Chitosan(CS),a natural polymer derived from chitin found in the exoskeletons of crustaceans,has garnered significant interest in the pharmaceutical field due to its unique properties,including biocompatibility and bio...Chitosan(CS),a natural polymer derived from chitin found in the exoskeletons of crustaceans,has garnered significant interest in the pharmaceutical field due to its unique properties,including biocompatibility and biodegradability.In recent years,various studies have reported that CS can affect drug bioavailability,and interestingly,it works as an oral absorption enhancer and inhibitor.This review offers an in-depth analysis of the mechanisms underlying such a phenomenon and supports its application as a pharmaceutical excipient.CS enhances oral drug absorption through various mechanisms,such as interaction with the intestinal mucosa,tight junction modulation,inhibition of efflux transporters,enzyme inhibition,solubility and stability enhancement,and complexation.On the other side,CS exhibits the ability to inhibit the absorption of certain drugs by adsorbing to lipids and sterols,modulating bile acids and gut microbiota,altering drug-cell interaction at the polar interface,and mucus-mediated entrapment and interference.Future potential pharmaceutical research in this field includes elucidating the underneath absorption relevant mechanisms,rational use in formulations as excipient,exploring functional CS derivatives,and developing CS-based drug delivery systems.This comprehensive review highlights CS's versatile and significant role in enhancing and inhibiting oral drug absorption,providing insights into the complexities of drug delivery and the potential of CS to improve therapeutic outcomes.展开更多
Biochar and biochar composites are versatile materials that can be used in many applications.In this study,biochar was prepared from sawdust and combined with the yttrium iron garnet(YIG)nanocrystal to investigate the...Biochar and biochar composites are versatile materials that can be used in many applications.In this study,biochar was prepared from sawdust and combined with the yttrium iron garnet(YIG)nanocrystal to investigate the shielding effectiveness of the composite structure.Firstly,the effect of the pyrolysis temperature on the shielding effectiveness of biochar was investigated.Secondly,biochars combined with YIG nanocrystals with different contents and shielding effectiveness of the composites were investigated.The electromagnetic effectiveness of the samples was investigated within the X band(8-12 GHz).The findings indicate that biochar demonstrates enhanced absorption properties with elevated pyrolysis temperatures.Biochars demonstrated an approximate 40 d B shielding effectiveness,while YIG exhibited approximately 7 d B,corresponding to absorption at 8 GHz.However,the combination of biochar and YIG exhibited exceptional absorption,reaching 67.12 d B at 8 GHz.展开更多
Encapsulation of water-soluble cargoes in millimeter-sized capsules has enabled major advances in various fields,including pharmaceuticals,food,cosmetics,packaging,and materials.However,because of the lack of fabricat...Encapsulation of water-soluble cargoes in millimeter-sized capsules has enabled major advances in various fields,including pharmaceuticals,food,cosmetics,packaging,and materials.However,because of the lack of fabrication precision,low cargo retention,suboptimal mechanical properties,and difficulty in preventing water evaporation,this technique is more challenging than microencapsulation techniques.In this study,we developed a surfactant-free and organic solvent-free water-in-oil in-air emulsification approach for synthesizing double-layered“milli-capsules”for the precise encapsulation,enhanced retention,and force-triggered burst release of water-soluble bioactive cargoes.In particular,we synthesized milli-capsules with a first shell of poly(ethylene glycol dimethacrylate)for the efficient encapsulation of bioactive cargoes and a second shell of beeswax to prolong the retention of the entrapped bioactive compounds.Unlike traditional milli-capsules,which exhibit poor shape uniformity and mechanical stability,we introduced metallic ions to stabilize the interfacial tension and employed constant rotation to balance the gravity,buoyancy,inertial,and viscous forces imposed on the droplets,resulting in uniform and rigid milli-capsules with narrow rupture forces.Furthermore,additional hydrophobic beeswax coating prevented water volatilization and substantially prolonged the shelf life of the encapsulated compounds from a few days to a few months while maintaining their bioactivities.The proposed milli-capsule system addresses the challenge of precise fabrication of large carriers for water-soluble cargoes,representing a significant step toward the long-term storage and controlled release of bioactive cargoes for various industrial applications.展开更多
The rapid advancement of 5G/6G communication and radar technology has exacerbated issues of electromagnetic wave(EMW)leakage,interference,and thermal management.Therefore,developing lightweight EMW absorbers that inte...The rapid advancement of 5G/6G communication and radar technology has exacerbated issues of electromagnetic wave(EMW)leakage,interference,and thermal management.Therefore,developing lightweight EMW absorbers that integrate strong absorption,broad bandwidth,and thermal stability is crucial.Herein,a 3D MXene sponge/NiFe@NC heterostructure with tunable pore architecture is constructed by pyrolyzing a polyurethane(PU)foam template uniformly coated with NiFe-decorated Ti_(3)C_(2)T_(x)MXene nanosheets.The resulting porous dielectric-magnetic network integrates interconnected MXene pathways with uniformly dispersed NiFe@NC nanoparticles,enabling a synergistic effect of dielectric-magnetic loss through conduction loss,dipole/interface polarization,and magnetic loss.Precise pore structure design enhances impedance matching and promotes multi-scattering and internal reflection of EMWs.Notably,an“EMW-pore matching”mechanism is proposed,whereby pore size governs the impedance matching at specific frequencies,enabling tunable absorption performance.The optimized absorber achieves a reflection loss(RL)of-67.84 dB,while radar cross-section(RCS)simulations confirm its exceptional attenuation and stealth potential.Additionally,the 3D skeleton derived from PU foam confers remarkable thermal resistance and flame retardancy.This pore-regulation strategy provides a scalable route to designing lightweight,broadband,and thermally stable EMW absorbers for next-generation communication and stealth applications.展开更多
Conventional locking/release mechanisms often face challenges in aircraft wing separation processes,such as excessive impact loads and insufficient synchronization.These may cause structural damage to the airframe or ...Conventional locking/release mechanisms often face challenges in aircraft wing separation processes,such as excessive impact loads and insufficient synchronization.These may cause structural damage to the airframe or attitude instability,seriously compromising mission reliability.To address this engineering challenge,this paper proposes a multi-point low-impact locking/release mechanism based on the mobility model and energy conversion strategy.Through establishing a DOF constraint framework system,this paper systematically analyzes the energy transfer and conversion characteristics during the wing separation process,reveals the generation mechanism of impact loads,and conducts research on low-impact design based on energy conversion strategy.Building on this foundation,a single-point locking/release mechanism employing parallel trapezoidal key shaft structure was designed,which increases frictional contact time and reduces the energy release rate,thereby achieving low-impact characteristics.The mechanism's performance was validated through physical prototype development and systematic functional testing(including unlocking force,synchronization,and impact tests).Experimental results demonstrate:(1)Under 14 kN preload condition,the maximum unlocking force was only 92.54 N,showing a linear relationship with preload that satisfies the"strong-connection/weak-unlock"design requirement;(2)Wing separation was completed within 46 ms,with synchronization time difference among three separation mechanisms stably controlled within 12-14 ms,proving rapid and reliable operation;(3)The unlocking impact acceleration ranged between 26 and 73 g,below the 100 g design limit,confirming the effectiveness of the energy conversion strategy.The proposed low-impact locking/release mechanism design method based on energy conversion strategy resolves the traditional challenges of high impact and synchronization deficiencies.The synergistic optimization mechanism of"structural load reduction and performance improvement"provides a highly reliable technical solution for wing separable mechanisms while offering novel design insights for wing connection/separation systems engineering.展开更多
