Microwave Absorbing Magnetic Polymer Matrix Nanocomposites

Magnetic polymer matrix nanocomposites filled with a variety of nanofillers including iron, cobalt, nickel nanoparticles, carbon nanotubes, graphene nanoplatelets were prepared for microwave absorption at gigahertz frequency range. Surface treatment/functionalization was used to enhance the absorption performance. Parameters including filler surface coating thickness, filler composition, different filler combination, and the effect of surfactant were explored and the filler dispersion quality, morphology, and the magnetic properties (coercivity, saturation magnetization) were studied. In addition, relative complex permittivity and relative complex permeability are investigated and the corresponding microwave absorption performances were calculated within the tested frequency ranging from 2 - 20 GHz. Results indicate that silica coated iron core-shell nanoparticles were found to be able to reduce the eddy current effect of untreated iron nanoparticles in the polymer matrix. Meanwhile, carbon nanotubes coated with iron oxide nanoparticles can provide improve matching between magnetic and dielectric loss for enhanced microwave absorption.  Other reasons affecting the microwave absorption efficiency were also studied and discussed in detail.