High-efficiency electromagnetic wave absorption of epoxy composites filled with ultralow content of reduced graphene/carbon nanotube oxides

Abstract Graphene or carbon nanotube filled polymer materials with strong electromagnetic wave absorption, broad absorption band, thinness, low filler loading and facile fabricating technique are highly desirable in daily life and areas of electronics. However, there are still many obstacles to simultaneously satisfy the above critical requirements by utilizing the sole carbon absorbers. Herein, first, reduced graphene/CNT oxides (rGTO) are synthetized via simple modified Hummers and chemical reduction methods. Then we fabricate rGTO/epoxy nanocomposites by an in-suit polymerization method. Benefitting from the π-stacking interactions and mutual supporting between graphene and carbon nanotubes, good dispersion and interfacial interactions are formed between rGTO and the polymer matrix within ultralow filling content (1 wt%). Also, the defects and residual oxygen-containing groups in rGTO not only achieve ideal impedance matching but also introduce remarkable dielectric polarization loss. Thus, the rGTO/epoxy nanocomposites exhibit excellent microwave absorption performance with strong absorption (reflection loss is −61.8 dB), thinness (1.9 mm), broad bandwidth (effective absorption bandwidth is 5.38 GHz) and ultralow filler loading (1 wt%). More importantly, minimum RL value below −30 dB is obtained almost over the thickness range of 1.5–4.5 mm and the frequency of 4.2–18 GHz.