Studies on electromagnetic interference shielding effect mechanisms of leaf-like three-dimensional carbon nanotubes/graphene aerogel film and the composites with polydimethylsiloxane

The three-dimensional (3D) structure can improve electromagnetic interference (EMI) shielding effectiveness (SE) of carbon-materials, thereby satisfy the requirement of lightweight. Herein, a leaf-like 3D carbon nanotubes (CNTs)/graphene aerogel film (CGAF) is prepared in which the CNTs are seamlessly embedded in graphene, analogous to veins and mesophyll of a leaf, respectively. The assembly of mesophyll-like graphene into 3D materials not only improves EMI SE, but also changes the EMI shielding mechanism. The addition of veins-like CNTs further amplifies the change of EMI shielding mechanism. The total EMI SE (SEtot) of 3D CGAF is 26.6 dB, which was 3.0 dB and 5.1 dB higher than that of CGP (prepared by compressing CGAF) and GAF (CGAF without CNTs). Besides, the 3D structure makes the absorption SE (SEA) dominates the SEtot of CGAF, accounting for 66.5%, but the reflection SE (SER) is dominant in the SEtot of CGP and the theoretical SEtot of CGAF. This shows that 3D structure can improve the absorption effect by repeatedly reflecting electromagnetic waves (EMWs) from countless pore walls, and the addition of CNTs further synergizes this effect, thus enhancing the SEtot and SEA. Furthermore, the SEMA (SEtot divided by mass per unit area) of CGAF can reach 12091 dB cm2 g−1, which increases by 12.7% and 18.1% compared to CGP and GAF, respectively. In addition, by combining multilayer CGAF with polydimethylsiloxane (PDMS), the SEtot can reach 74.7 dB at 8.2 GHz, and its SEtot still retains 45.6 dB after 100 cycles of bending, still far above the industry standard (20 dB), showing excellent bending resistance.