Sustainable liquid metal-induced conductive nacre.

Nacre has inspired research to fabricate tough bulk composites for practical applications using inorganic nanomaterials as building blocks. However, with the considerable pressure to reduce global carbon emissions, preparing nacre-inspired composites remains a significant challenge using more economical and environmentally friendly building blocks. Here we demonstrate tough and conductive nacre by assembling aragonite platelets exfoliated from natural nacre, with liquid metal and sodium alginate used as the "mortar". The formation of GaOC coordination bonding between the gallium ions and sodium alginate molecules reduces the voids and improves compactness. The resultant conductive nacre exhibits much higher mechanical properties than natural nacre. It also shows excellent impact resistance attributed to the synergistic strengthening and toughening fracture mechanisms induced by liquid metal and sodium alginate. Furthermore, our conductive nacre exhibits exceptional self-monitoring sensitivity for maintaining structural integrity. The proposed strategy provides a novel avenue for turning natural nacre into a valuable green composite.

Tough and Conductive Nacre-inspired MXene/Epoxy Layered Bulk Nanocomposites.

A long-standing quest in materials science has been the development of tough epoxy resin nanocomposites for use in numerous applications. Inspired by nacre, here we report tough and conductive MXene/epoxy layered bulk nanocomposites. The orientation of MXene lamellar scaffolds is enhanced by annealing treatment. The improved interfacial interactions between MXene lamellar scaffold and epoxy through surface chemical modification resulted in a synergistic effect. Tailoring the interlayer spacing of MXene nanosheets to a critical distance resulted in a fracture toughness about eight times higher than that of pure epoxy, surpassing other epoxy nanocomposites. Our nacre-inspired MXene/epoxy layered bulk nanocomposites also show high electrical conductivity that provides self-monitoring capability for structural integrity and exhibits an excellent electromagnetic interference shielding efficiency. Our proposed strategy provides an avenue for fabricating high-performance epoxy nanocomposites.

Accordion-like reduced graphene oxide embedded with Fe nanoparticles between layers for tunable and broadband electromagnetic wave absorption.

Electromagnetic wave absorbers constructed by reduced graphene oxide (rGO) and magnetic nanoparticles are extremely desirable for enhancing electromagnetic wave absorption performance due to the effective integration of the properties of dielectric and magnetic materials. However, the arrangement of graphene sheets and the growth of magnetic nanoparticles have always been challenging. Herein, an in-situ growth process has been used to successfully prepare accordion-like graphene with homogeneously distributed Fe nanoparticles in the confined structure via ion absorption and pyrolysis. The as-prepared Fe/layered rGO composites show excellent electromagnetic wave absorption performance with thin thickness, low filler loading, and broad effective absorption bandwidth (EAB). The minimum reflection loss of the composites achieves -54.6 dB with 20 wt% filler loading, and the tunable EAB reach 6.8 GHz (2.2 mm with 10 wt% filler loading) and 4.6 GHz (2.8 mm with 30 wt% filler loading), which can cover the entire Ku-band and X-band. The mechanism analysis indicates that the superior absorption performance is attributed to the multi-component loss mechanism, enhanced impedance matching degree and attenuation ability caused by the synergistic effect of layered rGO sheets and magnetic nanoparticles. This work opens up a new avenue for constructing accordion-like graphene-based composites as highly efficient electromagnetic wave absorbers.

Regenerated and rotation-induced cellulose-wrapped oriented CNT fibers for wearable multifunctional sensors.

Recently, wearable multifunctional fibers have attracted widespread attention due to their applications in wearable smart textiles. However, stable application, large-scale production and more functions are still the greatest challenges for functional fiber devices. In this study, wearable multi-functional coaxial fibers with oriented carbon nanotubes (CNTs) were achieved for the first time coaxial wet-spinning with rotating coagulation bath. Specifically, the cellulose solution can be regenerated in the coagulation bath and the CNTs dispersion will be oriented under the rotating force. The synergy between hydrogen bonding and van der Waals interaction enhance the mechanical strength of coaxial fibers. Especially, CNTs can prevent the rotation of the cellulose chain and the bending of the glycosidic twist angle at the atomic scale as indicated by molecular dynamics (MD) simulations. When the fibers are strained, the cellulose sheath will drive the movement of CNTs, causing changes involving the effective contact area and number of conductive paths. Therefore, the high electrical resistance response change enables the as-obtained coaxial fibers to exhibit a great potential in wearable strain sensors. Furthermore, coaxial fibers can be made into electric heaters based on the Joule heating principle. The heating temperature reaches more than 160 °C within 6 s at 10 V, which is of a great value for large area flexible heaters. Besides, the coaxial fibers can further be used as temperature-sensitive devices to accurately perceive the external temperature. Therefore, the scalable synthesis of multifunctional coaxial fibers is significantly expected to provide a platform for the large-scale production of multifunctional wearable intelligent textiles.

