Abstract: SiC is promising for high-temperature electromagnetic wave absorption owing to its excellent thermal and chemical stability, yet pristine SiC particles typically suffer from severe agglomeration and insufficient dielectric loss. Herein, well-defined SiC microspheres with uniform size were first fabricated by spray drying, and then uniformly coated with polypyrrole (PPy) via in-situ polymerization, forming a SiC@PPy core-shell heterostructure. By varying the pyrrole monomer content and applying a subsequent pyrolysis under an argon, both SiC@PPy and carbonized SiC@C-PPy composites were obtained. Over the evaluated frequency range of 2-18 GHz, the dielectric properties and electromagnetic wave absorption performance can be effectively regulated by controlling the pyrrole monomer content and carbonization. The optimized SiC@PPy composite delivers a minimum reflection loss (RL_min) of -57.31 dB at 2.37 mm and an effective absorption bandwidth (EAB) of 6.56 GHz at 2.92 mm. In comparison, the SiC@C-PPy composite achieves an RL_min of -63.88 dB at 3.11 mm and an EAB of 5.57 GHz at an ultrathin thickness of 2.28 mm, covering nearly the entire Ku-band. The enhanced attenuation capability is attributed to the synergistic effects of core-shell interfacial polarization, conduction loss induced by the conductive PPy/carbon network, and multiple reflections and scattering enabled by the microsphere architecture, providing a route for engineering core-shell dielectric absorbers with tunable electromagnetic properties.

Key words: Electromagnetic wave absorption, SiC microspheres, Core-shell structure, Carbonization