Challenges and opportunities utilizing multilayer MXene as precursors for oriented TiC_x in ceramic composites

MXenes, as two-dimensional (2D) materials, offer significant potential for various nanoscience applications due to their diverse chemistry, high conductivity, and large surface area. However, their use in creating unique microstructures with binary carbide/nitride MX phases has been minimally explored. This study investigates the use of multilayered Ti₃C₂T_z MXene as a precursor for forming bulk TiC_x/Al₂O₃ composites with highly oriented carbide reinforcement. To evaluate this prospect, we conducted a side-by-side comparison of the processing, microstructure, and properties of MXene-derived TiC_0.67/Al₂O₃ and conventional TiC/Al₂O₃ composites. The MXene-derived TiC_0.67/Al₂O₃ exhibited inferior mechanical properties due to the formation of AlF₃ or Ti_2.25Al_0.75O₅ phases alongside the TiC_0.67 particles. Not only did the fluorine present in the precursor MXene cause formation of these undesirable phases, but it also weakened the alumina matrix, leading to significant grain growth and compromised mechanical integrity. Despite these challenges, the proposed approach shows promise. As the desired preferred orientation was achieved, with particles elongated perpendicular to the applied pressure during sintering. This new morphology reached the percolation threshold and demonstrated high electrical conductivity with roughly a third of the TiC content required in conventional composites. The findings underscore the need for optimizing precursor MXene preparation and controlling surface terminations to maximize the benefits of MXene-derived reinforcements in ceramic composites.