Magnetic carbon nanofibers containing uniformly dispersed Fe/Co/Ni nanoparticles as stable and high-performance electromagnetic wave absorbers
Carbon nanofibers with ferromagnetic metal nanoparticles (CNF–M, M = Fe, Co, and Ni) have been synthesized by carbonizing electrospun polyacrylonitrile nanofibers including metal acetylacetonate in an argon atmosphere, and their phase composition, microstructure, magnetic properties and electromagnetic (EM)-wave absorbability have been studied. The microstructure analysis shows that the in situ formed metal nanoparticles are well distributed along carbon-based nanofibers and encapsulated by ordered graphite layers. The investigation of magnetic properties and EM-wave absorbability reveals that the as-synthesized CNF–M has typical characteristics of ferromagnetic materials and exhibits excellent EM-wave absorption properties (reflection loss exceeding −20 dB) from the C-band to the Ku-band (4–18 GHz) over an absorber thickness of 1.1–5.0 mm due to the efficient complementarities of complex permeability and permittivity resulting from the magnetic metal nanoparticles and lightweight carbon, as well as the particular particle/graphite core/shell microstructures in CNF–M. Moreover, a minimum reflection loss value of −67.5, −63.1, and −61.0 dB is achieved at 16.6, 12.9, and 13.1 GHz with a matching thickness of 1.3, 1.6, and 1.7 mm for CNF–Fe, CNF–Co, and CNF–Ni, respectively. These magnetic carbon nanofibers are attractive candidates for the new type of high performance EM-wave absorbing materials.