One-step synthesis of Fe nanoparticles wrapped in N-doped carbon nanohorn microspheres as high-performance electromagnetic wave absorber

Abstract

Designing cost-effective and eco-friendly electromagnetic absorbing materials is important for their widespread practical applications. Herein, Fe nanoparticles wrapped in carbon nanohorn microspheres enriched with N (Fe@NCNHs) were produced by a simple one-step method, which is a nonequilibrium strategy that involves evaporating a graphite anode and Fe wire in an arc plasma. The total pore volume for CNHs was calculated to be 0.38 cm3 g−1, corresponding to its naturally inherited micropore and mesopore-dominate porosity. In addition, the N-doping content reached up to 9.3 at%. The electromagnetic wave-absorption performance of Fe@NCNHs can be controlled using the size and loading amount of Fe nanoparticles wrapped in CNHs, depending on the number of Fe wires inserted into the anode. When two Fe wires are inserted into the anode, Fe nanoparticles with uniform size are well wrapped in CNHs, exhibiting excellent electromagnetic wave absorption property with a minimum reflection loss (RL) of −44.52 dB at 10.86 GHz matching an extremely low thickness of 1.6 mm at X band. The effective absorption bandwidth (RL < −10 dB) was up to 13.86 GHz, and the matching thickness ranged between 1.2 and 5.0 mm. The results obtained in this study indicate that Fe@NCNHs are promising microwave-absorbing materials with enhanced dielectric loss and good impedance matching, which is attributed to the multiple reflections induced by the hollow structure of CNHs, interfacial polarization between the CNHs and Fe nanoparticles, dipole polarization induced by N-doping, and pentagonal and hexagonal defects on CNHs.