Synthesis and high electromagnetic wave absorption performance of carbon-enriched porous SiOC ceramics

The carbon-enriched porous SiOC ceramics with enhanced electromagnetic wave (EMW) absorption properties were synthesized through the hydrothermal method followed by a polymer-derived ceramics (PDCs) process. As the annealing temperature rises from 1200 degrees C to 1500 degrees C, SiC and SiO2 crystals are gradually separated from the porous amorphous SiOC matrix, and the degree of graphitization of free carbon increases. The porous SiOC ceramics annealed at 1400 degrees C exhibit the presence of SiC, SiO2, turbostratic graphite, and amorphous SiOC phases, which significantly impact the impedance matching and attenuation constant of the material. The minimum reflection loss (RLmin) value of the SiOC ceramics reaches-67.98 dB with a matching thickness of 3.19 mm and the effective absorption bandwidth (EAB) is 4.45 GHz at 1.39 mm. The carbon-enriched porous SiOC ceramics with strong absorption capacity and wide absorption bandwidth are primarily owing to appropriate impedance matching and multiple attenuation mechanisms, such as conduction loss, interfacial polarization, and defect-induced polarization, indicating that the SiOC ceramics exhibit significant potential as a highperformance EMW absorbing material.