Fabrication of ternary CoNi@SiO₂@RGO composites with enhanced electromagnetic (EM) wave absorption performances

The ternary hybrids composed of a CoNi inner unit along with SiO₂ and graphene outer units (CoNi@SiO₂@RGO) are synthesized via a facile solvothermal/sol–gel/hydrothermal strategy. The structures, chemical composition and morphologies of CoNi, CoNi@SiO₂ and CoNi@SiO₂@RGO are analyzed in detail. Besides, the electromagnetic (EM) wave absorption performances of the as-prepared products are invested on the basis of transmission lines theory. The results indicate that the ternary CoNi@SiO₂@RGO composites display enhanced microwave-absorbing characteristics in terms of both the maximum reflection loss and the absorption bandwidth, compared with the pristine CoNi alloy and CoNi@SiO₂ microparticles. The maximum R_L of CoNi@SiO₂@RGO reaches as high as −50.3 dB at 6.8 GHz, and the absorption bandwidth below −10 dB is up to 4.0 GHz with a thickness of 4 mm. A possible mechanism of microwave absorption is explained, drawing a conclusion that the improvement of absorption property is mainly ascribed to the synergic effect of combining magnetic and dielectric components, and the interface interactions of multi-component hierarchical structure.