The electromagnetic wave absorption of silicon carbide nanowires is improved by their uniform and diverse cross-structures.This study introduces a sustainable and high value-added method for synthesizing silicon carbi...The electromagnetic wave absorption of silicon carbide nanowires is improved by their uniform and diverse cross-structures.This study introduces a sustainable and high value-added method for synthesizing silicon carbide nanowires using lignite and waste silicon powder as raw materials through carbothermal reduction.The staggered structure of nanowires promotes the creation of interfacial polarization,impedance matching,and multiple loss mechanisms,leading to enhanced electromagnetic absorption performance.The silicon carbide nanowires demonstrate outstanding electromagnetic absorption capabilities with the minimum reflection loss of-48.09 d B at10.08 GHz and an effective absorption bandwidth(the reflection loss less than-10 d B)ranging from 8.54 to 16.68 GHz with a thickness of 2.17 mm.This research presents an innovative approach for utilizing solid waste in an environmentally friendly manner to produce broadband silicon carbide composite absorbers.展开更多
Sandwich structures are widely favored for their lightweight,high strength and superior impact mitigation capabilities in blast mitigation and transportation safety applications.Their application in large-scale,high-e...Sandwich structures are widely favored for their lightweight,high strength and superior impact mitigation capabilities in blast mitigation and transportation safety applications.Their application in large-scale,high-energy rockfall protection remains limited due to their relatively low volumetric energy absorption efficiency and the complex fabrication processes of key energy-absorbing components.To address these limitations,this study proposes a novel sandwich structure incorporating mild steel tubes as core energy absorbers to efficiently mitigate highenergy rockfall impacts.A finite element model was developed in LS-DYNA to systematically investigate the deformation and energy absorption behaviors.Comprehensive parametric analyses were conducted to quantify the effects of key design variables,including tube wall thickness,tube spacing(number of tubes),and infill materials.The results demonstrate that increasing tube wall thickness significantly enhances ultimate energy absorption,with 12-mm-thick tubes absorbing 2.2 times more energy than 6-mm-thick tubes.Lateral constraints induced by adjacent tubes improve specific energy absorption per unit displacement by approximately 30%-45%.Furthermore,incorporating infill materials considerably enhances energy absorption,with aluminum foam infills achieving an 81%increase compared to empty tubes.Nevertheless,higher energy absorption capacity typically leads to greater peak impact forces,increasing the number of tubes offers a better balance between energy absorption and impact force,optimizing the structural performance.These findings provide valuable theoretical insights and practical guidelines for designing sandwich structures in civil and infrastructure engineering applications for effective rockfall protection.展开更多
Low-velocity impact tests are carried out to explore the energy absorption characteristics of bio-inspired lattices,mimicking the architecture of the marine sponge organism Euplectella aspergillum.These sea sponge-ins...Low-velocity impact tests are carried out to explore the energy absorption characteristics of bio-inspired lattices,mimicking the architecture of the marine sponge organism Euplectella aspergillum.These sea sponge-inspired lattice structures feature a square-grid 2D lattice with double diagonal bracings and are additively manufactured via digital light processing(DLP).The collapse strength and energy absorption capacity of sea sponge lattice structures are evaluated under various impact conditions and are compared to those of their constituent square-grid and double diagonal lattices.This study demonstrates that sea sponge lattices can achieve an 11-fold increase in energy absorption compared to the square-grid lattice,due to the stabilizing effect of the double diagonal bracings prompting the structure to collapse layer-bylayer under impact.By adjusting the thickness ratio in the sea sponge lattice,up to 76.7%increment in energy absorption is attained.It is also shown that sea-sponge lattices outperform well-established energy-absorbing materials of equal weight,such as hexagonal honeycombs,confirming their significant potential for impact mitigation.Additionally,this research highlights the enhancements in energy absorption achieved by adding a small amount(0.015 phr)of Multi-Walled Carbon Nanotubes(MWCNTs)to the photocurable resin,thus unlocking new possibilities for the design of innovative lightweight structures with multifunctional attributes.展开更多
Three-dimensional(3D)-printedgraphene aerogels hold promise for electromagneticwave absorption(EWA)engineering due to itsultralow density,outstanding electromagnetic dissipationwith the flexibility and precision of ma...Three-dimensional(3D)-printedgraphene aerogels hold promise for electromagneticwave absorption(EWA)engineering due to itsultralow density,outstanding electromagnetic dissipationwith the flexibility and precision of manufacturingstrategies.However,their high conductivitycauses severe impedance mismatch,limiting EWAperformance.3D printing requirements also constrainthe dielectric properties of printable grapheneinks,hindering the integration of high-performanceabsorbers with advanced manufacturing.This studyproposes a polyacrylic acid(PAA)gel-mediated3D porous graphene oxide(GO)aerogel multiscaleregulation strategy.Precise gel content control enablesdual-gradient tuning of the rheology(Benefitingdirect ink writing(DIW))and dielectric loss(Enhancing EWA)of GO/PAA composites and reduces aerogel density(6.9 mg cm^(-3)from28.2 mg cm^(-3)).Thermal reduction decomposes PAA into amorphous carbon nanoparticles anchored on reduced graphene oxide(rGO),enhancingimpedance matching and absorption via synergistic 0D/2D interfacial polarization and conductive loss.The optimized rGO/PAA aerogelachieves a minimum reflection loss(RL)of-39.86 dB at 2.5 mm and an effective absorption bandwidth(EAB)of 8.36 GHz(9.64-18 GHz)at3.2 mm.Combining DIW and this aerogel,we design a metamaterial absorber(MA)with dual material(dielectric loss)and structural gradients.This MA exhibits an ultrawide EAB of 14 GHz(4-18 GHz)with a total thickness of 7.8 mm.This work establishes a coupled design paradigmof“composition-structure-performance,”providing an engineerable solution for developing lightweight,broadband EWA materials.展开更多
