Magnetic-conductive bi-gradient structure design of CP/PGFF/Fe3O4 composites for highly absorbed EMI shielding and balanced mechanical strength

Developing excellent absorption-dominant electromagnetic interference (EMI) shielding composites is an urgent demand for the rapid development of 5 G technology and electronic equipment. Herein, a simple strategy is employed to fabricate carbon nanotubes-polypropylene fibers (CP) /polypropylene-glass fibers felt (PGFF)/Fe3O4 composites with superior EMI shielding effectiveness and low reflection due to the magnetic-conductive bi-gradient structure which is naturally formed by deposition during the vacuum-assisted filtration process. The difference in dimensionality between one-dimensional CNT with outstanding electrical conductivity and zero-dimensional magnetic Fe3O4 nanoparticles is the theoretical basis for the successful construction of the magnetic-conductive bi-gradient structure in a gap-rich PGFF matrix that endows the composites with "absorb-reflect-reabsorb" EMI shielding mechanism. When the electromagnetic waves are incident from the magnetic layer, the EMI shielding effectiveness (SE) reaches 48.9 dB as the weight percentage of the conductive layer increases, more importantly, the reflection coefficients are reduced by more than 0.32 compared with that of another incident pattern. What's more, the resultant composites exhibit an outstanding signal shielding function in the application. This work paves a convenient pathway for designing a magnetic-conductive bi-gradient structure and efficient absorbing EMI shielding composites applied in the next-generated electronic information and communication field.