Rational design of carbon-rich silicon oxycarbide nanospheres for high-performance microwave absorbers

Polymer-derived-ceramics (PDCs) are considered as a promising candidate for excellent microwave absorption under harsh environments due to their controllable microstructure at the molecular level. Herein, a series of silicon oxycarbide (SiOC) nanospheres are successfully fabricated through a PDC method and then pyrolyzed under argon atmosphere at different temperatures and the evolutions of microstructure and their microwave absorption properties are investigated simultaneously. It is found that the microwave absorption properties mainly depend on carbon content. With a relative carbon content of 38.13%, the carbon-rich SiOC nanospheres-1 pyrolyzed at 1400 °C possess excellent microwave absorption properties with a minimum reflection loss (RL) value of −56.28 dB at 6.8 GHz with a thickness of 2.93 mm. Electromagnetic analysis demonstrates that proper impedance matching, intrinsic attenuation ability, and the multiple reflection are responsible for the excellent RL. This work will provide a novel approach to obtain the PDCs with excellent microwave absorption properties.