Flexible materials play a crucial role in protecting against behind armour blunt trauma(BABT).However,their compliance complicates the understanding of failure mechanisms and energy absorption.This study used a combin...Flexible materials play a crucial role in protecting against behind armour blunt trauma(BABT).However,their compliance complicates the understanding of failure mechanisms and energy absorption.This study used a combined experimental and numerical approach to investigate the response and failure modes of a flexible ultra-high-molecular-weight polyethylene(UHMWPE)foam protective sandwich structure(UFPSS)under low-velocity impact(LVI).A finite element(FE)model,accounting for nonlinear large deformation and strain-rate-dependent material behavior,was developed for a woven-UFPSS(featuring a plain-woven fabric structure)subjected to a 50 J impact.Experimental and numerical results showed strong agreement in peak force(error<5%),maximum displacement(error<6%),and buffer time(error<8%).The impact's kinetic energy was mainly converted into internal energy of the fabric and foam materials(~50%),viscous dissipation in the foam core(12%-15%),frictional work at the contact interfaces(5%-6%),and work by the pneumatic fixture clamping force(~38%).This study provides the first investigation of the LVI performance of sandwich structures with all soft material layers,offering significant insights for the application of compliant materials in protective fields.展开更多
Microwave absorption(MA)materials often face poor synergy between impedance matching and attenuation in the low-frequency range.Balancing permittivity and permeability through magnetic-dielectric synergy is a promisin...Microwave absorption(MA)materials often face poor synergy between impedance matching and attenuation in the low-frequency range.Balancing permittivity and permeability through magnetic-dielectric synergy is a promising strategy to address this issue.To realize the synergy,herein,Sn whiskers with an in situ oxide layer served as substrates for magnetic-loss-active CoNi nanosheet growth,forming a hierarchical CoNi@SnO_(2)@Sn(CNS)heterostructure.The CNS absorber achieves a minimum reflection loss(RL_(min))value of-62.29 dB with an effective absorption bandwidth(EAB)of 2.2 GHz,covering the entire C-band with 70%absorption at only 2.61 mm thickness.The nanosheet design of CoNi enhances magnetic anisotropy to promote natural resonance,while the conductive Sn core and abundant Sn/SnO_(2) and CoNi/SnO_(2) heterointerfaces facilitate conduction loss and dielectric polarization.When composited into a thermoplastic polyurethane(TPU)matrix,the resulting CNS/TPU-2 film(20 wt%CNS)exhibits an RL_(min) value of-61.04 dB and a 2.5 GHz EAB.Its in-plane and through-plane thermal conductivities reach 2.41 and 0.51 W m^(-1) K^(-1),representing 4.1 and 2.6 times those of pure TPU films,respectively,facilitating heat dissipation from protected devices.This work provides valuable insights into magnetic-dielectric synergy for low-frequency MA of 1D metal-based materials,offering promising potential for 5G communications and flexible electronics.展开更多
Directional three-dimensional carbon-based foams are emerging as highly attractive candidates for promising electromagnetic wave absorbing materials(EWAMs)thanks to their unique architecture,but their construction usu...Directional three-dimensional carbon-based foams are emerging as highly attractive candidates for promising electromagnetic wave absorbing materials(EWAMs)thanks to their unique architecture,but their construction usually involves complex procedures and extremely depends on unidirectional freezing technique.Herein,we propose a groundbreaking approach that leverages the assemblies of salting-out protein induced by ammonium metatungstate(AM)as the precursor,and then acquire directional three-dimensional carbon-based foams through simple pyrolysis.The electrostatic interaction between AM and protein ensures well dispersion of WC_(1−x)nanoparticles on carbon frameworks.The content of WC_(1−x)nanoparticles can be rationally regulated by AM dosage,and it also affects the electromagnetic(EM)properties of final carbon-based foams.The optimized foam exhibits exceptional EM absorption performance,achieving a remarkable minimum reflection loss of−72.0 dB and an effective absorption bandwidth of 6.3 GHz when EM wave propagates parallel to the directional pores.Such performance benefits from the synergistic effects of macroporous architecture and compositional design.Although there is a directional dependence of EM absorption,radar stealth simulation demonstrates that these foams can still promise considerable reduction in radar cross section with the change of incident angle.Moreover,COMSOL simulation further identifies their good performance in preventing EM interference among different electronic components.展开更多
With growing concerns regarding electromagnetic pollution,low-cost,environmentally friendly,and high-performance electromagnetic wave absorption(EWA)materials have attracted significant attention.This paper reports on...With growing concerns regarding electromagnetic pollution,low-cost,environmentally friendly,and high-performance electromagnetic wave absorption(EWA)materials have attracted significant attention.This paper reports on the synthesis of porous Fe_(3)O_(4)/C composites that incorporate dielectric and magnetic loss mechanisms via the carbothermal reduction method and optimization of waste ratio to enhance EWA performance.The Fe_(3)O_(4)/C composites with 10wt%soybean residues(Fe_(3)O_(4)/C-10),demonstrated the best EWA performance,achieving the minimum reflection loss of−56.4 dB and a bandwidth of 2.14 GHz at a thickness of 2.23 mm.This enhanced EWA performance is primarily attributable to improved impedance matching and the synergistic effect between dielectric and magnetic losses.Furthermore,radar cross-sectional simulations confirmed the practical feasibility of the porous Fe_(3)O_(4)/C composites.This study proposes a viable strategy for utilizing soybean residue and electrolytic manganese residue,highlighting their potential applications in EWA.展开更多
Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures ...Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures were prepared through digital light processing(DLP)3D printing,polymer-derived ceramics(PDCs),chemical vapor infiltration(CVI),and oxidation technologies.The incorporation of the CVISiC phase effectively increases the dissipation capability,while the synergistic interaction between the gyroid structure and SiO_(2)phase significantly improves impedance matching performance.The SiOC/SiC/SiO_(2)composite achieved a minimum reflection loss(RL min)of-62.2 d B at 4.3 mm,and the effective absorption bandwidth(EAB)covered the X-band,with a thickness range of 4.1 mm-4.65 mm.The CST simulation results explain the broadband and low-frequency absorption characteristics,with an EAB of 8.4 GHz(9.6-18 GHz)and an RL min of-21.5 dB at 5 GHz.The excellent EM wave attenuation performance is associated primarily with polarization loss,conduction loss,the gyroid structure's enhancement of multiple reflections and scattering of EM waves,and the resonance effect between the structural units.The SiOC/SiC/SiO_(2)composite also demonstrated strong mechanical properties,with a maximum compressive failure strength of 31.6 MPa in the height direction.This work opens novel prospects for the development of multifunctional structural wave-absorbing materials suitable for broadband microwave absorption and load-bearing properties.展开更多
