Absorption properties and mechanism of lightweight and broadband electromagnetic wave-absorbing porous carbon by the swelling treatment

Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness.In this study,KOH was evenly distributed on biomass Tremella using the swelling induction method,leading to the preparation of a three-dimensional network-structured hierarchical porous carbon(HPC)through carbonization.The achieved microwave absorption intensity is robust at-47.34 dB with a thin thickness of 2.1 mm.Notably,the widest effective absorption bandwidth,reaching 7.0 GHz(11–18 GHz),is attained at a matching thickness of 2.2 mm.The exceptional broadband and reflection loss performance are attributed to the 3D porous networks,interface effects,carbon network defects,and dipole relaxation.HPC has outstanding absorption characteristics due to its excellent impedance matching and high attenuation constant.The uniform pore structures considerably optimize the impedance-matching performance of the material,while the abundance of interfaces and defects enhances the dielectric loss,thereby improving the attenuation constant.Furthermore,the impact of carbonization temperature and swelling rate on microwave absorption performance was systematically investigated.This research presents a strategy for preparing absorbing materials using biomass-derived HPC,showcasing considerable potential in the field of electromagnetic wave absorption.

Rational construction of heterointerfaces in biomass sugarcane-derived carbon for superior electromagnetic wave absorption

The pervasive adoption of 5th generation mobile communication technology propels electromagnetic wave(EW)absorbents to achieve high-level performance.The heterointerface construction is crucial to the improvement of absorption ability.Herein,a series of ultralight composites with rational heterointerfaces(Co/ZnO@N-doped C/layer-stacked C,MSC)is fabricated by calcination with ration-al construction of sugarcane and CoZn-zeolitic imidazolate framework(ZIF).The components and structures of as-prepared composites were investigated,and their electromagnetic parameters could be adjusted by the content of CoZn-ZIFs.All composites possess excellent EW absorption performance,especially MSC-3.The optimal minimum reflection loss and effective absorption band of MSC-3 can reach−42 dB and 7.28 GHz at the thickness of only 1.6 mm with 20wt%filler loading.This excellent performance is attributed to the syner-gistic effect of dielectric loss stemming from the multiple heterointerfaces and magnetic loss induced by magnetic single Co.The sugar-cane-derived layer-stacked carbon has formed consecutive conductive networks and has further dissipated the electromagnetic energy through multiple reflection and conduction losses.Moreover,the simulated radar cross section(RCS)technology manifests that MSC-3 possesses outstanding EW attenuation capacity under realistic far-field conditions.This study provides a strategy for building efficient ab-sorbents based on biomass.

Synthesis of flower-like WS_(2) by chemical vapor deposition

Flower-like tungsten disulfide(WS_(2))with a diameter of 5-10μm is prepared by chemical vapor deposition(CVD).Scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),Raman spectroscopy,and ultraviolet-visible(UV-vis)spectroscopy are used to characterize its morphological and optical properties,and its growth mechanism is discussed.The key factors for the formation of flower-like WS_(2)are determined.Firstly,the cooling process causes the generation of nucleation dislocations,and then the"leaf"growth of flower-like WS_(2)is achieved by increasing the temperature.

Dual strategy of A-site ion substitution and self-assembled MoS_(2) wrapping to boost permittivity for reinforced microwave absorption performance

With the rapid development of electronic technology,how to effectively eliminate electromagnetic pollu-tion has become a serious problem.Perovskite oxides have shown great potential in the field of electro-magnetic wave absorption due to their unique structure and excellent physicochemical properties.Herein,by rationally manipulating the A-site ion substitution strategy,the theoretically directed doping of Sr ions into La ionic sites was utilized and the layered MoS_(2) was loaded by the hydrothermal process to modify its surface.Consequently,the introduced polarization phenomenon improved the dielectric performance of the perovskite oxides,achieving a collaborative dielectric/magnetic loss mechanism.Accordingly,the prepared La0.7Sr0.3FeO3(LSFO)/MoS_(2) as coating filler in the epoxy resin coating system can obtain the minimum reflection loss of-67.09 dB at 1.9 mm and the maximum effective absorption bandwidth of 7.28 GHz at 2.3 mm.More importantly,it also exhibits excellent absorption performance for multi-band electromagnetic waves,covering a wide range of specified frequency bands.It provides inspiration for ex-ploring novel perovskite oxide-based electromagnetic wave absorbing coatings and broadens the choice of ideal candidate materials for designing highly efficient,multi-band absorbers to cope with sophisticated electromagnetic environments.

