Expanded graphite–nanoferrite–fly ash composites for shielding of electromagnetic pollution

Expanded graphite (EG) was incorporated into fly ash matrix along with nanoferrite γ-Fe2O3 particles so that the resultant conductive fly ash composite can be used for electromagnetic shielding in microwave range. Conductivity of composites lies in the range 0.34–32.86S/cm. TEM images show that fly ash particle (0.87μm) is covered by sheets of EG containing the magnetic nanoparticles. Complex parameters have been calculated from experimental scattering parameters (S11 and S21) using theoretical calculations given in Nicholson–Ross and Weir algorithms. The microwave absorption properties of the composites have been studied in the 8.2–12.4GHz (X-band) frequency range which shows a shielding effectiveness up-to 90dB, which strongly depends on dielectric loss and weight fraction of fly ash and γ-Fe2O3 in EG matrix.