Facile synthesis of hollow SiC/C nanospheres for high-performance electromagnetic wave absorption

Hollow silicon carbide/carbon (SiC/C) nanospheres have found wide applications owing to their excellent dielectric properties, high surface area, thermal insulation, and low effective density at high temperatures. However, their hollow structure is typically obtained by removing the templates using strong acids, which can lead to massive waste and severe pollution. Herein, a three-layer nanospheres containing resorcinol-formaldehyde (RF) and SiO₂ (RF@SiO₂@RF) were first prepared by a simple one-step method and used as precursors. Subsequently, monodispersed hollow SiC/C nanospheres (90 ± 5 nm in diameter) prepared in-situ through carbon thermal reduction. The hollow structure was formed by pyrolysis, eliminating the extra procedure to remove templates. The structure, size, and composition of the nanospheres were precisely controlled via synthesis temperatures (1400, 1450, 1500 °C) and using different raw material ratios. The obtained hollow SiC/C nanospheres demonstrated remarkable resistance to high temperature resistance. The specific surface area of the optimised hollow SiC/C nanospheres reached 301.9 m² g⁻¹. Their reflection loss (RL) value achieved −41.34 dB at 14.58 GHz, and the effective absorption bandwidth(EAB)was 4.0 GHz (12.77–16.78 GHz) with a thickness of 1.70 mm. The results of this study confirm that the proposed method allows for an in-situ synthesis of hollow SiC/C nanospheres for high temperature microwave absorption with low matching thickness.