Rabbits with the body weight of （2.0 ± 0.5 ） kg were chosen, to study the effects of sustained-release calcium hydroxide and sustained-release hydro- chloric acid on nutrient digestion and absorption of rabbits...Rabbits with the body weight of （2.0 ± 0.5 ） kg were chosen, to study the effects of sustained-release calcium hydroxide and sustained-release hydro- chloric acid on nutrient digestion and absorption of rabbits. The results showed that sustained-release calcium hydroxide promoted digestion and absorption of nutri- ents, especially calcium and crude protein. The digestibility of calcium and crude protein was increased from 89.8% and 93.8% to 41.0% and 65.2%, respec- tively. Sustained-release hydrochloric acid was adverse to digestion and absorption of nutrients, especially calcium and crude protein. The digestibility of calcium and crude protein were decreased from 55.5% and 84.9% to 28.4% and 68.7%, respectively. The promotion effects of sustained-release hydrochloride on diges- tion lasted for 3 -4 d. Therefore, sustained-release calcium hydroxide promoted digestion and absorption of calcium and protein, while digestion and absorption of fat remained at a high level no matter what the condition was. Consequently, increasing the intake of fat would cause over nutrition. However, taking sustained-re- lease hydrochloric acid would reduce nutrient digestion and absorption.展开更多
This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure （XANES） and atomic a...This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure （XANES） and atomic absorption spectrometry.Total arsenic （As） concentrations in the soil were more than 200 mg/kg.Over four months of laboratory experiments,less than 0.8% As was released into solution after reduction experiments.The 71% to 83% As was chemically reduced into arsenite （As（III）） and partially weathering into the soluble phase.The kinetic dissolution and re-precipitation of As,Fe,Pb and sulfate in this area of paddy soils merits further study.展开更多
Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,how...Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,however,constrain their delicate constructions.Herein,an innovative alternative is proposed:carrageenan-assistant cations-regulated(CACR)strategy,which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon matrix.This unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction,benefiting the delicate construction of defects-rich heterostructures in M_(x)S_(y)/carbon composites(M-CAs).Impressively,these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and,simultaneously,induct local asymmetry of electronic structure to evoke large dipole moment,ultimately leading to polarization coupling,i.e.,defect-type interfacial polarization.Such“Janus effect”(Janus effect means versatility,as in the Greek two-headed Janus)of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first time.Consequently,the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm,compared to sulfur vacancies-free CAs without any dielectric response.Harnessing defects-rich heterostructures,this one-pot CACR strategy may steer the design and development of advanced nanomaterials,boosting functionality across diverse application domains beyond electromagnetic response.展开更多
Developing advanced stealth devices to cope with radar-infrared(IR)fusion detection and diverse application scenarios is increasingly demanded,which faces significant challenges due to conflicting microwave and IR clo...Developing advanced stealth devices to cope with radar-infrared(IR)fusion detection and diverse application scenarios is increasingly demanded,which faces significant challenges due to conflicting microwave and IR cloaking mechanisms and functional integration limitations.Here,we propose a multiscale hierarchical structure design,integrating wrinkled MXene IR shielding layer and flexible Fe_(3)O_(4)@C/PDMS microwave absorption layer.The top wrinkled MXene layer induces the intensive diffuse reflection effect,shielding IR radiation signals while allowing microwave to pass through.Meanwhile,the permeable microwaves are assimilated into the bottom Fe_(3)O_(4)@C/PDMS layer via strong magneto-electric synergy.Through theoretical and experimental optimization,the assembled stealth devices realize a near-perfect stealth capability in both X-band(8–12 GHz)and long-wave infrared(8–14μm)wavelength ranges.Specifically,it delivers a radar cross-section reduction of−20 dB m^(2),a large apparent temperature modulation range(ΔT=70℃),and a low average IR emissivity of 0.35.Additionally,the optimal device demonstrates exceptional curved surface conformability,self-cleaning capability(contact angle≈129°),and abrasion resistance(recovery time≈5 s).This design strategy promotes the development of multispectral stealth technology and reinforces its applicability and durability in complex and hostile environments.展开更多
Developing effective strategies to regulate graphene’s conduction loss and polarization has become a key to expanding its application in the electromagnetic wave absorption(EMWA)field.Based on the unique energy band ...Developing effective strategies to regulate graphene’s conduction loss and polarization has become a key to expanding its application in the electromagnetic wave absorption(EMWA)field.Based on the unique energy band structure of graphene,regulating its bandgap and electrical properties by introducing heteroatoms is considered a feasible solution.Herein,metal-nitrogen doping reduced graphene oxide(M–N-RGO)was prepared by embedding a series of single metal atoms M–N_(4) sites(M=Mn,Fe,Co,Ni,Cu,Zn,Nb,Cd,and Sn)in RGO using an N-coordination atom-assisted strategy.These composites had adjustable conductivity and polarization to optimize dielectric loss and impedance matching for efficient EMWA performance.The results showed that the minimum reflection loss(RL_(min))of Fe–N-RGO reaches−74.05 dB(2.0 mm)and the maximum effective absorption bandwidth(EAB_(max))is 7.05 GHz(1.89 mm)even with a low filler loading of only 1 wt%.Combined with X-ray absorption spectra(XAFS),atomic force microscopy,and density functional theory calculation analysis,the Fe–N_(4) can be used as the polarization center to increase dipole polarization,interface polarization and defect-induced polarization due to d-p orbital hybridization and structural distortion.Moreover,electron migration within the Fe further leads to conduction loss,thereby synergistically promoting energy attenuation.This study demonstrates the effectiveness of metal-nitrogen doping in regulating the graphene′s dielectric properties,which provides an important basis for further investigation of the loss mechanism.展开更多
基金financially supported by National Key Research and Development Program of China (No.2021YFD1800900)National Natural Science Foundation of China (No.82073790)+2 种基金Special Fund for Youth Team of Southwest University (No.SWUXJLJ202306)Chongqing Science and Technology Commission (Nos.CSTB2022TIAD-LUX0001,CSTB2023NSCQ-JQX0002)Innovation Research 2035 Pilot Plan of Southwest University (No.SWUXDPY22007)。
文摘Chitosan(CS),a natural polymer derived from chitin found in the exoskeletons of crustaceans,has garnered significant interest in the pharmaceutical field due to its unique properties,including biocompatibility and biodegradability.In recent years,various studies have reported that CS can affect drug bioavailability,and interestingly,it works as an oral absorption enhancer and inhibitor.This review offers an in-depth analysis of the mechanisms underlying such a phenomenon and supports its application as a pharmaceutical excipient.CS enhances oral drug absorption through various mechanisms,such as interaction with the intestinal mucosa,tight junction modulation,inhibition of efflux transporters,enzyme inhibition,solubility and stability enhancement,and complexation.On the other side,CS exhibits the ability to inhibit the absorption of certain drugs by adsorbing to lipids and sterols,modulating bile acids and gut microbiota,altering drug-cell interaction at the polar interface,and mucus-mediated entrapment and interference.Future potential pharmaceutical research in this field includes elucidating the underneath absorption relevant mechanisms,rational use in formulations as excipient,exploring functional CS derivatives,and developing CS-based drug delivery systems.This comprehensive review highlights CS's versatile and significant role in enhancing and inhibiting oral drug absorption,providing insights into the complexities of drug delivery and the potential of CS to improve therapeutic outcomes.
