In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial w...In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial weight percent of Sr_(2)TiMoO_(6),were synthesized using the solid-state reaction method.Compared with STM100,some equilibrium phases,including SrTiO_(3),Mo,Sr_(8)(Al1_(2)O_(24))(MoO_(4))_(2)and a few undefined ones,are presented in the composites as evidenced by X-ray diffraction results and scanning electron microscopy due to the chemical reaction between Sr_(2)TiMoO_(6)and Al_(2)O_(3)component.Besides conductance loss,heterogeneous interfaces between various equilibrium phases introduce interfacial polarization,which causes an enhancement of dissipation for the incident electromagnetic wave.Among the synthesized samples,STM80 presents the best microwave absorbing properties.It has a minimum reflection loss(RLmin)of-26 dB and an effective absorbing bandwidth up to 2.7 GHz when the thickness is only 1 mm.This indicates that STM80 is a new type of microwave absorbing material with strong absorption and ultrathin thickness.展开更多
Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms ...Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms of scalability and mass production for practical application.In this work,we reported a successful attempt in modifying the 3D structure of mesoporous lanthanum oxide(La_(2)O_(3))for effective broadband MAMs candidate via simple co-precipitation process.The inclusion of cetyltrimethylammonium bromide(CTAB)and hydrothermal aging treatment result in a significant transformation of La_(2)O_(3)particles from their original polygonal form to a 3D coral-like and nano needle-like structure.The utilization of CTAB and hydrothermal aging results in the increase of surface area and a two-fold increase in pore volume of the resulting La_(2)O_(3).Due to its unique 3D structure,the 3D coral-like and nano needle-like La_(2)O_(3)materials possess a broadband electromagnetic(EM)wave absorption characteristic with the effective absorption bandwidth(EAB)covering the C-band frequency range.Specifically,in the La_(2)O_(3)C-H sample(with CTAB-with hydrothermal),it exhibits strong EM wave absorption with a reflection loss(RL)value of-33.07 dB which equals to 99.95%EM wave absorption at a thickness of only 1.50 mm.The detailed analysis of EM wave absorption properties reveals that the improvement of La_(2)O_(3)materials to attenuate EM wave energy arises from the dielectric loss phenomenon,the enhanced interfacial polarization,multiple reflections mechanism,and conduction loss mechanism induced by the 3D structural formation of the La_(2)O_(3)structure.This work proposes a novel and efficient approach in synthesizing and modifying 3D materials for effective broadband EM wave absorption.展开更多
The development of microwave absorption materials(MAMs) is a considerable important topic because our living space is crowed with electromagnetic wave which threatens human’s health.And MAMs are also used in radar st...The development of microwave absorption materials(MAMs) is a considerable important topic because our living space is crowed with electromagnetic wave which threatens human’s health.And MAMs are also used in radar stealth for protecting the weapons from being detected.Many nanomaterials were studied as MAMs,but not all of them have the satisfactory performance.Recently,metal-organic frameworks(MOFs) have attracted tremendous attention owing to their tunable chemical structures,diverse properties,large specific surface area and uniform pore distribution.MOF can transform to porous carbon(PC) which is decorated with metal species at appropriate pyrolysis temperature.However,the loss mechanism of pure MOF-derived PC is often relatively simple.In order to further improve the MA performance,the MOFs coupled with other loss materials are a widely studied method.In this review,we summarize the theories of MA,the progress of different MOF-derived PC-based MAMs,tunable chemical structures incorporated with dielectric loss or magnetic loss materials.The different MA performance and mechanisms are discussed in detail.Finally,the shortcomings,challenges and perspectives of MOF-derived PC-based MAMs are also presented.We hope this review could provide a new insight to design and fabricate MOF-derived PC-based MAMs with better fundamental understanding and practical application.展开更多
Microwave has been widely used in many fields,including communication,medical treatment and military industry;however,the corresponding generated radiations have been novel hazardous sources of pollution threating hu...Microwave has been widely used in many fields,including communication,medical treatment and military industry;however,the corresponding generated radiations have been novel hazardous sources of pollution threating human’s daily life.Therefore,designing high-performance microwave absorption materials(MAMs)has become an indispensable requirement.Recently,metal-organic frameworks(MOFs)have been considered as one of the most ideal precursor candidates of MAMs because of their tunable structure,high porosity and large specific surface area.Usually,MOF-derived MAMs exhibit excellent electrical conductivity,good magnetism and sufficient defects and interfaces,providing obvious merits in both impedance matching and microwave loss.In this review,the recent research progresses on MOF-derived MAMs were profoundly reviewed,including the categories of MOFs and MOF composites precursors,design principles,preparation methods and the relationship between mechanisms of microwave absorption and microstructures of MAMs.Finally,the current challenges and prospects for future opportunities of MOF-derived MAMs are also discussed.展开更多
Due to the rapid development of radar technology,the demand for absorbing stealth materials is increas-ing,and ultra-broadband absorption(effective absorption bandwidth>8 GHz)has become an inevitable requirement.As...Due to the rapid development of radar technology,the demand for absorbing stealth materials is increas-ing,and ultra-broadband absorption(effective absorption bandwidth>8 GHz)has become an inevitable requirement.As a new type of two-dimensional material,MXene material possesses the characteristics of excellent wave absorbing material due to its easy preparation,easy modulation of defects and sur-face functional groups,and high conductivity.This work summarizes the absorbing theory and research progress on MXene-based absorbing materials in recent years,including pure MXene absorbing materials and MXene-based magnetic or dielectric composite materials with multiple losses.Some shortcomings and research directions of MXene-based materials were pointed out.Currently,research on MXene-based absorbent materials is thriving and in a state of vigorous development.Excellent absorbent materials have been reported,but their shortcomings are also apparent.The factors that affect the performance of MXene-based absorbent materials are complex,and the absorption mechanism is relatively simple.Further systematic and detailed research is needed to clarify these influencing mechanisms,broaden the absorption bandwidth,and reduce the matching thickness to meet practical usage requirements in the future.展开更多
