Gradient structure silicone rubber composites for selective electromagnetic interference shielding enhancement and low reflection

Electromagnetic interference (EMI) shielding composites with gradient filler distributions were fabricated with the application of an induced magnetic field. The selective enrichment of nickel-coated carbon fibers within a core-shell structure effectively strengthens the overlap between fillers. This composite exhibited outstanding conductivities (98.2 S/m) that were two orders of magnitude greater than composites that possessed uniformly dispersed fillers because of the favorable inductive effect and the perfect loading of Ni nanoparticles. In addition, the sandwich structure causes the electromagnetic (EM) waves to reflect multiple times, further improving the EMI shielding effectiveness (SE) of the composite and resulting in a maximum SE of 60.8 dB. The introduction of magnetic Fe3O4@MWCNTs greatly increased the EM wave absorption efficiency from 14% to 45%, which resulted in low reflection peaks due to the resonant cancellation of the incident and reflected EM waves. The reflectivity of the composite was only 4% at 8.2 GHz, indicating a high absorption rate of 96% at this frequency. Furthermore, the composite shows excellent EMI shielding stability after 1000 repeated bends. This work thus describes a new approach to the preparation of high-performance (high-efficiency and low-reflectivity) EMI shielding materials and broadens their applicability to precision electronic devices and flexible wearable devices.