Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction...Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood.In this study,we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride(ChCl)and ethylene glycol(EG).Owing to the unique properties of deep eutectic gels,the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded.Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG,with HB-induced conductive loss following similar pat-terns.At a ChCl and EG molar ratio of 2.4,the gel labeled G22-CE2.4 exhibited the best EMW absorption performance,characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm.This superior performance is attributed to the synergistic ef-fects of excellent conductive loss and impedance matching generated by the optimal number of HB.This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.展开更多
Excellent impedance matching and high conduction loss are important factors for the preparation of high-performance electromagnetic wave(EMW)absorbing materials,but these two properties are of-ten contradictory.In thi...Excellent impedance matching and high conduction loss are important factors for the preparation of high-performance electromagnetic wave(EMW)absorbing materials,but these two properties are of-ten contradictory.In this work,three absorbers with unique hollow structures,H-Ag/CuO@CuS,H-O-Ag/CuO@CuS,and H-P-Ag/CuO@CuS,are designed and synthesized by adopting hollow CuO@CuS with double shell as carrier and silver nitrate as the structural regulator.The more voids coming from hol-low structures,window-opened structures,and stacked pores improve the impedance matching of these absorbers,and the introduction of elemental Ag effectively regulates the conduction loss.Therefore,a balance between impedance matching and conduction loss is achieved to improve the reflection loss(RL)value and broadens the absorbing band of the absorbers.In comparison to H-Ag/CuO@CuS and H-O-Ag/CuO@CuS(hollow structure with open window)in which elemental Ag is uniformly dispersed in the CuO layer,H-P-Ag/CuO@CuS exhibits more excellent EMW absorption performance due to more voids and an optimized conductive network arising from Ag/CuO pieces distributed between the hol-low Ag/CuO@CuS particles and Ag distributed in the CuS layer.When the thickness is 2.3 mm,H-P-Ag/CuO@CuS provides an ultra-wide electromagnetic absorption band of 8.56 GHz(9.44-18 GHz),in which the RL<-10 dB and the minimum reflection loss of-41 dB.展开更多
Understanding the microstructure-property relationship from the microscopic and macroscopic perspectives,instead of semi-empirical rules,can facilitate the design of microcosmic morphology to adjust the impedance matc...Understanding the microstructure-property relationship from the microscopic and macroscopic perspectives,instead of semi-empirical rules,can facilitate the design of microcosmic morphology to adjust the impedance matching and dielectric loss of the carbon-based materials,which are still lacking so far.In this study,a clear correlation between microstructure and conduction loss was revealed in agarosederived carbon using a facile salt-etching strategy,in which ferric nitrate acted more as a morphology modifier for bulky carbon rather than a component regulator.Specifically,with the increasing amount of ferric nitrate,the original smooth bulky carbon was etched with caves,which gradually enlarged in size and depth and thus thinned in wall,and eventually transformed into a three-dimensional(3D)interconnected cellular structure,accompanied by a gradual increase in conductivity.Benefiting from the optimal impedance matching and strong conduction loss originating from the unique 3D cellular structure of agarose-derived carbon,AF-3 exhibited super-wide and strong absorption with an effective absorption bandwidth of 7.28 GHz(10.32-17.60 GHz,2.9 mm)and a minimum reflection loss of-46.6 dB(15.6 GHz,2.5 mm).This study establishes the relationship between microstructure,dielectric properties,and loss mechanism in carbon-based materials and also provides a new insight into the fine modulation of EMW-absorbing properties from morphological design.展开更多
Polarization and conduction losses are the two most crucial dielectric loss mechanisms for carbon-based composites,but their synergistic effects in different frequency bands need to be further revealed.More importantl...Polarization and conduction losses are the two most crucial dielectric loss mechanisms for carbon-based composites,but their synergistic effects in different frequency bands need to be further revealed.More importantly,for polarization and conduction losses,the strengthening of one party always comes at the expense of the other,which inevitably limits the overall performance of the absorbers.Herein,we have developed a composite of CNT and NiCo hybrid particles via a scalable wet chemical process and an-nealing method.Through the adjustment of the precursor and the annealing temperature,the conduction and polarization losses of the composite are optimized simultaneously.The optimized samples achieved the full absorption of the X and Ku bands under conditions of low filling rate and thin thickness.Further theoretical and experimental studies have revealed conduction loss and polarization loss laws at different frequency ranges.The synergistic effect of conductive loss and magnetic loss in the low-frequency region ensures that the sample exhibits high microwave dissipation performance.However,in the medium and high-frequency part,the magnetic loss can be almost ignored and the timely replenishment of polar-ization loss keeps the wave-absorbing performance at a high level.The excellent multi-band absorption characteristics make the as-obtained absorbers meet the needs of future applications.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
The rational construction of lightweight composites with multiple heterogeneous interfaces represents an effective strategy for achieving efficient electromagnetic wave(EMW)absorption.However,the impact of multiple he...The rational construction of lightweight composites with multiple heterogeneous interfaces represents an effective strategy for achieving efficient electromagnetic wave(EMW)absorption.However,the impact of multiple heterogeneous interfaces on electromagnetic performance still needs further exploration.Herein,reduced graphene oxide(rGO)@Ni-FeCo layered hydroxide(LDH)derivatives with multiple heterostructures were synthesized by a series of processes including electrostatic self-assembly,freeze-drying and thermal annealing.The conductive network in rGO and the cavities inside LDH facilitate electron migration and effectively prolong the propagation path of EMW,thereby enhancing conductivity loss.The abundant heterogeneous interfaces between carbon components and metal nanoparticles induce interfacial polarization.In addition,the catalytic activity differences of different metal particles generate different dielectric electromagnetic interfaces,which further promote interfacial polarization.The natural and exchange resonance formed by magnetic particles under a magnetic field provides magnetic losses.Therefore,the successful construction of multiple heterogeneous interfaces effectively enhances the conductivity loss and polarization loss.With a thickness of only 1.4 mm,the composite achieves a minimum reflection loss of-51.8 dB and an effective absorption bandwidth of 4.5 GHz.This work provides an effective strategy for achieving thin thickness and efficient EMW absorption through precise structural design and multi-component construction of absorbers.展开更多
