Phase stability and microstructural formations in the niobium carbides

Smith, Chase J.; Weinberger, Christopher R.; Thompson, Gregory B.

doi:10.1016/j.jeurceramsoc.2018.06.041

Cited by 25 publications

(3 citation statements)

References 34 publications

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“…These materials often exhibit complex phase diagrams, which result from the mixed metallic covalent-ionic bonding and their propensity for non-stoichiometry and order-disorder phase transitions. As a result, their equilibria have not been concretely established, despite prior experimental and computational studies addressing these issues (Smith et al, 1987;Gusev, 2000;Gusev et al, 2001;Zeng et al, 2013;Smith et al, 2018;.…”

Section: Introductionmentioning

confidence: 99%

The crystal structure and phase stability of the zeta phase in the group VB transition metal carbides: a computational investigation

Weinberger

Thompson

2019

Acta Crystallogr Sect B

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The crystal structure and composition of the zeta phase in the group VB transition metal carbides are not completely understood despite decades of experimental studies. As such, the phase rarely appears on phase diagrams of the group VB transition metal carbides. There is currently renewed interest in this phase, as tantalum carbide composites exhibit high fracture toughness in the presence of this phase. This work extends the initial computational study using density functional theory of the phase stability of the zeta phase in the tantalum carbide system, where the tantalum carbide zeta‐phase crystal structure and stability were determined, to the niobium and vanadium carbides. It is shown that the zeta phases in the three systems share the same crystal structure and it is an equilibrium phase at low temperatures. The carbon atom ordering in the three different phases is explored and it is demonstrated that the zeta phase in the tantalum carbides prefers to order carbon atoms differently than in the niobium and vanadium carbide zeta phases. Finally, the properties of this crystal are computed, including elastic constants, electronic densities of states and phonon dispersion curves, to illustrate that this crystal structure is similar to other transition metal carbides.

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Section: Introductionmentioning

confidence: 99%

The crystal structure and phase stability of the zeta phase in the group VB transition metal carbides: a computational investigation

Weinberger

Thompson

2019

Acta Crystallogr Sect B

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“…For example, a high temperature above 1,600 °C lasting for tens of hours is typically applied to transform the rigid lattice of Nb crystals into a relaxed state and then, allow carbon atoms to diffuse into the interstitial sites of Nb crystals to form new Nb−C bonds ( SI Appendix , Fig. S17 ) ( 58 , 59 ). To overcome these limitations, the low-pressure CR strategy was applied to synthesize r MC by low-pressure CR of their corresponding oxides.…”

Section: Resultsmentioning

confidence: 99%

A general method for rapid synthesis of refractory carbides by low-pressure carbothermal shock reduction

Han

Liu

Sun

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Refractory carbides are attractive candidates for support materials in heterogeneous catalysis because of their high thermal, chemical, and mechanical stability. However, the industrial applications of refractory carbides, especially silicon carbide (SiC), are greatly hampered by their low surface area and harsh synthetic conditions, typically have a very limited surface area (<200 m 2 g −1 ), and are prepared in a high-temperature environment (>1,400 °C) that lasts for several or even tens of hours. Based on Le Chatelier’s principle, we theoretically proposed and experimentally verified that a low-pressure carbothermal reduction (CR) strategy was capable of synthesizing high–surface area SiC (569.9 m 2 g −1 ) at a lower temperature and a faster rate (∼1,300 °C, 50 Pa, 30 s). Such high–surface area SiC possesses excellent thermal stability and antioxidant capacity since it maintained stability under a water-saturated airflow at 650 °C for 100 h. Furthermore, we demonstrated the feasibility of our strategy for scale-up production of high–surface area SiC (460.6 m 2 g −1 ), with a yield larger than 12 g in one experiment, by virtue of an industrial viable vacuum sintering furnace. Importantly, our strategy is also applicable to the rapid synthesis of refractory metal carbides (NbC, Mo 2 C, TaC, WC) and even their emerging high-entropy carbides (VNbMoTaWC 5 , TiVNbTaWC 5 ). Therefore, our low-pressure CR method provides an alternative strategy, not merely limited to temperature and time items, to regulate the synthesis and facilitate the upcoming industrial applications of carbide-based advanced functional materials.

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“…The C ratio in MC, namely the atomic ratio of C/(C + M), is 0.5 in the stoichiometric composition. In binary C-Ti and C-Nb systems, using X-ray diffraction, equilibrium MC (M = Ti, Nb) phases were confirmed to have off-stoichiometric compositions with a wide range of C ratios less than 0.5 with the NaCl-type (B1) structure with disordered or ordered vacancies at C sites (C vacancies) (Albertsen & Schaller, 1995;Lipatnikov et al, 1998;Smith et al, 1990;Smith et al, 2018). On the other hand, Wei & Tsuzaki (2006) predicted that few C vacancies exist in the TiC precipitates in the ferrite matrix using ThermoCalc.…”

Section: Introductionmentioning

confidence: 99%

Determination of the Chemical Compositions of Fine titanium Carbide and Niobium Carbide Precipitates in Isothermally Aged Ferritic Steel by Atom Probe Tomography Analysis

et al. 2020

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Phase stability and microstructural formations in the niobium carbides

Cited by 25 publications

References 34 publications

The crystal structure and phase stability of the zeta phase in the group VB transition metal carbides: a computational investigation

The crystal structure and phase stability of the zeta phase in the group VB transition metal carbides: a computational investigation

A general method for rapid synthesis of refractory carbides by low-pressure carbothermal shock reduction

Determination of the Chemical Compositions of Fine titanium Carbide and Niobium Carbide Precipitates in Isothermally Aged Ferritic Steel by Atom Probe Tomography Analysis

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