Preparation and microwave absorption mechanism of cobalt ferrite/coal slime-based carbon composites

Transforming low-ash coal slime into electromagnetic wave-absorbing materials can not only meet the growing demand for electromagnetic protection but also holds significant importance for promoting the transformation and upgrading of the coal industry. In this study, a series of cobalt ferrite/coal slime-based carbon composite absorbing materials were successfully prepared by loading cobalt ferrite nanoparticles onto a coal slime-based carbon substrate via a co-precipitation method. The results demonstrate that the composite exhibits optimal wave-absorption performance when the cobalt ferrite loading amount is 12.52 wt%. At a matching thickness of 3.5 mm, the minimum reflection loss reaches -32.08 dB at 12.73 GHz, with an effective absorption bandwidth as high as 8.84 GHz (covering 9.16-18.00 GHz). The microwave absorption mechanism of the composite is primarily attributed to magnetic loss induced by cobalt ferrite, including natural resonance and eddy current loss, as well as dielectric loss caused by coal slime-based carbon, involving interfacial polarization and dipole polarization. The effective combination of coal slime-based carbon and cobalt ferrite significantly optimizes the impedance matching characteristics of the composite. This research provides theoretical guidance for the high-value utilization of low-ash coal slime in the field of electromagnetic wave absorption.