Purpose To investigate the perinatal risk factors for conductive hearing loss(CHL)in infancy and develop an initial prediction model to facilitate accurate diagnosis and early detection of CHL.Method This retrospectiv...Purpose To investigate the perinatal risk factors for conductive hearing loss(CHL)in infancy and develop an initial prediction model to facilitate accurate diagnosis and early detection of CHL.Method This retrospective study utilized data from the Newborn Cohort Study of Hearing Loss(ChiCTR2100049765).Infants who underwent diagnostic audiological assessments at our hospital between January 2003 and June 2024 were included.Data analysis was conducted using R(version 4.4.1)to construct an initial prediction model for CHL in infancy,applying the LASSO regression technique.Results A total of 661 infants(1322 ears)were included,with 1253 ears in the normal hearing group and 69 ears in the CHL group.Statistically significant differences were observed between the groups in the following factors:parent-reported infant response to sound,craniofacial deformities,neonatal hemolysis,jaundice treatment,and neonatal hypoglycemia.A multivariate prediction model and nomogram for CHL in infancy were developed and validated,achieving an accuracy of 92.5%and a specificity of 91.3%.Conclusions This study identified key risk factors for CHL in infancy and developed a preliminary predictive model,improving the diagnostic accuracy for CHL.Improved diagnostic precision can decrease misdiagnoses,reduce delays in treatment,and limit unnecessary antimicrobial prescriptions for infants.展开更多
Impedance matching characteristics and loss capabilities including magnetic loss,polarization loss and conduction loss are critical factors to improve microwave absorption performances(MAPs).To elevate these aspects,h...Impedance matching characteristics and loss capabilities including magnetic loss,polarization loss and conduction loss are critical factors to improve microwave absorption performances(MAPs).To elevate these aspects,herein,yolk-shell structured CoNi@Air@C/SiO_(2)@Polypyrrole(PPy)magnetic multicomponent nanocubes(MCNCs)were designed and successfully fabricated in high efficiency through a continuous co-precipitation route,classical Stöber method,thermal treatment and polymerization reaction.The obtained results indicated that the formation of SiO_(2) effectively stabilized the cubic geometrical morphology and yolk-shell structure during the high-temperature pyrolysis process.The introduction of PPy greatly boosted their polarization loss and conductive loss capabilities.Therefore,the as-prepared yolkshell structured CoNi@Air@C/SiO_(2)@PPy MCNCs presented superior MAPs compared to CoNi@Air@C/SiO_(2) MCNCs.Furthermore,by regulating the content of PPy,the obtained CoNi@Air@C/SiO_(2)@PPy MCNCs displayed tunable and excellent comprehensive MAPs in terms of strong absorption capabilities,broad frequency bandwidths and thin matching thicknesses,which could be ascribed to the unique structure and excellent magnetic-dielectric synergistic effect.Therefore,our findings provided an alternative pathway to effectively utilize the magnetic-dielectric synergy and loss capabilities for the developing yolk-shell structured magnetic MCNCs as the strong wideband microwave absorbers.展开更多
Objective:To investigate the effects of conductive hearing loss (CHL) on vestibular evoked myogenic potentials (VEMPs) using a simulated CHL model, and to provide the basis for future studies. Methods:Twenty-one healt...Objective:To investigate the effects of conductive hearing loss (CHL) on vestibular evoked myogenic potentials (VEMPs) using a simulated CHL model, and to provide the basis for future studies. Methods:Twenty-one healthy subjects were recruited in this study. We measured ocular VEMPs (oVEMPs) and cervical VEMPs (cVEMPs) in these subjects by air-conduction sound (ACS) stimulation. CHL was simulated later by blocking the right external auditory canal with a soundproof earplug to evaluate its impacts on VEMPs. Subjects' responses before simulated CHL served as the control, and were compared to their responses following simulated CHL. Results: oVEMPs following simulated CHL showed decreased response rate, elevated thresholds, attenuated amplitudes and prolonged N1 latencies compared with those before simulated CHL, and the differences were statistically significant. Similarly, cVEMPs following simulated CHL also showed decreased response rate, elevated thresholds and attenuated amplitudes, with prolonged P1 latencies compared with those before simulated CHL, although only differences in response rate, threshold and amplitude were significant. Conclusions:Conductive hearing loss affects the response rate and other response parameters in oVEMPs and cVEMPs.展开更多
The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollu...The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollution.Herein,Graphene nanosheets(GN)were firstly fabricated via a facile high-energy ball milling method,subsequently high-purity 1T-MoS_(2) petals were uniformly anchored on the surface of GN to prepare 1T-MoS_(2)@GN nanocomposites.Plentiful multiple reflection and scattering of EM waves in a distinctive multidimensional structure formed by GN and 1T-MoS_(2),copious polarization loss consisting of interfacial polarization loss and dipolar polarization loss severally derived from multitudinous heterointerfaces and profuse electric dipoles in 1T-MoS_(2)@GN,and mighty conduction loss originated from plentiful induced current in 1T-MoS_(2)@GN generated via the migration of massive electrons,all of which endowed 1T-MoS_(2)@GN nanocomposites with exceptional EM wave absorption performances.The minimum reflection loss(RLmin)of 1T-MoS_(2)@GN reached–50.14 dB at a thickness of only 2.10 mm,and the effective absorption bandwidth(EAB)was up to 6.72 GHz at an ultra-thin matching thickness of 1.84 mm.Moreover,the radar scattering cross section(RCS)reduction value of 36.18 dB m2 at 0°could be achieved as well,which ulteriorly validated the tremendous potential of 1T-MoS_(2)@GN nanocomposites in practical applications.展开更多
The effective construction of electromagnetic(EM)wave absorption materials with thin matching thickness,broad bandwidth,and remarkable absorption is a great solution to EM pollution,which is a hot topic in current env...The effective construction of electromagnetic(EM)wave absorption materials with thin matching thickness,broad bandwidth,and remarkable absorption is a great solution to EM pollution,which is a hot topic in current environmental governance.In this study,N-doped reduced graphene oxide(N-rGO)was first prepared using a facile hydrothermal method.Then,high-purity 1T-MoS_(2)petals were homogeneously anchored to the wrinkled surface of N-rGO to fabricate 1T-MoS_(2)@N-rGO nanocomposites.The numerous electric di-poles and profuse heterointerfaces in 1T-MoS_(2)@N-rGO would induced the multiple reflection and scattering of EM waves in a distinct-ive multidimensional structure formed by two-dimensional N-rGO and 1T-MoS_(2)microspheres with plentiful thin nanosheets,remarkable conduction loss derived from the migration of massive electrons in a well-constructed conductive network formed by 1T-MoS_(2)@N-rGO,and abundant polarization loss(including dipolar polarization loss and interfacial polarization loss).All of these gave the 1T-MoS_(2)@N-rGO nanocomposites superior EM wave absorption performances.The effective absorption bandwidth of 1T-MoS_(2)@N-rGO reached 6.48 GHz with a relatively thin matching thickness of 1.84 mm,and a minimum reflection loss of-52.24 dB was achieved at 3.84 mm.Additionally,the radar scattering cross-section reduction value of 1T-MoS_(2)@N-rGO was up to 35.42 dB·m^(2) at 0°,which further verified the huge potential of our fabricated 1T-MoS_(2)@N-rGO nanocomposites in practical applications.展开更多