Magnesium-substituted Mn0.8Zn0.2Fe2O4 ferrite is synthesized by the sol–gel combustion method using citrate acid as the complex agent. The electromagnetic absorbing behaviors of ferrite/polymer coatings fabricated by...Magnesium-substituted Mn0.8Zn0.2Fe2O4 ferrite is synthesized by the sol–gel combustion method using citrate acid as the complex agent. The electromagnetic absorbing behaviors of ferrite/polymer coatings fabricated by dispersing Mn–Zn ferrite into epoxy resin （EP） are studied. The microstructure and morphology are characterized by X-ray diffraction and scanning electron microscope. Complex permittivity, complex permeability, and reflection loss of ferrite/EP composite coating are investigated in a low frequency range. It is found that the prepared ferrite particles are traditional cubic spinel ferrite particles with an average size of 200 nm. The results reveal that the electromagnetic microwave absorbing properties are significantly influenced by the weight ratio of ferrite to polymer. The composites with a weight ratio of ferrite/polymer being 3：20 have a maximum reflection loss of –16 dB and wide absorbing band. Thus, the Mn–Zn ferrite is the potential candidate in electromagnetic absorbing application in the low frequency range （10 MHz–1 GHz）.展开更多
High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increa...High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorp-tion(EMWA)performance at elevated temperatures,which severely restricts their practical application.In this study,we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide(RGO)/epoxy resin(EP)metacomposites that integrate both electromagnetic parameters and metamaterial design concepts.Due to the discrete distribution of the units,electromagnetic waves can more easily penetrate the interior of materials,thereby exhibiting stable microwave absorption(MA)performance and impedance-matching characteristics suitable across a wide temperature range.Consequently,exceptional MA properties can be achieved within the tem-perature range from 298 to 473 K.Furthermore,by carefully controlling the structural parameters in RGO metacomposites,both the resonant frequency and effective absorption bandwidth(EAB)can be optimized based on precise manipulation of equivalent electromagnetic parameters.This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.展开更多
in this paper, an experimental research the effect of ablating material on the reflection and the transmission of microwaves in arc-heated plasma flow is presented by using the C band microwave measuring system. The ...in this paper, an experimental research the effect of ablating material on the reflection and the transmission of microwaves in arc-heated plasma flow is presented by using the C band microwave measuring system. The results show that the ablating material with accidented surface and its high temperature have remarkably affected the reflection and the transmission of microwaves. The experiment proves that the system has outstanding precision and reliability.展开更多
A facile microwave-assisted hydrothermal route has been developed for a synthesis of versatile carbon materials. The monosaccharide fructose aqueous solution was adopted as the starting material, and the p H of the so...A facile microwave-assisted hydrothermal route has been developed for a synthesis of versatile carbon materials. The monosaccharide fructose aqueous solution was adopted as the starting material, and the p H of the solution was adjusted to be in acidic（pH 4）, neutral（pH 7） and basic（pH 10.5） conditions. The p H buffered fructose solutions were treated at different temperatures by a microwave-assisted hydrothermal technique. As-prepared carbon materials displayed p H and temperature dependent multi-morphologies（porous, spherical or core-shell）, which were determined by transmission and scanning electron microscopic analyses（TEM and SEM）. And the hypothesis of dehydration mechanism of hydrothermal synthesis was analyzed by ultraviolet extinction and Fourier transform infrared spectroscopy. It was found that as compared with normal hydrothermal synthesis, microwave assistance could efficiently increase the production yield and improve the spherical geometry of the carbon particles in neutral condition. By changing the p H of the system, acidic p H induces aggregation of the spheres, while basic p H produces more trends toward core-shell or sponge-like porous structure. The study opens a novel route to the production of polytropic carbon materials and suggests a potential niche market established from the green synthesis.展开更多
Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In t...Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In this study,a flake-like nickel cobaltate/re-duced graphene oxide/melamine-derived carbon foam(FNC/RGO/MDCF)was successfully fabricated through a combination of solvo-thermal treatment and high-temperature pyrolysis.Results indicated that RGO was evenly distributed in the MDCF skeleton,providing ef-fective support for the load growth of FNC on its surface.Sample S3,the FNC/RGO/MDCF composite prepared by solvothermal method for 16 h,exhibited a minimum reflection loss(RL_(min))of-66.44 dB at a thickness of 2.29 mm.When the thickness was reduced to 1.50 mm,the optimal effective absorption bandwidth was 3.84 GHz.Analysis of the absorption mechanism of FNC/RGO/MDCF revealed that its excellent absorption performance was primarily attributed to the combined effects of conduction loss,multiple reflection,scattering,in-terface polarization,and dipole polarization.展开更多
A Y-type hexaferrite rod with the composition of Ba2COl.8Cuo.2Fe12022 was presented as an absorbing material with high absorb- anee. Its high absorbance and wide absorption band result from ferromagnetic resonance （...A Y-type hexaferrite rod with the composition of Ba2COl.8Cuo.2Fe12022 was presented as an absorbing material with high absorb- anee. Its high absorbance and wide absorption band result from ferromagnetic resonance （FMR） that is self-biased by strong shape and mag- netocrystaUine anisotropy fields. Around the FMR frequency the specimen of the ferrite rods exhibits very high absorbance and the FMR frequency can be tuned by the rod dimension. In addition to the high absorbance and the wide tunable absorption band, the microwave ab- sorber has another advantage of light weight due to the use of the ferrite rods instead of ferrite slabs.展开更多
