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Strengthening and functioning effects of Fe 3 O 4 nanowires (Fe 3 O 4 NWs)-reduced graphene oxide (FeNWs-rGO) hybrid on gas barrier, microwave absorption, and electromagnetic interference (EMI) shielding performance of epoxy (EP) composites were systematically evaluated. FeNWs-rGO hybrid was successfully prepared through dopamine (DA) derived onepot coprecipitation, associated with the synchronous surface reduction on GO. The in situ growth mechanism of Fe 3 O 4 NWs on rGO sheets was properly discussed, in which the DA/Fe 3+ /Fe 2+ molar ratio and pH value in the reaction solution were found to be the determining factors in obtaining high quality FeNWs-rGO with a large amount and long length of Fe 3 O 4 NWs. The magnetism feature of FeNWs-rGO endowed the possibility of controlling their distribution state in EP matrix under the action of external magnetic field. The oxygen transmission and moisture diffusion coefficients of EP composites with magnetically aligned FeNWs-rGO at the intensity of 35 mT were clearly reduced as much as 33.6% and 68.0% compared with those of EP composites with randomly distributed FeNWs-rGO, respectively. More importantly, EP composites with different FeNWs-rGO distributions exhibited obvious anisotropy in microwave absorption and EMI shielding performance. Specifically, when FeNWs-rGO was aligned vertical to the direction of incident wave, the remarkable microwave absorption and EMI shielding capabilities of EP composites were achieved at only 2.0 wt % loading content of FeNWs-rGO, mainly due to strong interfacial polarization effect induced by plentiful heterointerfaces and strengthened multiple reflections inside FeNWs-rGO sheets by maximizing their interaction area with the incident wave.

The challenge for fully exerting the excellent nature of graphene oxide (GO) within polymer composites was to realize its uniform dispersion and strong interfacial bonding in the polymer matrix through an efficient surface reduction approach. In this work, via the in situ activation effect of microwaves (MWs), a butyl glycidyl ether-modified ionic liquid (BIL)-GO hybrid was successfully synthesized at an ultrafast speed by introducing BIL into the two-dimensional lamellar structure of GO through chemically induced intercalation and noncovalent functions. Both GO and BIL components of BIL-GO had the positive synergism in absorbing MWs, which contributed much to enhancing its dispersibility in the epoxy (EP) matrix as compared with pristine GO. Superior to GO-filled systems, BIL-GO/EP composites showed lower activation energies (E a1 and E a2 reduced by 11.2 and 17.3%, respectively) over the range of cure following inside-out solidification modes because of the introduction of BIL because uniformly dispersed BIL-GO with exfoliated interlayers acted as trap centers of MWs. Additionally, BIL-GO/EP composites possessed a 22.1% increase in the strength of the transverse fiber bundle test over that of GO/EP composites, indicating better BIL-GO/EP interfacial bonding. The obtained results manifested that the advantageous effect of BIL through the in situ activation of MWs was to enhance the interface stress transfer and form a uniform BIL-GO network, thereby significantly enhancing the mechanical, thermal, and electrical properties of BIL-GO composites.

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