Hollow engineering plays a crucial role in enhancing interfacial polarization,which is an essential factor in microwave absorption.Herein,an in-situ growth approach was adopted to successively coating C layer and WS_(...Hollow engineering plays a crucial role in enhancing interfacial polarization,which is an essential factor in microwave absorption.Herein,an in-situ growth approach was adopted to successively coating C layer and WS_(2) nanosheets on the surface SiO_(2) nanosphere.The obtained results suggested that the formed SiO_(2)@Void@C@WS_(2) multi-component nanocomposites(MCNCs)reveal a representative flower-like yolk-shell structure,which were manufactured massively through a simple channel.Additionally,the obtained SiO_(2)@Void@C@WS_(2) MCNCs presented a more and more obvious yolk-shell structure and reduced WS_(2) content with decreasing the addition of SiO_(2)@C or tungsten and sulfur sources.Because of their distinc-tive structures and remarkable cooperative effects,the SiO_(2)@Void@C@WS_(2) displayed excellent microwave absorption performances.Through the majorization of hollow structure and WS_(2),improved properties of SiO_(2)@Void@C@WS_(2) MCNCs could be acquired owing to their boosted polarization and conductive loss capabilities.Amongst,the resulting SiO_(2)@Void@C@WS_(2) MCNCs exhibited the effective absorption band and minimum reflection loss values of 5.40 GHz and−45.50 dB with matching thicknesses of 1.78 and 1.55 mm,respectively.Therefore,our findings employed hollow engineering and optimization strategies for components to design and fabricate the yolk-shell structure flower-like MCNCs,which acted as highly efficient wide-band microwave absorbing materials.展开更多
Conduction and/or polarization loss play a key role in improving electromagnetic wave(EMW)absorption.In this work,a combined polymerization and high-heat treatment process was utilized to efficiently fabricate core@sh...Conduction and/or polarization loss play a key role in improving electromagnetic wave(EMW)absorption.In this work,a combined polymerization and high-heat treatment process was utilized to efficiently fabricate core@shell structure SiO_(2)@C adopting SiO_(2)nanospheres as a hard template.The acquired SiO_(2)@C nanocomposites displayed unsatisfied EMW absorption performances with minimum reflection loss value of-34.92 dB at 6.35 mm,and effective absorption bandwidth value of 3.20 GHz at 4.83 mm,respectively.In order to further comprehensively boost its microwave absorption performances(MAPs),a facile self-assembly strategy was adopted to load Au nanoparticles on the outer surface of SiO_(2)@C nanospheres,constructing core@shell SiO_(2)@C-Au multicomponent nanocomposites(MCNCs).By regulating the volume of Au nanoparticles,different Au contents of SiO_(2)@C-Au MCNCs could be selectively produced in high efficiencies.The obtained outcomes demonstrated that the SiO_(2)@C-Au MCNCs presented improved properties including EMW attenuation,impedance matching,conduction loss and polarization loss with increasing the content of Au nanoparticles.Thanks to the introduction of conductive Au nanoparticles and excellent interfacial effects,the SiO_(2)@C-Au MCNCs presented the greatly improved antimicrobial and EMW absorption performances including strong absorption,wide bandwidth and small thicknesses.Consequently,this finding offered a novel strategy to construct core@shell SiO_(2)@C-Au MCNCs,which simultaneously boosted conduction and polarization loss capabilities for EMW absorption.展开更多
Porous SiOC ceramic was successfully prepared by pyrolysis of dimethylsilicone oil,silane coupling agent and melamine foam.The microwave absorbing properties of porous SiOC were studied for the first time.At the match...Porous SiOC ceramic was successfully prepared by pyrolysis of dimethylsilicone oil,silane coupling agent and melamine foam.The microwave absorbing properties of porous SiOC were studied for the first time.At the matching layer thickness of 3.0 mm,the paraffin-based composite with porous SiOC displays a minimum reflection coefficient(RC)of-39.13 d B(11.76 GHz)and an effective absorption bandwidth(EAB)of 4.64 GHz which are much larger than that of paraffin-based composite with ordinary SiOC.It is found that the porous structure of SiOC is crucial to achieve its high microwave absorption performance by improving both the polarization loss and conduction loss.The enhanced polarization loss is originated from the dipole polarization and interfacial polarization,while the improvement of conduction loss is attributed to the carbon skeleton of porous SiOC.These results indicate that porous SiOC ceramic is a promising candidate for high-performance ceramic-based microwave absorbing materials.展开更多
In order to obtain high-performance electromagnetic wave absorbers,the adjustment of structure and components is essential.Based on the above requirements,this system forms a three-dimensional frame structure consisti...In order to obtain high-performance electromagnetic wave absorbers,the adjustment of structure and components is essential.Based on the above requirements,this system forms a three-dimensional frame structure consisting of MXene and transition metal oxides(TMOs)through efficient electrostatic self-assembly.This three-dimensional network structure has rich heterojunction structures,which can cause a large amount of interface polarization and conduction losses in incident electromagnetic waves.Hollow structures cause multiple reflections and scattering of electromagnetic waves,which is also an important reason for further increasing electromagnetic wave losses.When the doping ratio is 1:1,the system has the best impedance matching,the maximum effective absorption bandwidth(EAB max)can reach 5.12 GHz at 1.7 mm,and the minimum reflection loss(RL_(min))is-50.30 dB at 1.8 mm.This provides a reference for the subsequent formation of 2D-MXene materials into 3D materials.展开更多
Solid state circuit breakers(SSCBs)based on fullcontrolled devices such as IGBT and based on half-controlled devices such as thyristor have their respective advantages.The mixture device solid state circuit breaker(M-...Solid state circuit breakers(SSCBs)based on fullcontrolled devices such as IGBT and based on half-controlled devices such as thyristor have their respective advantages.The mixture device solid state circuit breaker(M-SSCB)combines the advantages together and can achieve lower loss,high efficiency,active and reliable blocking at the same time.However,the conduction loss will increase significantly when the topology expanding to a bidirectional topology because the bidirectional line commutation switch(LCS)structure composed of two groups of IGBTs in reverse series.In this paper,a novel discrete branch mixture SSCB(DBM-SSCB)is proposed,bidirectional current only flows through one IGBT that has the obvious conduction losses advantage at the same voltage and current level.Only one energy-absorbing component is shared by two discrete branches can guarantee optimal costs and volume.By calculation,the proposed DBM-SSCB can reduce the conduction loss about 30.4%in 10 k V MVDC system,while retaining other advantages of the mixture device SSCB,such as without introducing additional thyristors,charging power supply and the ability to actively interrupt bidirectional fault currents.The blocking principles and designing guidelines are presented in detail,the feasibility is verified by 500 V-18 A simulation results and scale-down experiment,the engineering calculation and simulation of 10 k V-1 k A prototype is completed and compared with other DCCBs.Experimental results and comparative analysis show that the proposed DBM-SSCB has both lower losses and significant performance advantages thus has a good engineering application prospect.展开更多