Radar Absorbing Materials(RAM)are a class of composites that can attenuate incident electromagnetic waves to avoid radar detection.Most carbon allotropes that have the potential to be used as RAM are either carbon nan...Radar Absorbing Materials(RAM)are a class of composites that can attenuate incident electromagnetic waves to avoid radar detection.Most carbon allotropes that have the potential to be used as RAM are either carbon nano-tubes(CNTs),graphene,carbon black(CB)and ultimately,sustainable porous carbon(SPC).Here,black wattle bark waste(following tannin extraction)was used as a sustainable source to produce SPC made from biomass waste.It was characterized and used as afiller for a silicone rubber matrix to produce aflexible RAM.The elec-tromagnetic performance of this composite was compared with composites made with commercial CB and CNT through reflection loss(RL),where-10 dB is equivalent to 90%of attenuation.These composites were evaluated in single-layer,double-layer,and as radar absorbing structures(RAS)with the aim of improving their effective absorption bandwidth(EAB)performances and a reduction in costs.The CNT composite presented a RL of-26.85 dB at 10.89 GHz and an EAB of 2.6 GHz with a 1.9 mm thickness,while the double-layer structures using CNT and SPC provided a RL of-19.74 dB at 10.75 GHz and an EAB of 2.51 GHz.Furthermore,the double-layer structures are~42%cheaper than the composite using only CNT since less material is used.Finally,the largest EAB was achieved with a RAS using SPC,reaching~2.8 GHz and a RL of-49.09 dB at 10.4 GHz.Summarizing,SPC made of black wattle bark waste can be a competitive,alternative material for use as RAM and RAS since it is cheaper,sustainable,and suitable for daily life uses such as absorbers for anechoic chambers,sensors,and elec-tromagnetic interference shields for electronics,wallets,vehicles,and others.展开更多
The experiment samples of La1-xSrxMn1-y FeyO3（x = 0. 15, 0.20, 0.23; y = 0. 10, 0. 12, 0.14, 0.16） were prepared by sol-gel process, and the loss tangent and absorption coefficient in the range of 2 - 18 GHz were me...The experiment samples of La1-xSrxMn1-y FeyO3（x = 0. 15, 0.20, 0.23; y = 0. 10, 0. 12, 0.14, 0.16） were prepared by sol-gel process, and the loss tangent and absorption coefficient in the range of 2 - 18 GHz were measured by HP8722 net analyzing apparatus. It is found that changing the content of Sr or Fe would effect the microwave absorbing. When the thickness of La1-x SrxMn1-y FeyO3 is 2 mm and x =0.20, y = 0.14, the capability of microwave absorbing is the best one. There are two absorption peaks; the maximum is 34 dB and effective band width with 10 dB and more reaches 6.2 GHz.展开更多
The film and the material have been confused in current microwave absorption theory.This confusion has led to the establishment of the wrong theory of impedance matching and the wrong absorption mechanism.Progress on ...The film and the material have been confused in current microwave absorption theory.This confusion has led to the establishment of the wrong theory of impedance matching and the wrong absorption mechanism.Progress on this subject has been reviewed in this work,and it shows that the wave mechanics theory which was proposed recently in the field of microwave absorption can be used to explain all aspects of the behavior of microwave absorption in film.Important aspects of the theory have been reviewed in detail involving the different absorption properties between film and material,the inverse relationship between frequency and film thickness that is related to the quarter-wavelength theory.展开更多
With the rapid advancement of information technology,electromagnetic radiation has become deeply integrated into nearly every aspect of modern life,from personal communication and industrial manufacturing to aerospace...With the rapid advancement of information technology,electromagnetic radiation has become deeply integrated into nearly every aspect of modern life,from personal communication and industrial manufacturing to aerospace and national defense infrastructures.As the electromagnetic environment has become increasingly complex and congested,electromagnetic waves have not only brought unprecedented convenience but also introduced serious challenges,including electromagnetic interference,radiation pollution,and information insecurity.Consequently,the rational design and development of microwave absorption materials(MAMs)are critically important for protecting human health,mitigating electromagnetic pollution,and strengthening information security in the information age.展开更多
Dielectric loss microwave absorbing materials have been widely used to mitigate electromagnetic interference and achieve radar stealth.Their design and optimization involve multiple electromagnetic parameters,such as ...Dielectric loss microwave absorbing materials have been widely used to mitigate electromagnetic interference and achieve radar stealth.Their design and optimization involve multiple electromagnetic parameters,such as dielectric constant,magnetic permeability,and loss factors.Traditional optimization methods typically require extensive computation and experimentation,making them inefficient and prone to local optima.In recent years,neural network algorithms,as effective nonlinear modeling and optimization tools,have found growing applications in optimizing the performance of absorbing materials.This paper explores the application of neural networks in optimizing electromagnetic parameters of dielectric loss microwave absorbing materials.Using neural networks,we predict the reflectivity values under different electromagnetic parameters and examine the patterns of variation with frequency and thickness.The results show that optimal reflectivity for various frequencies corresponds to different sets of electromagnetic parameters and matching thicknesses.As the frequency increases,the optimal dielectric constant values(both real and imaginary parts)concentrate in a lower range,especially when the material thickness is small.Finally,the consistency between predicted and experimentally measured reflectivity values confirms the reliability of the neural network-based predictions.展开更多
