramic phase and metal phase) were presented in the material. Besides, for the (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25)C phase, the Hf, Ta, Zr and Ti distributed uniformly, and no secondary phase was detected. The metal phase was homogeneous along the ceramic phase. No pores and gaps existed between the ceramic phase and metal phase. Good bonding was obtained, caused by some Hf, Ta, Zr or Ti atoms diffusing in the metal phase. The fracture toughness and hardness of the high-entropy (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25)C ceramic-metal composite were 14.2 MPa m 1/2 and 1620 HV (30). The excellent comprehensive performance was caused by good bonding between the ceramic phase and metal phase and mass disorder in the (Zr 0.25 Hf 0.25 Ta 0.25 Ti 0.25)C phase.

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First-principles investigation of intrinsic defects and self-diffusion in ordered phases of V₂C

Cited by 22 publications

References 53 publications

Processing and Properties of High-Entropy Ultra-High Temperature Carbides

Processing and Properties of High-Entropy Ultra-High Temperature Carbides

Electric field assisted solid‐state interfacial joining of TaC‐HfC ceramics without filler

Preparation of High-Entropy (Zr0.25Hf0.25Ta0.25Ti0.25)C-Ni-Co Composite by Spark Plasma Sintering

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First-principles investigation of intrinsic defects and self-diffusion in ordered phases of V2C

Cited by 22 publications

References 53 publications

Processing and Properties of High-Entropy Ultra-High Temperature Carbides

Processing and Properties of High-Entropy Ultra-High Temperature Carbides

Electric field assisted solid‐state interfacial joining of TaC‐HfC ceramics without filler

Preparation of High-Entropy (Zr0.25Hf0.25Ta0.25Ti0.25)C-Ni-Co Composite by Spark Plasma Sintering

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First-principles investigation of intrinsic defects and self-diffusion in ordered phases of V₂C