Engineering the mechanical properties of Ti₃C₂T_x MXene films via thermal annealing treatment

Films fabricated from two-dimensional (2D) materials introduce a distinct assembly structure that imparts the inherent properties of pristine 2D materials into a macroscopic scale. Freestanding Ti₃C₂T_x MXene films have a highly compacted structure of hierarchically assembled nanoflakes and are candidates for various applications. We experimentally investigated various factors impacting the mechanical properties of Ti₃C₂T_x MXene films for acquiring improved strength and toughness. To scrutinize the effect of the fabrication technique and the thickness of the Ti₃C₂T_x MXene films, vacuum-assisted filtration (VAF) and casting processes were utilized to fabricate Ti₃C₂T_x MXene films with varying thicknesses. Additionally, the influence of annealing temperature on the acquired Ti₃C₂T_x MXene films' mechanical properties, under various straining rates, was elucidated. The annealing temperature, ranging between room temperature (RT) and 300 ​°C, has a major impact on the obtained mechanical properties of Ti₃C₂T_x MXene films. For all strain rates, ranging between 10⁻¹ ​min⁻¹ and 10⁻⁵ min⁻¹, the tensile strength of the film increases with an increase of temperature, to 200 ​°C. Annealing treatment at 200 ​°C improved the average tensile strength and Young's modulus by about 44.6 ​% and 35.1 ​%, respectively, for films made via VAF. Similarly, they increased by 32.8 ​% and 20 ​%, respectively, for films made via casting process. This behavior is independent of the fabrication technique and the thickness. However, thin Ti₃C₂T_x MXene films showed superior mechanical properties compared to thick films. Additionally, the mechanical properties of casted films were inferior to those fabricated via VAF process. The obtained deformation mechanism seems to be highly dependent on the structural features of the film and the characteristics of interlayer spacing between adjacent Ti₃C₂T_x MXene flakes.