High-entropy alloys(HEAs)show excellent prospects in microwave absorbing materials due to their designable composition and variable electromagnetic properties.In this work,FeCoCrAl_(0.4)V_(x)HEAs with body-centered cu...High-entropy alloys(HEAs)show excellent prospects in microwave absorbing materials due to their designable composition and variable electromagnetic properties.In this work,FeCoCrAl_(0.4)V_(x)HEAs with body-centered cubic(BCC)single-phase solid solution structure were prepared by mechanical alloying and heat treatment.By varying the content of vanadium(V),the grain size,lattice constant,crystallinity,particle size,and microscopic morphology can be effectively adjusted,thereby enabling the optimization of their electromagnetic properties and microwave absorption performance.Doping a small amount of V element can refine the BCC grains,regulate the particle size,and enhance the electrical conductivity,which significantly improves the polarization relaxation,conduction loss,and eddy current loss of HEAs.In addition,the increased crystallinity and reduced lattice defects can enhance natural resonance loss at a high frequency(GHz),which will contribute to the improvement of impedance matching and electromagnetic attenuation.The annealed FeCoCrAl_(0.4)V_(0.2)HEAs exhibit excellent wave absorption properties,achieving a maximum reflection loss of-44.3 dB at 1.8 mm thickness and an effective absorption bandwidth of 4.0 GHz at 1.2 mm,respectively.This study provides a new strategy for developing lightweight and high-performance high-entropy alloys microwave absorbing materials.展开更多
Ag（Nb0.8Ta0.2）O3 ceramics were prepared by the traditional solid-state reaction method. The effect of CaF2 addition on the structure and dielectric properties of Ag（Nb0.8Ta0.2）O3 ceramics was investigated. The add...Ag（Nb0.8Ta0.2）O3 ceramics were prepared by the traditional solid-state reaction method. The effect of CaF2 addition on the structure and dielectric properties of Ag（Nb0.8Ta0.2）O3 ceramics was investigated. The addition of CaF2 led the ceramics to a larger grain size and distortion of lattice. With the addition of 4.5 wt.% CaF2, the permittivity of the ceramics increased from 442 to 1028, the dielectric loss decreased sharply from 6.12 × 10^-3 to 8.6 × 10^-4, and the temperature coefficient of capacitance decreased from 1834 ppm/℃ to -50 ppm/℃ （at 1 MHz）. These results indicated that the high permittivity was related with a large grain size, a low grain boundary density, and the weak Ta-O or Nb-O bond strength caused by the addition of CaF2.展开更多
The rise in electromagnetic pollution is a pressing issue,and the need for high-efficiency microwaveabsorbing materials(MAMs) is critical in safeguarding against this growing menace.This study employs a threestep synt...The rise in electromagnetic pollution is a pressing issue,and the need for high-efficiency microwaveabsorbing materials(MAMs) is critical in safeguarding against this growing menace.This study employs a threestep synthesis strategy:(ⅰ) using in situ synthesis technology to grow ZIF-67 on multi-walled carbon nanotubes to enhance the material's dielectric loss effect to improve microwave absorption(MA) properties.(ⅱ) High-temperature carbonization of ZIF-67 in a tube furnace yields MWCNTs@Co/C magnetic composites,where graphitic carbon and Co particles synergistic ally optimize dielectricmagnetic coupling.(ⅲ) The MWCNTs@Co/C@PANI ternary core-shell structure composites were coated with a poly aniline wrapping layer with moderate thickness using a common polymerization reaction,resulting in MWCNTs@Co/C@PANI ternary core-shell structural composites.The thickness of the polyaniline(PANI)coating on the surface of MWCNTs@Co/C can be modulated by changing the aniline concentration in the polymerization reaction.We systematically investigated the effects of different thickness layers of poly aniline on the MA properties of MWCNTs@Co/C and analyzed the reasons for their effects.The introduction of PANI increases heterointerfaces,enhancing interfacial polarization and optimizing impedance matching.With an optimal PANI coating thickness,the composite achieves ultra-wide absorption bandwidth and efficient microwave absorption.The results show that when the thickness of the coaxial annular absorber made of 20 wt% MWCNTs@Co/C@PANI is just 2.5 mm,the minimum reflection loss(RLmin) is-50.6 dB,and an extremely wide effective absorption bandwidth(EAB) of 7.09 GHz can be achieved when the thickness is just 2.4 mm.In this study,conductive polymers were compounded on the surfaces of carbon materials and magnetic nanomaterials derived from MOFs to form a ternary core-shell structure,providing a novel tunable approach for the research and development of MAMs.展开更多
A plasma-microwave absorptive material(MAM)-plasma sandwich structure is presented to protect the electronic device against high power electromagnetic pulse.The model of electromagnetic wave reflected by and transmitt...A plasma-microwave absorptive material(MAM)-plasma sandwich structure is presented to protect the electronic device against high power electromagnetic pulse.The model of electromagnetic wave reflected by and transmitting through the structure is established.Based on the characteristic parameters of plasma generated by discharge and usual MAM,the electromagnetic transmissive properties of the sandwich structure are investigated by the method of finite difference in time domain.The results indicate that in a rather broad frequency range,the electromagnetic attenuations by the structure are obviously better than the sum of attenuations resulted from plasma and MAM respectively.The models and results presented are instructive for electromagnetic pulse protection.展开更多
基金supported by the National Natural Science Foundation of China(No.52402078)Yunnan Major Scientific and Technological Projects(No.202302AG050010)+1 种基金Yunnan Fundamental Research Projects(No.202201BE070001-008)the National Key Research and Development Program of China(No.2022YFB3708600)。
文摘In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial weight percent of Sr_(2)TiMoO_(6),were synthesized using the solid-state reaction method.Compared with STM100,some equilibrium phases,including SrTiO_(3),Mo,Sr_(8)(Al1_(2)O_(24))(MoO_(4))_(2)and a few undefined ones,are presented in the composites as evidenced by X-ray diffraction results and scanning electron microscopy due to the chemical reaction between Sr_(2)TiMoO_(6)and Al_(2)O_(3)component.Besides conductance loss,heterogeneous interfaces between various equilibrium phases introduce interfacial polarization,which causes an enhancement of dissipation for the incident electromagnetic wave.Among the synthesized samples,STM80 presents the best microwave absorbing properties.It has a minimum reflection loss(RLmin)of-26 dB and an effective absorbing bandwidth up to 2.7 GHz when the thickness is only 1 mm.This indicates that STM80 is a new type of microwave absorbing material with strong absorption and ultrathin thickness.
