Activated carbon fiber/Fe₃O₄ composite with enhanced electromagnetic wave absorption properties

To obtain a low-density material that is capable of absorbing electromagnetic waves over a wide bandwidth, an activated carbon fiber/Fe₃O₄ composite material (ACF/Fe₃O₄) was prepared using an in situ reduction method. Scanning electron microscopy images show that Fe₃O₄ nanoparticles, approximately 10-40 nm in size, were spread uniformly over the surface of the ACF. The resulting composite exhibited superparamagnetic behavior at room temperature. The ability of the ACF and ACF/Fe₃O₄ composite to absorb electromagnetic waves over a frequency range of 8.2-18 GHz was measured using the arch method. The results showed that the maximum reflectivity of an ACF felt was -12.9 dB at 18 GHz, and the effective microwave-absorbing bandwidth (R < -10 dB) was 1.9 GHz (16.10-18 GHz). The absorption performance of the ACF was greatly enhanced by being loaded with Fe₃O₄ nanoparticles; the maximum reflectivity of the 2 mm layer of the ACF/Fe₃O₄ composite was -30.07 dB at 16.45 GHz, and the effective bandwidth (R < -10 dB) increased to 8.62 GHz (9.38-18 GHz). Coating with nano-Fe₃O₄ magnetic particles can effectively improve the absorption of electromagnetic waves by the ACF, and this technique therefore has great potential for application to the field of electromagnetic shielding.