Surface modification by CO2 plasma boosting core shells structural Fe/Fe3C/FeN @ graphite carbon nanoparticles toward high performance microwave absorber

The surface modification of three-dimensional (3D) materials is an efficient method for adjusting their interfacial defect concentration, electronic conductivity and content of functional groups with extensive applications in catalysis, electrode materials and bioengineering. In this work, a multiphase iron nanocrystals consisting of Fe₃C, Fe and FeN nanoparticles encapsulated in hierarchical structure of graphite carbon (denoted as Fe/Fe₃C/FeN@GC) is synthesized for the first time by a novel high temperature plasma method. Meanwhile, more defects and functional groups are introduced by surface modification of graphite carbon layer of Fe/Fe₃C/FeN@GC with controllable CO₂ (low temperature) plasma. Benefiting from the advantages of multiple heterogenous interface and the abundant interfacial polarization relaxation that represent strong electromagnetic (EM) wave dissipation as well as an applicable impedance matching, the optimized Fe/Fe₃C/FeN@GC demonstrate superior microwave absorption (MA) properties. The minimum reflection loss (RL) achieves −54.4 dB (more than 99.9% MA) at 17.6 GHz with a thin thickness of 1.8 mm, and the maximum effective absorption bandwidth (EAB, RL < −10 dB) is up to 6.2 GHz (11.8–18.0 GHz) at 2.0 mm. The above results reveal that the optimized Fe/Fe₃C/FeN@GC composites with strong absorption, broad EAB, light mass (only filling content of 30 wt%) and ultrathin thickness are prospective candidate for high performance EM wave absorbers.