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

Tarek Ali ElMelegy, Maxim Sokol, Michel W. Barsoum

Research output: Contribution to journalArticlepeer-review

Abstract

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)2AlC 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)2AlC in natural air in the 1000–1400 °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)2AlC and (Mo2/3Y1/3)2AlC 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)2AlC at 1300 °C for 12 h leads to formation of a thick, porous oxide of Y2Mo3O12.

Original languageEnglish
Article number158930
JournalJournal of Alloys and Compounds
Volume867
DOIs
StatePublished - 25 Jun 2021

Keywords

  • Ceramics
  • Chemical order
  • Oxidation
  • Synthesis
  • Transition metal alloys and compounds
  • i-MAX phase

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