Magnetic and microwave absorbing properties of polyaniline/γ-Fe2O3 nanocomposite

The conducting protonated polyaniline (ES)/gamma-Fe2O3 nanocomposite with the different gamma-Fe2O3 content were synthesized by in-situ polymerization. Its morphology, microstructure, DC conductivity and magnetic properties of samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), four-wire-technique, and vibrating sample magnetometer (VSM), respectively. The microwave absorbing properties of the nanocomposite powders dispersing in wax coating with the coating thickness of 2 mm were investigated using a vector network analyzers in the frequency range of 7-18 GHz. The pure ES has shown the absorption band with a maximum absorption at approximately 16 GHz and a width (defined as frequency difference between points where the absorption is more than 8 dB) of 3.24 GHz, when 10% gamma-Fe2O3 by weight is incorporated, the width is broadened to 4.13 GHz and some other absorption bands appear in the range of 7-13 GHz. The parameter dielectric loss tan delta(e) (= epsilon ''/epsilon') in the 7-18 GHz is found to decrease with increasing g-Fe2O3 contents with 10%, 20%, 30%, respectively, but magnetic loss tan delta(m) = (=mu ''/mu') increases with increasing gamma-Fe2O3 contents. The results show that moderate content of gamma-Fe2O3 nanoparticles embedded in protonated polyaniline matrix may create advanced microwave absorption properties due to simultaneous adjusting of dielectric loss and magnetic loss. (C) 2008 Elsevier B.V. All rights reserved.