Wide-Band Tunable Microwave-Absorbing Ceramic Composites Made of Polymer-Derived SiOC Ceramic and in Situ Partially Surface-Oxidized Ultra-High-Temperature Ceramics

Abstract

Microwave-absorbing materials in a high-temperature harsh environment are highly desired for electronics and aerospace applications. This study reports a novel high-temperature microwave-absorbing ceramic composites made of polymer-derived SiOC ceramic and in situ partially surface-oxidized ultra-high-temperature ceramic (UHTC) ZrB₂ nanoparticles. The fabricated composites with a normalized weight fraction of ZrB₂ nanoparticles at 40% has a significantly wide microwave absorption bandwidth of 13.5 GHz (26.5-40 GHz) covering the entire <i>K</i>_a-band. This is attributed to the extensive nanointerfaces introduced in the composites, attenuation induced by the interference of electromagnetic wave, attenuation from the formed current loops, and the electronic conduction loss provided by the partially surface-oxidized ZrB₂ nanoparticles. The minimum reflection coefficient (RC) was -29.30 dB at 29.47 GHz for a thickness of 1.26 mm for the composites with a normalized weight fraction of ZrB₂ nanoparticles at 32.5%. The direct current (dc) conductivity of the nanocomposites showed a clear percolation phenomenon as the normalized weight fraction of ZrB₂ nanoparticles increases to 30.49%. The results provide new insights in designing microwave-absorbing materials with a wide absorption frequency range and strong absorption loss for high-temperature harsh environment applications.