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
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
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DOI：
10.1016/j.jallcom.2021.158930
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发表时间：
2021-01
影响因子：
6.2
通讯作者：
Tarek Aly Elmeligy;M. Sokol;M. Barsoum
中科院分区：
文献类型：
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作者：
Tarek Aly Elmeligy;M. Sokol;M. Barsoum
最近，发现了一个具有面内化学顺序的新 MAX 相族 i-MAX，它包含了扩展 MAX 相族的新元素。i-MAX 相仍有待以单相块状形式合成以进行表征。在此，我们表明，通过反应热压金属间前体 Y2.23Al（代替元素 Y），结合过量的总 Al 和亚化学计量分数的碳，我们将 (Cr2/3Y1/3)2AlC 的产率提高到 85±3 wt% (86±3 mol%)。杂质 Y2O3 相和不需要的三元 Cr2AlC 的分数都减少了。随后在 1000–1400 °C 温度范围内的自然空气中等温氧化 (Cr2/3Y1/3)2AlC 揭示了 Y3Al2(AlO4)3(YAG)、Cr2O3 和 Y2O3 的形成，而没有连续的 Cr7C3 子层。此外，我们表明，从 Y2.23Al 试剂开始，我们合成了致密块体 (W2/3Y1/3)2AlC 和 (Mo2/3Y1/3)2AlC 样品，其增强的 i-MAX 产率分别为 72±3 wt% (59±2 mol%) 和 91±3 wt% (72±2 mol%)。 (Mo2/3Y1/3)2AlC 在 1300°C 下氧化 12 小时会形成厚的多孔 Y2Mo3O12 氧化物。
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 Y2O3phase 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), Cr2O3and Y2O3, without a continuous Cr7C3sub-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 enhancedi-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.