High‐Resolution Transmission Electron Microscopy of Ti4AlN3, or Ti3Al2N2 Revisited

Barsoum, Michel W.; Farber, L.; Levin, Igor; Procopio, Adam; El‐Raghy, T.; Berner, A.

doi:10.1111/j.1151-2916.1999.tb02117.x

Cited by 137 publications

(64 citation statements)

References 16 publications

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“…The history of theoretical predictions of new MAX phases begins with the debate on the structure of Ti 4 AlN 3 , which in the 1990s was proposed to be either Ti 3 AlN 2 or Ti 3 Al 2 N 2 [83,84], but was finally determined to be Ti 4 AlN 3 [85,86,87]. This conclusion inspired Holm et al [88] [89], and it was logical to proceed with an attempt to synthesize Ti 4 SiC 3 .…”

Section: Predictions Of New Max Phasesmentioning

confidence: 98%

The M+1AX phases: Materials science and thin-film processing

et al. 2010

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This article is a critical review of the M n+1 AX n phases ("MAX phases", where n =1, 2, or 3) from a materials science perspective. MAX phases are a class of hexagonal-structure ternary carbides and nitrides ("X") of a transition metal ("M") and an A-group element. The most well known are Ti 2 AlC, Ti 3 SiC 2 , and Ti 4 AlN 3 . There are ~60 MAX phases with at least 9 discovered in the last five years alone. What makes the MAX phases fascinating and potentially useful is their remarkable combination of chemical, physical, electrical, and mechanical properties, which in many ways combine the characteristics of metals and ceramics. For example, MAX phases are typically resistant to oxidation and corrosion, elastically stiff, but at the same time they exhibit high thermal and electrical conductivities and are machinable. These properties stem from an inherently nanolaminated crystal structure, with M n+1 X n slabs intercalated with pure A-element layers. The research on MAX phases has been accelerated by the introduction of thin-film processing methods.Magnetron sputtering and arc deposition have been employed to synthesize single-crystal material by epitaxial growth, which enables studies of fundamental materials properties. However, the surface-initiated decomposition of M n+1 AX n thin films into MX compounds at temperatures of 1000-1100 °C is much lower than the decomposition temperatures typically reported for the corresponding bulk material. We also review the prospects for low-temperature synthesis, which is essential for deposition of MAX phases onto technologically important substrates. While deposition of MAX phases from the archetypical Ti-Si-C and Ti-Al-N systems typically require synthesis temperatures of ~800 °C, recent results have demonstrated that V 2 GeC and Cr 2 AlC can be deposited at ~450 °C. Also, thermal spray of Ti 2 AlC powder has been used to produce thick coatings. We further treat progress in the use of first-principles calculations for predicting hypothetical MAX phases and their properties. Together with advances in processing and materials 3 analysis, this progress has led to recent discoveries of numerous new MAX phases such as Ti 4 SiC 3 , Ta 4 AlC 3 , and Ti 3 SnC 2 . Finally, important future research directions are discussed. These include charting the unknown regions in phase diagrams to discover new equilibrium and metastable phases, as well as research challenges in understanding their physical properties, such as the effects of anisotropy, impurities, and vacancies on the electrical properties, and unexplored properties such as superconductivity, magnetism, and optics. 4

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Section: Predictions Of New Max Phasesmentioning

confidence: 98%

The M+1AX phases: Materials science and thin-film processing

et al. 2010

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“…22) As is well known, nonmetal vacancies were generally found in MAX phases. [23][24][25] Therefore, the discrepancy between the calculated and experimental thermal expansion coefficient of Ti 2 SC and Ti 2 AlC can be attributed to the vacancies effects.…”

Section: Computational Detailsmentioning

confidence: 99%

First-Principles Study on Thermodynamic Properties of Ti2AlC and Ti2SC

Sun

Hashimoto

et al. 2009

Mater. Trans.

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First-principles calculations of the thermodynamic properties of Ti 2 AlC and Ti 2 SC were carried out. The temperature dependence of bulk modulus, the pressure dependence of normalized volume V=V 0 , thermal expansion coefficient, specific heats, and Debye temperature were successfully obtained through the quasi-harmonic Debye model in the temperature range from 0 to 1000 K and the pressure range from 0 to 50 GPa. The calculated results were compared with available experimental data. The effects of the bonding strength of Ti-S and Ti-Al on the thermodynamic properties were discussed.

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“…Furthermore, C-vacancies are most probably present. 48 In the rest of this study, we focus only on two starting compositions with the proper stoichiometric ratios that resulted in Mo 2 TiAlC 2 and Mo 2 Ti 2 AlC 3 , viz., 2Mo:Ti:1.1Al:2C and 2Mo:2Ti:1.1Al:2.7C, respectively.…”

Section: Alcmentioning

confidence: 99%

Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3

Anasori

Dahlqvist

Halim

et al. 2015

Journal of Applied Physics

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262

180

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Herein, we report on the phase stabilities and crystal structures of two newly discovered ordered, quaternary MAX phases-Mo 2 TiAlC 2 and Mo 2 Ti 2 AlC 3 -synthesized by mixing and heating different elemental powder mixtures of mMo:(3-m)Ti:1.1Al:2C with 1.5 m 2.2 and 2Mo: 2Ti:1.1Al:2.7C to 1600 C for 4 h under Ar flow. In general, for m ! 2 an ordered 312 phase, (Mo 2 Ti)AlC 2 , was the majority phase; for m < 2, an ordered 413 phase (Mo 2 Ti 2 )AlC 3 , was the major product. The actual chemistries determined from X-ray photoelectron spectroscopy (XPS) are Mo 2 TiAlC 1.7 and Mo 2 Ti 1.9 Al 0.9 C 2.5 , respectively. High resolution scanning transmission microscopy, XPS and Rietveld analysis of powder X-ray diffraction confirmed the general ordered stacking sequence to be Mo-Ti-Mo-Al-Mo-Ti-Mo for Mo 2 TiAlC 2 and Mo-Ti-Ti-Mo-Al-Mo-Ti-TiMo for Mo 2 Ti 2 AlC 3 , with the carbon atoms occupying the octahedral sites between the transition metal layers. Consistent with the experimental results, the theoretical calculations clearly show that M layer ordering is mostly driven by the high penalty paid in energy by having the Mo atoms surrounded by C in a face-centered configuration, i.e., in the center of the M nþ1 X n blocks. At 331 GPa and 367 GPa, respectively, the Young's moduli of the ordered Mo 2 TiAlC 2 and Mo 2 Ti 2 AlC 3 are predicted to be higher than those calculated for their ternary end members. Like most other MAX phases, because of the high density of states at the Fermi level, the resistivity measurement over 300 to 10 K for both phases showed metallic behavior. V C 2015 AIP Publishing LLC.

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High‐Resolution Transmission Electron Microscopy of Ti₄AlN₃, or Ti₃Al₂N₂ Revisited

Cited by 137 publications

References 16 publications

The M+1AX phases: Materials science and thin-film processing

The M+1AX phases: Materials science and thin-film processing

First-Principles Study on Thermodynamic Properties of Ti<SUB>2</SUB>AlC and Ti<SUB>2</SUB>SC

Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3

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