Core–shell-like nanocrystalline FeSiB/amorphous carbon composite powder with remarkable and tunable microwave absorption properties

Abstract

Micron-sized Fe90Si7B3/carbon composite powder with 8–15 wt% C has been synthesized by ball milling. The powder possesses a core–shell-like structure, in which the Fe90Si7B3 core is composed of α-Fe nanocrystalline/amorphous dual phases, and the carbon shell is amorphous. The composites exhibit high permeability, matchable permittivity, and excellent microwave absorption properties including strong reflection loss of −54.8 dB at 12.7 GHz and large effective absorption bandwidth of 6.5 GHz with 1.9 mm in absorber thickness. The superior microwave absorption properties are benefited from the enhanced impedance matching and synergistic effect of strong magnetic and dielectric losses as contributed by the nature resonance and eddy current effect of the nanocrystalline Fe90Si7B3 core, and multiple polarizations and conduction loss between the Fe90Si7B3/carbon components, respectively. The microwave absorption performance can be tuned by changing carbon content and/or annealing. The Fe90Si7B3/carbon composites are promising as a new type of high-performance microwave absorbers.