Enhanced yield synthesis of bulk dense (M2/3Y1/3)2AlC (M = Cr, W, Mo) in-plane chemically ordered quaternary atomically laminated i-MAX phases and oxidation of (Cr2/3Y1/3)2AlC and (Mo2/3Y1/3)2AlC

JOURNAL OF ALLOYS AND COMPOUNDS

卷:867

Article

ElMelegy, Tarek Ali¹  Sokol, Maxim^1,2  Barsoum, Michel W.¹ 

[1] Drexel Univ, Dept Mat Sci & Engn, Philadelphia, PA 19104 USA

[2] Tel Aviv Univ, Dept Mat Sci & Engn, IL-6997801 Ramat Aviv, Israel

关键词: Chemical order;    Synthesis;    i-MAX phase;    Oxidation;    Ceramics;    Transition metal alloys and compounds;   

DOI  :  10.1016/j.jallcom.2021.158930

来源: Elsevier

【 摘 要 】

Recently, a new family of MAX phases with in-plane chemical order, i-MAX, have been discovered which incorporate new elements expanding the family of MAX phases. i-MAX phases remain to be synthesized in single-phase bulk form for characterization. Herein, we show that by reactively hot pressing an intermetallic precursor, Y2.23Al, instead of elemental Y, in combination with excess overall Al and a sub-stoichiometric fraction of carbon, we enhance the yield of (Cr2/3Y1/3)(2)AlC to 85 +/- 3 wt% (86 +/- 3 mol%). Both the fractions of the impurity Y2O3 phase and the undesirable ternary Cr2AlC are reduced. Subsequent isothermal oxidation of (Cr2/3Y1/3)(2)AlC in natural air in the 1000-1400 degrees C temperature range reveals the formation of Y3Al2(AlO4)(3) (YAG), Cr2O3 and Y2O3, without a continuous Cr7C3 sub-layer. Additionally, we show that by starting with Y2.23Al reagent we synthesize dense bulk (W2/3Y1/3)(2)AlC and (Mo2/3Y1/3)(2)AlC samples with enhanced i-MAX yields of 72 +/- 3 wt% (59 +/- 2 mol%) and 91 +/- 3 wt% (72 +/- 2 mol%), respectively. Oxidation of (Mo2/3Y1/3)(2)AlC at 1300 degrees C for 12 h leads to formation of a thick, porous oxide of Y2Mo3O12. (C) 2021 Elsevier B.V. All rights reserved.

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