Directionally Aligned, Defect-Suppressed Non-oxidatively Exfoliated Graphene Flakes for High EMI Shielding Performance

In this study, we report the development of high-performance electromagnetic interference (EMI) shielding composites incorporating directionally aligned non-oxidatively exfoliated graphene flakes (NOGF) within a polydimethylsiloxane (PDMS) matrix. The NOGF was synthesized via exfoliation of graphite intercalation compounds without oxidative treatment, thereby preserving their intrinsic graphitic structure with minimal defect formation. A unidirectional freeze-casting process was employed to fabricate anisotropically aligned NOGF aerogels, which were subsequently infiltrated with PDMS. The resulting NOGF/PDMS composites with a loading of 1.9 wt % exhibited significantly enhanced EMI shielding effectiveness (SE) compared to reduced graphene oxide (rGO)/PDMS counterparts with a loading of 1.7 wt %, achieving a mean SE of 67.2 dB at 2.3 mm thickness, while th rGO/PDMS composites reached 31.1 dB at 2.5 mm. Directional alignment was also found to play a critical role, as longitudinally cut samples consistently outperformed those in the transverse direction. This work highlights the potential of low-filler-content graphene composites for multifunctional EMI shielding applications.