MXene Effects on SiC Crystallization and Thermal Conductivity in Polymer-Derived SiOC Composites

Abstract Integrating MXene into polymer-derived silicon oxycarbide (SiOC) ceramics offers a promising strategy to tailor their functional properties, yet the relationship between MXene content, microstructure, and performance remains unclear. This work for the first time illustrates how MXene’s role changes with its concentration from a catalytic enhancer at low loading to a disruptive phase at higher levels, with 5 wt% MXene addition producing the most balanced microstructure. The formation of Ti–O–Si bonds ensures strong interfacial bonding and uniform MXene dispersion. During pyrolysis, MXene transforms into TiC nanocrystals that catalyze earlier crystallization of β-SiC at 1200 °C and promote carbon graphitization, leading to a dense, homogeneous nanocomposite. This optimized structure achieves a high thermal conductivity of 12.0 W·m⁻¹·K⁻¹ and a superior electrical conductivity of 29.93 S·m⁻ 1 after pyrolysis at 1500 °C, demonstrating the formation of a continuous, percolating network for both phonon and electron transport. However, increasing MXene to 10 wt% causes TiC agglomeration and oxidative disruption of the SiOC network, which fragments the conductive pathways and severely degrades both thermal and electrical performance. The functional properties of MXene/SiOC composites depend not only on the MXene content but also on achieving a well-integrated nanoscale architecture, offering important guidance for designing advanced multifunctional ceramic composites.