Carbothermally synthesized core–shell carbon–magnetite porous nanorods for high-performance electromagnetic wave absorption and the effect of the heterointerface

Abstract

A high-performance microwave absorbing composite based on heterostructured nanorods with porous magnetite core and carbon shell was realized by combining a hydrothermal carbonization (HTC) coating process and a controlled carbothermal reduction. Goethite nanorods as the precursor for magnetite nanorods were successfully prepared by an ethylenediaminetetraacetic acid-assisted hydrothermal process with high efficiency, low cost, morphology tunability and mass production capability. The X and Ku frequency bands were completely covered with a minimum suitable RL of −10dB by composite layers with the thicknesses being less than 2mm; with increasing the thickness, other frequency bands were also acceptably covered. The heterostructured magnetite nanorods exhibited more enhanced EM properties than simple magnetite nanorods and other similar structures. The excellent EM properties arose from effective complementarities between the magnetic loss and the dielectric loss. The formation of carbon shells on the nanorods during the controlled carbothermal reduction process tailored the dielectric constants in a manner that increased the dielectric loss and the impedance matching of the composites, conjointly. In this regard, multiple interfacial polarization relaxations at core–shell and nanorod–matrix interfaces were effectively involved. These results indicated that the fabrication of heterostructured magnetite nanorods by HTC coating and controlled carbothermal reduction could be a promising method to manufacture highly efficient and economic EM wave absorbing materials.