Interpreting experimental diagnostics data in tokamaks,while considering non-ideal effects,is challenging due to the complexity of plasmas.To address this challenge,a general synthetic diagnostics(GSD)platform has bee...Interpreting experimental diagnostics data in tokamaks,while considering non-ideal effects,is challenging due to the complexity of plasmas.To address this challenge,a general synthetic diagnostics(GSD)platform has been established that facilitates microwave imaging reflectometry and electron cyclotron emission imaging.This platform utilizes plasma profiles as input and incorporates the finite-difference time domain,ray tracing and the radiative transfer equation to calculate the propagation of plasma spontaneous radiation and the external electromagnetic field in plasmas.Benchmark tests for classical cases have been conducted to verify the accuracy of every core module in the GSD platform.Finally,2D imaging of a typical electron temperature distribution is reproduced by this platform and the results are consistent with the given real experimental data.This platform also has the potential to be extended to 3D electromagnetic field simulations and other microwave diagnostics such as cross-polarization scattering.展开更多
As rice consumption increases,ensuring its safety has become a priority for the food industry.To address this concern,the industry is exploring a single-pass microbial inactivation treatment at the rough rice stage.In...As rice consumption increases,ensuring its safety has become a priority for the food industry.To address this concern,the industry is exploring a single-pass microbial inactivation treatment at the rough rice stage.In this study,a long-grain rice variety,RT7321[21.2%wet basis(WB)and a 20 mm bed thickness]was exposed to microwave radiation(915 MHz frequency)at powers of 16,18,and 20 kW for durations of 1,2,and 3 min.We found that the highest microwave power(20 kW)and the longest exposure duration(3 min)produced the greatest reduction in total aerobic count and total fungal count,reducing them by up to 1.21 and 5.01 log(CFU/g),respectively.Our findings provided insights into the used to high-power,shortduration 915 MHz microwave technology for decontamination purposes in rough rice to help improve the microbial safety of rice.The aim is to develop a single-pass drying approach for microbial inactivation in rice processing facilities while ensuring that the yield and quality is not compromised.展开更多
High-performance microwave absorption(MA) materials must be studied immediately since electromagnetic pollution has become a problem that cannot be disregarded. A straightforward composite material, comprising hollow ...High-performance microwave absorption(MA) materials must be studied immediately since electromagnetic pollution has become a problem that cannot be disregarded. A straightforward composite material, comprising hollow MXene spheres loaded with C–Co frameworks, was prepared to develop multiwalled carbon nanotubes(MWCNTs). A high impedance and suitable morphology were guaranteed by the C–Co exoskeleton, the attenuation ability was provided by the MWCNTs endoskeleton, and the material performance was greatly enhanced by the layered core–shell structure. When the thickness was only 2.04 mm, the effective absorption bandwidth was 5.67 GHz, and the minimum reflection loss(RLmin) was-70.70 d B. At a thickness of 1.861 mm, the sample calcined at 700 ℃ had a RLmin of-63.25 d B. All samples performed well with a reduced filler ratio of 15 wt%. This paper provides a method for making lightweight core–shell composite MA materials with magnetoelectric synergy.展开更多
Urea holds promise as an alternative water-oxidation substrate in electrolytic cells.High-valence nickelbased spinel,especially after heteroatom doping,excels in urea oxidation reactions(UOR).However,traditional spine...Urea holds promise as an alternative water-oxidation substrate in electrolytic cells.High-valence nickelbased spinel,especially after heteroatom doping,excels in urea oxidation reactions(UOR).However,traditional spinel synthesis methods with prolonged high-temperature reactions lack kinetic precision,hindering the balance between controlled doping and highly active two-dimensional(2D)porous structures design.This significantly impedes the identification of electron configuration-dependent active sites in doped 2D nickel-based spinels.Herein,we present a microwave shock method for the preparation of 2D porous NiCo_(2)O_(4)spinel.Utilizing the transient on-off property of microwave pulses for precise heteroatom doping and 2D porous structural design,non-metal doping(boron,phosphorus,and sulfur)with distinct extranuclear electron disparities serves as straightforward examples for investigation.Precise tuning of lattice parameter reveals the impact of covalent bond strength on NiCo_(2)O_(4)structural stability.The introduced defect levels induce unpaired d-electrons in transition metals,enhancing the adsorption of electron-donating amino groups in urea molecules.Simultaneously,Bode plots confirm the impact mechanism of rapid electron migration caused by reduced band gaps on UOR activity.The prepared phosphorus-doped 2D porous NiCo_(2)O_(4),with optimal electron configuration control,outperforms most reported spinels.This controlled modification strategy advances understanding theoretical structure-activity mechanisms of high-performance 2D spinels in UOR.展开更多
