New MAX‐Phase Compounds in the V–Cr–Al–C System

Zhou, Yanchun; Meng, Fanling; Zhang, Jie

doi:10.1111/j.1551-2916.2008.02279.x

Cited by 113 publications

(90 citation statements)

References 27 publications

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“…and Hu et al [251,252]), Nb 4 AlC 3 (discovered by Hu et al [241]), the solid solution (V,Cr) 4 [47] have been reported.…”

Section: Ion Bombardment Effectsmentioning

confidence: 99%

“…Zhou et al [47] recently reported a 523 phase, (V,Cr) 5 Al 2 C 3 , as a minority phase in bulk samples consisting primarily of (V,Cr) 2 AlC and (V,Cr) 3 AlC 2 . Figure 5, reproduced from Ref.…”

Section: Intergrown Structures -Hybrid "523" and "725" Max Phasesmentioning

confidence: 99%

“…Figure 5, reproduced from Ref. 47, shows non-filtered and filtered high-resolution Z-contrast TEM images showing the alternating stacking of two and three transition metal carbide layers in one slab, forming an ordered structure of (V 0.5 Cr 0.5 ) 5 Al 2 C 3 . The existence of (V,Cr) 5 Al 2 C 3 is noteworthy and suggests that there may be many more "523" and "725" phases.…”

Section: Intergrown Structures -Hybrid "523" and "725" Max Phasesmentioning

confidence: 99%

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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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“…and Hu et al [251,252]), Nb 4 AlC 3 (discovered by Hu et al [241]), the solid solution (V,Cr) 4 [47] have been reported.…”

Section: Ion Bombardment Effectsmentioning

confidence: 99%

Section: Intergrown Structures -Hybrid "523" and "725" Max Phasesmentioning

confidence: 99%

Section: Intergrown Structures -Hybrid "523" and "725" Max Phasesmentioning

confidence: 99%

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

et al. 2010

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“…The solid solution space is particularly interesting, as solid solutions often provide improved mechanical properties over their end members 9,34,35 and in some cases are stable even when neither end member is. 36 The ability to accurately determine phase stability from first-principles calculations hinges largely on our ability to identify the most stable competing phases for each composition. Hand-selecting these phases without error from experimental phase diagrams requires meticulous and time-consuming analysis that is only feasible for a small number of compounds at a time.…”

Section: Introductionmentioning

confidence: 99%

Computational discovery of stableM2AXphases

et al. 2016

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The family of layered Mn+1AXn compounds provides a large class of materials with applications ranging from magnets, to high-temperature coatings, to nuclear cladding. In this work, we employ a density-functional theory based discovery approach to identify a large number of thermodynamically stable Mn+1AXn compounds, where n = 1, M = Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta; A = Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, Pb; and X = C, N. We calculate the formation energy for 216 pure M2AX compounds and 10,314 solid solutions, (MM )2(AA )(XX ), relative to their competing phases. We find that the 49 experimentally known M2AX phases exhibit formation energies less than 30 meV/atom. Among the 10,530 compositions considered, 3,140 exhibit formation energies below 30 meV/atom, most of which have yet to be experimentally synthesized. A significant subset of 301 compositions exhibits strong exothermic stability in excess of 100 meV/atom, indicating favorable synthesis conditions. We identify empirical design rules for stable M2AX compounds. Among the metastable M2AX compounds are two Cr-based compounds with ferromagnetic ordering and expected Curie temperatures around 75K. These results can serve as a map for the experimental design and synthesis of previously unknown M2AX compounds.

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“…Zhou et al [12] later reported another "523" phase, (V,Cr) 5 Al 2 C 3 . These compounds have only been observed as minority phases in samples consisting primarily of M 2 AC and M 3 AC 2 (for "523" phases) or M 3 AC 2 and M 4 AC 3 (for "725" phases).…”

mentioning

confidence: 99%