Synthesis of embedded ZrC-SiC-C microspheres via carbothermal reduction for thermal stability and electromagnetic wave absorption

Development of a novel material with electromagnetic wave (EMW) absorbing capability and high-temperature resistance is a definite trend. As an ultra-high temperature ceramic, zirconium carbide (ZrC) can be used in a harsh high-temperature environment. However, ZrC has high electrical conductivity and poor low-temperature oxidation resistance. The introduction of silicon carbide (SiC) and carbon (C) into ZrC to modulate its phase composition and microstructure is a feasible method that can improve the sensitivity of ZrC to oxidizing atmospheres and electromagnetic wave absorption properties. In this study, submicron ZrC-SiC-C microspheres were successfully synthesized by the carbothermal reduction reaction combined with the template method, in which nanoscale ZrC and SiC were uniformly embedded in unreacted C. The results exhibit that nano-sized SiC and ZrC grains nucleate and grow on carbon microspheres successively, forming unique interlocking structures. The minimum reflection coefficient (RC_min) of ZrC-SiC-C microspheres attains −34.8 dB with a thickness of 1.65 mm at 13.8 GHz and the RC is below −10 dB from 12.0 to 16.0 GHz. The structure that nano-sized ZrC, SiC, and unreacted C are embedded into each other leads to dramatic increase in the heterogeneous interface, which is conducive to the loss of EMW. The incipient oxidation temperature of the ZrC-SiC-C microspheres is 411 °C, which is much higher than that of ZrC particles. The unique structure and composition increase the oxygen diffusion path and improve the oxidation resistance of ZrC. The results indicate that ZrC-SiC-C microspheres can be promisingly used as EMW absorbents in ultra-high temperature environments.