The voltagefluctuation in electric circuits has been identified as key issue in different electric systems.As the usage of electricity growing in rapid way,there exist higherfluctuations in powerflow.To maintain theflow or...The voltagefluctuation in electric circuits has been identified as key issue in different electric systems.As the usage of electricity growing in rapid way,there exist higherfluctuations in powerflow.To maintain theflow or stabi-lity of power in any electric circuit,there are many circuit models are discussed in literature.However,they suffer to maintain the output voltage and not capable of maintaining power stability.To improve the performance in power stabilization,an efficient IC pattern based power factor maximization model(ICPFMM)in this article.The model is focused on improving the power stability with the use of IC(Inductor and Conductor)towards identifying most efficient circuit for the current duty cycle according to the input voltage,voltage in capacitor and output voltage required.The model with boost converter diverts the incoming voltage through number of conductors and inductors.By triggering specific inductor,a specific capacitor gets charged and a particular circuit gets on.The model maintains num-ber of IC(Inductor and Conductor)patterns through which the powerflow occurs.According to that,the pattern available,the mofset controls the level of power to be regulated through any circuit.From the pattern,the model computes the Cir-cuits Switching Loss and Circuits Conduction Loss for various circuits.Accord-ing to the input voltage,the model estimates Circuit Power Stabilization Support(CPSS)according to the voltage available in any capacitor and input voltage.Using the value of CPSS,the model trigger optimal number of circuits to maintain voltage stability.In this approach,more than one circuit has been triggered to maintain output voltage and to get charged.The proposed model not only main-tains power stability but also reduces the wastage in voltage which is not utilized.The proposed model improves the performance in voltage stability with less switching loss.展开更多
By rationally controlling the growth of zeolite-imidazolium salt skeleton(ZIF-67)nanoparticles on the hollow indium oxide(In_(2)O_(3))and the subsequent pyrolysis process,In-Co-C hollow rod-like composites with multip...By rationally controlling the growth of zeolite-imidazolium salt skeleton(ZIF-67)nanoparticles on the hollow indium oxide(In_(2)O_(3))and the subsequent pyrolysis process,In-Co-C hollow rod-like composites with multiple components were successfully prepared in this work.The synergistic impact of diverse components including In_(2)O_(3),C,Co_(3)InC_(0.75),and In not only optimizes impedance matching and improves conductive loss,but also creates significant interfacial polarization.Furthermore,the addition of Co source and pyrolysis temperature was found to have a significant affected on impedance matching and mi-crowave absorption.The optimized In-Co-C sample displayed ultra-broad absorption bandwidth(EAB)of up to 7.12 GHz(10.88–18.0 GHz)at 2.26 mm thickness,which could cover the whole Ku band and part of X-band,outperforming the previously reported MOFs-derived composites.Furthermore,by adjusting the thickness to 2.91 mm and 4.01 mm,the EAB could cover the entire X band and most of the C band.The attenuation mechanisms were systematically investigated through the delta function method and ANSYS high-frequency structure simulator.These findings suggest that the MOFs-derived In-Co-C hollow nanorods could serve as high-performance microwave absorbers with ultra-broad absorption.展开更多
The emergence of wearable and foldable electronic devices urges advanced electromagnetic(EM)wave absorbers with maintained performance under deformation.Here FeCo@MoS_(2)poly vinyl alcohol(PVA)aerogels have been fabri...The emergence of wearable and foldable electronic devices urges advanced electromagnetic(EM)wave absorbers with maintained performance under deformation.Here FeCo@MoS_(2)poly vinyl alcohol(PVA)aerogels have been fabricated with the assistance of EM waves for simultaneous splitting of the MoS_(2)flakes and dispersive growth of FeCo nanoparticles.The resultants in-return have been used for EM wave absorption with excellent performance,providing minimum reflection loss(RL_(min))of-40.7 dB and a broad effective absorption bandwidth(EAB)of 6.4 GHz at a thickness of 2.5 mm.Real-time compression has been introduced to reveal the evolution of EM parameters.The aerogels maintain satisfactory performance even under 50%compression due to the balance of impedance matching and attenuation.Despite the deterioration of impedance matching,the attenuation is significantly enhanced due to both strengthened conductive loss and magnetic loss.In addition,features such as lightweight,self-cleaning and refractory can be achieved for the aerogels for applications in complex environments.As such this work not only provides a versatile synthetic route assisted by EM wave energy,but also insights on the evolution of absorption performance under deformation together with the design strategy of multifunctional flexible wave absorbers.展开更多
MXenes,a family of two-dimensional(2D)materials,exhibit peculiar microwave-absorbing behaviors due to their unique chemical composition and structure.Although laminated Ti_(3)C_(2)T_(x) MXenes with a multilayer struct...MXenes,a family of two-dimensional(2D)materials,exhibit peculiar microwave-absorbing behaviors due to their unique chemical composition and structure.Although laminated Ti_(3)C_(2)T_(x) MXenes with a multilayer structure have been used for microwave absorption,real 2D MXenes with a single-layer structure have not yet been investigated.Here,the electromagnetic wave response behavior of single-layer Ti_(3)C_(2)T_(x) MXenes was explored in detail.The permittivity of Ti_(3)C_(2)T_(x) MXene rises dramatically with an increase in filler loading,and Ti_(3)C_(2)T_(x) MXene features a distinct dielectric response wherein dipolar polarization and interfacial polarization makes a greater contribution at low filler loading;conductive loss becomes more prominent at high filler loading.Versus laminated Ti_(3)C_(2)T_(x) MXene,single-layer Ti_(3)C_(2)T_(x) MXene delivers superior absorbing capability:The RLminvalue of SL-Ti_(3)C_(2)T_(x)-22%reaches-43.5 d B at 6.5 GHz,and a broad EAB of 6.88 GHz can be attained at a thickness of 1.8 mm due to enhanced dipolar polarization,interfacial polarization,and conductive loss.This work is of great significance in guiding the future development of MXene-based absorbers.展开更多
基金supported by the National Nat-ural Science Foundation of China(Nos.51872238,52074227,and 21806129)the Fundamental Research Funds for the Central Universities,China(Nos.3102018zy045 and 3102019AX11)+2 种基金the Guangdong Basic and Applied Basic Research Foundation,China(No.2024A1515010298)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2017JQ5116 and 2020JM-118)the Key Laboratory of Icing and Anti/De-icing of CARDC(No.IADL20220401).
文摘Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood.In this study,we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride(ChCl)and ethylene glycol(EG).Owing to the unique properties of deep eutectic gels,the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded.Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG,with HB-induced conductive loss following similar pat-terns.At a ChCl and EG molar ratio of 2.4,the gel labeled G22-CE2.4 exhibited the best EMW absorption performance,characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm.This superior performance is attributed to the synergistic ef-fects of excellent conductive loss and impedance matching generated by the optimal number of HB.This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.
基金support from the Natural Science Basic Research Plan in Shaanxi Province of China (No.2020JM-087).