基金Project supported by National Research and Innovation Agency through Rumah Program Organisasi Riset Nanoteknologi dan Material Maj u(ORNM)2024Indonesia Ministry of Finance through the competitive research program of RISPRO Kompetisi(PRJ-68/LPDP/2023)。
文摘Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms of scalability and mass production for practical application.In this work,we reported a successful attempt in modifying the 3D structure of mesoporous lanthanum oxide(La_(2)O_(3))for effective broadband MAMs candidate via simple co-precipitation process.The inclusion of cetyltrimethylammonium bromide(CTAB)and hydrothermal aging treatment result in a significant transformation of La_(2)O_(3)particles from their original polygonal form to a 3D coral-like and nano needle-like structure.The utilization of CTAB and hydrothermal aging results in the increase of surface area and a two-fold increase in pore volume of the resulting La_(2)O_(3).Due to its unique 3D structure,the 3D coral-like and nano needle-like La_(2)O_(3)materials possess a broadband electromagnetic(EM)wave absorption characteristic with the effective absorption bandwidth(EAB)covering the C-band frequency range.Specifically,in the La_(2)O_(3)C-H sample(with CTAB-with hydrothermal),it exhibits strong EM wave absorption with a reflection loss(RL)value of-33.07 dB which equals to 99.95%EM wave absorption at a thickness of only 1.50 mm.The detailed analysis of EM wave absorption properties reveals that the improvement of La_(2)O_(3)materials to attenuate EM wave energy arises from the dielectric loss phenomenon,the enhanced interfacial polarization,multiple reflections mechanism,and conduction loss mechanism induced by the 3D structural formation of the La_(2)O_(3)structure.This work proposes a novel and efficient approach in synthesizing and modifying 3D materials for effective broadband EM wave absorption.
基金financial support from Ministry of Science and Technology of China(MoST,2016YFA0200200)the National Natural Science Foundation of China(NSFC,21875114,51373078,and 51422304)NSF of Tianjin City(15JCYBJC17700)。
文摘The development of microwave absorption materials(MAMs) is a considerable important topic because our living space is crowed with electromagnetic wave which threatens human’s health.And MAMs are also used in radar stealth for protecting the weapons from being detected.Many nanomaterials were studied as MAMs,but not all of them have the satisfactory performance.Recently,metal-organic frameworks(MOFs) have attracted tremendous attention owing to their tunable chemical structures,diverse properties,large specific surface area and uniform pore distribution.MOF can transform to porous carbon(PC) which is decorated with metal species at appropriate pyrolysis temperature.However,the loss mechanism of pure MOF-derived PC is often relatively simple.In order to further improve the MA performance,the MOFs coupled with other loss materials are a widely studied method.In this review,we summarize the theories of MA,the progress of different MOF-derived PC-based MAMs,tunable chemical structures incorporated with dielectric loss or magnetic loss materials.The different MA performance and mechanisms are discussed in detail.Finally,the shortcomings,challenges and perspectives of MOF-derived PC-based MAMs are also presented.We hope this review could provide a new insight to design and fabricate MOF-derived PC-based MAMs with better fundamental understanding and practical application.
基金Open access funding provided by Shanghai Jiao Tong University.
文摘Microwave has been widely used in many fields,including communication,medical treatment and military industry;however,the corresponding generated radiations have been novel hazardous sources of pollution threating human’s daily life.Therefore,designing high-performance microwave absorption materials(MAMs)has become an indispensable requirement.Recently,metal-organic frameworks(MOFs)have been considered as one of the most ideal precursor candidates of MAMs because of their tunable structure,high porosity and large specific surface area.Usually,MOF-derived MAMs exhibit excellent electrical conductivity,good magnetism and sufficient defects and interfaces,providing obvious merits in both impedance matching and microwave loss.In this review,the recent research progresses on MOF-derived MAMs were profoundly reviewed,including the categories of MOFs and MOF composites precursors,design principles,preparation methods and the relationship between mechanisms of microwave absorption and microstructures of MAMs.Finally,the current challenges and prospects for future opportunities of MOF-derived MAMs are also discussed.
基金Natural Science Foundation of Shandong Province(Nos.ZR2023QE329 and ZR2022ZD09)National Natural Science Foundation of China(Nos.52075524 and 21972153)+1 种基金Youth Innovation Promotion Association of the CAS(2022429)Gansu Province Science and Technology Plan(No.22JR5RA094).
