Synthesis of CoNi/SiO₂ core-shell nanoparticles decorated reduced graphene oxide nanosheets for enhanced electromagnetic wave absorption properties

In this research, the nanocomposites, CoNi/SiO₂ core-shell nanoparticles decorated reduced graphene oxide (RGO) nanosheets, are successfully synthesized via liquid-phase reduction reactions combined with a sol-gel route. The structures, morphologies, chemical composition and magnetic properties of CoNi nanoparticles, CoNi/SiO₂ core-shell nanoparticles and RGO/CoNi/SiO₂ nanocomposites have been investigated in exhaustive detail. The electromagnetic (EM) parameters of RGO/CoNi/SiO₂ nanocomposites are measured using a vector network analyzer. The results reveal that the RGO/CoNi/SiO₂ nanocomposites display enhanced EM wave absorption properties with the maximum reflection loss (R_L) of − 46.3 dB at 6.2 GHz with a matching thickness of 4.2 mm. Additionally, the absorption bandwidth corresponding to the R_L less than − 10 dB is up to 14.3 GHz (3.7–18.0 GHz) with a matching thickness range of 2.0–5.0 mm. To comprehensively consider the absorption bandwidth and the maximum R_L, the integrational method which defines ΔS as the integration area of R_L (R_L < − 10 dB) and R_E as EM wave absorption efficiency is adopted to reveal that the RGO/CoNi/SiO₂ nanocomposites exhibit the excellent absorption properties with the matching thickness of only 2.0 mm. Accordingly, the as-prepared RGO/CoNi/SiO₂ nanocomposites could be applied as promising EM wave absorption materials.