Polymer-derived silicon oxycarbonitride bowls with hollow structures and hetero-nanodomains for electromagnetic wave absorption

Contourable design and morphological synthesis represent promising strategies for modulating the electromagnetic wave (EMW) response of nano–micro absorbers. Herein, hollow bridged polysilsesquioxane derived silicon oxycarbonitride (SiOCN) ceramic bowls were synthesized via a template-free and thermolysis method. The concave surface structure and internal cavities of SiOCN improve impedance matching and promote multiple reflections/scattering, contributing to increased microwave attenuation. Additionally, the presence of hetero-nanodomains between the free carbon phase and the amorphous SiOCN matrix generates numerous sites for dipolar and interfacial polarization, further boosting the microwave attenuation capabilities. The as-prepared SiOCN bowls exhibit a minimal reflection loss (RLmin) of −52.93 dB at 10.44 GHz (X band) with a relatively low thickness of 2.3 mm. The efficient absorption bandwidth spans 3.88 GHz with a thickness of merely 1.6 mm. Furthermore, the ability to achieve multi-band EMW absorption is facilitated by varying the absorber thickness. Radar cross-sectional (RCS) simulations indicated that the RCS reduction achieved by the perfect electric conductor shielded with hollow SiOCN bowls exceeds 15 dB m2 across frequencies ranging from the S to Ku bands. Therefore, this morphologically innovative design lays the groundwork for further exploration of polymer-derived ceramics as advanced EMW absorbers.