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Journal article
Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3
Journal of applied physics, v 118(9), p094304
07 Sep 2015
Abstract
Herein, we report on the phase stabilities and crystal structures of two newly discovered ordered, quaternary MAX phases-Mo2TiAlC2 and Mo2Ti2AlC3-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 degrees C for 4 h under Ar flow. In general, for m >= 2 an ordered 312 phase, (Mo2Ti) AlC2, was the majority phase; for m< 2, an ordered 413 phase (Mo2Ti2)AlC3, was the major product. The actual chemistries determined from X-ray photoelectron spectroscopy (XPS) are Mo2TiAlC1.7 and Mo2Ti1.9Al0.9C2.5, 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 Mo2TiAlC2 and Mo-Ti-Ti-Mo-Al-Mo-Ti-Ti-Mo for Mo2Ti2AlC3, 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 Mn+1Xn blocks. At 331 GPa and 367 GPa, respectively, the Young's moduli of the ordered Mo2TiAlC2 and Mo2Ti2AlC3 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 10K for both phases showed metallic behavior. (C) 2015 AIP Publishing LLC.
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Details
- Title
- Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3
- Creators
- Babak Anasori - Drexel UniversityMartin Dahlqvist - Linköping UniversityJoseph Halim - Drexel UniversityEun Ju Moon - Drexel UniversityJun Lu - Linköping UniversityBrian C. Hosler - Drexel UniversityEl'ad N. Caspi - Drexel Univ, Dept Mat Sci & Engn, Philadelphia, PA 19104 USASteven J. May - Drexel UniversityLars Hultman - Linköping UniversityPer Eklund - Linköping UniversityJohanna Rosen - Linköping UniversityMichel W. Barsoum - Drexel UniversityElad N Caspi - Materials Science and Engineering
- Publication Details
- Journal of applied physics, v 118(9), p094304
- Publisher
- American Institute of Physics
- Number of pages
- 14
- Grant note
- 258509 / ERC; European Research Council (ERC); European Commission Swedish Foundation for Strategic Research through the Synergy Grant FUNCASE Functional Carbides for Advanced Surface Engineering Future Research Leaders 5 Program W911NF-12-1-0132; W911NF-11-1-0283 / U.S. Army Research Office 621-2011-4420; 642-2013-8020; 621-2014-4890 / Swedish Research Council; European Commission Knut and Alice Wallenberg Foundation; Knut & Alice Wallenberg Foundation
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Materials Science and Engineering
- Web of Science ID
- WOS:000360926500020
- Scopus ID
- 2-s2.0-84941114267
- Other Identifier
- 991019169589504721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Physics, Applied