Permeability, Permittivity and EM-wave Absorption Properties of Polymer Composites Filled with MnZn Ferrite and Carbon Black

Composite materials based on manganese-zinc ferrite (MnZn) and carbon black (CB) as fillers, and natural butadiene rubber (NBR) as a polymeric non-magnetic matrix have been prepared by means of a hot-pressing route. Frequency dispersion of complex (relative) permeability mu and permittivity epsilon was measured on composite samples using combined impedance/transmission line method and is ascribed to magnetic and dielectric loss in association with domain wall resonance, spin precession resonance, and interfacial polarization. Electromagnetic wave absorption characteristics of composites (such as return loss RL, matching thickness d(m), matching frequency f(m), bandwidth Delta f for RL <= -20 dB, and the minimum of return loss RLmin) were evaluated through numerical simulations depending on the relation between material parameters (mu, epsilon) and the content of hybrid MnZn/CB filler. The synthesized composites appear to be excellent electromagnetic shields within the frequency interval 300 MHz-2 GHz.