Theoretical stability and materials synthesis of a chemically ordered MAX phase, Mo₂ScAlC₂, and its two-dimensional derivate Mo₂ScC₂ MXene

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• 作者：Rahele Meshkian ; ^{rahele.meshkian@liu.se} ; Quanzheng Tao ; Martin Dahlqvist ; Jun Lu ; Lars Hultman ; Johanna Rosen
• 关键词：Laminated structure ; Out-of-plane chemical order ; MAX phase ; 2D material ; MXene ; DFT calculations
• 刊名：Acta Materialia
• 出版年：2017
• 出版时间：15 February 2017
• 年：2017
• 卷：125
• 期：Complete
• 页码：476-480
• 全文大小：1240 K
• 卷排序：125

文摘

We present theoretical prediction and experimental evidence of a new MAX phase alloy, Mo2ScAlC2, with out-of-plane chemical order. Evaluation of phase stability was performed by ab initio calculations based on Density Functional Theory, suggesting that chemical order in the alloy promotes a stable phase, with a formation enthalpy of −24 meV/atom, as opposed to the predicted unstable Mo3AlC2 and Sc3AlC2. Bulk synthesis of Mo2ScAlC2 is achieved by mixing elemental powders of Mo, Sc, Al and graphite which are heated to 1700 °C. High resolution transmission electron microscopy reveals a chemically ordered structure consistent with theoretical predictions with one Sc layer sandwiched between two MoC layers. The two-dimensional derivative, the MXene, is produced by selective etching of the Al-layers in hydrofluoric acid, resulting in the corresponding chemically ordered Mo2ScC2, i.e. the first Sc-containing MXene. The here presented results expands the attainable range of MXene compositions and widens the prospects for property tuning.