Self-etching Ti3C2Tx-SiOC ceramics: effects of MXene surface terminations on high-temperature ceramic nanocomposites

Abstract

Abstract Ti 3 C 2 T x (MXenes) are novel 2D nanomaterials with exceptional electrical conductivity. Their surfaces are covered with functional groups that may significantly affect material properties such as hydrophobicity, electrical conductivity, and oxidation resistance. The role of these terminations in high-temperature ceramic systems with regard to phase and microstructural evolution has not been investigated. In this study, Ti 3 C 2 T x -SiOC 2D nanocomposites were fabricated with -F and -OH terminated MXene to evaluate the role of surface terminations in silane coupling and phase formation during the polymer-to-ceramic transformation. X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) identified self-etching mechanisms caused by F-terminated Ti 3 C 2 T x and revealed that the F surface terminations were retained in the MXene structure until evolution at ~ 550 °C. Evolved F reacted with Si–H bonds in the transforming ceramic matrix, causing additional mass loss and volumetric deformation. LiOH alkalization was shown to suppress the self-etching phenomenon through the substitution of F groups with OH on the nanosheet surface. Furthermore, F terminations were determined to only engage in hydrogen bonding with silane molecules as opposed to covalent linkages with OH terminations, which accelerated silane removal and Ti 3 C 2 T x degradation. The study provides a fundamental understanding of the nature and behavior of MXene surface terminations in the context of high-temperature ceramic nanocomposite fabrication.

Topics & Concepts