Ordering effects in nonstoichiometric titanium carbide

Lipatnikov, V. N.; Kottar, A.; Zueva, L. V.; Гусев, А. И.

doi:10.1007/bf02758018

Cited by 18 publications

(15 citation statements)

References 9 publications

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“…De Novion et al proposed an ordered Ti 3 C 2 superstructure via Monte Carlo simulations with a space group of C222 1 and pointed out the results were consistent with their experiments. Lipatnikov et al provided direct experimental evidence for the existence of this phase using X‐ray diffraction. In contrast, using neutron diffraction, Tashmetov et al did not find this compound in their detailed study of the Ti‐C system suggesting perhaps the phase is difficult to synthesize.…”

Section: Experimental Observations Of Specific Crystal Structuresmentioning

confidence: 94%

“…Lipatnikov et al reported some additional reflections in their XRD studies of TiC 0.8 that suggested possible ordering which they speculated to be the monoclinic (presumably C2/m) Ti 6 C 5 phase. Later work by Lipatnikov et al did not reveal ordering below 500°C, which they interpreted to suggest that Ti 6 C 5 phase had an order‐disorder transition temperature near 500°C.…”

Section: Experimental Observations Of Specific Crystal Structuresmentioning

confidence: 99%

“…The most studied of the group IVB carbides in this composition range is the Ti‐C system, with numerous reports of vacancy ordering at and near the Ti 2 C composition . Thus, the existence of an ordered Ti 2 C compound is well accepted, but reports differ on its structure.…”

Section: Experimental Observations Of Specific Crystal Structuresmentioning

confidence: 99%

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Review of phase stability in the group IVB and VB transition‐metal carbides

Weinberger

Thompson

2018

J Am Ceram Soc

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This review summarizes the phase stability in the group IVB (Ti‐C; Zr‐C; Hf‐C) and group VB (V‐C; Nb‐C; Ta‐C) transition‐metal carbides. The order parameter functional (OPF) method and density functional theory (DFT) method have been used to predict phase equilibria in these systems. Extensive experimental investigations have attempted to determine both phase stability as a function of composition as well the crystal structures present using X‐ray diffraction, neutron diffraction, electron backscatter detection, and selected area electron diffraction. These investigations have demonstrated that the structures that form are based on the close‐packing of the metal atoms and the arrangement of the carbon atoms in the octahedral interstices. In general, the rocksalt B1 phase is stable for all of the transition‐metal carbides, with their substoichiometry tolerance increasing with temperature; vanadium carbide is the exception due to its negative vacancy formation energy. Vacancy‐ordered M6C5 phases have been predicted and experimentally confirmed in both groups of carbides; however, kinetic limitations often inhibit the formation of vacancy‐ordered phases, which has contributed to controversy in phase identification. The vacancy‐ordered M4C3 phase has been predicted for select carbides and has only been observed in zirconium carbide. In contrast, the stacking fault phase ζ‐M4C3−x has been readily reported in the group VB carbides (but not in the group IVB carbides). The vacancy‐ordered M3C2 has been predicted by DFT for the group IVB carbides but not in the group VB carbides, whereas OPF predicts its stability in both carbides. Vacancy‐ordered M3C2 phases have been experimentally observed in the Ti‐C and Hf‐C systems. Finally, the M2C phase has been predicted in both group carbides, except for hafnium carbide, with an order‐disorder transition with temperature. These factors result in phase diagrams that are similar among all the carbides, but each phase diagram is unique due to subtle differences in bonding that result in slight differences in thermodynamically stable phases.

