Facile construction of low-cost and high-efficiency microwave absorbent of Co/C/CG composite with dual-enhancement performance

Abstract

Carbon-based composite microwave absorption (MA) materials have been regarded as promising light and high-efficient microwave absorbers, but the cumbersome synthesis procedures of carbon matrix have hindered its large-scale application. Thus, it is necessary to find another environmentally friendly, reproducible and low-cost carrier for replacing these carbon materials, further tackling these issues. Herein, with coal gangue (CG) as the relatively low-quality carbon-contained matrix, starch as the cheap supplementary carbon source, CoCG composite was constructed by a solution impregnation and then a carbothermal reduction process at different temperatures. It was found that the state of carbon and Co species in these composites were strongly determined by carbothermal temperature further determining the electromagnetic properties, especially the dielectric properties. The optimal sample CoCG-600 obtained the best MA properties, which possesses the minimum reflection loss of −39.8 dB at 11.8 GHz, the effect absorption bandwidth of 4.7 GHz with the thickness of 2.5 mm. And the widest effective absorption bandwidth of 5.5 GHz can be achieved as decreasing the thickness to 2 mm. Compared with the Fe/C/CG composite in our previous work, Co/C/CG composite exhibited the dual-enhancement MA performance, due to the magnetic and conductive Co phase can be wholly preserved at the relatively high temperature. The dominant MA mechanism, dielectric loss, was mainly included the conductive loss caused by nono-crystalline graphite and Co particles. Finally, the superior selection principle of magnetic component for constructing another MA composite based other impure low- and high-quality carbon-contained matrix was reasonably conjectured.