Ultra-high-temperature application of MXene: Stabilization of 2D Ti₃C₂T_x for cross-scale strengthening and toughening of 3D TiC

Transition metal carbide/nitride cores within MXenes make them considerably useful for ultra-high-temperature reinforcement. However, extensive research on Ti₃C₂T_x MXene has revealed its tendency to undergo a phase transition to TiC_y at temperatures above 800 ℃ due to high activity of a superficial Ti atomic layer. Herein, spark plasma sintering of Ti₃C₂T_x and TiC is performed to prevent the Ti₃C₂T_x phase transition at temperatures up to 1900 ℃ through the fabrication of composites at a pressure of 50 MPa. Using a focused ion beam scanning electron microscope to separate layered substances in the composites and examining selected area diffraction spots in a transmission electron microscope enabled identification of non-phase-transitioned MXene. First-principles calculations based on density functional theory indicated the formation of strong chemical bonding interfaces between Ti₃C₂T_x and TiC, which imposed a stability constraint on the Ti atomic layer at the Ti₃C₂T_x surface. Mechanical performance tests, such as three-point bending and fracture toughness analysis, demonstrated that the addition of Ti₃C₂T_x can effectively improve the cross-scale strengthening and toughening of the TiC matrix, providing a new path for designing and developing two-dimensional (2D) carbides cross-scale-enhanced three-dimensional (3D) carbides with the same elements relying on a wide variety of MXenes.