RESUMO
Simultaneously realizing high electromagnetic interference (EMI) shielding and superhydrophobic properties of materials to ensure long-term stability in harsh environments is a very challenging task. In this work, an efficient superhydrophobic EMI shielding composite with a gradient conductivity and porous structure was prepared by chemical plating, in situ polymerization, and spraying processes. Benefiting from the structural characteristics of porous multilayers and the rational distribution of electromagnetic two-component fillers in the composite, as well as the synergistic effect of various electromagnetic loss mechanisms, a perfect unification of high EMI shielding effectiveness of 62 dB and high absorption coefficient (A) of 0.77 was achieved. Meanwhile, a thin layer with further enhanced impedance matching was constructed on the surface of the composite using double-sized mixed particles of Fe3O4 and graphite particles (GP) in conjunction with the spraying process. The rough surface microstructure of the thin layer bestows the composite superhydrophobicity, and even after long-term immersion in acidic and alkali solutions or repetitive bending, the water contact angle still remains at a high level. Additionally, the sprayed materials also endow the composite with outstanding photothermal conversion properties that enhance the ability to adapt to environmental changes, significantly raising the practical application value.
RESUMO
The evolution of contemporary electronics urgently requires the use of versatile electromagnetic interference (EMI) shielding materials in complex environments. Interlayer polydimethylsiloxane (PDMS)/Fe3O4@multiwalled carbon nanotubes (MWCNTs) foams were prepared by a simple physical foaming method with excellent flexibility and electromagnetic wave absorption. The bottom nickel aramid paper (NiP) layer creates a dense conductive network by chemical plating technology, which ensures excellent EMI effectiveness. The upper carbon black (CB)/Fe3O4 layer further improves the absorption performance via conductive loss and magnetic loss. With the effective layout of the impedance matching layer, absorbing layer, and conductive shielding layer, the CB/Fe3O4-PDMS/Fe3O4@MWCNTs-NiP composite material achieves an EMI shielding effectiveness (EMI SE) of 61.7 dB and an absorption coefficient of 0.58 at X-band. In addition, the composite foam provides photothermal conversion and hydrophobicity due to the effective stacking of PDMS and CB/Fe3O4. Thus, the multifunctional composite foam presents a broad range of possible applications, benefiting EMI shielding as well as other specific areas.
RESUMO
Achieving absorption-dominated electromagnetic interference (EMI) shielding composites with high shielding effectiveness (SE) remains a great challenge due to their minimization of secondary EM radiation pollution, which is highly desired for next-generation electronic devices. Herein, an ingenious approach is proposed to develop asymmetric hierarchical polycaprolactone (PCL) composites composed of an impedance matching layer and a conductive layer through the combination of alternate casting and electroless plating methods, while the polarization loss caused by the difference in conductivity between the two layers would further attenuate the EM waves. The gradient distribution of the shielding fillers creates a positive conductive gradient and a negative magnetic gradient; the higher the gradient, the more it induces magnetic and dielectric losses, which results in an enhanced absorption mechanism that could overcome the restrictions of the nonadjustable reflective properties. The obtained Fe3O4@rGO/Ni/Ag/PCL composite possesses a remarkable EMI SE of 47.6 dB, while the power coefficient of reflectivity (R) could be significantly reduced to 0.27. This research provides a feasible strategy for developing absorption-dominated shielding materials with tunable EM performance that are appropriate for the next generation of electronic devices.