文摘Excellent impedance matching and high conduction loss are important factors for the preparation of high-performance electromagnetic wave(EMW)absorbing materials,but these two properties are of-ten contradictory.In this work,three absorbers with unique hollow structures,H-Ag/CuO@CuS,H-O-Ag/CuO@CuS,and H-P-Ag/CuO@CuS,are designed and synthesized by adopting hollow CuO@CuS with double shell as carrier and silver nitrate as the structural regulator.The more voids coming from hol-low structures,window-opened structures,and stacked pores improve the impedance matching of these absorbers,and the introduction of elemental Ag effectively regulates the conduction loss.Therefore,a balance between impedance matching and conduction loss is achieved to improve the reflection loss(RL)value and broadens the absorbing band of the absorbers.In comparison to H-Ag/CuO@CuS and H-O-Ag/CuO@CuS(hollow structure with open window)in which elemental Ag is uniformly dispersed in the CuO layer,H-P-Ag/CuO@CuS exhibits more excellent EMW absorption performance due to more voids and an optimized conductive network arising from Ag/CuO pieces distributed between the hol-low Ag/CuO@CuS particles and Ag distributed in the CuS layer.When the thickness is 2.3 mm,H-P-Ag/CuO@CuS provides an ultra-wide electromagnetic absorption band of 8.56 GHz(9.44-18 GHz),in which the RL<-10 dB and the minimum reflection loss of-41 dB.
基金supported by the National Natural Science Foundation of China(No.52362024 and 22004106).
文摘Understanding the microstructure-property relationship from the microscopic and macroscopic perspectives,instead of semi-empirical rules,can facilitate the design of microcosmic morphology to adjust the impedance matching and dielectric loss of the carbon-based materials,which are still lacking so far.In this study,a clear correlation between microstructure and conduction loss was revealed in agarosederived carbon using a facile salt-etching strategy,in which ferric nitrate acted more as a morphology modifier for bulky carbon rather than a component regulator.Specifically,with the increasing amount of ferric nitrate,the original smooth bulky carbon was etched with caves,which gradually enlarged in size and depth and thus thinned in wall,and eventually transformed into a three-dimensional(3D)interconnected cellular structure,accompanied by a gradual increase in conductivity.Benefiting from the optimal impedance matching and strong conduction loss originating from the unique 3D cellular structure of agarose-derived carbon,AF-3 exhibited super-wide and strong absorption with an effective absorption bandwidth of 7.28 GHz(10.32-17.60 GHz,2.9 mm)and a minimum reflection loss of-46.6 dB(15.6 GHz,2.5 mm).This study establishes the relationship between microstructure,dielectric properties,and loss mechanism in carbon-based materials and also provides a new insight into the fine modulation of EMW-absorbing properties from morphological design.
基金This work was financially supported by the Natural Science Foundation of Sichuan Province(No.2023NSFSC0435)National Natural Science Foundation of China(No.52272288)+2 种基金Science and Technology Innovation Cultivation Project of Department of Science and Technology of Sichuan Province(Grant No.2021JDRC0091)the Key R&D project of Department of Science and Technology of Sichuan province(Grant No.2020YFN0025)Sichuan Agricul-tural University double support(No.035-2221993150).The authors also acknowledge the assistance of DUT Instrumental Analysis Center and Nanjing XFNANO Materials Tech Co.,Ltd.We also thank Xinnan Wang at School of Chemical Engineering of Dalian Univer-sity of Technology for help with the SEM data analysis.
文摘Polarization and conduction losses are the two most crucial dielectric loss mechanisms for carbon-based composites,but their synergistic effects in different frequency bands need to be further revealed.More importantly,for polarization and conduction losses,the strengthening of one party always comes at the expense of the other,which inevitably limits the overall performance of the absorbers.Herein,we have developed a composite of CNT and NiCo hybrid particles via a scalable wet chemical process and an-nealing method.Through the adjustment of the precursor and the annealing temperature,the conduction and polarization losses of the composite are optimized simultaneously.The optimized samples achieved the full absorption of the X and Ku bands under conditions of low filling rate and thin thickness.Further theoretical and experimental studies have revealed conduction loss and polarization loss laws at different frequency ranges.The synergistic effect of conductive loss and magnetic loss in the low-frequency region ensures that the sample exhibits high microwave dissipation performance.However,in the medium and high-frequency part,the magnetic loss can be almost ignored and the timely replenishment of polar-ization loss keeps the wave-absorbing performance at a high level.The excellent multi-band absorption characteristics make the as-obtained absorbers meet the needs of future applications.
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.
基金supported by the National Natural Science Foundation of China(Nos.52103334,52071053,U1704253,52272288,52401035)the Fundamental Research Funds for the Central Universities(No.DUT24GF102).
文摘The rational construction of lightweight composites with multiple heterogeneous interfaces represents an effective strategy for achieving efficient electromagnetic wave(EMW)absorption.However,the impact of multiple heterogeneous interfaces on electromagnetic performance still needs further exploration.Herein,reduced graphene oxide(rGO)@Ni-FeCo layered hydroxide(LDH)derivatives with multiple heterostructures were synthesized by a series of processes including electrostatic self-assembly,freeze-drying and thermal annealing.The conductive network in rGO and the cavities inside LDH facilitate electron migration and effectively prolong the propagation path of EMW,thereby enhancing conductivity loss.The abundant heterogeneous interfaces between carbon components and metal nanoparticles induce interfacial polarization.In addition,the catalytic activity differences of different metal particles generate different dielectric electromagnetic interfaces,which further promote interfacial polarization.The natural and exchange resonance formed by magnetic particles under a magnetic field provides magnetic losses.Therefore,the successful construction of multiple heterogeneous interfaces effectively enhances the conductivity loss and polarization loss.With a thickness of only 1.4 mm,the composite achieves a minimum reflection loss of-51.8 dB and an effective absorption bandwidth of 4.5 GHz.This work provides an effective strategy for achieving thin thickness and efficient EMW absorption through precise structural design and multi-component construction of absorbers.
基金supported by the grants of the National Key Research and Development Program of China(Grant No.2023YFC2508400)the National Natural Science Foundation of China(Grant No.82350005).
文摘Purpose To investigate the perinatal risk factors for conductive hearing loss(CHL)in infancy and develop an initial prediction model to facilitate accurate diagnosis and early detection of CHL.Method This retrospective study utilized data from the Newborn Cohort Study of Hearing Loss(ChiCTR2100049765).Infants who underwent diagnostic audiological assessments at our hospital between January 2003 and June 2024 were included.Data analysis was conducted using R(version 4.4.1)to construct an initial prediction model for CHL in infancy,applying the LASSO regression technique.Results A total of 661 infants(1322 ears)were included,with 1253 ears in the normal hearing group and 69 ears in the CHL group.Statistically significant differences were observed between the groups in the following factors:parent-reported infant response to sound,craniofacial deformities,neonatal hemolysis,jaundice treatment,and neonatal hypoglycemia.A multivariate prediction model and nomogram for CHL in infancy were developed and validated,achieving an accuracy of 92.5%and a specificity of 91.3%.Conclusions This study identified key risk factors for CHL in infancy and developed a preliminary predictive model,improving the diagnostic accuracy for CHL.Improved diagnostic precision can decrease misdiagnoses,reduce delays in treatment,and limit unnecessary antimicrobial prescriptions for infants.
