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.

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.

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.

Effect of Kushen(Radix Sophorae flavescentis) extract on laryngeal neoplasm Hep2 cells

OBJECTIVE:To evaluate the effect of fermented extract of Kushen(Radix Sophorae Flavescentis) or non-fermented ESF on laryngeal neoplasms Hep2 cells.METHODS:Use 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay to explore the effect of fermented ESF and non-fermented ESF on Hep2 cells,and detect the mRNA and protein expression level of Bcl-2,Bax and Caspase-3 with reverse transcription polymerase chain reaction(RT-PCR) andWestern blot.RESULTS:Both fermented ESF and non-fermented ESF could inhibit laryngeal neoplasm's Hep2 cells,but and the cells did not response to the dilution 1:320 of fermented ESF,nor to the 1:1280 dilution of non-fermented ESF.As time progressed,the dilution 1:80 of fermented ESF and 1:320 dilution of non-fermented ESF could significantly reduce Bcl-2 mRNA and protein expression and down-regulate Caspase-3 mRNA and protein expression.Bax mRNA and protein were not expressed in Hep2 cells.CONCLUSIONS:Both fermented ESF and non-fermented ESF could inhibit the proliferation of Hep2 cells,and the effect of non-fermented ESF was significantly better than that of the fermented.