文摘Due to the rapid development of radar technology,the demand for absorbing stealth materials is increas-ing,and ultra-broadband absorption(effective absorption bandwidth>8 GHz)has become an inevitable requirement.As a new type of two-dimensional material,MXene material possesses the characteristics of excellent wave absorbing material due to its easy preparation,easy modulation of defects and sur-face functional groups,and high conductivity.This work summarizes the absorbing theory and research progress on MXene-based absorbing materials in recent years,including pure MXene absorbing materials and MXene-based magnetic or dielectric composite materials with multiple losses.Some shortcomings and research directions of MXene-based materials were pointed out.Currently,research on MXene-based absorbent materials is thriving and in a state of vigorous development.Excellent absorbent materials have been reported,but their shortcomings are also apparent.The factors that affect the performance of MXene-based absorbent materials are complex,and the absorption mechanism is relatively simple.Further systematic and detailed research is needed to clarify these influencing mechanisms,broaden the absorption bandwidth,and reduce the matching thickness to meet practical usage requirements in the future.
基金Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20121101110014)
文摘Magnesium-substituted Mn0.8Zn0.2Fe2O4 ferrite is synthesized by the sol–gel combustion method using citrate acid as the complex agent. The electromagnetic absorbing behaviors of ferrite/polymer coatings fabricated by dispersing Mn–Zn ferrite into epoxy resin （EP） are studied. The microstructure and morphology are characterized by X-ray diffraction and scanning electron microscope. Complex permittivity, complex permeability, and reflection loss of ferrite/EP composite coating are investigated in a low frequency range. It is found that the prepared ferrite particles are traditional cubic spinel ferrite particles with an average size of 200 nm. The results reveal that the electromagnetic microwave absorbing properties are significantly influenced by the weight ratio of ferrite to polymer. The composites with a weight ratio of ferrite/polymer being 3：20 have a maximum reflection loss of –16 dB and wide absorbing band. Thus, the Mn–Zn ferrite is the potential candidate in electromagnetic absorbing application in the low frequency range （10 MHz–1 GHz）.
基金supported by the National Nature Science Foundation of China(Nos.22305066 and 52372041).
文摘High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorp-tion(EMWA)performance at elevated temperatures,which severely restricts their practical application.In this study,we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide(RGO)/epoxy resin(EP)metacomposites that integrate both electromagnetic parameters and metamaterial design concepts.Due to the discrete distribution of the units,electromagnetic waves can more easily penetrate the interior of materials,thereby exhibiting stable microwave absorption(MA)performance and impedance-matching characteristics suitable across a wide temperature range.Consequently,exceptional MA properties can be achieved within the tem-perature range from 298 to 473 K.Furthermore,by carefully controlling the structural parameters in RGO metacomposites,both the resonant frequency and effective absorption bandwidth(EAB)can be optimized based on precise manipulation of equivalent electromagnetic parameters.This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.
文摘in this paper, an experimental research the effect of ablating material on the reflection and the transmission of microwaves in arc-heated plasma flow is presented by using the C band microwave measuring system. The results show that the ablating material with accidented surface and its high temperature have remarkably affected the reflection and the transmission of microwaves. The experiment proves that the system has outstanding precision and reliability.
基金Funded by the National Natural Science Foundation of China(NSFC)(Nos.51408073,51678080 and 51678081)
文摘A facile microwave-assisted hydrothermal route has been developed for a synthesis of versatile carbon materials. The monosaccharide fructose aqueous solution was adopted as the starting material, and the p H of the solution was adjusted to be in acidic（pH 4）, neutral（pH 7） and basic（pH 10.5） conditions. The p H buffered fructose solutions were treated at different temperatures by a microwave-assisted hydrothermal technique. As-prepared carbon materials displayed p H and temperature dependent multi-morphologies（porous, spherical or core-shell）, which were determined by transmission and scanning electron microscopic analyses（TEM and SEM）. And the hypothesis of dehydration mechanism of hydrothermal synthesis was analyzed by ultraviolet extinction and Fourier transform infrared spectroscopy. It was found that as compared with normal hydrothermal synthesis, microwave assistance could efficiently increase the production yield and improve the spherical geometry of the carbon particles in neutral condition. By changing the p H of the system, acidic p H induces aggregation of the spheres, while basic p H produces more trends toward core-shell or sponge-like porous structure. The study opens a novel route to the production of polytropic carbon materials and suggests a potential niche market established from the green synthesis.
基金support of the Key Science Research Project in Colleges and Universities of Anhui Province,China(No.2022AH050813)the Medical Special Cultivation Project of Anhui University of Science and Technology,China(No.YZ2023H2A002).
文摘Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In this study,a flake-like nickel cobaltate/re-duced graphene oxide/melamine-derived carbon foam(FNC/RGO/MDCF)was successfully fabricated through a combination of solvo-thermal treatment and high-temperature pyrolysis.Results indicated that RGO was evenly distributed in the MDCF skeleton,providing ef-fective support for the load growth of FNC on its surface.Sample S3,the FNC/RGO/MDCF composite prepared by solvothermal method for 16 h,exhibited a minimum reflection loss(RL_(min))of-66.44 dB at a thickness of 2.29 mm.When the thickness was reduced to 1.50 mm,the optimal effective absorption bandwidth was 3.84 GHz.Analysis of the absorption mechanism of FNC/RGO/MDCF revealed that its excellent absorption performance was primarily attributed to the combined effects of conduction loss,multiple reflection,scattering,in-terface polarization,and dipole polarization.
