Controllable synthesis and electromagnetic interference shielding properties of magnetic CoNi alloy nanoparticles coated on biocarbon nanofibers

CoNi alloy nanoparticles with different molar ratios of Co:Ni were uniformly coated on the surface of biocarbon nanofibers (BCF) by electroless plating. Transmission electron microscopy, X-ray diffraction and vibration sample magnetometry were employed to characterize the morphologies, phase structures and magnetic properties of the coated BCF. The permittivity behavior of coated BCF-paraffin wax matrix composites was studied in the frequency range of 8.2-12.4 GHz by vector network analysis. Magnetic measurements showed that the saturation magnetizations increased linearly with increasing Co content in CoNi deposits and that the coercivity is insensitive towards the Co content. Of the four synthesized BCF with various Co:Ni molar ratios, the BCF with Co:Ni molar ratio of 1:2 displayed higher electromagnetic interference shielding efficiencies of 30.7 dB (99.91 % attenuation) due to its higher permittivity.