Carbon vacancies regulation strategy for boosting the high-temperature microwave absorption performance of (Co0.2Mo0.2V0.2Nb0.2Ta0.2)Cx high-entropy carbides

Abstract

High-entropy carbides with controlled carbon content have the advantages of high thermal stability and good oxidation resistance, which give them potential for application as high-temperature microwave absorbing materials. In this study, (Co_0.2Mo_0.2V_0.2Nb_0.2Ta_0.2)C_x high-entropy ceramic (HEC) powders are successfully prepared using a mechanical alloying method. Herein, reduction of the conductive graphite content leads to an increase in the concentration of carbon vacancies and a decrease in conductivity, which coordinates the polarization loss and conductivity loss capabilities. The dielectric loss capacity is enhanced by the combined effect of enhanced polarization loss and weakened conductivity loss. Simultaneously, the saturation magnetization intensity increases with the increase of carbon vacancy concentration, which leads to an enhanced magnetic loss capability. Ultimately, the sample (Co_0.2Mo_0.2V_0.2Nb_0.2Ta_0.2)C_0.8 with good impedance matching and attenuation ability achieves microwave absorption optimization at 293–573 K. The minimum reflection loss of (Co_0.2Mo_0.2V_0.2Nb_0.2Ta_0.2)C_0.8 reaches −57.77 dB (473 K) and the effective absorption bandwidth reaches 3.34 GHz (573 K), covering nearly 80% of the X-band with a thickness of only 2.2 mm. This work provides valuable insights into optimizing the high-temperature microwave absorption performance of high entropy carbides.