The incorporation of partial A-site substitution in perovskite oxides represents a promising strategy for precisely controlling the electronic configuration and enhancing its intrinsic catalytic activity.Conventional ...The incorporation of partial A-site substitution in perovskite oxides represents a promising strategy for precisely controlling the electronic configuration and enhancing its intrinsic catalytic activity.Conventional methods for A-site substitution typically involve prolonged high-temperature processes.While these processes promote the development of unique nanostructures with highly exposed active sites,they often result in the uncontrolled configuration of introduced elements.Herein,we present a novel approach for synthesizing two-dimensional(2D)porous GdFeO_(3) perovskite with A-site strontium(Sr)substitution utilizing microwave shock method.This technique enables precise control of the Sr content and simultaneous construction of 2D porous structures in one step,capitalizing on the advantages of rapid heating and cooling(temperature~1100 K,rate~70 K s^(-1)).The active sites of this oxygen-rich defect structure can be clearly revealed through the simulation of the electronic configuration and the comprehensive analysis of the crystal structure.For electrocatalytic oxygen evolution reaction application,the synthesized 2D porous Gd_(0.8)Sr_(0.2)FeO_(3) electrocatalyst exhibits an exceptional overpotential of 294 mV at a current density of 10 mA cm^(-2)and a small Tafel slope of 55.85 mV dec^(-1)in alkaline electrolytes.This study offers a fresh perspective on designing crystal configurations and the construction of nanostructures in perovskite.展开更多
The three-orbit constellation can comprehensively increase the spatial coverage of polar-orbiting satellites,but the polar-orbiting satellites currently in operation are only mid-morning-orbit and afternoon-orbit sate...The three-orbit constellation can comprehensively increase the spatial coverage of polar-orbiting satellites,but the polar-orbiting satellites currently in operation are only mid-morning-orbit and afternoon-orbit satellites.Fengyun-3E(FY-3E)was launched successfully on 5 July 2021 in China.As an early-morning-orbit satellite,FY-3E can help form a complete three-orbit observation system together with the mid-morning and afternoon satellites in the current mainstream operational system.In this study,we investigate the added benefit of FY-3E microwave sounding observations to the midmorning-orbit Meteorological Operational satellite-B(Met Op-B)and afternoon-orbit Fengyun-3D(FY-3D)microwave observations in the Chinese Meteorological Administration global forecast system(CMA-GFS).The results show that the additional FY-3E microwave temperature sounder-3(MWTS-3)and microwave humidity sounder-2(MWHS-2)data can increase the global coverage of microwave temperature and humidity sounding data by 14.8% and 10.6%,respectively.It enables the CMA-GFS to achieve nearly 100% global coverage of microwave-sounding observations at each analysis time.Furthermore,after effective quality control and bias correction,the global biases and standard deviations of the differences between observations and model simulations are also reduced.Based on the Advanced Microwave Sounding Unit A and the Microwave Humidity Sounder onboard Met Op-B,and the MWTS-2 and MWHS-2 onboard FY-3D,adding the microwave sounding data of FY-3E can further reduce the errors of analysis results and improve the global prediction skills of CMA-GFS,especially for the southern-hemisphere forecasts within 96 hours,all of which are significant at the 95% confidence level.展开更多