基金supported by the Fund of Fok Ying Tung Education Foundation,the Major Research Project of innovative Group of Guizhou province(No.2018-013)the National Science Foundation of China(Nos.11604060 and 11964006)the Foundation of the National Key Project for Basic Research(No.2012CB932304).
文摘Impedance matching characteristics and loss capabilities including magnetic loss,polarization loss and conduction loss are critical factors to improve microwave absorption performances(MAPs).To elevate these aspects,herein,yolk-shell structured CoNi@Air@C/SiO_(2)@Polypyrrole(PPy)magnetic multicomponent nanocubes(MCNCs)were designed and successfully fabricated in high efficiency through a continuous co-precipitation route,classical Stöber method,thermal treatment and polymerization reaction.The obtained results indicated that the formation of SiO_(2) effectively stabilized the cubic geometrical morphology and yolk-shell structure during the high-temperature pyrolysis process.The introduction of PPy greatly boosted their polarization loss and conductive loss capabilities.Therefore,the as-prepared yolkshell structured CoNi@Air@C/SiO_(2)@PPy MCNCs presented superior MAPs compared to CoNi@Air@C/SiO_(2) MCNCs.Furthermore,by regulating the content of PPy,the obtained CoNi@Air@C/SiO_(2)@PPy MCNCs displayed tunable and excellent comprehensive MAPs in terms of strong absorption capabilities,broad frequency bandwidths and thin matching thicknesses,which could be ascribed to the unique structure and excellent magnetic-dielectric synergistic effect.Therefore,our findings provided an alternative pathway to effectively utilize the magnetic-dielectric synergy and loss capabilities for the developing yolk-shell structured magnetic MCNCs as the strong wideband microwave absorbers.
基金supported by grants from the National Natural Science Foundation of China, China (No. 81670945, 81541040)Fundamental Research Funds for the Central Universities, China (No. 2012jdhz13)+1 种基金Shaanxi Major International Cooperative Project, China (No. 2013KW-28)Key Science and Technology Program of Xi'an, China (No. SF1315(1))
文摘Objective:To investigate the effects of conductive hearing loss (CHL) on vestibular evoked myogenic potentials (VEMPs) using a simulated CHL model, and to provide the basis for future studies. Methods:Twenty-one healthy subjects were recruited in this study. We measured ocular VEMPs (oVEMPs) and cervical VEMPs (cVEMPs) in these subjects by air-conduction sound (ACS) stimulation. CHL was simulated later by blocking the right external auditory canal with a soundproof earplug to evaluate its impacts on VEMPs. Subjects' responses before simulated CHL served as the control, and were compared to their responses following simulated CHL. Results: oVEMPs following simulated CHL showed decreased response rate, elevated thresholds, attenuated amplitudes and prolonged N1 latencies compared with those before simulated CHL, and the differences were statistically significant. Similarly, cVEMPs following simulated CHL also showed decreased response rate, elevated thresholds and attenuated amplitudes, with prolonged P1 latencies compared with those before simulated CHL, although only differences in response rate, threshold and amplitude were significant. Conclusions:Conductive hearing loss affects the response rate and other response parameters in oVEMPs and cVEMPs.
基金supported by the PhD Start-up Fund of the Science and Technology Department of Liaoning Province(No.2022-BS-306)the General Cultivation Scientific Research Project of Bohai University(No.0522xn058)the PhD Research Startup Foundation of Bohai University(No.0521bs021).
文摘The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollution.Herein,Graphene nanosheets(GN)were firstly fabricated via a facile high-energy ball milling method,subsequently high-purity 1T-MoS_(2) petals were uniformly anchored on the surface of GN to prepare 1T-MoS_(2)@GN nanocomposites.Plentiful multiple reflection and scattering of EM waves in a distinctive multidimensional structure formed by GN and 1T-MoS_(2),copious polarization loss consisting of interfacial polarization loss and dipolar polarization loss severally derived from multitudinous heterointerfaces and profuse electric dipoles in 1T-MoS_(2)@GN,and mighty conduction loss originated from plentiful induced current in 1T-MoS_(2)@GN generated via the migration of massive electrons,all of which endowed 1T-MoS_(2)@GN nanocomposites with exceptional EM wave absorption performances.The minimum reflection loss(RLmin)of 1T-MoS_(2)@GN reached–50.14 dB at a thickness of only 2.10 mm,and the effective absorption bandwidth(EAB)was up to 6.72 GHz at an ultra-thin matching thickness of 1.84 mm.Moreover,the radar scattering cross section(RCS)reduction value of 36.18 dB m2 at 0°could be achieved as well,which ulteriorly validated the tremendous potential of 1T-MoS_(2)@GN nanocomposites in practical applications.
基金supported by the PhD Start-up Fund of Science and Technology Department of Liaoning Province,China(No.2022-BS-306)the General Cultivation Scientific Research Project of Bohai University,China(No.0522xn058)+2 种基金the PhD Research Startup Foundation of Bohai University,China(No.0521bs021)the Youth Project of Natural Science Foundation of Hunan Province,China(No.2022JJ40338)the Scientific Research Youth Project by Education Department of Hunan Province,China(No.22B0556).
文摘The effective construction of electromagnetic(EM)wave absorption materials with thin matching thickness,broad bandwidth,and remarkable absorption is a great solution to EM pollution,which is a hot topic in current environmental governance.In this study,N-doped reduced graphene oxide(N-rGO)was first prepared using a facile hydrothermal method.Then,high-purity 1T-MoS_(2)petals were homogeneously anchored to the wrinkled surface of N-rGO to fabricate 1T-MoS_(2)@N-rGO nanocomposites.The numerous electric di-poles and profuse heterointerfaces in 1T-MoS_(2)@N-rGO would induced the multiple reflection and scattering of EM waves in a distinct-ive multidimensional structure formed by two-dimensional N-rGO and 1T-MoS_(2)microspheres with plentiful thin nanosheets,remarkable conduction loss derived from the migration of massive electrons in a well-constructed conductive network formed by 1T-MoS_(2)@N-rGO,and abundant polarization loss(including dipolar polarization loss and interfacial polarization loss).All of these gave the 1T-MoS_(2)@N-rGO nanocomposites superior EM wave absorption performances.The effective absorption bandwidth of 1T-MoS_(2)@N-rGO reached 6.48 GHz with a relatively thin matching thickness of 1.84 mm,and a minimum reflection loss of-52.24 dB was achieved at 3.84 mm.Additionally,the radar scattering cross-section reduction value of 1T-MoS_(2)@N-rGO was up to 35.42 dB·m^(2) at 0°,which further verified the huge potential of our fabricated 1T-MoS_(2)@N-rGO nanocomposites in practical applications.