基金supported by the National Natural Science Foundation of China (No.50702005)the Natural Science Foundation of the Education Department of Henan Province,China (No.2010A430012)
文摘A Y-type hexaferrite rod with the composition of Ba2COl.8Cuo.2Fe12022 was presented as an absorbing material with high absorb- anee. Its high absorbance and wide absorption band result from ferromagnetic resonance （FMR） that is self-biased by strong shape and mag- netocrystaUine anisotropy fields. Around the FMR frequency the specimen of the ferrite rods exhibits very high absorbance and the FMR frequency can be tuned by the rod dimension. In addition to the high absorbance and the wide tunable absorption band, the microwave ab- sorber has another advantage of light weight due to the use of the ferrite rods instead of ferrite slabs.
文摘Radar Absorbing Materials(RAM)are a class of composites that can attenuate incident electromagnetic waves to avoid radar detection.Most carbon allotropes that have the potential to be used as RAM are either carbon nano-tubes(CNTs),graphene,carbon black(CB)and ultimately,sustainable porous carbon(SPC).Here,black wattle bark waste(following tannin extraction)was used as a sustainable source to produce SPC made from biomass waste.It was characterized and used as afiller for a silicone rubber matrix to produce aflexible RAM.The elec-tromagnetic performance of this composite was compared with composites made with commercial CB and CNT through reflection loss(RL),where-10 dB is equivalent to 90%of attenuation.These composites were evaluated in single-layer,double-layer,and as radar absorbing structures(RAS)with the aim of improving their effective absorption bandwidth(EAB)performances and a reduction in costs.The CNT composite presented a RL of-26.85 dB at 10.89 GHz and an EAB of 2.6 GHz with a 1.9 mm thickness,while the double-layer structures using CNT and SPC provided a RL of-19.74 dB at 10.75 GHz and an EAB of 2.51 GHz.Furthermore,the double-layer structures are~42%cheaper than the composite using only CNT since less material is used.Finally,the largest EAB was achieved with a RAS using SPC,reaching~2.8 GHz and a RL of-49.09 dB at 10.4 GHz.Summarizing,SPC made of black wattle bark waste can be a competitive,alternative material for use as RAM and RAS since it is cheaper,sustainable,and suitable for daily life uses such as absorbers for anechoic chambers,sensors,and elec-tromagnetic interference shields for electronics,wallets,vehicles,and others.
文摘The experiment samples of La1-xSrxMn1-y FeyO3（x = 0. 15, 0.20, 0.23; y = 0. 10, 0. 12, 0.14, 0.16） were prepared by sol-gel process, and the loss tangent and absorption coefficient in the range of 2 - 18 GHz were measured by HP8722 net analyzing apparatus. It is found that changing the content of Sr or Fe would effect the microwave absorbing. When the thickness of La1-x SrxMn1-y FeyO3 is 2 mm and x =0.20, y = 0.14, the capability of microwave absorbing is the best one. There are two absorption peaks; the maximum is 34 dB and effective band width with 10 dB and more reaches 6.2 GHz.
文摘The film and the material have been confused in current microwave absorption theory.This confusion has led to the establishment of the wrong theory of impedance matching and the wrong absorption mechanism.Progress on this subject has been reviewed in this work,and it shows that the wave mechanics theory which was proposed recently in the field of microwave absorption can be used to explain all aspects of the behavior of microwave absorption in film.Important aspects of the theory have been reviewed in detail involving the different absorption properties between film and material,the inverse relationship between frequency and film thickness that is related to the quarter-wavelength theory.
文摘With the rapid advancement of information technology,electromagnetic radiation has become deeply integrated into nearly every aspect of modern life,from personal communication and industrial manufacturing to aerospace and national defense infrastructures.As the electromagnetic environment has become increasingly complex and congested,electromagnetic waves have not only brought unprecedented convenience but also introduced serious challenges,including electromagnetic interference,radiation pollution,and information insecurity.Consequently,the rational design and development of microwave absorption materials(MAMs)are critically important for protecting human health,mitigating electromagnetic pollution,and strengthening information security in the information age.
文摘Dielectric loss microwave absorbing materials have been widely used to mitigate electromagnetic interference and achieve radar stealth.Their design and optimization involve multiple electromagnetic parameters,such as dielectric constant,magnetic permeability,and loss factors.Traditional optimization methods typically require extensive computation and experimentation,making them inefficient and prone to local optima.In recent years,neural network algorithms,as effective nonlinear modeling and optimization tools,have found growing applications in optimizing the performance of absorbing materials.This paper explores the application of neural networks in optimizing electromagnetic parameters of dielectric loss microwave absorbing materials.Using neural networks,we predict the reflectivity values under different electromagnetic parameters and examine the patterns of variation with frequency and thickness.The results show that optimal reflectivity for various frequencies corresponds to different sets of electromagnetic parameters and matching thicknesses.As the frequency increases,the optimal dielectric constant values(both real and imaginary parts)concentrate in a lower range,especially when the material thickness is small.Finally,the consistency between predicted and experimentally measured reflectivity values confirms the reliability of the neural network-based predictions.
基金supported by the National Natural Science Foundation of China(No.52401035)the Foundation of National Key Laboratory for Remanufacturing(No.61420052023WD019)+2 种基金the Natural Science Foundation of Liaoning Province(No.2024-BS-201)the Basic Scientific Research Project of Liaoning Provincial Department of Education(No.JYTQN2023004)the Dalian High-level Talents Innovation Support Program(No.2021RD06).
