Improving the electromagnetic shielding of fabricated NdFeB particles by a coating thin carbonaceous layer

Abstract

Fabrication and improvement of electromagnetic interference (EMI) shielding products have recently been the subject of intense research. In the present study, the NdFeB magnetic powder was used in prolonged high-energy wet ball milling to synthesize and enhance properties of the magnetic filler of EMI shielding composites. The physicochemical changes induced in particles prepared by the process confirmed that the applied oleic acid surfactant was simply converted into a thin amorphous carbon layer on NdFeB nanoparticles. Increasing the amount of surfactant in the ball milling procedure caused a thicker layer of the carbonaceous blend to be formed on magnetic nanoparticles. We found that the thicker layer of the amorphous carbon covering the synthesized magnetic particles increased the real and imaginary dielectric permittivity of the resulting product about 15% and 95%, respectively. This also increased the shielding absorption efficiency (SEA) about 40% and the total shielding efficiency (SET) about 30% at some frequencies. Furthermore, more carbonaceous surfactant in composite (II) improved impedance matching, leading to a decrease in reflection loss and an increase in microwave absorption of the composite.