La_(0.8)A_(0.2)NiO_(3) (A=K,Ba,Y) catalysts supported on the microwave-absorbing ceramic heating carrier were prepared by the sol-gel method.The crystalline phase and the catalytic activity of the La_(0.8)A_(0.2)NiO_(...La_(0.8)A_(0.2)NiO_(3) (A=K,Ba,Y) catalysts supported on the microwave-absorbing ceramic heating carrier were prepared by the sol-gel method.The crystalline phase and the catalytic activity of the La_(0.8)A_(0.2)NiO_(3)catalysts were characterized by XRD and H_(2) temperature-programmed reduction (TPR).The effects of reaction temperature,oxygen concentration,and gas flow rate on the direct decomposition of nitric oxide over the synthesized catalysts were studied under microwave irradiation (2.45 GHz).The XRD results indicated that the La_(0.8)A_(0.2)NiO_(3) catalysts formed an ABO_(3) perovskite structure,and the H_(2)-TPR results revealed that the relative reducibility of the catalysts increased in the order of La_(0.8)K_(0.2)NiO_(3)>La_(0.8)Ba_(0.2)NiO_(3)>La_(0.8)Y_(0.2)Ni O_(3).Under microwave irradiation,the highest NO conversion amounted to 98.9%,which was obtained with the La_(0.8)K_(0.2)NiO_(3) catalyst at 400℃.The oxygen concentration did not inhibit the NO decomposition on the La_(0.8)A_(0.2)NiO_(3) catalysts,thus the N_(2) selectivity exceeded 99.8%under excess oxygen at 550℃.The NOconversion of the La_(0.8)A_(0.2)NiO_(3) catalysts decreased linearly with the increase in the gas flow rate.展开更多
The well-designed composite with satisfactory electromagnetic microwave absorption at high temperatures remains a serious challenge.Herein,we fabricated a resorcinol-formaldehyde/silica dioxide composite aerogel(RF/Si...The well-designed composite with satisfactory electromagnetic microwave absorption at high temperatures remains a serious challenge.Herein,we fabricated a resorcinol-formaldehyde/silica dioxide composite aerogel(RF/SiO_(2))with a three-dimensional network structure using sol-gel,atmospheric pressure drying technique as well as heat-treated processes to achieve enhanced microwave absorption capabilities in the low frequency range.The pristine RF/SiO_(2)aerogel presented a typical micropores structure with a surface area,porous volume,and density of 146.82 m^(2)/g,62.40%,and 0.28 cm^(3)/g,respectively.Remarkably,the RF/SiO_(2)aerogel showed an effective absorption bandwidth of 3.56 GHz and a minimum reflection loss value of-46.10 d B at 2.25 mm after being heat-treated at 1500°C,while the maximum effective absorption bandwidth was 3.60 GHz at 2.30 mm.The intricate three-dimensional networks possessed remarkable impedance matching,multiple attenuation mechanisms,interfacial polarization,and dielectric loss,which were attributed to the exceptional ability to absorb electromagnetic microwaves.It offered a fresh approach to creating adaptable and effective microwave absorption materials in military defense.展开更多
Sea surface temperature(SST)is one of the important parameters of global ocean and climate research,which can be retrieved by satellite infrared and passive microwave remote sensing instruments.While satellite infrare...Sea surface temperature(SST)is one of the important parameters of global ocean and climate research,which can be retrieved by satellite infrared and passive microwave remote sensing instruments.While satellite infrared SST offers high spatial resolution,it is limited by cloud cover.On the other hand,passive microwave SST provides all-weather observation but suffers from poor spatial resolution and susceptibility to environmental factors such as rainfall,coastal effects,and high wind speeds.To achieve high-precision,comprehensive,and high-resolution SST data,it is essential to fuse infrared and microwave SST measurements.In this study,data from the Fengyun-3D(FY-3D)medium resolution spectral imager II(MERSI-II)SST and microwave imager(MWRI)SST were fused.Firstly,the accuracy of both MERSIII SST and MWRI SST was verified,and the latter was bilinearly interpolated to match the 5km resolution grid of MERSI SST.After pretreatment and quality control of MERSI SST and MWRI SST,a Piece-Wise Regression method was employed to correct biases in MWRI SST.Subsequently,SST data were selected based on spatial resolution and accuracy within a 3-day window of the analysis date.Finally,an optimal interpolation method was applied to fuse the FY-3D MERSI-II SST and MWRI SST.The results demonstrated a significant improvement in spatial coverage compared to MERSI-II SST and MWRI SST.Furthermore,the fusion SST retained true spatial distribution details and exhibited an accuracy of–0.12±0.74℃compared to OSTIA SST.This study has improved the accuracy of FY satellite fusion SST products in China.展开更多
