Multi-componential metal intercalated graphite hybrids synthesized by co-intercalation polymerization towards highefficient microwave absorptions

Magnetic expanded graphite(EG)hybrids were synthesized by co-intercalation polymerization of aniline together with transition metal ions.Experimental results show that metal ions(Fe,Co,Ni,Cu)and even their mixtures can co-intercalate into graphite interlayers with flexibly controllable ratios and contents.Among these co-intercalation compounds,Fe/Ni-intercalated graphite with a predesigned mole ratio of 1:3 transforms into NiFe_(2)O_(4)/FeNi_(3)@EG during the annealing process.The synthesized magnetic EG hybrids present multiband microwave absorption in C and X bands due to improved impedance match as well as significantly enhanced interfacial polarization relaxation induced by multi-componential metals.The reflection values of−39.1 dB at 6.95 GHz and−25.7 dB at 9.4 GHz are achieved with an ultra-low loading of 5 wt.%.This work provides a flexible approach for tuning the components and structures of magnetic EG hybrids,which may contribute to the development of microwave absorption materials with superior performances.

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.

Multiaxial electrospun generation of hollow graphene aerogel spheres for broadb and high-performance microwave absorption

Although graphene aerogels(GA)have been attracted great attention,the easy-operation and large-scale production of GA are still challenges.Further,most GA have a monolith-like appearance,limiting their application-specific needs.Herein,we highlight graphene aerogel spheres with controllable hollow structures(HGAS)that are delicately designed and manufactured via coaxial electrospinning coupled with freeze-drying and calcination.The HGAS exhibit a spherical configuration at the macroscale,while the construction elements of graphene on the microscale showing an interconnected radial microchannel structure.Further ball-in-ball graphene aerogel spheres(BGAS)are obtained by reference to the triaxial electrospinning technology.The as-prepared spheres possess the controllable integrated conductive networks,leading to the effective dielectric loss and impedance matching thus bringing on high-performance microwave absorption.The as-obtained HGAS shows a minimum reflection loss of-52.7 dB and a broad effective absorption bandwidth(f)of 7.0 GHz with thickness of 2.3 mm.Further,the fe reaches 9.3 GHz for BGAS with thickness of 3.4 mm.Aforementioned superior microwave absorption of HGAS and BGAS confirms combination of multiaxial electrospinning and freeze-drying on the multiscale is an effective strategy for scalable fabrication of advanced microwave.absorbing functional graphene aerogel spheres.

High-purity helical carbon nanotubes by trace-water- assisted chemical vapor deposition： Large-scale synthesis and growth mechanism

Helical carbon nanotubes （HCNTs） are highly desirable due to their unique geometrical elegance and inherent physical properties; however, high-efficiency synthesis of high-purity HCNTs with high yield and full elucidation of their growth mechanism remains challenging. Traditional methods to achieve the high-yield growth of HCNTs mainly focus on controlling the size of catalytic particles. Herein, we found that addition of trace water greatly benefits large-scale synthesis of HCNTs. Uniform HCNTs with - 100% purity can be obtained, and the yield of HCNTs can reach ~ 8,078% in a run of 6 h, much higher than that obtained without trace water and any of the reported yields. Experiments and theoretical simulations are performed to reveal that the trace water can react with the dangling bond on carbon, thus inhibiting the generation of amorphous species. Furthermore, the trace water can enhance the anisotropy of the catalyst surface. This results in different segregation rates of carbon atoms coming out of different crystal planes and further periodic mismatch of the graphite layers, thus leading to the formation of HCNTs. Therefore, this new and efficient method is promising for practical, large-scale production of HCNTs.

Progress in graphene-based magnetic hybrids towards highly efficiency for microwave absorption

Nowadays, the yearning for microwave absorption materials(MAMs) are more and more urgent for dealing with the increasingly serious electromagnetic pollution and the demand of modern military security.Among potential candidates, the graphene(GE) based magnetic hybrids have advantages in structural controllable and designing flexibility, providing opportunities for achieving highly efficiency of microwave absorption(MA). Thus, the structural regulation and MA performances of GE-based magnetic hybrids arouse great attention in related fields. In this review, we summarize the recently progress in MA performance of GE-based magnetic hybrids. Typical absorption process and corresponding mechanism are firstly introduced, for guiding the design of GE-based magnetic MAMs. Then, the magnetic components, synthesis methods, structural features and regulation strategies of these GE-related magnetic materials are reviewed, and their influences on MA performances have also been discussed. Challenges, and prospects of the GE-based magnetic MAMs are suggested. This review provides a brief but systematic introduction to GE-based magnetic MAMs, which may pave the way for the design of MAMs with highly efficient MA performances.

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.

Preparation,Properties,and Applications of Natural Cellulosic Aerogels:A Review

With the depletion of fossil fuel and increasing environmental concerns,the modernized era of technology is urgently in need for sustainable and eco-friendly materials.The industrial sector certainly possesses enough resources for the production of available cost-effective,renewable,reusable,and sustainable raw materials.Ul-tralight,eco-friendly and renewable cellulosic aerogels are one of the most accentuated materials in the polymer research field due to their highly abundant and inexpensive raw material,biocompatibility,high specific surface area and other feasible properties.This review summarizes the recent progress in cellulosic aerogels,their main processing route,including a detailed description of versatile new solvents along with some essential properties of cellulosic aerogels and illustrate how their variety of chemical functionalities can be adjusted for applications in the fields of thermal insulation,fire retardant,antibacterial,CO 2 capture and energy storage systems.A de-tailed morphological analysis has been elaborated and effect of processing route,solvent medium and drying procedure on the morphology of cellulosic aerogels is also decribed.Finally,we propose some suggestions to the functionalization such as silanized cellulosic aerogels and their applications in antibacterial activity yet they are still in progress and need further study for future research.

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.