Hierarchical composite of biomass derived magnetic carbon framework and phytic acid doped polyanilne with prominent electromagnetic wave absorption capacity

To solve the electromagnetic pollution,herein,a CoFe_(2)O_(4)/C/PANI composite was developed by a green route,which was constructed with spinel of metal oxide,graphitized carbon and conductive polymer composites.Benefiting from the designable interfaces and increased dipoles,the microwave dielectric response capability can be boosted significantly and resulted in the enhanced microwave absorbing performance.As revealed by the reflection loss curve,the minimum reflection loss(RLmin) reached-51.81 dB at 12.4 GHz under a matched thickness of 2.57 mm.At 2.5 mm,the effective absorbing band covered 8.88 GHz,suggesting the desirable wideband feature.In our case,the method of utilization of a novel green way to fabricate multiple-component EM absorber can be a promising candidate for high-performance EM absorber.

Annealing effects on the optical and electrochemical properties of tantalum pentoxide films

Tantalum pentoxide(Ta_(2)O_(5)) has attracted intensive attention due to their excellent physicochemical properties.Ta_(2)O_(5) films were synthesized via electron beam evaporation(EBE)and subsequently annealed at different temperatures ranging from 300 to 900℃.X-ray diffraction(XRD)results show that amorphous Ta_(2)O_(5) thin films form from 300 to 700℃ and then a phase transition to polycrystalline β-Ta_(2)O_(5) films occurs since 900℃.The surface morphology of the Ta_(2)O_(5) films is uniform and smooth.The resulted Ta_(2)O_(5)films exhibit excellent transmittance properties for wavelengths ranging from 300 to 1100 nm.The bandgap of the Ta_(2)O_(5) films is broadened from 4.32 to 4.46 eV by annealing.The 900℃ polycrystalline film electrode has improved electrochemical stability,compared to the other amorphous counterparts.

Building biointegration of Fe_(2)O_(3)-FeOOH coated titanium implant by regulating NIR irradiation in an infected model

Killing bacteria,eliminating biofilm and building soft tissue integration are very important for percutaneous implants which service in a complicated environment.In order to endow Ti implants with above abilities,multifunctional coatings consisted of Fe_(2)O_(3)-FeOOH nanograins as an outer layer and Zn doped microporous TiO2 as an inner layer were fabricated by micro-arc oxidation,hydrothermal treatment and annealing treatment.The microstructures,physicochemical properties and photothermal response of the coatings were observed;their antibacterial efficiencies and cell response in vitro as well as biofilm elimination and soft tissue integration in vivo were evaluated.The results show that with the increased annealing temperature,coating morphologies didn’t change obviously,but lattices of β-FeOOH gradually disorganized into amorphous state and rearranged to form Fe_(2)O_(3).The coating annealed at 450℃(MA450)had nanocrystallized Fe_(2)O_(3) and β-FeOOH.With a proper NIR irradiation strategy,MA450 killed adhered bacteria efficiently and increased fibroblast behaviors via up-regulating fibrogenic-related genes in vitro;in an infected model,MA450 eliminated biofilm,reduced inflammatory response and improved biointegration with soft tissue.The good performance of MA450 was due to a synergic effect of photothermal response and released ions(Zn^(2+)and Fe^(3+)).

Thermal conductivity and dielectric properties of bismaleimide/cyanate ester copolymer

The blend was synthesised with bismaleimide(BMI)resin and bisphenol A-based cyanate ester(BADCy)resin.The BMI/BADCy copolymer showed excellent dielectric and thermal conductivity properties.The volume resistivity of the copolymer was a little lower than BADCy system.The volume resistivity of blend was 7.8×10^(15)Ω·cm when the BMI content was 20 wt%,which still showed good insulation performance.The dielectric property of modified BADCy copolymer remained the good stability from 0.1 Hz to 1 MHz.Compared to pure BADCy system,the breakdown property of BMI/BADCy blend reached the maximum value of 77.9 kV/mm when the content of BMI was 20 wt%,which was still about 1.22 times.The thermal property and thermal conductivity property of the copolymer were higher than BADCy system.

Multi-level hollow sphere rich in heterojunctions with dual function:Efficient microwave absorption and antiseptic

Effective electromagnetic wave absorption is now possible thanks to the design of the dielectric-magnetic double loss mechanism and the rich heterogeneous structure.In this study,hollow carbon spheres with rich heterostructures were synthesized using an easy and effective in situ growing approach.In addition to improving impedance matching,the hollow structure also reduces material density and weight.By modifying the load,this system can alter the dielectric characteristics of MXene,which in turn affects the sample’s ability to absorb electromagnetic waves.MXene and the carbon material create a thick conductive network during the whole electromagnetic wave absorption process,creating the ideal environment for conduction loss.The sample’s ability to attenuate electromagnetic waves is further improved by the interfacial polarization that the rich heterogeneous structure can produce.Co-magnetic nanoparticle nanoparticles are the main source of magnetic loss.The MXene@Co/C-100–800(MCC-100–800)exhibits excellent electromagnetic wave absorption performance under the synergy of multiple loss mechanisms,with the maximum effective absorption bandwidth(EAB_(max))reaching 7.20 GHz and the minimum reflection loss(RL_(min))being–53.99 dB at 2.10 mm.Finally,this work is guided by the coating engineering of MXene and provides new ideas for the rational design of heterostructures of nanomaterials.