Ultra‐Low Loading of Ultra‐Small Fe₃O₄ Nanoparticles on Nonmodified CNTs to Improve Green EMI Shielding Capability of Rubber Composites

Abstract

From a material design perspective, the incorporation of Fe3O4@carbon nanotube (Fe3O4@CNT) hybrids is an effective approach for reconciling the contradictions of high shielding and low reflection coefficients, enabling the fabrication of green shielding materials and reducing the secondary electromagnetic wave pollution. However, the installation of Fe3O4 nanoparticles on nonmodified and nondestructive CNT walls remains a formidable challenge. Herein, a novel strategy for fabricating the above‐mentioned Fe3O4@CNTs and subsequently assembling segregated Fe3O4@CNT networks in natural rubber (NR) matrices is proposed. The advanced and unique structure, magnetism, and lossless conductivity endow the as‐obtained Fe3O4@CNT/NR with a shielding effectiveness (SE) of 63.8 dB and a low reflection coefficient of 0.24, which indicates a prominent green‐shielding capability that surpasses those of previously reported green‐shielding materials. Moreover, the specific SE reaches 531 dB cm−1, exceeding that of those of previously reported carbon/polymer composites. Meanwhile, the outstanding conductivity enables the composite to reach a saturation temperature of ≈95 °C at a driving voltage of 1.5 V with long‐term stability. Therefore, the as‐fabricated Fe3O4@CNT/rubber composites represent an important development in green‐shielding materials that are applied in cold environment.

Enhanced Sensing and Electromagnetic Interference Shielding Performance of Hydrogels by the Incorporation of Ionic Liquids

“…When the value of A is greater than 0.5, the material displays the absorption-dominated shielding mechanism. Conversely, when the value of R is greater than 0.5, the material displays the reflection-dominated shielding mechanism . This is due to the fact that ILs, known as ionic conductors, confer the SA/PAM/IL@PGO hydrogel with ionic conductive properties, imparting the property of ionic conductivity to the SA/PAM/IL@PGO hydrogel.…”

“…Conversely, when the value of R is greater than 0.5, the material displays the reflection-dominated shielding mechanism. 5 This is due to the fact that ILs, known as ionic conductors, confer the SA/PAM/IL@PGO hydrogel with ionic conductive properties, imparting the property of ionic conductivity to the SA/PAM/IL@PGO hydrogel. Fluids containing freely moving ions contribute to reducing the reflection of electromagnetic waves, as observed in electrically insulating ionic solutions.…”

“…More recently, the use of flexible, wearable sensors based on conductive polymer composites (CPCs) has enabled the detection of a variety of human physical activities, including joint flexion, heart rate, walking, talking, blinking, and breathing. , However, when working with the above-mentioned sensors, signal transmission is severely impaired by electromagnetic interference (EMI) waves. − To solve the above problems, many flexible wearable sensors based on CPCs with high EMI shielding effectiveness (SE) have been designed and developed, such as reduced graphene oxide/rubber composites, conductive metal–organic frameworks/films, AgNWs/hydrogels, Cu/polydimethylsiloxane (PDMS)/Cu materials, and so on.…”

Graphene-Based Hybrid Fillers for Rubber Composites

“…For instance, combining graphene magnetic hybrid fillers with specific structures, such as gradient structures, layer-by-layer structures, or porous structures, can be an effective method for enhancing material absorption while reducing reflection. This is particularly significant for the preparation of “green” EMI-shielding materials with low reflection and high absorption [ 218 , 219 , 220 ]. Diversified rubber matrices: Exploring the blending of the rubber matrix with other materials, such as chitosan, gelatin, polyurethane, and epoxy, can endow the composites with more advantages.…”

“…For instance, combining graphene magnetic hybrid fillers with specific structures, such as gradient structures, layer-by-layer structures, or porous structures, can be an effective method for enhancing material absorption while reducing reflection. This is particularly significant for the preparation of “green” EMI-shielding materials with low reflection and high absorption [ 218 , 219 , 220 ].…”