Morphology engineering of heterogeneous carbon particles toward boosted dielectric polarization for ultrathin and strong loss absorber

Micron-carbon particles with polymorphous concave polyhedron have been easily prepared via high-efficiency spray drying-carbonization process, which is aimed at boosting dielectric polarization toward the feature of high the real part of the complex permittivity accompanied with low level dielectric loss for achieving ultrathin absorber. In addition, the effect of geometry on the microstructure and microwave absorption (MA) performances was systematically studied for the first time. A minimum reflection loss (RL_min) of −55.07 dB under ultrathin thickness of 1.23 mm and a broad effective absorption bandwidth (<-10 dB) of 4.0 GHz at 1.3 mm were obtained for composites filled with polymorphous concave polyhedral carbon particles, meanwhile the loading contents have been reduced from 30 wt% spherical filler to 22.5 wt% polymorphous concave polyhedral filler. Optimized MA performance with strong loss and ultrathin thickness has been identified as attenuation mechanism dominated by interference cancellation and assisted by dielectric loss for the first time. This work not only provides an insight to realize engineering applications of carbonaceous absorbents but also reveals the intrinsic attenuation mechanism of microwave absorbing materials.