B.W. Wyatt, B. Anasori
Purdue University,
United States
Keywords: MXenes, 2D carbides, high-temperature, phase transformation, extreme
Summary:
2D MXenes have a wide array of impressive properties due to their inherent transition metal carbide cores with abundant surface functionalities. While MXenes can be rapidly oxidized in air at high temperatures, they can be transformed into ultra-high temperature carbides when annealed under an inert atmosphere or vacuum. By annealing stacks of 2D MXene flakes, we can fabricate refractory carbides with controlled morphologies and crystal orientations. In this talk, we present our current understanding of the phase transformation of different MXenes, including Ti3C2Tx and Mo2TiC2Tx, by annealing them in the 600 °C to 2000 °C range under argon. We used a combination of ex-situ and in-situ characterization techniques and identified the effect of defects, such as vacancies and cation decorations, on phase stability and the transformation of MXenes to refractory carbides. Particularly, we examine the defect engineering mechanism of metal cations on defects to show the partial occupation of cations in the defective metal sites of different MXenes. Our results suggest that MXenes can be used as nanosized building blocks for ultra-high temperature coatings or ceramic composite additives.