Multicomponent nanocomposites with carbonyl Fe-CoFe2O4-CaTiO3 fillers for microwave absorption applications

Epoxy nanocomposites with magnetic and dielectric loading are developed and characterized with regard to the microwave absorption performance in the X-band (8-12.4 GHz). Therefore, single-phase nanoscale cobalt ferrite CoFe2O4 and calcium titanate CaTiO3 with different morphological features were synthesized via hydrothermal method. By studying the composites filled separately with 40 wt% of the as-prepared CoFe2O4, CaTiO3 or carbonyl iron powder we deduce the superior performance of magnetic fillers compared to the dielectric one. The former show strong but narrowband absorption up to 40 dB. By combining all filler types, we produced magnetodielectric composites with attenuation still as high as 33 dB and wider bandwidth of operation. Moreover, by varying the material thickness from 2.8 mm to 4 mm, zones of high attenuation values (>10 dB) can be tuned throughout the X-band range. The combined magnetic and dielectric properties apparently favor the fulfilment of the impedance matching conditions for quarter-wavelength thickness. The improved microwave absorbing performance of the multicomponent composites is verified by characterizations with the waveguide and free-space technique. (C) 2016 Elsevier Ltd. All rights reserved.