RESUMO
Two nanocomposites with a hierarchical structure (GO@CuSilicate@Fe3O4 and GO@Fe3O4@CuSilicate) were fabricated in this paper. These as-synthesized nanocomposites were analyzed for their structural, compositional, and morphological features by X-ray diffraction, scanning electron microscopy (SEM), Raman spectroscopy, and Brunauer-Emmett-Teller methods. SEM images showed that both nanocomposites had a core-shell structure, and their shells were composed of CuSilicate nanoneedle arrays. Further, their total electromagnetic shielding efficiency was measured and compared in a wide frequency range of 8-12 GHz (X-band). Because of the "antenna" role of CuSilicate nanoneedle arrays and the polarization at the interface between graphene oxide (GO) and Fe3O4, GO@Fe3O4@CuSilicate showed higher electromagnetic shielding performance than that of GO@CuSilicate@Fe3O4. With 1 mm thickness, GO@Fe3O4@CuSilicate showed a high electromagnetic shielding efficiency (over 40 dB) in the whole X-band (8.2-12.4 GHz) and reached a maximum value (41.8 dB) at 8.2 GHz. Its total electromagnetic shielding efficiency was mainly contributed by absorption rather than reflection. This study provided an idea for the structural design of high-performance electromagnetic shielding materials in the GHz frequency range (X band).