Regulation of microwave absorbing performance of magnetic alloy/ferrite/ carbon ternary composites by changing polydopamine-induced carbothermal reduction

Magnetic alloy/ferrite/nitrogen-doped carbon composites (CoFe/CoFe2O4/N-C) spheres were synthesized by controlled carbothermal reduction of Co-doped Fe2O3 nanospheres wrapped in polydopamine. Different dopamine hydrochloride dosages not only affected components and nanostructures, but also regulated the electromagnetic properties of CoFe/CoFe2O4/N-C composites. The results show that with the increase of dopamine hydrochloride dosage, graphitic degree of N-doped carbon layer would decrease after an initial increase, while the Ms values exhibit an opposite trend. All samples show similar mu r spectra, and negative mu '' values can be obtained at high frequency, which should be related to eddy current and dielectric resonance. With the increment of polydopamine, epsilon r would first increase due to generation of CoFe and the increase in graphitic degree, and then decrease owing to the agglomeration of spherical particles. Further research on microwave absorption shows that RL peak frequency coincides with the frequency of perfect impedance matching when good impedance matching has been achieved across a wide range of frequencies. Thanks to the synergistic effects of conduction loss, interfacial polarization, dipole polarization, natural resonance, eddy current, and complete interference cancellation, S-100 has a wide effective absorption bandwidth of 4.88 GHz at 2.0 mm and a low RL peak value of-70.48 dB at 1.95 mm. This work could offer new insights into multi-component magnetic MAMs design and illuminate the relationships between reflection loss, impedance matching, interference cancellation, phase composition, and composite structure.

Automated summary

Magnetic alloy/ferrite/nitrogen-doped carbon composites were synthesized by controlled carbothermal reduction. The properties of the composites were influenced by the dosage of dopamine hydrochloride. The research provides new insights into the design of multi-component magnetic materials and their microwave absorption properties.