Microwave-absorbing characteristics of epoxy resin composites containing nanoparticles of NiZn- and NiCuZn-ferrites

NiZn- and NiCuZn-ferrite nanoparticles (50-70 nm) with the chemical formula Ni0.5Zn0.5Fe2O4 (NiZn) and Ni0.35Cu0.15Zn0.5Fe2O4 (NiCuZn) were synthesized by a combustion synthesis method. The nanocrystallite of these materials was characterized by structural and magnetic methods. Saturation magnetization increases from 83 emu/g (NiZn) to 91 emu/g (NiCuZn). Magnetic permeability and dielectric permittivity were measured on sintered samples (pellets and toroids) in the frequency range of 1 MHz-1.8 GHz. Reflection losses (R-L) for both samples were calculated from complex permeability and permittivity. Cu substitution in NiZn-ferrite enhances permeability and R-L. In order to explore microwave-absorbing proper-ties in X-band, magnetic nanoparticles were mixed with an epoxy resin to be converted into a microwave-absorbing composite and microwave behaviors of both materials were studied using a microwave vector network analyzer from 7.5 to 13.5 GHz. Cu substitution diminishes absorption intensity in the range 11.5-12.5 GHz. (C) 2009 Elsevier B.V. All rights reserved.