High-attenuation and broadband microwave absorption of robust and thermally stable SiOC ceramic aerogels derived from interpenetrating silicone double network structure

• Developed a SiOC ceramic aerogel from a silicone double network structure. • Achieved microwave attenuation with –73.8 dB loss (>99.99999% absorption) at 8.01 GHz. • Aerogel has low density (0.66-1.21 g/cm 3 ) and high strength (9.0-56.9 MPa). • Features thermal conductivity of 0.226-0.358 W·m −1 ·K −1 and excellent oxidation resistance . Polymer-derived SiOC (PD-SiOC) ceramic aerogels (CA) are widely recognized as ideal electromagnetic wave (EMW) absorbers; however, achieving high-attenuation microwave absorption and gaining an in-depth understanding of dielectric loss mechanisms remain challenging. Herein, a robust and thermally stable PD-SiOC CA was synthesized by pyrolyzing a silicone aerogel with an interpenetrating double network structure, which exhibited EMW attenuation performance. Notably, the interpenetrating double network structure containing both a carbon-rich and a silica-rich framework, facilitates the formation of numerous SiO 2 -C heterogeneous interfaces, enhancing dielectric polarization and improving impedance matching. The highly porous structure of CAs (porosity > 49 %) enhances macroscopic interfacial polarization and multiple scattering, further attenuating EMW energy. As a result, CA-1400 demonstrates exceptionally high attenuation, with a reflection loss of –73.8 dB (>99.99999 % absorption) at 8.01 GHz and a thickness of 4.28 mm, along with a wide effective absorption bandwidth of 6.72 GHz at thickness of 2.71 mm. Additionally, CAs exhibit lightweight characteristics with a density ranging from 0.66 to 1.21 g/cm 3 , excellent mechanical properties with compressive strengths ranging from 9.0 to 56.9 MPa, outstanding oxidation resistance , and superior thermal insulation with thermal conductivities ranging from 0.226 to 0.358 W·m −1 ·K −1 . This work thoroughly investigates the high-temperature structural evolution and dielectric polarization loss mechanisms of PD-SiOC CAs, offering a novel approach for the practical application of high-performance CA microwave absorbers.