Construction of Fe 0.64 Ni 0.36 @graphite nanoparticles via corrosion-like transformation from NiFe 2 O 4 and surface graphitization in flexible carbon nanofibers to achieve strong wideband microwave absorption.

Recently, microwave absorption (MA) materials have attracted intensive research attention for their ability to counteract the effects of ever-growing electromagnetic pollution. However, conventional microwave absorbers suffer from complex fabrication processes, poor stability and different optimal thicknesses for minimum reflection loss (RL min ) and widest effective absorption bandwidth (EAB). To address these issues, we have used electrospinning followed by high-temperature annealing in argon to develop a flexible microwave absorber with strong wideband absorption. The MA properties of the carbon nanofibers (CNFs) can be tuned by adjusting annealing temperature, and are dependent on the composition and microstructure of the CNFs. The absorber membrane obtained at 800 °C consists of Fe 0.64 Ni 0.36 @graphite core-shell nanoparticles (NPs) embedded in CNFs, formed via a corrosion-like transformation from NiFe 2 O 4 to Fe 0.64 Ni 0.36 followed by surface graphitization. This nanostructure greatly enhances magnetic-dielectric synergistic loss to achieve superior MA properties, with an RL min of -57.7 dB and an EAB of 6.48 GHz (11.20-17.68 GHz) both acquired at a thickness of 2.1 mm. This work provides useful insights into structure-property relationship of the CNFs, sheds light on the formation mechanism of Fe 0.64 Ni 0.36 @graphite NPs, and offers a simple synthesis route to fabricate light-weight and flexible microwave absorbers.