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Section: Experimental Observations Of Specific Crystal Structuresmentioning

confidence: 94%

Section: Experimental Observations Of Specific Crystal Structuresmentioning

confidence: 99%

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Review of phase stability in the group IVB and VB transition‐metal carbides

Weinberger

Thompson

2018

J Am Ceram Soc

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“…[72] Different kinds of ordering of carbon vacancies may take place, depending on the composition and temperature. [73][74][75][76][77][78] The number of vacancies per Ti atom in the off-stoichiometric titanium carbide (TiC x ) is 1 Ϫ x. The value of x in equilibrium TiC x was calculated by the Thermo-Calc method, and the result is shown in Figure 25 as a function of temperature for both the 0.05C-0.20Ti-2.0Ni and 0.42C-0.30Ti steels.…”

Section: Trap Sites At Incoherent Tic Particlesmentioning

confidence: 99%

Quantitative analysis on hydrogen trapping of TiC particles in steel

Wei

Tsuzaki

2006

Metall Mater Trans A

293

169

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The change in the hydrogen-trapping behavior of a TiC particle accompanying its coherent to incoherent interfacial-character transition in a 0.05C-0.20Ti-2.0Ni steel that was quenched and tempered in a partially protective argon atmosphere and in ultrahigh vacuum (UHV) has been studied by thermal desorption spectrometry (TDS). The results indicated that (semi)coherent TiC precipitates demonstrate distinctly different hydrogen-trapping features from that of incoherent TiC particles with respect to hydrogen capacity, interaction energy with hydrogen, locations available for hydrogen occupation, and the capability of hydrogen absorption from the environment. The broad (semi)coherent interface of the disc-shaped (semi)coherent TiC precipitate does not trap hydrogen during tempering in a partially protected argon atmosphere, but traps hydrogen during cathodic charging at room temperature. The semicoherent interface traps 1.3 atoms/nm 2 of hydrogen at the core of the misfit dislocation with short-time charging (1 hour), which is characterized by a desorption activation energy of 55.8 kJ/mol. The side interface of the (semi)coherent TiC precipitate acts like the broad interface when the precipitate is small. As the precipitate grows, the side interface gradually loses its coherency and results in a simultaneous increase in the trapping activation energy and the binding energy. An increase in the trapping activation energy, i.e., the energy barrier for trapping, makes hydrogen trapping more difficult in cathodic charging at room temperature, while an increase in the binding energy enhances the capability of hydrogen absorption from the atmosphere during heat treatment. An incoherent TiC particle is not able to trap hydrogen during cathodic charging at room temperature due to its high energy barrier for trapping, but absorbs hydrogen during heat treatment at high temperatures. The amount of hydrogen that is trapped by incoherent TiC particles depends on their volume, which strongly indicates that incoherent TiC particles trap hydrogen within them rather than at the particle/matrix interface. Octahedral carbon vacancies are supposedly the hydrogen trap sites in incoherent TiC particles.

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“…For a certain range of composition, the cubic phase seems to be thermodynamically stable solely at high temperatures. Several off-stoichiometric ordered structures of TiC x have been reported and investigated in the range of 0.48 < x < 0.96 [4][5][6]. In particular, the existence of at least two vacancy-ordered structures, the cubic and trigonal forms of hemicarbide Ti 2 C, is now well established experimentally [4,5].…”

Section: Introductionmentioning

confidence: 99%

Tight-Binding Description of Tic_{x}

Turchi¹,

Shevchenko²,

Ivashchenko³

et al. 2004

Condens. Matter Phys.

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A parametrized non-orthogonal tight-binding (TB) method combined with the coherent-potential-approximation is applied to the study of the electronic structure of disordered off-stoichiometric TiC x , the lattice relaxation and the electronic spectra of the TiC (001) surface, the local relaxation and energetic states of TiC structures with one or two vacancies in both the non-metal and metal sublattices. The calculated results are in good agreement with available experimental and theoretical data. The importance of the overlap matrix elements of the TB Hamiltonian in describing the electronic structure of this class of compounds is emphasized.

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Ordering effects in nonstoichiometric titanium carbide

Cited by 18 publications

References 9 publications

Review of phase stability in the group IVB and VB transition‐metal carbides

Review of phase stability in the group IVB and VB transition‐metal carbides

Quantitative analysis on hydrogen trapping of TiC particles in steel

Tight-Binding Description of Tic_{x}

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