Hollow graphite spheres embedded in porous amorphous carbon matrices as lightweight and low-frequency microwave absorbing material through modulating dielectric loss

Abstract

Relative high filling ratio and poor reflection loss performance in low frequency are two major challenges in promoting microwave response of current carbon material which could be overcome by rational structure engineering. Herein, hollow graphite spheres embedded in porous amorphous carbon matrix has been prepared by etching Fe3Ni/C composites derived from Fe2Ni MIL-88 nanorods. Construction of conductive network and intrinsic high electrical conductivity contribute to the decrease of percolation threshold. Reflection loss performance in Ku and X band has been ameliorated by modulated dielectric loss mechanisms. Conduction loss models are established to verify the role of Fe3Ni nanoparticles, hollow graphite spheres and amorphous carbon matrix. Polarization modes have been tuned by interface strategy which leads to varied interfacial polarization loss in distinct frequency. Dipole polarization loss has also been controlled by strengthening or weakening interaction which can be influenced by filling ratio. As a result, with a low filling ratio of 10 wt%, effective absorption can be achieved in 12.76–18 GHz and 8.24–12 GHz. It is believed that this work would lay a foundation to design lightweight carbon-based microwave response materials in a wide frequency range.