Single-crystal octahedral CoFe2O4 nanoparticles loaded on carbon balls as a lightweight microwave absorbent

Since electromagnetic pollution is becoming more and more serious, the lightweight and highly efficient microwave absorbents are urgently needed to absorb unwanted electromagnetic microwaves. In this work, single-crystal octahedral CoFe2O4 nanoparticles with the diameter of about 20-25 nm were successfully incorporated into the porous carbon balls (CB) via a one-step hydrothermal method. The incorporation of the CoFe2O4 nanoparticles into CB reduced the dielectric loss and increased the magnetic loss, resulting in better impedance matching. When the CoFe2O4 content in CoFe2O4/CB composites was 10 wt.%, the minimum reflection loss (RL) was as low as −37.2 dB, and the frequency band of RL below −10 dB was 12.9-17.1 GHz obtained with 1.5 mm thickness. This excellent microwave absorption performance was much better than that of the pure octahedral CoFe2O4 nanoparticles, CB, and CoFe2O4/CB composites with CoFe2O4 content of 8.5 wt.%. Owing to the low density of 1.1-1.2 g/cm3 and good microwave absorption, the CoFe2O4/CB composite can meet the multiple requirements of microwave absorbent.