The preparation process of sodium molybdate has the disadvantages of high energy consumption,low thermal efficiency,and high raw material requirement of molybdenum trioxide,in order to realize the green and efficient ...The preparation process of sodium molybdate has the disadvantages of high energy consumption,low thermal efficiency,and high raw material requirement of molybdenum trioxide,in order to realize the green and efficient development of molybdenum concentrate resources,this paper proposes a new process for efficient recovery of molybdenum from molybdenum concentrate and preparation of sodium molybdate by microwave-enhanced roasting and alkali leaching.Thermodynamic analysis indicated the feasibility of oxidation roasting of molybdenum concentrate.The effects of roasting temperature,holding time,and power-to-mass ratio on the oxidation product and leaching product sodium molybdate (Na_(2)MoO_(4)·2H_(2)O) were investigated.Under the optimal process conditions:roasting temperature of 700℃,holding time of 110 min,and power-to-mass ratio of 110 W/g,the molybdenum state of existence was converted from MoS_(2) to Mo O3.The process of preparing sodium molybdate by alkali leaching of molybdenum calcine was investigated,the optimal leaching conditions include a solution concentration of 2.5 mol/L,a liquid-to-solid ratio of 2 mL/g,a leaching temperature of 60℃,and leaching solution termination at pH 8.The optimum conditions result in a leaching rate of sodium molybdate of 96.24%.Meanwhile,the content of sodium molybdate reaches 94.08wt%after leaching and removing impurities.Iron and aluminum impurities can be effectively separated by adjusting the pH of the leaching solution with sodium carbonate solution.This research avoids the shortcomings of the traditional process and utilizes the advantages of microwave metallurgy to prepare high-quality sodium molybdate,which provides a new idea for the highvalue utilization of molybdenum concentrate.展开更多
BACKGROUND Microwave endometrial ablation(MEA)is a minimally invasive treatment method for heavy menstrual bleeding.However,additional treatment is often required after recurrence of uterine myomas treated with MEA.Ad...BACKGROUND Microwave endometrial ablation(MEA)is a minimally invasive treatment method for heavy menstrual bleeding.However,additional treatment is often required after recurrence of uterine myomas treated with MEA.Additionally,because this treatment ablates the endometrium,it is not indicated for patients planning to become pregnant.To overcome these issues,we devised a method for ultrasound-guided microwave ablation of uterine myoma feeder vessels.We report three patients successfully treated for heavy menstrual bleeding,secondary to uterine myoma,using our novel method.CASE SUMMARY All patients had a favorable postoperative course,were discharged within 4 h,and experienced no complications.Further,no postoperative recurrence of heavy menstrual bleeding was noted.Our method also reduced the myoma’s maximum diameter.CONCLUSION This method does not ablate the endometrium,suggesting its potential appli-cation in patients planning to become pregnant.展开更多
BACKGROUND Transarterial chemoembolization(TACE)combined with microwave ablation(MWA)is an effective treatment strategy for patients with advanced gastric cancer and liver metastasis.However,it may cause severe postop...BACKGROUND Transarterial chemoembolization(TACE)combined with microwave ablation(MWA)is an effective treatment strategy for patients with advanced gastric cancer and liver metastasis.However,it may cause severe postoperative pain and inflammatory responses.The paravertebral block(PVB)is a regional anesthetic technique that provides analgesia to the thoracic and abdominal regions.AIM To evaluate the effect of PVB on postoperative analgesia and inflammatory response in patients undergoing TACE combined with MWA for advanced gastric cancer and liver metastasis.METHODS Sixty patients were randomly divided into PVB and control groups.The PVB group received ultrasound-guided PVB with 0.375%ropivacaine preoperatively,whereas the control group received intravenous analgesia with sufentanil.The primary outcome was the visual analog scale(VAS)score for pain at 6 h,12 h,24 h,and 48 h after the procedure.Secondary outcomes were the dose of sufentanil used,incidence of adverse events,and levels of inflammatory markers(white blood cell count,neutrophil percentage,C-reactive protein,and procalcitonin)before and after the procedure.RESULTS The PVB group had significantly lower VAS scores at 6 h,12 h,24 h,and 48 h after the procedure compared with the control group(P<0.05).The PVB group also had a significantly lower consumption of sufentanil and a lower incidence of nausea,vomiting,and respiratory depression than did the control group(P<0.05).Compared with the control group,the PVB group had significantly lower levels of inflammatory markers 24 h and 48 h after the procedure(P<0.05).CONCLUSION PVB can effectively reduce postoperative pain and inflammatory responses and improve postoperative comfort and recovery in patients with advanced gastric cancer and liver metastasis treated with TACE combined with MWA.展开更多