Hybridization-Induced Polarization of Graphene Sheets by Intercalation-Polymerized Polyaniline toward High Performance of Microwave Absorption.

An intercalation polymerization is applied to regulate the hybridizing structures of polyaniline@graphene (PANI@GE). Polarization of GE sheets is realized, which is attributed to the hybridization by the in situ intercalation-polymerized PANI molecules. The polarizing effect on GE is confirmed by characterizations and density functional theory calculations, and the results indicate that distinct p-π and π-π interactions exist between the PANI molecules and the GE sheets. As a result, this new structural hybrid leads to a high performance of microwave absorption. The minimum reflection loss (RL) of the optimized PANI@GE hybrid can be as low as -64.3 dB at 10.1 GHz with the RL bandwidth of -10 dB being 5.1 GHz (from 8.6 to 13.7 GHz). A further study reveals a special mechanism for the electromagnetic energy consumptions by the structural resonance of the polarized GE-based hybrids, a complex macromolecule. In addition, the fully separated GE provides a good impedance matching, together with the widely held multiscaled relaxations of the interfacial polarization.

Interface Modulating CNTs@PANi Hybrids by Controlled Unzipping of the Walls of CNTs To Achieve Tunable High-Performance Microwave Absorption.

Making full use of the interface modulation-induced interface polarization is an effective strategy to achieve excellent microwave absorption (MA). In this study, we develop an interfacial modulation strategy for achieving this goal in the commonly reported dielectric carbon nanotubes@polyaniline (CNTs@PANi) hybrid microwave absorber by optimizing the CNT nanocore structure. The heterogeneous interfaces from PANi and CNTs can be well regulated by longitudinal unzipping of the walls of CNTs to form 1D CNT- and 3D CNT-bridged graphene nanoribbons and 2D graphene nanoribbons. By controlling the oxidation peeling degree of CNTs, their interface area and defects are enhanced, thus producing more polarization centers to generate interfacial polarization and polarization relaxation, and also introducing more PANi loadings. Furthermore, more interface contact area can be produced between CNTs and PANi. This could induce a strong dielectric resonant and further improve the impedance matching, leading to significant enhancement of MA performance. With filler loading of only 10 wt % and a thinner coating thickness of 2.4 mm, the optimized CNTs@PANi exhibits excellent MA performance with the minimum reflection loss (RLmin) value of -45.7 dB at 12.0 GHz and the effective bandwidth is from 10.2 to 14.8 GHz. Meanwhile, the broadest effective bandwidth reaches 5.6 GHz, covering the range of 12.4-18.0 GHz with a thin thickness of 2.0 mm and its RLmin reaches -29.0 dB at 14.6 GHz. It is believed that the proposed interfacial modulation strategy can provide new opportunities for designing efficient MA absorbers.

Intercalation Polymerization Approach for Preparing Graphene/Polymer Composites.

The rapid development of society has promoted increasing demand for various polymer materials. A large variety of efforts have been applied in order for graphene strengthened polymer composites to satisfy different requirements. Graphene/polymer composites synthesized by traditional strategies display some striking defects, like weak interfacial interaction and agglomeration of graphene, leading to poor improvement in performance. Furthermore, the creation of pre-prepared graphene while being necessary always involves troublesome processes. Among the various preparation strategies, an appealing approach relies on intercalation and polymerization in the interlayer of graphite and has attracted researchers' attention due to its reliable, fast and simple synthesis. In this review, we introduce an intercalation polymerization strategy to graphene/polymer composites by the intercalation of molecules/ions into graphite interlayers, as well as subsequent polymerization. The key point for regulating intercalation polymerization is tuning the structure of graphite and intercalants for better interaction. Potential applications of the resulting graphene/polymer composites, including electrical conductivity, electromagnetic absorption, mechanical properties and thermal conductivity, are also reviewed. Furthermore, the shortcomings, challenges and prospects of intercalation polymerization are discussed, which will be helpful to researchers working in related fields.