Fabrication and pore structure optimization of porous SiC/C microspheres via carbothermal reduction and post-oxidation for enhanced microwave absorption

Engineering hierarchical mesopores in SiC/C microspheres via selective oxidative etching for tuned pore architecture. • Achieving near-electrical-insulation (2 wt% carbon) without sacrificing Ku-band absorption performance. • Realizing an exceptional RL min of −37.21 dB and ultrabroad EAB of 4.55 GHz at merely 2.4 mm thickness. • Demonstrating that mesopore architecture reconciles the impedance matching-attenuation trade-off in lightweight absorbers. Ku-band (12-18 GHz) satellite communications and high-resolution radar demand electromagnetic wave (EMW) absorbing materials that integrate strong absorption, broad bandwidth, light weight, and electrical insulation. Carbon and silicon carbide (SiC) are attractive candidates due to their low density and complementary loss mechanisms—conduction loss and dielectric loss, respectively. However, conductive carbon absorbers suffer from poor impedance mismatch, whereas insulating SiC lacks sufficient dielectric loss. Simply mixing the two phases does not fundamentally resolve this trade-off. Herein, we advance beyond composition tuning by engineering a porous architecture. SiC/C microspheres were fabricated via carbothermal reduction followed by selective oxidation etching, using porous carbon spheres as templates. This post-treatment reduced the carbon content from ∼40 wt% to ∼2 wt% and simultaneously transformed the microporous architecture into a highly interconnected mesoporous network (81.18% mesopore ratio). The resulting material exhibits near-insulating behavior while delivering exceptional Ku-band absorption: a minimum reflection loss of −37.21 dB and an effective absorption bandwidth of 4.55 GHz (covering 11.05–15.6 GHz, most of the Ku-band) at a thickness of 2.4 mm. This work demonstrates that mesopore engineering effectively reconciles the attenuation-impedance matching trade-off, offering a novel path toward lightweight, insulating, and high-performance EMW absorbers for Ku-band applications.