Abstract
In this work, 3D highly electrically conductive cellulose nanofibers (CNF)/Ti3C2Tx MXene aerogels (CTA) with aligned porous structures are fabricated by directional freezing followed by freeze-drying technique, and the thermally annealed CTA (TCTA)/epoxy nanocomposites are then fabricated by thermal annealing of CTA, subsequent vacuum-assisted impregnation and curing method. Results show that TCTA/epoxy nanocomposites possess 3D highly conductive networks with ultralow percolation threshold of 0.20 vol% Ti3C2Tx. When the volume fraction of Ti3C2Tx is 1.38 vol%, the electrical conductivity (σ), electromagnetic interference shielding effectiveness (EMI SE), and SE divided by thickness (SE/d) values of the TCTA/epoxy nanocomposites reach 1672 S m−1, 74 dB, and 37 dB mm−1, respectively, which are almost the highest values compared to those of polymer nanocomposites reported previously at the same filler content. In addition, compared to those of the samples without Ti3C2Tx, the storage modulus and heat-resistance index of TCTA/epoxy nanocomposites are enhanced to 9792.5 MPa and 310.7°C, increased by 62% and 6.9°C, respectively, presenting outstanding mechanical properties and thermal stabilities. The fabricated lightweight, easy-to-process, and shapeable TCTA/epoxy nanocomposites with superior EMI SE values, excellent mechanical properties, and thermal stabilities greatly broaden the applications of MXene-based polymer composites in the field of EMI shielding.
Highlights
With the rapid development of modern electronic information technology, especially the aerospace weapons and equipment technology, electromagnetic interference (EMI) pollution caused by high-frequency and high-power electronic equipment is becoming more and more severe, and the request for EMI shielding performances of existing materials in service becomes increasingly demanding [1,2,3,4]
Eswaraiah et al improved the dispersion of graphene in polyvinylidene fluoride (PVDF) by surface prefunctionalization of graphene sheets, and the EMI shielding effectiveness (SE) value of 7 wt% functionalized graphene/PVDF was up to 26 dB [11]
Sun et al reported that PS@Ti3C2Tx nanocomposites fabricated by electrostatic self-assembly and molding method demonstrated excellent EMI SE values, because of the contribution of 3D highly conductive networks embedded with the matrix [19]
Summary
With the rapid development of modern electronic information technology, especially the aerospace weapons and equipment technology, electromagnetic interference (EMI) pollution caused by high-frequency and high-power electronic equipment is becoming more and more severe, and the request for EMI shielding performances of existing materials in service becomes increasingly demanding [1,2,3,4]. The EMI SE value of 35 wt% 3D graphene nanoplatelets/polystyrene (GNPs/PS) prepared by electrospinning method reached 33 dB, which was improved by 106% compared to that (16 dB) of randomly dispersed GNPs/PS at the same loading of GNPs [13]. The improvement effect is limited based on the abovementioned methods, and it still demands a large amount of conductive fillers to achieve ideal EMI SE. Sun et al reported that PS@Ti3C2Tx nanocomposites fabricated by electrostatic self-assembly and molding method demonstrated excellent EMI SE values, because of the contribution of 3D highly conductive networks embedded with the matrix [19]. The EMI SE values based on 3D conductive networks are greatly increased compared to those of the composites prepared by blend-casting method with randomly oriented filler microstructure, they have the similar problems including energy-consuming, limited sample sizes, and uncontrollable shape. The effect of the volume fraction of Ti3C2Tx nanosheets on σ, EMI SE values, mechanical properties, and thermal stabilities of TCTA/epoxy nanocomposites is investigated, and the mechanism of EMI SE improvement of the nanocomposites is proposed
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