Ultrafast carbothermal shock synthesis of submicron high-entropy carbides: Dual enhancement of oxidation resistance and microwave absorption

Abstract

Improvement in both the oxidation resistance and microwave absorption of ceramic materials is crucial for advancing their aerospace applications in extreme thermal and electromagnetic environments. Here, submicron-scale (∼440 nm) five- and eight-cation high-entropy carbides (HECs) were rapidly synthesized via the carbothermal shock method. This non-equilibrium synthesis process resulted in HECs with amorphous carbon interfaces and significant lattice distortion, endowing them with superior oxidation resistance and microwave absorption properties. The oxidation onset temperature was found to be 565 °C, with a minimum reflection loss of −43 dB and an effective absorption bandwidth of 5.12 GHz at a thickness of 1.2 mm. Additionally, a reduction in radar cross-section of more than 30 dBm² was also observed. This enhanced performance is attributed to the fact that the amorphous carbon phase acts both as an oxygen protective barrier and a conductive network, thereby promoting electrical conduction loss. Furthermore, the lattice distortion-induced vacancy defects enhance both the polarization and conduction losses of the ceramics. This study demonstrates an effective and scalable strategy for enhancing both oxidation resistance and electromagnetic wave absorption properties of ceramic materials.