基金support provided by the Center for Fabrication and Application of Electronic Materials at Dokuz Eylül University,Türkiye。
文摘Biochar and biochar composites are versatile materials that can be used in many applications.In this study,biochar was prepared from sawdust and combined with the yttrium iron garnet(YIG)nanocrystal to investigate the shielding effectiveness of the composite structure.Firstly,the effect of the pyrolysis temperature on the shielding effectiveness of biochar was investigated.Secondly,biochars combined with YIG nanocrystals with different contents and shielding effectiveness of the composites were investigated.The electromagnetic effectiveness of the samples was investigated within the X band(8-12 GHz).The findings indicate that biochar demonstrates enhanced absorption properties with elevated pyrolysis temperatures.Biochars demonstrated an approximate 40 d B shielding effectiveness,while YIG exhibited approximately 7 d B,corresponding to absorption at 8 GHz.However,the combination of biochar and YIG exhibited exceptional absorption,reaching 67.12 d B at 8 GHz.
基金supported by the National Natural Science Foundation of China(Nos.52273102,31870957,and 52302344)the Fundamental Research Funds for the Central Universities(Nos.DUT24YG155,DUT20YG103,and DUT22LAB601)Liaoning Provincial Science and Technology Plan Joint Plan(No.2023JH2/101700341)。
文摘Encapsulation of water-soluble cargoes in millimeter-sized capsules has enabled major advances in various fields,including pharmaceuticals,food,cosmetics,packaging,and materials.However,because of the lack of fabrication precision,low cargo retention,suboptimal mechanical properties,and difficulty in preventing water evaporation,this technique is more challenging than microencapsulation techniques.In this study,we developed a surfactant-free and organic solvent-free water-in-oil in-air emulsification approach for synthesizing double-layered“milli-capsules”for the precise encapsulation,enhanced retention,and force-triggered burst release of water-soluble bioactive cargoes.In particular,we synthesized milli-capsules with a first shell of poly(ethylene glycol dimethacrylate)for the efficient encapsulation of bioactive cargoes and a second shell of beeswax to prolong the retention of the entrapped bioactive compounds.Unlike traditional milli-capsules,which exhibit poor shape uniformity and mechanical stability,we introduced metallic ions to stabilize the interfacial tension and employed constant rotation to balance the gravity,buoyancy,inertial,and viscous forces imposed on the droplets,resulting in uniform and rigid milli-capsules with narrow rupture forces.Furthermore,additional hydrophobic beeswax coating prevented water volatilization and substantially prolonged the shelf life of the encapsulated compounds from a few days to a few months while maintaining their bioactivities.The proposed milli-capsule system addresses the challenge of precise fabrication of large carriers for water-soluble cargoes,representing a significant step toward the long-term storage and controlled release of bioactive cargoes for various industrial applications.
基金supported by the National Natural Science Foundation of China(52562043)Jiangxi Provincial Natural Science Foundation(20244BAB28050)。
文摘The rapid advancement of 5G/6G communication and radar technology has exacerbated issues of electromagnetic wave(EMW)leakage,interference,and thermal management.Therefore,developing lightweight EMW absorbers that integrate strong absorption,broad bandwidth,and thermal stability is crucial.Herein,a 3D MXene sponge/NiFe@NC heterostructure with tunable pore architecture is constructed by pyrolyzing a polyurethane(PU)foam template uniformly coated with NiFe-decorated Ti_(3)C_(2)T_(x)MXene nanosheets.The resulting porous dielectric-magnetic network integrates interconnected MXene pathways with uniformly dispersed NiFe@NC nanoparticles,enabling a synergistic effect of dielectric-magnetic loss through conduction loss,dipole/interface polarization,and magnetic loss.Precise pore structure design enhances impedance matching and promotes multi-scattering and internal reflection of EMWs.Notably,an“EMW-pore matching”mechanism is proposed,whereby pore size governs the impedance matching at specific frequencies,enabling tunable absorption performance.The optimized absorber achieves a reflection loss(RL)of-67.84 dB,while radar cross-section(RCS)simulations confirm its exceptional attenuation and stealth potential.Additionally,the 3D skeleton derived from PU foam confers remarkable thermal resistance and flame retardancy.This pore-regulation strategy provides a scalable route to designing lightweight,broadband,and thermally stable EMW absorbers for next-generation communication and stealth applications.
文摘Conventional locking/release mechanisms often face challenges in aircraft wing separation processes,such as excessive impact loads and insufficient synchronization.These may cause structural damage to the airframe or attitude instability,seriously compromising mission reliability.To address this engineering challenge,this paper proposes a multi-point low-impact locking/release mechanism based on the mobility model and energy conversion strategy.Through establishing a DOF constraint framework system,this paper systematically analyzes the energy transfer and conversion characteristics during the wing separation process,reveals the generation mechanism of impact loads,and conducts research on low-impact design based on energy conversion strategy.Building on this foundation,a single-point locking/release mechanism employing parallel trapezoidal key shaft structure was designed,which increases frictional contact time and reduces the energy release rate,thereby achieving low-impact characteristics.The mechanism's performance was validated through physical prototype development and systematic functional testing(including unlocking force,synchronization,and impact tests).Experimental results demonstrate:(1)Under 14 kN preload condition,the maximum unlocking force was only 92.54 N,showing a linear relationship with preload that satisfies the"strong-connection/weak-unlock"design requirement;(2)Wing separation was completed within 46 ms,with synchronization time difference among three separation mechanisms stably controlled within 12-14 ms,proving rapid and reliable operation;(3)The unlocking impact acceleration ranged between 26 and 73 g,below the 100 g design limit,confirming the effectiveness of the energy conversion strategy.The proposed low-impact locking/release mechanism design method based on energy conversion strategy resolves the traditional challenges of high impact and synchronization deficiencies.The synergistic optimization mechanism of"structural load reduction and performance improvement"provides a highly reliable technical solution for wing separable mechanisms while offering novel design insights for wing connection/separation systems engineering.
