Facile synthesis and excellent microwave absorption properties of FeCo-C core–shell nanoparticles

FeCo-C core–shell nanoparticles (NPs) with diameters of 10–50 nm have been fabricated on a large scale by one-step metal-organic chemical vapor deposition using the mixture of cobalt acetylacetonate and iron acetylacetonate as the precursor. The Fe/Co molar ratio of the alloy nanocores and graphitization degree of C shells, and thus the magnetic and electric properties of the core–shell NPs, can be tuned by the deposition temperature ranging from 700 °C to 900 °C. Comparative tests reveal that a relatively high Fe/Co molar ratio and low graphitization degree benefit the microwave absorption (MA) performance of the core–shell NPs. The composite with 20 wt% core–shell NP obtained at 800 °C and 80 wt% paraffin exhibits an optimal reflection loss $\left(RL\right)$ of −60.4 dB at 7.5 GHz with a thickness of 3.3 mm, and an effective absorption bandwidth (frequency range for RL ≤10 dB) of 9.2 GHz (8.8–18.0 GHz) under an absorber thickness of 2.5 mm. Our study provides a facile route for the fabrication of alloy-C core–shell nanostructures with high MA performance. (paper)