Effect of carbon shell thickness on the microwave absorption of magnetite-carbon core-shell nanoparticles

Carbon coated magnetite nanoparticles with two different shell thicknesses were synthesized by a facile two-step method using glucose as a source of carbon. At first, hematite nanoparticles were synthesized by hydrothermal process. Carbon shells were coated on hematite nanoparticles by hydrothermal carbonization process, and the carbon coat thickness on particles was controlled by the amount of glucose in the second step. The hematite-carbon core-shell nanoparticles were then heat treated under argon gas flow in order to produce magnetite-carbon nanocapsules. Phase transformation during the heat treatment was studied by X-ray diffraction (XRD). The existence of carbon shell on nanoparticles was investigated by transmission electron microscopy (TEM) and Raman spectroscopy. The effect of carbon shell thickness variation on the relative complex permittivity (εr=ε′+iε″) and permeability (μr=μ′+iμ″) was studied in a frequency range of 1-18 GHz. The effect of carbon shell thickness on the Fe3O4-C nanoparticles reflection loss was also studied. The results showed that the microwave properties of the carbon coated magnetite nanoparticles can be controlled effectively by adjusting carbon shell thickness.