An Efficient Electrolytic Preparation of MAX-Phased Ti-Al-C

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 TiC_xO_y is the main intermediate. The generation of refractory and highly conducting TiC_xO_y 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.