In-situ formation mechanism of a superlattice (Ti,Zr,Hf,Nb,Ta)C high-entropy carbide via reactive melt infiltration

High-entropy carbide ceramics are promising ultrahigh-temperature materials due to their excellent thermal stability and mechanical properties. However, their synthesis typically relies on energy-intensive techniques such as high temperatures and pressures, which severely limits their practical application. This study presents a novel alloyed reactive melt infiltration process to fabricate dense (Ti,Zr,Hf,Nb,Ta)C ceramics. The effects of RMI temperature on the microstructure and phase composition of the (Ti,Zr,Hf,Nb,Ta)C ceramics were examined. The (Ti,Zr,Hf,Nb,Ta)C high-entropy carbide ceramic is primarily composed of (Ti,Zr,Hf,Nb,Ta)C with minor amounts of (Ti,Zr,Hf,Ta)C and (Ti,Zr,Nb,Ta)(C,O). Microstructure analysis in combination with thermodynamic calculation elucidated the in-situ formation process of high-entropy ceramics involves three stages: reaction stage, solid-solution process and cooling crystallization stage. Crucially, the (Ti,Zr,Hf,Nb,Ta)C ceramic exhibits a high thermal conductivity of 26.38 W·m⁻¹·K⁻¹ at room temperature. This may be due to the combined effects of low overall porosity, the short-period vacancy-ordered superlattice in the continuous main (Ti,Zr,Hf,Nb,Ta)C carbide phase, and a small amount of alloy-derived phase. This work demonstrates a scalable synthesis strategy for high-entropy carbide ceramics and provides a theoretical foundation for their future application in composite materials.