基金supported by the Guizhou Provincial Science and Technology Projects for Platform and Talent Team Plan(No.GCC[2023]007)the Innovation Group of Guizhou University([2024]08)+1 种基金Fok Ying Tung Education Foundation(No.171095)the National Natural Science Foundation of China(No.11964006).
文摘Hollow engineering plays a crucial role in enhancing interfacial polarization,which is an essential factor in microwave absorption.Herein,an in-situ growth approach was adopted to successively coating C layer and WS_(2) nanosheets on the surface SiO_(2) nanosphere.The obtained results suggested that the formed SiO_(2)@Void@C@WS_(2) multi-component nanocomposites(MCNCs)reveal a representative flower-like yolk-shell structure,which were manufactured massively through a simple channel.Additionally,the obtained SiO_(2)@Void@C@WS_(2) MCNCs presented a more and more obvious yolk-shell structure and reduced WS_(2) content with decreasing the addition of SiO_(2)@C or tungsten and sulfur sources.Because of their distinc-tive structures and remarkable cooperative effects,the SiO_(2)@Void@C@WS_(2) displayed excellent microwave absorption performances.Through the majorization of hollow structure and WS_(2),improved properties of SiO_(2)@Void@C@WS_(2) MCNCs could be acquired owing to their boosted polarization and conductive loss capabilities.Amongst,the resulting SiO_(2)@Void@C@WS_(2) MCNCs exhibited the effective absorption band and minimum reflection loss values of 5.40 GHz and−45.50 dB with matching thicknesses of 1.78 and 1.55 mm,respectively.Therefore,our findings employed hollow engineering and optimization strategies for components to design and fabricate the yolk-shell structure flower-like MCNCs,which acted as highly efficient wide-band microwave absorbing materials.
基金support from Guizhou Provincial Basic Research Program(Natural Science)(No.ZD[2025]Key 086)Platform of Science and Technology and Talent Team Plan of Guizhou province(No.GCC[2023]007)Innovation Group of Guizhou University(No.[2024]08)for financial support.
文摘Conduction and/or polarization loss play a key role in improving electromagnetic wave(EMW)absorption.In this work,a combined polymerization and high-heat treatment process was utilized to efficiently fabricate core@shell structure SiO_(2)@C adopting SiO_(2)nanospheres as a hard template.The acquired SiO_(2)@C nanocomposites displayed unsatisfied EMW absorption performances with minimum reflection loss value of-34.92 dB at 6.35 mm,and effective absorption bandwidth value of 3.20 GHz at 4.83 mm,respectively.In order to further comprehensively boost its microwave absorption performances(MAPs),a facile self-assembly strategy was adopted to load Au nanoparticles on the outer surface of SiO_(2)@C nanospheres,constructing core@shell SiO_(2)@C-Au multicomponent nanocomposites(MCNCs).By regulating the volume of Au nanoparticles,different Au contents of SiO_(2)@C-Au MCNCs could be selectively produced in high efficiencies.The obtained outcomes demonstrated that the SiO_(2)@C-Au MCNCs presented improved properties including EMW attenuation,impedance matching,conduction loss and polarization loss with increasing the content of Au nanoparticles.Thanks to the introduction of conductive Au nanoparticles and excellent interfacial effects,the SiO_(2)@C-Au MCNCs presented the greatly improved antimicrobial and EMW absorption performances including strong absorption,wide bandwidth and small thicknesses.Consequently,this finding offered a novel strategy to construct core@shell SiO_(2)@C-Au MCNCs,which simultaneously boosted conduction and polarization loss capabilities for EMW absorption.
基金the National Natural Science Foundation of China(Nos.51532009 and 91326102)the China NationalScience and Technology Major Special Project‘Research on Accident Tolerant Fuels Key Technology’(No.2015ZX06004-001)+2 种基金the Science and Technology Development Foundation of China Academy of Engineering Physics(No.2013A0301012)the foundation by the Recruitment Program of Global Youth Expertsthe Youth Hundred Talents Project of Sichuan Province。
文摘Porous SiOC ceramic was successfully prepared by pyrolysis of dimethylsilicone oil,silane coupling agent and melamine foam.The microwave absorbing properties of porous SiOC were studied for the first time.At the matching layer thickness of 3.0 mm,the paraffin-based composite with porous SiOC displays a minimum reflection coefficient(RC)of-39.13 d B(11.76 GHz)and an effective absorption bandwidth(EAB)of 4.64 GHz which are much larger than that of paraffin-based composite with ordinary SiOC.It is found that the porous structure of SiOC is crucial to achieve its high microwave absorption performance by improving both the polarization loss and conduction loss.The enhanced polarization loss is originated from the dipole polarization and interfacial polarization,while the improvement of conduction loss is attributed to the carbon skeleton of porous SiOC.These results indicate that porous SiOC ceramic is a promising candidate for high-performance ceramic-based microwave absorbing materials.
基金supported by the National Natural Science Foundation of China(Nos.51407134,52002196)Natural Science Foundation of Shandong Province(Nos.ZR2019YQ24,ZR2020QF084)+1 种基金Taishan Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)the Qingchuang Talents Induction Program of Shandong Higher Education Institution(Research and Innovation Team of Structural-Functional Polymer Composites)and Special Financial of Shandong Province(Structural Design of High-efficiency Electromagnetic Wave-absorbing Composite Materials and Construction of Shandong Provincial Talent Teams(No.37000022P990304116449)).
文摘In order to obtain high-performance electromagnetic wave absorbers,the adjustment of structure and components is essential.Based on the above requirements,this system forms a three-dimensional frame structure consisting of MXene and transition metal oxides(TMOs)through efficient electrostatic self-assembly.This three-dimensional network structure has rich heterojunction structures,which can cause a large amount of interface polarization and conduction losses in incident electromagnetic waves.Hollow structures cause multiple reflections and scattering of electromagnetic waves,which is also an important reason for further increasing electromagnetic wave losses.When the doping ratio is 1:1,the system has the best impedance matching,the maximum effective absorption bandwidth(EAB max)can reach 5.12 GHz at 1.7 mm,and the minimum reflection loss(RL_(min))is-50.30 dB at 1.8 mm.This provides a reference for the subsequent formation of 2D-MXene materials into 3D materials.