基金supported by the National Natural Science Foundation of China(No.52436008)the Inner Mongolia Science and Technology Projects,China(Nos.JMRHZX20210003 and 2023YFCY0009)+3 种基金the Huaneng Group Co Ltd.,China(No.HNKJ23-H50)the National Natural Science Foundation of China(No.22408044)the China Postdoctoral Science Foundation(No.2024M761877)the National Key R&D Program of China(No.SQ2024YFD2200039)。
文摘The electromagnetic wave absorption of silicon carbide nanowires is improved by their uniform and diverse cross-structures.This study introduces a sustainable and high value-added method for synthesizing silicon carbide nanowires using lignite and waste silicon powder as raw materials through carbothermal reduction.The staggered structure of nanowires promotes the creation of interfacial polarization,impedance matching,and multiple loss mechanisms,leading to enhanced electromagnetic absorption performance.The silicon carbide nanowires demonstrate outstanding electromagnetic absorption capabilities with the minimum reflection loss of-48.09 d B at10.08 GHz and an effective absorption bandwidth(the reflection loss less than-10 d B)ranging from 8.54 to 16.68 GHz with a thickness of 2.17 mm.This research presents an innovative approach for utilizing solid waste in an environmentally friendly manner to produce broadband silicon carbide composite absorbers.
基金supported by the National Key R&D Program of China(Grant No.2019YFC1509703)the Tianjin Science and Technology Program Project(Grant No.23YFYSHZ00130)。
文摘Sandwich structures are widely favored for their lightweight,high strength and superior impact mitigation capabilities in blast mitigation and transportation safety applications.Their application in large-scale,high-energy rockfall protection remains limited due to their relatively low volumetric energy absorption efficiency and the complex fabrication processes of key energy-absorbing components.To address these limitations,this study proposes a novel sandwich structure incorporating mild steel tubes as core energy absorbers to efficiently mitigate highenergy rockfall impacts.A finite element model was developed in LS-DYNA to systematically investigate the deformation and energy absorption behaviors.Comprehensive parametric analyses were conducted to quantify the effects of key design variables,including tube wall thickness,tube spacing(number of tubes),and infill materials.The results demonstrate that increasing tube wall thickness significantly enhances ultimate energy absorption,with 12-mm-thick tubes absorbing 2.2 times more energy than 6-mm-thick tubes.Lateral constraints induced by adjacent tubes improve specific energy absorption per unit displacement by approximately 30%-45%.Furthermore,incorporating infill materials considerably enhances energy absorption,with aluminum foam infills achieving an 81%increase compared to empty tubes.Nevertheless,higher energy absorption capacity typically leads to greater peak impact forces,increasing the number of tubes offers a better balance between energy absorption and impact force,optimizing the structural performance.These findings provide valuable theoretical insights and practical guidelines for designing sandwich structures in civil and infrastructure engineering applications for effective rockfall protection.
基金supported by the Khalifa University of Science and Technology internal grants(Nos.2021-CIRA-109,2020-CIRA-007,and 2020-CIRA-024).
文摘Low-velocity impact tests are carried out to explore the energy absorption characteristics of bio-inspired lattices,mimicking the architecture of the marine sponge organism Euplectella aspergillum.These sea sponge-inspired lattice structures feature a square-grid 2D lattice with double diagonal bracings and are additively manufactured via digital light processing(DLP).The collapse strength and energy absorption capacity of sea sponge lattice structures are evaluated under various impact conditions and are compared to those of their constituent square-grid and double diagonal lattices.This study demonstrates that sea sponge lattices can achieve an 11-fold increase in energy absorption compared to the square-grid lattice,due to the stabilizing effect of the double diagonal bracings prompting the structure to collapse layer-bylayer under impact.By adjusting the thickness ratio in the sea sponge lattice,up to 76.7%increment in energy absorption is attained.It is also shown that sea-sponge lattices outperform well-established energy-absorbing materials of equal weight,such as hexagonal honeycombs,confirming their significant potential for impact mitigation.Additionally,this research highlights the enhancements in energy absorption achieved by adding a small amount(0.015 phr)of Multi-Walled Carbon Nanotubes(MWCNTs)to the photocurable resin,thus unlocking new possibilities for the design of innovative lightweight structures with multifunctional attributes.
基金supported by ZJNSF LZ25E030006Zhejiang Provincial Key Research and Development Program(2024C01157)+2 种基金NSFC under Grant Nos.52473267 and 52401249the National Key Research and Development Program of China under Grant No.2021YFB3501504Zhejiang University Ningbo“Five in One”Campus Project(K-20213539)。
文摘Three-dimensional(3D)-printedgraphene aerogels hold promise for electromagneticwave absorption(EWA)engineering due to itsultralow density,outstanding electromagnetic dissipationwith the flexibility and precision of manufacturingstrategies.However,their high conductivitycauses severe impedance mismatch,limiting EWAperformance.3D printing requirements also constrainthe dielectric properties of printable grapheneinks,hindering the integration of high-performanceabsorbers with advanced manufacturing.This studyproposes a polyacrylic acid(PAA)gel-mediated3D porous graphene oxide(GO)aerogel multiscaleregulation strategy.Precise gel content control enablesdual-gradient tuning of the rheology(Benefitingdirect ink writing(DIW))and dielectric loss(Enhancing EWA)of GO/PAA composites and reduces aerogel density(6.9 mg cm^(-3)from28.2 mg cm^(-3)).Thermal reduction decomposes PAA into amorphous carbon nanoparticles anchored on reduced graphene oxide(rGO),enhancingimpedance matching and absorption via synergistic 0D/2D interfacial polarization and conductive loss.The optimized rGO/PAA aerogelachieves a minimum reflection loss(RL)of-39.86 dB at 2.5 mm and an effective absorption bandwidth(EAB)of 8.36 GHz(9.64-18 GHz)at3.2 mm.Combining DIW and this aerogel,we design a metamaterial absorber(MA)with dual material(dielectric loss)and structural gradients.This MA exhibits an ultrawide EAB of 14 GHz(4-18 GHz)with a total thickness of 7.8 mm.This work establishes a coupled design paradigmof“composition-structure-performance,”providing an engineerable solution for developing lightweight,broadband EWA materials.
