Space-confined fabrication of hydrophobic magnetic carbon nanofibers for lightweight and enhanced microwave absorption

Advanced microwave absorbers (MAs) containing magnetic particles and carbon nanofibers (CNFs) have raised widespread attention in the rapid popularization of electronic communication equipment. However, it is quite challenging to control the growth of magnetic particles in CNFs to improve electromagnetic waves (EMWs) loss and attenuation. Herein, a novel space-confined strategy was adopted to develop Co/CoO/SiO2/CNFs, in which Co/CoO nanoparticles (NPs) with single domain size and dispersed distribution could achieve enhanced magnetic loss and dielectric loss. The introduction of nano-SiO2 in the system could enhance the dielectric confinement effect of the nanofibers (NFs), while an interfacial confinement network could also be constructed to realize the refinement of Co/CoO NPs, enhance the electromagnetic (EM) loss, and ultimately ameliorate the microwave absorption performance of as-obtained NFs. When the additive amount of nano-SiO2 in the spinning solution was 1.0 mg, the as-prepared Co/CoO/SiO2/CNFs reached the optimal reflection loss (RL) of -52.9 dB at 12.64 GHz with a thickness of 2.5 mm, and the effective bandwidth (EBW) reached 5.67 GHz (10.46-16.13 GHz). Furthermore, the excellent hydrophobic properties of the CNFs endow them with potential self-cleaning function. The confinement strategy proposed in this work lays a foundation for the design of low-filling ratio and high-performance CNFs-based microwave absorbers, and presents a general approach for the synthesis of one-dimensional composite materials with controllable structures.