NiFe2O4/coal-based carbon composites with magnetic properties and microwave absorption capacity prepared through microwave radiation and hydrothermal reaction

Nickel ferrite/coal-based carbon (NiFe 2 O 4 /CBC) composites were synthesized by using microwave irradiation and simple hydrothermal method . The effects of reaction conditions on particle size, morphology, magnetic, and microwave absorption properties of the NiFe 2 O 4 /CBC composites were systematically studied. In all NiFe 2 O 4 /CBC composites, NiFe 2 O 4 microspheres with different shapes and sizes were anchored on the surface of CBC. By adjusting size of the NiFe 2 O 4 particles, dielectric and magnetic properties of the NiFe 2 O 4 /CBC composites could be optimized simultaneously. For the NiFe 2 O 4 /CBC sample with the average particle size of NiFe 2 O 4 to be 4.69 nm, when the thickness was 4.42 mm, the minimum reflection loss (RL min ) could reach − 63.15 dB at 9.89 GHz. Meanwhile, the maximum effective absorption bandwidth (EAB max ) was 4.91 GHz (6.31–11.22 GHz) at a thickness of 5 mm, which almost covered the whole X-band. The s-shaped hysteresis loop of the sample revealed that it had typical superparamagnetic characteristics. The possible mechanism of microwave absorption was also discussed. Our NiFe 2 O 4 /CBC composites could be used as a new and efficient microwave absorption material.