Effect of fluorine doping on the performance of multi−heteroatom doped carbons (F,N,B−C or F,N,S−C) for microwave absorption

Heteroatom-doped porous carbon materials offer great promise as microwave absorbers. However, template−free methods for synthesizing porous carbon materials rich in heteroatoms (N,F,B and S), necessary for tuning impedance matching and optimizing attenuation losses, need to be dicovered. In this article, we report the successful preparation of porous fluorine−doped multi−heteroatom carbons (F,N,B−C and F,N,S-C) by the high−temperature pyrolysis of polypyrrole-based precursors. The introduction of the heteroatoms created defective carbon structures with high microwave absorption ability. In particular, the F,N,S−C absorber offered an excellent loss capacity, including an RLmin of −38.0 dB at 13.2 GHz (2.5 mm thickness) and an EAB of 6.3 GHz from 11.7−18 GHz (2.0 mm thickness) using a filler amount of only 9.0 wt.%. The outstanding microwave absorption properties are the result of the interactions between incoming microwaves and carbon defects/pores, which together provide a moderate conductive loss, good polarization relaxation (interfacial polarization and defect/dipole polarization) as well as scattering of microwaves via reflection.