Preparation, magnetism and microwave absorption performance of ultra-thin Fe₃O₄/carbon nanotube sandwich buckypaper

Graphical abstract: Fe₃O₄/multi-walled carbon nanotubes (MWCNTs) sandwich buckypapers were fabricated with monodispersion solutions of MWCNTs and Fe₃O₄ nanoparticles through layer by layer vacuum filtration method. The Fe₃O₄/MWCNTs sandwich buckypaper can be co-cured on the surface of fiber reinforce composites and exhibits excellent magnetism and microwave absorbing ability only with a 0.1 mm thickness absorbing layer. - Highlights: • Sandwich buckypapers were fabricated with MWCNTs/Fe₃O₄ monodispersions through vacuum filtration. • Composite with a 0.1 mm thickness sandwich buckypaper exhibits strong microwave absorbing ability. • The sandwich buckypaper has higher magnetic loss and suitable dielectric loss. • The sandwich buckypaper can fulfil the impedance matching and attenuation characteristics. - Abstract: Fe₃O₄/multi-walled carbon nanotubes (MWCNTs) sandwich buckypapers were fabricated with monodisperse solutions of MWCNTs and Fe₃O₄ nanoparticles through layer by layer vacuum filtration method and can be co-cured with composites for microwave absorbing application. The morphology, element composition and magnetic properties of sandwich buckypapers were characterized by field-emission scanning electron microscope, energy dispersive spectrometer, X-ray diffraction and vibrating sample magnetometer. The complex permittivity and permeability, the reflection loss properties of polymer composites surface coated buckypapers were investigated in the frequency range of 8.2–18 GHz. The results indicate that, due to the electromagnetic matching of magnetic loss and dielectric loss, the microwave absorption properties of the Fe₃O₄/MWCNTs sandwich buckypaper attached polymer composites are evidently improved. When the blending Fe₃O₄ content in sandwich buckypaper is 20 wt%, the composite displays a larger and wider absorption peak (−12.62 dB at 17.72 GHz), and the bandwidth of the reflection loss below −5 dB is larger than 5.6 GHz with a absorbing thickness of 0.1 mm