Carbon-Coated Octahedral Fe<sub>3</sub>O<sub>4</sub>/Fe<sub>2</sub>O<sub>3</sub> Nanocomposites for Enhanced Electromagnetic Wave Absorption
Longxin Wang, Yishan Wang, Yishan Wang, Dongdong Liu, Yao Wang, Yao Wang, Xuji Zhang, Xuji Zhang, Guangwu Wen, Xueqian Zhang, Xueqian Zhang, Xiaoxiao Huang
Abstract
The application of heterostructures and complex morphology has been favored by researchers of electromagnetic wave-absorbing materials. Herein, Fe 3 O 4 /Fe 2 O 3 /C composites with carbon-coated octahedral structures were prepared and obtained using a polymer self-assembly-guided nonhomogeneous structure engineering strategy to form hierarchical polyhedral structures (200–400 nm in size). The electrostatic attraction of anionic polyacrylamide (APAM) is used to chelate Fe 3+ . Due to the synergistic effect of intermolecular forces, APAM can be used as a “bridge” to connect multiple micellar particles, and this bridging and entanglement effect facilitates the formation of octahedral Fe 3 O 4 /Fe 2 O 3 . Compared with nanoparticles, the octahedral structure easily forms a conductive network, and the presence of sharp corners can effectively promote the concentration of charge, promote polarization loss, and extend the reflection and scattering path. Through the high-temperature reduction of APAM, the conversion of part of Fe 2 O 3 to Fe 3 O 4 is realized, which effectively improves the electromagnetic parameters and thus optimizes the impedance matching. Meanwhile, the synergistic effect between the magnetic loss (ferromagnetic resonance) of Fe 3 O 4 and the dielectric loss (interfacial polarization, dipole polarization, and conduction loss) of Fe 3 O 4 /Fe 2 O 3 /C enhances the absorption of electromagnetic waves. Unsurprisingly, the synthesized Fe 3 O 4 /Fe 2 O 3 /C composites exhibit excellent EMW absorption performance, with a reflection loss of up to −34.7 dB at 30% paraffin filler ratio and an effective absorption bandwidth (EAB) of 8.64 GHz at 1–3 mm.