Economical preparation of Fe3O4/C/CG and Fe/C/CG composites as microwave absorbents by recycling of coal gangue

Abstract

Pollution is a pressing problem in the context of sustainable development, a solution to which is to reutilize waste resources. Herein, coal gangue was recycled to prepare Fe3O4/C/CG and Fe/C/CG composites for microwave absorption via a facile method. The synthesis process involves loading a precursor solution of starch and ferric nitrate onto coal gangue matrix and then conducting the in-situ carbothermal reduction. The initial starch mass and carbothermal temperature significantly affect the dielectric and magnetic properties, further affect microwave absorption performance of the composites. For the Fe3O4/C/CG and Fe/C/CG composite, the minimum reflection loss could reach −45.1 dB and −27.8 dB, respectively. And the maximum effective absorption bandwidth of Fe/C/CG was 4.7 GHz. The strong microwave attenuation and impedance matching, which stemmed from the conductive graphitized carbon, the abundant interfaces of the highly dispersed carbon and iron species on the matrix, must account for the excellent performance.