An impregnation-reduction method to prepare graphite nanosheet/alumina composites and its high-frequency dielectric properties

The nano-graphite sheet/alumina composites were prepared in situ by a facile impregnation-reduction process. The microstructure of the composites was analyzed by X-ray diffraction (XRD), and the final phase composition after reduction is Al2O3, metal Fe and graphite crystal. Scanning electron microscopy (SEM) images show that the particle size of Fe is about 20 nm, and the lamellae thickness of the graphite is about 30 nm. Then, the dielectric properties and conductive mechanism of the composites were investigated experimentally in the frequency range of 0.01–1.00 GHz by impedance analyzer. The results show that the real part of permittivity of composites increases with Fe3+ concentration, which is due to the increase in interfacial polarization between Fe and Al2O3 and the three-dimensional network of lamellar graphite formation. Therefore, tunable microtopography and electrical parameters of nano-graphite sheet/alumina composites can be realized by changing Fe3+ concentration.