Ti₃C₂T_x MXene-Zirconium Diboride Based Ultra-High Temperature Ceramics

MXenes are a family of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides with potential applications in ceramics and composites due to their nanometer-thick morphology, hydrophilic surfaces, and negative zeta potentials. In this study, we investigated titanium carbide MXene (Ti₃C₂T_x) as an additive in ultra-high-temperature ceramics (UHTCs), specifically zirconium diboride (ZrB₂). Homogeneous green bodies of Ti₃C₂T_x and ZrB₂ were synthesized via electrostatic self-assembly in aqueous media without surfactants and subsequently densified using field-assisted (spark plasma) sintering. The incorporation of 0.5 wt.% MXene enhanced the relative density of ZrB₂ from ≈89% (pure ZrB₂) to ≈96% under identical sintering conditions. MXene addition significantly reduced the oxygen content from ≈5 at.% in pure ZrB₂ to ≈2-3 at.% at 2.5 wt.% MXene loading. The presence of MXene also facilitates the formation of a core-shell microstructure, where (Zr,Ti)B₂ shells encapsulate ZrB₂ cores, with arrays of dislocations observed at the core-shell interface. Mechanical characterizations show substantial improvements, including a 36% increase in hardness, a ≈12% enhancement in Young's modulus, and a ≈15% increase in flexural strength at 2.5 wt.% MXene loading. These findings demonstrate the potential of MXenes as effective sintering aids and reinforcement agents in UHTCs, offering promising pathways for advancing materials designed for extreme environments.