Synthesis and electromagnetic absorption properties of Fe₃O₄@C nanofibers/bismaleimide nanocomposites

Carbon nanofibers containing Fe₃O₄ nanoparticles (Fe₃O₄@C nanofibers) were synthesized by electrospinning technique followed by heat treatment, and then the as-prepared nanofibers were loaded in bismaleimide (BMI) resin to prepare nanocomposites. The phase structure and morphology of nanofibers were characterized by X-ray diffraction and scanning electron microscope, respectively. The complex permittivity and permeability of nanocomposites were measured by vector network analyzer using a coaxial line method in the frequency range of 1–18 GHz, and the microwave absorption performance was accordingly evaluated. The results indicated that the Fe₃O₄@C nanofibers/BMI composites showed excellent low-frequency electromagnetic wave absorption properties with a minimum RL value of −22 dB at 2.1 GHz corresponding to a thickness of 6 mm and exceeding −10 dB with thickness of 3–6 mm in the whole S band (2–4 GHz). The strong absorption in low frequency is attributed to good matching characteristics of dielectric loss and magnetic loss, which can be efficiently tailored by combination of magnetic Fe₃O₄ and dielectric carbon layer through electrospining technology. The novel Fe₃O₄@C nanofibers loaded in BMI resin can provide an effective solution for pressing problem in present that how to produce lightweight microwave absorbing nanocomposites with excellent low-frequency electromagnetic absorption properties.