An Efficient Electrolytic Preparation of MAX-Phased Ti-Al-C
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Large-scale deployment of MAX-phased Ti-Al-C with intriguing mechanical and physicochemical properties is significantly retarded by its harsh preparation conditions, in which costly precursors, high temperature and non-atmospheric pressure are generally imperative. We herein report an efficient electrolytic preparation of MAX-phased Ti-Al-C by direct electro-reduction of solid TiO2-Al2O3-C in molten CaCl2 at 1223 K under normal pressure. Homogeneous layered Ti3AlC2 with an oxygen content of 4300 ppm is prepared under a voltage of 3 V between the solid cathode and graphite anode for only 4 hours. The electro-reduction of TiO2-Al2O3-C exhibits a much faster speed compared with the electrolysis employing TiO2, TiO2-C and TiO2-Al2O3 as the precursors. Time-dependent electrolysis indicates that TiCxOy is the main intermediate. The generation of refractory and highly conducting TiCxOy intermediate enhances the reduction. Density functional theory simulations show a weak affinity towards oxygen of the resulting Ti3AlC2, which is beneficial to fast and thorough deoxidation. The formation of a layered structure of Ti3AlC2 is attributed to the template effect of the precursory graphite. By simply varying the precursory stoichiometry, layered Ti2AlC is also prepared. The present protocol featuring affordable feedstock, low temperature, ambient pressure, high energy efficiency and controllable stoichiometry is promising for large-scale application.
This work was funded by the National Natural Science Foundation of China (51722404 and 51674177).
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