基金supported by the Zhenjiang Key R&D Plan(GY2021009)Lianyungang City Major Technology Breakthrough(CGJBGS2104)+2 种基金National Natural Science Foundation of China under Grant(12302456)National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact under Grant(6142902241601)China Postdoctoral Science Foundation under Grants(2025M774217)。
文摘Flexible materials play a crucial role in protecting against behind armour blunt trauma(BABT).However,their compliance complicates the understanding of failure mechanisms and energy absorption.This study used a combined experimental and numerical approach to investigate the response and failure modes of a flexible ultra-high-molecular-weight polyethylene(UHMWPE)foam protective sandwich structure(UFPSS)under low-velocity impact(LVI).A finite element(FE)model,accounting for nonlinear large deformation and strain-rate-dependent material behavior,was developed for a woven-UFPSS(featuring a plain-woven fabric structure)subjected to a 50 J impact.Experimental and numerical results showed strong agreement in peak force(error<5%),maximum displacement(error<6%),and buffer time(error<8%).The impact's kinetic energy was mainly converted into internal energy of the fabric and foam materials(~50%),viscous dissipation in the foam core(12%-15%),frictional work at the contact interfaces(5%-6%),and work by the pneumatic fixture clamping force(~38%).This study provides the first investigation of the LVI performance of sandwich structures with all soft material layers,offering significant insights for the application of compliant materials in protective fields.
基金supported by the National Natural Science Foundation of China(52171033,52431003,U23A20574)the Fundamental Research Funds for the Central Universities(2242025K20004)the SEU Innovation Capability Enhancement Plan for Doctoral Students(CXJH_SEU 24148,CXJH_SEU 25036).
文摘Microwave absorption(MA)materials often face poor synergy between impedance matching and attenuation in the low-frequency range.Balancing permittivity and permeability through magnetic-dielectric synergy is a promising strategy to address this issue.To realize the synergy,herein,Sn whiskers with an in situ oxide layer served as substrates for magnetic-loss-active CoNi nanosheet growth,forming a hierarchical CoNi@SnO_(2)@Sn(CNS)heterostructure.The CNS absorber achieves a minimum reflection loss(RL_(min))value of-62.29 dB with an effective absorption bandwidth(EAB)of 2.2 GHz,covering the entire C-band with 70%absorption at only 2.61 mm thickness.The nanosheet design of CoNi enhances magnetic anisotropy to promote natural resonance,while the conductive Sn core and abundant Sn/SnO_(2) and CoNi/SnO_(2) heterointerfaces facilitate conduction loss and dielectric polarization.When composited into a thermoplastic polyurethane(TPU)matrix,the resulting CNS/TPU-2 film(20 wt%CNS)exhibits an RL_(min) value of-61.04 dB and a 2.5 GHz EAB.Its in-plane and through-plane thermal conductivities reach 2.41 and 0.51 W m^(-1) K^(-1),representing 4.1 and 2.6 times those of pure TPU films,respectively,facilitating heat dissipation from protected devices.This work provides valuable insights into magnetic-dielectric synergy for low-frequency MA of 1D metal-based materials,offering promising potential for 5G communications and flexible electronics.
基金financially supported by the National Natural Science Foundation of China(Nos.22475057 and No.52373262).
文摘Directional three-dimensional carbon-based foams are emerging as highly attractive candidates for promising electromagnetic wave absorbing materials(EWAMs)thanks to their unique architecture,but their construction usually involves complex procedures and extremely depends on unidirectional freezing technique.Herein,we propose a groundbreaking approach that leverages the assemblies of salting-out protein induced by ammonium metatungstate(AM)as the precursor,and then acquire directional three-dimensional carbon-based foams through simple pyrolysis.The electrostatic interaction between AM and protein ensures well dispersion of WC_(1−x)nanoparticles on carbon frameworks.The content of WC_(1−x)nanoparticles can be rationally regulated by AM dosage,and it also affects the electromagnetic(EM)properties of final carbon-based foams.The optimized foam exhibits exceptional EM absorption performance,achieving a remarkable minimum reflection loss of−72.0 dB and an effective absorption bandwidth of 6.3 GHz when EM wave propagates parallel to the directional pores.Such performance benefits from the synergistic effects of macroporous architecture and compositional design.Although there is a directional dependence of EM absorption,radar stealth simulation demonstrates that these foams can still promise considerable reduction in radar cross section with the change of incident angle.Moreover,COMSOL simulation further identifies their good performance in preventing EM interference among different electronic components.
基金supported by the National Natural Science Foundation of China(No.52471221)the Natural Science Foundation of Hunan Province,China(No.2024JJ7145)the National Sustainable Development Agenda Innovation Demonstration Zone Hunan special project,China(No.2022sfq09).
文摘With growing concerns regarding electromagnetic pollution,low-cost,environmentally friendly,and high-performance electromagnetic wave absorption(EWA)materials have attracted significant attention.This paper reports on the synthesis of porous Fe_(3)O_(4)/C composites that incorporate dielectric and magnetic loss mechanisms via the carbothermal reduction method and optimization of waste ratio to enhance EWA performance.The Fe_(3)O_(4)/C composites with 10wt%soybean residues(Fe_(3)O_(4)/C-10),demonstrated the best EWA performance,achieving the minimum reflection loss of−56.4 dB and a bandwidth of 2.14 GHz at a thickness of 2.23 mm.This enhanced EWA performance is primarily attributable to improved impedance matching and the synergistic effect between dielectric and magnetic losses.Furthermore,radar cross-sectional simulations confirmed the practical feasibility of the porous Fe_(3)O_(4)/C composites.This study proposes a viable strategy for utilizing soybean residue and electrolytic manganese residue,highlighting their potential applications in EWA.
基金financially supported by National Natural Science Foundation of China(Grant Nos.12141203,52202083,W2421013)the Natural Science Foundation Project of Shaanxi Province(Grant No.2024JC-YBMS-450)+1 种基金the Sichuan Science and Technology Program(Grant No.2024YFHZ0265)the Open Project of High-end Equipment Advanced Materials and Manufacturing Technology Laboratory(Grant No.2023KFKT0005)。
文摘Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures were prepared through digital light processing(DLP)3D printing,polymer-derived ceramics(PDCs),chemical vapor infiltration(CVI),and oxidation technologies.The incorporation of the CVISiC phase effectively increases the dissipation capability,while the synergistic interaction between the gyroid structure and SiO_(2)phase significantly improves impedance matching performance.The SiOC/SiC/SiO_(2)composite achieved a minimum reflection loss(RL min)of-62.2 d B at 4.3 mm,and the effective absorption bandwidth(EAB)covered the X-band,with a thickness range of 4.1 mm-4.65 mm.The CST simulation results explain the broadband and low-frequency absorption characteristics,with an EAB of 8.4 GHz(9.6-18 GHz)and an RL min of-21.5 dB at 5 GHz.The excellent EM wave attenuation performance is associated primarily with polarization loss,conduction loss,the gyroid structure's enhancement of multiple reflections and scattering of EM waves,and the resonance effect between the structural units.The SiOC/SiC/SiO_(2)composite also demonstrated strong mechanical properties,with a maximum compressive failure strength of 31.6 MPa in the height direction.This work opens novel prospects for the development of multifunctional structural wave-absorbing materials suitable for broadband microwave absorption and load-bearing properties.
