Core-shell nickel@copper nanowires associated with multilayered gradient architecture design towards excellent absorption-dominant electromagnetic interference shielding

Exploiting high-performance absorption-dominant electromagnetic interference (EMI) shielding composites is urgently desired yet challenging for minimizing secondary electromagnetic radiation pollution. Herein, a nickel (Ni) shell was in-situ grown on a copper nanowires (CuNWs) core to greatly improve the stability of CuNWs, while maintaining excellent electrical conductivity. Afterward, Ni nanowires/Ni@Cu nanowires/graphite paper/waterborne polyurethane (NiNWs/Ni@CuNWs/graphite paper/WPU, nNi-mNi@Cu-G) composite foams with the multilayered gradient architectures were fabricated by a facile multi-step freeze-casting method. In the resultant composite foams, the lowly conductive porous NiNWs/WPU layer plays a role as the impedance matching layer, the moderately conductive porous Ni@CuNWs/WPU layer acts as the transition layer, and the highly conductive graphite paper layer serves as the reflection layer. Arising from the rational layout of multilayered gradient magnetic-electrical networks, nNi-mNi@Cu-G foam holds the superior averaged total EMI shielding effectiveness (EMI SE_T) of 75.2 dB and optimal absorption coefficient (A) of 0.93 at the incident direction from NiNWs/WPU layer, suggesting the dominant absorption in EMI shielding mechanism and efficiently alleviating the secondary electromagnetic pollution. Furthermore, nNi-mNi@Cu-G foam also exhibits fascinating compressive properties with a compressive strength of 49.3 kPa, which is essential for its practical application. This multilayered gradient architecture design provides valuable insight into high-efficiently constructing absorption-dominant EMI shielding composites.