Magnetic-Dielectric Complementary Fe-Co-Ni Alloy/Carbon Composites for High-Attenuation C-Band Microwave Absorption via Carbothermal Reduction of Solid-Solution Precursor

Ferromagnetic alloys/carbon composites with excellent electrical and magnetic properties are highly desirable as electromagnetic wave absorption materials, but achieving high-attenuation performance in C-band (4-8 GHz) remains a challenge. Herein, a direct carbothermal reduction of organic gluconate solid-solution precursor method is developed to synthesize ferromagnetic Fe-Co-Ni alloy/carbon composites, which realize high-attenuation electromagnetic wave absorption in C-band. By virtue of Fe, Co, and Ni elements homogeneously dispersing at the molecular level in the solid-solution precursor with the regulated mole ratio, serial FeCo2Ni/C, Co7Fe3/C, FeNi3/C, and Co3Ni/C composites can be deliberately prepared. First-principles calculations and off-axis electron holograms can clearly unravel that these Fe-Co-Ni alloys could perform as excellent dielectric-magnetic complementary loss units to trigger synergistic electronic dipole polarization oscillation, magnetic moment resonance, and magnetic coupling interaction. Meanwhile, the rich alloy-carbon interfaces and conductive carbon skeleton can facilitate delightful interfacial polarization and conductive loss. Combining these positive electromagnetic energy dissipation characteristics, FeCo2Ni/C with strengthened dipole polarization oscillation and outstanding impedance matching realizes an extremely high-attenuation absorption performance with a minimum reflection loss of -82.2 dB at 5.21 GHz. This work provides a feasible and flexible insight into producing magnetic-dielectric complementary Fe-Co-Ni alloys/carbon composites with various alloy compositions as excellent electromagnetic wave absorbers.