Strong,tough,and thermally conductive nacre-inspired boron nitride nanosheet/epoxy layered nanocomposites

Thermally conductive polymer nanocomposites integrated with lightweight,excellent flexural strength,and high fracture toughness(KIc)would be of great use in many fields.However,achieving all of these properties simultaneously remains a great challenge.Inspired by natural nacre,here we demonstrate a lightweight,strong,tough,and thermally conductive boron nitride nanosheet/epoxy layered(BNNEL)nanocomposite.Because of the layered structure and enhancing the interfacial interactions through hydrogen bonding and Si–O–B covalent bonding,the resulting nacre-inspired BNNEL nanocomposites show high fracture toughness of~4.22 MPa·m^(1/2),which is 7 folds as high as pure epoxy.Moreover,the BNNEL nanocomposites demonstrate sufficient flexural strength(~168.90 MPa,comparable to epoxy resin),while also being lightweight(~1.23 g/cm^(3)).Additionally,the BNNEL nanocomposites display a thermal conductivity(κ)of~0.47 W/(m·K)at low boron nitride nanosheet loading of 2.08 vol.%,which is 2.7 times higher than that of pure epoxy resin.The developed nacre-inspired strategy of layered structure design and interfacial enhancement provides an avenue for fabricating high mechanical properties and thermally conductive polymer nanocomposites.

可持续液态金属诱导的导电贝壳

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 Ga-O-C 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.

Wheat straw-derived magnetic carbon foams: In-situ preparation and tunable high-performance microwave absorption

Recently,biomass-derived three-dimensional (3D) porous carbon materials have been gaining more interest as promising microwave absorbers due to their low cost,vast availability,and sustainability.Here,a novel 3D interconnected porous magnetic carbon foams are in-situ synthesized via a combination of sol-gel and carbonization process with wheat straw as the carbon source and FeCl3·6H2O as the magnetic regulating agent.During the process of foams formation,the lignocelluloses from the steam-exploded wheat straw are converted into interconnected carbon sheet networks with hierarchical porous structures,and the precursor FeCl3·6H2O is converted into magnetic nanoparticles uniformly embedded in the porous carbon foams.The generated magnetic nanoparticles are benefit to enhance the interface polarization and magnetic loss ability to improve the efficient complementarities between the dielectric and magnetic loss,thus increasing the impedance matching.The obtained sample treated at 600 ℃ displays the best microwave absorption (MA) performance.It presents a minimal reflection loss (RL) of-43.6 dB at 7.1 GHz and the effective bandwidth (RL <-10 dB) is 3.3 GHz with the thickness of 4.7 mm.The 3D porous structure,multi-interfaces and the synergy of dielectric loss and magnetic loss make great contribution to the outstanding MA performance.

Generation of graphene-based aerogel microspheres for broadband and tunable high-performance microwave absorption by electrospinning-freeze drying process

Despite recent progress in the synthesis and application of graphene-based aerogels, some challenges such as scalable and cost-effective production, and miniaturization still remain, which hinder the practical application of these materials. Here we report a large-scale electrospinning method to generate graphene-based aerogel microspheres （AMs）, which show broadband, tunable and high-performance microwave absorption. Graphene/Fe3O4 AMs with a large number of openings with hierarchical connecting radial microcharmels can be obtained via electrospinning-freeze drying followed by calcination. Importantly, for a given Fe3O4：graphene mass ratio, altering the shape of aerogel monoliths or powders into aerogel microspheres leads to unique electromagnetic wave properties. As expected, the reflection loss of graphene/Fe3O4 AMs-1：1 with only 5 wt.% absorber loading reaches -51.5 dB at 9.2 GHz with a thickness of 4.0 mm and a broad absorption bandwidth （RL 〈-10 dB） of 6.5 GHz. Furthermore, switching to coaxial electrospinning enables the fabrication of SiO2 coatings to construct graphene/Fe3O4@SiO2 core-shell AMs. The coatings influence the electromagnetic wave absorption of graphene/Fe3O4 AMs significantly. In view of these advantages, we believe that this processing technique may be extended to fabricate a wide range of unique graphene-based architectures for functional design and applications.

Recent advances in surface-functionalised photosensitive antibacterials with synergistic effects

The alarm has been ringing over the gradually increasing drug-resistant bacteria,which calls for the development of safer antibacterial materials.Photosensitive antibacterials are considered as a promising alternative solution due to their unique light-activated antimicrobial mechanism,which in-situ produces highly reactive oxygen species on the multiple and variable active sites for the inactivation of various microbes.However,there are some factors,including phototoxicity,oxygen consumption and the risk of microbial contamination,greatly limit the efficiency and application of photosensitisers(PSs)in practical biomedical applications.Some studies have explored the synergistic effects of PSs by antibiotics,photothermal agents,antibacterial nanoparticles and biofilm-disrupting enzymes.Moreover,novel synergistic methods for improving the antibacterial ability of PSs under low-energy irradiation,hypoxia conditions and dull conditions,have been rarely reviewed yet.Herein,the authors summarised some synergistic methods and related applications of surface-functionalised photosensitive antimicrobials,which were prepared with organic antimicrobial materials,superhydrophobic surfaces,upconversion nanoparticles and energy storage structures in recent years.Finally,the authors presented the advantages and challenges of these synergistic mechanisms,and further analysed the development trend and application prospects of the surface-functionalised photosensitive antibacterials in biomedical fields.