文摘High-entropy alloys(HEAs)show excellent prospects in microwave absorbing materials due to their designable composition and variable electromagnetic properties.In this work,FeCoCrAl_(0.4)V_(x)HEAs with body-centered cubic(BCC)single-phase solid solution structure were prepared by mechanical alloying and heat treatment.By varying the content of vanadium(V),the grain size,lattice constant,crystallinity,particle size,and microscopic morphology can be effectively adjusted,thereby enabling the optimization of their electromagnetic properties and microwave absorption performance.Doping a small amount of V element can refine the BCC grains,regulate the particle size,and enhance the electrical conductivity,which significantly improves the polarization relaxation,conduction loss,and eddy current loss of HEAs.In addition,the increased crystallinity and reduced lattice defects can enhance natural resonance loss at a high frequency(GHz),which will contribute to the improvement of impedance matching and electromagnetic attenuation.The annealed FeCoCrAl_(0.4)V_(0.2)HEAs exhibit excellent wave absorption properties,achieving a maximum reflection loss of-44.3 dB at 1.8 mm thickness and an effective absorption bandwidth of 4.0 GHz at 1.2 mm,respectively.This study provides a new strategy for developing lightweight and high-performance high-entropy alloys microwave absorbing materials.
基金supported by the Program for New Century Excellent Talents in Universities (NCET)the National High-Tech Research and Development Program of China (No. 2007AA03Z423)China Postdoctoral Science Foundation
文摘Ag（Nb0.8Ta0.2）O3 ceramics were prepared by the traditional solid-state reaction method. The effect of CaF2 addition on the structure and dielectric properties of Ag（Nb0.8Ta0.2）O3 ceramics was investigated. The addition of CaF2 led the ceramics to a larger grain size and distortion of lattice. With the addition of 4.5 wt.% CaF2, the permittivity of the ceramics increased from 442 to 1028, the dielectric loss decreased sharply from 6.12 × 10^-3 to 8.6 × 10^-4, and the temperature coefficient of capacitance decreased from 1834 ppm/℃ to -50 ppm/℃ （at 1 MHz）. These results indicated that the high permittivity was related with a large grain size, a low grain boundary density, and the weak Ta-O or Nb-O bond strength caused by the addition of CaF2.
基金financially supported by the National Natural Science Foundation of China Project(No.52163001)Guizhou Provincial Science and Technology Program Project Grant(Nos.Qiankehe Platform Talents-CXTD[2021]005,Qiankehe Platform Talents-GCC[2022]010-1,Qiankehe Platform Talents-GCC[2023]035,and Qiankehe Platform TalentsCXTD[2023]003)+6 种基金Guizhou Minzu University Research Platform Grant(No.GZMUGCZX[2021]01)the Central Guided Local Science and Technology Development Funds Project(No.Qiankehe Zhong Yindi[2023]035)the Green Chemistry and Resource Environment Innovation Team of Guizhou Higher Education Institutions(No.Guizhou Education and Technology[2022]No.13)the Doctor Startup Fund of Guizhou Minzu University(No.GZMUZK[2024]QD77)Guizhou Province Special Fund for innovative capacity building of scientific research institutions(No.Qiankehe Fuqi[2023]001,and Qiankehe Fuqi[2024]002-1)Guizhou Provincial Science and Technology Program Project(No.Qiankehe Platform KXJZ[2024]022)the Centralized Guided Local Science and Technology Development Funds Project(No.Qianke Hezhong Cidi(2025)013)
文摘The rise in electromagnetic pollution is a pressing issue,and the need for high-efficiency microwaveabsorbing materials(MAMs) is critical in safeguarding against this growing menace.This study employs a threestep synthesis strategy:(ⅰ) using in situ synthesis technology to grow ZIF-67 on multi-walled carbon nanotubes to enhance the material's dielectric loss effect to improve microwave absorption(MA) properties.(ⅱ) High-temperature carbonization of ZIF-67 in a tube furnace yields MWCNTs@Co/C magnetic composites,where graphitic carbon and Co particles synergistic ally optimize dielectricmagnetic coupling.(ⅲ) The MWCNTs@Co/C@PANI ternary core-shell structure composites were coated with a poly aniline wrapping layer with moderate thickness using a common polymerization reaction,resulting in MWCNTs@Co/C@PANI ternary core-shell structural composites.The thickness of the polyaniline(PANI)coating on the surface of MWCNTs@Co/C can be modulated by changing the aniline concentration in the polymerization reaction.We systematically investigated the effects of different thickness layers of poly aniline on the MA properties of MWCNTs@Co/C and analyzed the reasons for their effects.The introduction of PANI increases heterointerfaces,enhancing interfacial polarization and optimizing impedance matching.With an optimal PANI coating thickness,the composite achieves ultra-wide absorption bandwidth and efficient microwave absorption.The results show that when the thickness of the coaxial annular absorber made of 20 wt% MWCNTs@Co/C@PANI is just 2.5 mm,the minimum reflection loss(RLmin) is-50.6 dB,and an extremely wide effective absorption bandwidth(EAB) of 7.09 GHz can be achieved when the thickness is just 2.4 mm.In this study,conductive polymers were compounded on the surfaces of carbon materials and magnetic nanomaterials derived from MOFs to form a ternary core-shell structure,providing a novel tunable approach for the research and development of MAMs.
文摘A plasma-microwave absorptive material(MAM)-plasma sandwich structure is presented to protect the electronic device against high power electromagnetic pulse.The model of electromagnetic wave reflected by and transmitting through the structure is established.Based on the characteristic parameters of plasma generated by discharge and usual MAM,the electromagnetic transmissive properties of the sandwich structure are investigated by the method of finite difference in time domain.The results indicate that in a rather broad frequency range,the electromagnetic attenuations by the structure are obviously better than the sum of attenuations resulted from plasma and MAM respectively.The models and results presented are instructive for electromagnetic pulse protection.
