Facile synthesis and influences of Fe/Ni ratio on the microwave absorption performance of ultra-small FeNi-C core-shell nanoparticles

A facile and scalable metal-organic chemical vapor deposition method is proposed for the fabrication of ultra-small FeNi-C core-shell nanoparticles. As-synthesized nanoparticles are composed of ultra-small FeNi nanocores of an average diameter of ∼ 6.2 nm and thin shells of 1–3 nm in thickness, which are stable in air atmosphere up to 210 °C. The ratio of Fe/Ni in the nanocores was tuned by varying the reaction temperature, suggesting a simple route to tailor the magnetic and microwave absorption properties of the synthesised nanostructures. These core-shell nanoparticles with a filler loading of 16.7% in paraffin wax exhibited a low minimum reflection loss (RL) of -63.7 dB, together with a great effective bandwidth (BW) of 6.5 GHz at a thickness of 2.2 mm, attributing to their ultra-small size and unique magnetic-dielectric core-shell nanostructure. Such core-shell nanoparticles should be a strong candidate as a light-weighted absorber with tunable microwave absorption performance.