Conducting ferrofluid: a high-performance microwave shielding material

Conducting materials based on reduced graphene oxide (RGO) sheets have become the focus of considerable research interest in recent years because of the scientific and technological significance of these materials. Herein, we report the fabrication of conducting ferrofluid composites of reduced graphene oxide and nanoscale Fe3O4 (5-20 nm) particles made using a simple yet versatile co-precipitation method. Raman spectroscopy was performed to elucidate the graphitic structure of RGO and interaction between ferrofluid nanoparticles and RGO, which shows a slight shift in the peak position of RGO (shifting from 1360 to 1348 cm(-1) in the D band and 1604 to 1593 cm(-1) in the G band) and ferrofluid. This shift in the bands is an evidence of a strong interaction between these two components. The magnetic and electromagnetic shielding properties of these conducting ferrofluid composites having different loadings of reduced graphene oxide sheets were investigated. In addition, the high value of microwave shielding, 41 dB (99.9% attenuation) results from the combined effect of magnetic losses (natural resonance and eddy currents) due to ferrofluid and dielectric losses (natural resonance, dipole relaxation, electron polarization related relaxation, interfacial polarization, residual defects in RGO sheets and higher conductivity) due to reduced graphene oxide. The as-synthesized conducting ferrofluid could be a promising candidate for the next generation building block material in microwave shielding applications with vast utilities in the radio frequency range.