Rational design of FeCo imbedded 3D porous carbon microspheres as broadband and lightweight microwave absorbers

With the aim to obtain microwave (MW) absorber possessing simultaneous light weight and broad absorption bandwidth, FeCo imbedded 3D porous carbon network microspheres (3DC@FeCo) were synthesized via spray-drying followed by calcination processes. 3DC@FeCo exhibits 3D porous carbon microspheres structure with submicrometer-sized macropores. The FeCo imbedded carbon structure not only restrains the growth and agglomeration of FeCo nanoparticles, but also effectively introduces polarization and suppresses the skin effect from FeCo. In addition, the 3D porous carbon microspheres provide more channels which enhance the multiple reflection for microwave. The microwave absorption performance of 3DC@FeCo can be adjusted through changing the carbonization temperature, and the sample after carbonized at 630 °C (3DC@FeCo-630) shows the best microwave absorption property. It is worth mentioning that there is only 21.8 wt% FeCo in 3DC@FeCo, indicating that the 3DC@FeCo microspheres proposed in this study are one kind of lightweight microwave absorbers. The minimum reflection loss (RL) value of 3DC@FeCo-630 is − 47.4 dB at 6.35 GHz and the effective absorption bandwidth (RL < − 10 dB) can reach up 5.66 GHz (12.08–17.74 GHz) with the matching thickness of only 2.7 mm. The excellent microwave absorption ability can be attributed to favorable impedance matching, strong dielectric loss, magnetic loss, FeCo imbedded carbon and unique 3D porous structure. 3DC@FeCo microspheres as broadband and lightweight microwave absorbers exhibit a promising prospect applied in complex electromagnetic environments.