Superflexible porous PCS_nf-Fe₃O₄/CNT-PANI BP/PCS_nf-Fe₃O₄ sandwich composite films with excellent electromagnetic wave absorption performance based on integral assembly by electrospinning

Polycarbosilane nanofiber-ferroferric oxide (PCS_nf-Fe₃O₄) films were assembled on both sides of carbon nanotube-polyaniline buckypaper (CNT-PANI BP) by electrospinning to obtain PCS_nf-Fe₃O₄/CNT-PANI BP/PCS_nf-Fe₃O₄ sandwich porous composites, with a diameter of 110–120 mm and a thickness of 150–200 µm. The Fe₃O₄ nanoparticles adhered on the PCS nanofibers formed a bamboo-like or plum-like structure. The PANI nanoparticles were uniformly embedded in the CNT network. Both PCS_nf-Fe₃O₄ film skin layers were well bonded to the CNT-PANI BP core layer, with two main forms of the interlayer interface of rattan-like and root-like entanglement. The sandwich composite film (SCF) with 15.1 wt% Fe₃O₄ in the skin layers had a density of 0.97 g/cm³, a porosity of 61% and a total pore area of 30.1 m²/g, with a multimodal pore size distribution. The SCFs were superflexible, being tightly wound around a 4 mm diameter glass rod and repeated 100 times without damage. The absorption performance of the SCF was significantly improved by introducing Fe₃O₄ nanoparticles into its skin layers. The SCF with 11.8 wt% Fe₃O₄ in its skin layers achieved optimal dielectric and magnetic loss matching, with minimum reflection loss of − 43.54 dB and maximum effective absorption bandwidth of 6.97 GHz.