Synthesis of core-shell ZnFe₂O₄@SiO₂ hollow microspheres/reduced graphene oxides for a high-performance EM wave absorber

The core-shell ZnFe₂O₄@SiO₂ hollow microspheres/reduced graphene oxides (RGO-ZnFe₂O₄@SiO₂) composites were successfully synthesized by a rational process. SEM and TEM results illustrate that the ZnFe₂O₄@SiO₂ hollow microspheres are of core-shell structure with an average diameter of about 1 µm mixed with graphene sheets. Compared with ZnFe₂O₄@SiO₂ hollow microspheres and RGO-ZnFe₂O₄ composites, the as-prepared RGO-ZnFe₂O₄@SiO₂ composites exhibit excellent electromagnetic (EM) wave absorption properties in terms of both the maximum reflection loss and the absorption bandwidth. The maximum reflection loss of RGO-ZnFe₂O₄@SiO₂ composites is −45.8 dB at 7.6 GHz with the thickness of 3.7 mm and the absorption bandwidth with the reflection loss below −10 dB is up to 14.5 GHz (from 3.5 to 18.0 GHz) with a thickness in the range of 2.0–6.0 mm. It may also be stressed that the developed composites cover the whole X band (8.0–12.0 GHz), which could be used for military radars and direct broadcast satellites (DBS).