基金Supported by National Natural Science Foundation of China(21576055)
文摘Rabbits with the body weight of （2.0 ± 0.5 ） kg were chosen, to study the effects of sustained-release calcium hydroxide and sustained-release hydro- chloric acid on nutrient digestion and absorption of rabbits. The results showed that sustained-release calcium hydroxide promoted digestion and absorption of nutri- ents, especially calcium and crude protein. The digestibility of calcium and crude protein was increased from 89.8% and 93.8% to 41.0% and 65.2%, respec- tively. Sustained-release hydrochloric acid was adverse to digestion and absorption of nutrients, especially calcium and crude protein. The digestibility of calcium and crude protein were decreased from 55.5% and 84.9% to 28.4% and 68.7%, respectively. The promotion effects of sustained-release hydrochloride on diges- tion lasted for 3 -4 d. Therefore, sustained-release calcium hydroxide promoted digestion and absorption of calcium and protein, while digestion and absorption of fat remained at a high level no matter what the condition was. Consequently, increasing the intake of fat would cause over nutrition. However, taking sustained-re- lease hydrochloric acid would reduce nutrient digestion and absorption.
基金supported by the "National" Science Council,Taiwan(No.NSC100-2313-B002-007)
文摘This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure （XANES） and atomic absorption spectrometry.Total arsenic （As） concentrations in the soil were more than 200 mg/kg.Over four months of laboratory experiments,less than 0.8% As was released into solution after reduction experiments.The 71% to 83% As was chemically reduced into arsenite （As（III）） and partially weathering into the soluble phase.The kinetic dissolution and re-precipitation of As,Fe,Pb and sulfate in this area of paddy soils merits further study.
基金financially supported by the National Natural Science Foundation of China(Grants nos.62201411,62371378,22205168,52302150 and 62304171)the China Postdoctoral Science Foundation(2022M722500)+1 种基金the Fundamental Research Funds for the Central Universities(Grants nos.ZYTS2308 and 20103237929)Startup Foundation of Xidian University(10251220001).
文摘Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,however,constrain their delicate constructions.Herein,an innovative alternative is proposed:carrageenan-assistant cations-regulated(CACR)strategy,which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon matrix.This unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction,benefiting the delicate construction of defects-rich heterostructures in M_(x)S_(y)/carbon composites(M-CAs).Impressively,these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and,simultaneously,induct local asymmetry of electronic structure to evoke large dipole moment,ultimately leading to polarization coupling,i.e.,defect-type interfacial polarization.Such“Janus effect”(Janus effect means versatility,as in the Greek two-headed Janus)of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first time.Consequently,the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm,compared to sulfur vacancies-free CAs without any dielectric response.Harnessing defects-rich heterostructures,this one-pot CACR strategy may steer the design and development of advanced nanomaterials,boosting functionality across diverse application domains beyond electromagnetic response.
基金financial support from the National Nature Science Foundation of China(No.52273247)the National Science and Technology Major Project of China(J2019-VI-0017-0132).
文摘Developing advanced stealth devices to cope with radar-infrared(IR)fusion detection and diverse application scenarios is increasingly demanded,which faces significant challenges due to conflicting microwave and IR cloaking mechanisms and functional integration limitations.Here,we propose a multiscale hierarchical structure design,integrating wrinkled MXene IR shielding layer and flexible Fe_(3)O_(4)@C/PDMS microwave absorption layer.The top wrinkled MXene layer induces the intensive diffuse reflection effect,shielding IR radiation signals while allowing microwave to pass through.Meanwhile,the permeable microwaves are assimilated into the bottom Fe_(3)O_(4)@C/PDMS layer via strong magneto-electric synergy.Through theoretical and experimental optimization,the assembled stealth devices realize a near-perfect stealth capability in both X-band(8–12 GHz)and long-wave infrared(8–14μm)wavelength ranges.Specifically,it delivers a radar cross-section reduction of−20 dB m^(2),a large apparent temperature modulation range(ΔT=70℃),and a low average IR emissivity of 0.35.Additionally,the optimal device demonstrates exceptional curved surface conformability,self-cleaning capability(contact angle≈129°),and abrasion resistance(recovery time≈5 s).This design strategy promotes the development of multispectral stealth technology and reinforces its applicability and durability in complex and hostile environments.
基金supported by National Natural Science Foundation of China(NSFC 52432002,52372041,52302087)Heilongjiang Touyan Team Program,the Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2021003)the Shanghai Aerospace Science and Technology Innovation Fund(SAST2022-60).
文摘Developing effective strategies to regulate graphene’s conduction loss and polarization has become a key to expanding its application in the electromagnetic wave absorption(EMWA)field.Based on the unique energy band structure of graphene,regulating its bandgap and electrical properties by introducing heteroatoms is considered a feasible solution.Herein,metal-nitrogen doping reduced graphene oxide(M–N-RGO)was prepared by embedding a series of single metal atoms M–N_(4) sites(M=Mn,Fe,Co,Ni,Cu,Zn,Nb,Cd,and Sn)in RGO using an N-coordination atom-assisted strategy.These composites had adjustable conductivity and polarization to optimize dielectric loss and impedance matching for efficient EMWA performance.The results showed that the minimum reflection loss(RL_(min))of Fe–N-RGO reaches−74.05 dB(2.0 mm)and the maximum effective absorption bandwidth(EAB_(max))is 7.05 GHz(1.89 mm)even with a low filler loading of only 1 wt%.Combined with X-ray absorption spectra(XAFS),atomic force microscopy,and density functional theory calculation analysis,the Fe–N_(4) can be used as the polarization center to increase dipole polarization,interface polarization and defect-induced polarization due to d-p orbital hybridization and structural distortion.Moreover,electron migration within the Fe further leads to conduction loss,thereby synergistically promoting energy attenuation.This study demonstrates the effectiveness of metal-nitrogen doping in regulating the graphene′s dielectric properties,which provides an important basis for further investigation of the loss mechanism.