基金supported in part by the National Key Research and Development Program of China under Grant 2023YFB2405905in part by The Institute of Electrical Engineering,CAS under Grant E155610301 and E155610201。
文摘Solid state circuit breakers(SSCBs)based on fullcontrolled devices such as IGBT and based on half-controlled devices such as thyristor have their respective advantages.The mixture device solid state circuit breaker(M-SSCB)combines the advantages together and can achieve lower loss,high efficiency,active and reliable blocking at the same time.However,the conduction loss will increase significantly when the topology expanding to a bidirectional topology because the bidirectional line commutation switch(LCS)structure composed of two groups of IGBTs in reverse series.In this paper,a novel discrete branch mixture SSCB(DBM-SSCB)is proposed,bidirectional current only flows through one IGBT that has the obvious conduction losses advantage at the same voltage and current level.Only one energy-absorbing component is shared by two discrete branches can guarantee optimal costs and volume.By calculation,the proposed DBM-SSCB can reduce the conduction loss about 30.4%in 10 k V MVDC system,while retaining other advantages of the mixture device SSCB,such as without introducing additional thyristors,charging power supply and the ability to actively interrupt bidirectional fault currents.The blocking principles and designing guidelines are presented in detail,the feasibility is verified by 500 V-18 A simulation results and scale-down experiment,the engineering calculation and simulation of 10 k V-1 k A prototype is completed and compared with other DCCBs.Experimental results and comparative analysis show that the proposed DBM-SSCB has both lower losses and significant performance advantages thus has a good engineering application prospect.
文摘The voltagefluctuation in electric circuits has been identified as key issue in different electric systems.As the usage of electricity growing in rapid way,there exist higherfluctuations in powerflow.To maintain theflow or stabi-lity of power in any electric circuit,there are many circuit models are discussed in literature.However,they suffer to maintain the output voltage and not capable of maintaining power stability.To improve the performance in power stabilization,an efficient IC pattern based power factor maximization model(ICPFMM)in this article.The model is focused on improving the power stability with the use of IC(Inductor and Conductor)towards identifying most efficient circuit for the current duty cycle according to the input voltage,voltage in capacitor and output voltage required.The model with boost converter diverts the incoming voltage through number of conductors and inductors.By triggering specific inductor,a specific capacitor gets charged and a particular circuit gets on.The model maintains num-ber of IC(Inductor and Conductor)patterns through which the powerflow occurs.According to that,the pattern available,the mofset controls the level of power to be regulated through any circuit.From the pattern,the model computes the Cir-cuits Switching Loss and Circuits Conduction Loss for various circuits.Accord-ing to the input voltage,the model estimates Circuit Power Stabilization Support(CPSS)according to the voltage available in any capacitor and input voltage.Using the value of CPSS,the model trigger optimal number of circuits to maintain voltage stability.In this approach,more than one circuit has been triggered to maintain output voltage and to get charged.The proposed model not only main-tains power stability but also reduces the wastage in voltage which is not utilized.The proposed model improves the performance in voltage stability with less switching loss.
基金supported by the National Natural Science Foundation of China(Nos.52377026 and 52301192)Natural Science Foundation of Shandong Province(No.ZR2019YQ24)+1 种基金Taishan Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)the Qingchuang Talents Induction Program of Shandong Higher Education Institution(Research and Innovation Team of Structural-Functional Polymer Composites),and Special Financial of Shandong Province(Structural Design of High-efficiency Electromagnetic Wave absorbing Composite Materials and Construction of Shandong Provincial Talent Teams).The authors acknowledge the support from Natural Science Foundation of Shandong Province(No.ZR2021QE164).
文摘By rationally controlling the growth of zeolite-imidazolium salt skeleton(ZIF-67)nanoparticles on the hollow indium oxide(In_(2)O_(3))and the subsequent pyrolysis process,In-Co-C hollow rod-like composites with multiple components were successfully prepared in this work.The synergistic impact of diverse components including In_(2)O_(3),C,Co_(3)InC_(0.75),and In not only optimizes impedance matching and improves conductive loss,but also creates significant interfacial polarization.Furthermore,the addition of Co source and pyrolysis temperature was found to have a significant affected on impedance matching and mi-crowave absorption.The optimized In-Co-C sample displayed ultra-broad absorption bandwidth(EAB)of up to 7.12 GHz(10.88–18.0 GHz)at 2.26 mm thickness,which could cover the whole Ku band and part of X-band,outperforming the previously reported MOFs-derived composites.Furthermore,by adjusting the thickness to 2.91 mm and 4.01 mm,the EAB could cover the entire X band and most of the C band.The attenuation mechanisms were systematically investigated through the delta function method and ANSYS high-frequency structure simulator.These findings suggest that the MOFs-derived In-Co-C hollow nanorods could serve as high-performance microwave absorbers with ultra-broad absorption.
基金financially supported by the National Natural Science Foundation of China(No.52122106)the Key Research and Development Program of Zhejiang Province(Nos.2021C01033 and 2021C01193)。
文摘The emergence of wearable and foldable electronic devices urges advanced electromagnetic(EM)wave absorbers with maintained performance under deformation.Here FeCo@MoS_(2)poly vinyl alcohol(PVA)aerogels have been fabricated with the assistance of EM waves for simultaneous splitting of the MoS_(2)flakes and dispersive growth of FeCo nanoparticles.The resultants in-return have been used for EM wave absorption with excellent performance,providing minimum reflection loss(RL_(min))of-40.7 dB and a broad effective absorption bandwidth(EAB)of 6.4 GHz at a thickness of 2.5 mm.Real-time compression has been introduced to reveal the evolution of EM parameters.The aerogels maintain satisfactory performance even under 50%compression due to the balance of impedance matching and attenuation.Despite the deterioration of impedance matching,the attenuation is significantly enhanced due to both strengthened conductive loss and magnetic loss.In addition,features such as lightweight,self-cleaning and refractory can be achieved for the aerogels for applications in complex environments.As such this work not only provides a versatile synthetic route assisted by EM wave energy,but also insights on the evolution of absorption performance under deformation together with the design strategy of multifunctional flexible wave absorbers.
基金the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2021JQ-190,2020JM-82)the Fundamental Research Funds for the Central Universities(No.QTZX2146)。
文摘MXenes,a family of two-dimensional(2D)materials,exhibit peculiar microwave-absorbing behaviors due to their unique chemical composition and structure.Although laminated Ti_(3)C_(2)T_(x) MXenes with a multilayer structure have been used for microwave absorption,real 2D MXenes with a single-layer structure have not yet been investigated.Here,the electromagnetic wave response behavior of single-layer Ti_(3)C_(2)T_(x) MXenes was explored in detail.The permittivity of Ti_(3)C_(2)T_(x) MXene rises dramatically with an increase in filler loading,and Ti_(3)C_(2)T_(x) MXene features a distinct dielectric response wherein dipolar polarization and interfacial polarization makes a greater contribution at low filler loading;conductive loss becomes more prominent at high filler loading.Versus laminated Ti_(3)C_(2)T_(x) MXene,single-layer Ti_(3)C_(2)T_(x) MXene delivers superior absorbing capability:The RLminvalue of SL-Ti_(3)C_(2)T_(x)-22%reaches-43.5 d B at 6.5 GHz,and a broad EAB of 6.88 GHz can be attained at a thickness of 1.8 mm due to enhanced dipolar polarization,interfacial polarization,and conductive loss.This work is of great significance in guiding the future development of MXene-based absorbers.