Two-dimensional(2D)transition metal chalcogenides(TMCs)hold great promise as novel microwave absorption materials owing to their interlayer interactions and unique magnetoelectric properties.However,overcoming the imp...Two-dimensional(2D)transition metal chalcogenides(TMCs)hold great promise as novel microwave absorption materials owing to their interlayer interactions and unique magnetoelectric properties.However,overcoming the impedance mismatch at the low loading is still a challenge for TMCs due to the restricted loss pathways caused by their high-density characteristic.Here,an interface engineering based on the heterostructure of 2D Cr_(5)Te_(8) and graphite is in situ constructed via a one-step chemical vapor deposit to modulate impedance matching and introduce multiple attenuation mechanisms.Intriguingly,the Cr_(5)Te_(8)@EG(ECT)heterostructure exhibits a minimum reflection loss of up to−57.6 dB at 15.4 GHz with a thin thickness of only 1.4 mm under a low filling rate of 10%.The density functional theory calculations confirm that the splendid performance of ECT heterostructure primarily derives from charge redistribution at the abundant intimate interfaces,thereby reinforcing interfacial polarization loss.Furthermore,the ECT coating displays a remarkable radar cross section reduction of 31.9 dB m^(2),demonstrating a great radar microwave scattering ability.This work sheds light on the interfacial coupled stimulus response mechanism of TMC-based heterogeneous structures and provides a feasible strategy to manipulate high-quality TMCs for excellent microwave absorbers.展开更多
Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature. Next, we propose an empirical equation for the fine-structure constant. Considering the compatibility among...Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature. Next, we propose an empirical equation for the fine-structure constant. Considering the compatibility among these empirical equations, the CMB temperature (T<sub>c</sub>) and gravitational constant (G) were calculated to be 2.726312 K and 6.673778 × 10<sup>−11</sup> m<sup>3</sup>∙kg<sup>−1</sup>∙s<sup>−2</sup>, respectively. Every equation could be explained in terms of the Compton length of an electron (λ<sub>e</sub>), the Compton length of a proton (λ<sub>p</sub>) and a. Furthermore, every equation could also be explained in terms of Avogadro’s number and the number of electrons in 1 C. However, the ratio of the gravitational force to the electric force cannot be uniquely determined when the unit of the Planck constant (Js) is changed. In this study, we showed that every equation can be described in terms of Planck constant. From the assumption of minimum mass, the ratio of gravitational force to electric force could be elucidated.展开更多
Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature that were mathematically connected. Next, we proposed an empirical equation for the fine-structure constant....Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature that were mathematically connected. Next, we proposed an empirical equation for the fine-structure constant. Considering the compatibility among these empirical equations, the CMB temperature (T<sub>c</sub>) and gravitational constant (G) were calculated to be 2.726312 K and 6.673778 × 10<sup>-11</sup> m<sup>3</sup>·kg<sup>-1</sup>·s<sup>-2</sup>, respectively. Every equation can be explained in terms of the Compton length of an electron (λ<sub>e</sub>), the Compton length of a proton (λ<sub>p</sub>) and α. However, these equations are difficult to follow. Using the correspondence principle with the thermodynamic principles in solid-state ionics, we propose a canonical ensemble to explain these equations in this report. For this purpose, we show that every equation can be explained in terms of Avogadro’s number and the number of electrons in 1 C.展开更多
Objective:To explore the effect of transarterial chemoembolization(TACE)+CT-guided microwave ablation(MWA)on treating patients with primary liver cancer.Methods:78 primary liver cancer cases were enrolled and divided ...Objective:To explore the effect of transarterial chemoembolization(TACE)+CT-guided microwave ablation(MWA)on treating patients with primary liver cancer.Methods:78 primary liver cancer cases were enrolled and divided into groups according to their assigned surgical plans.The control group was treated with TACE alone,and the observation group was treated with TACE+CT-guided MWA.The efficacy of the treatment and the liver function indicators and follow-up results of the patients of the two groups were compared.Results:The efficacy of the treatment received by the observation group was higher than that of the control group.Besides,the patients in the observation group exhibited better improvement in liver function indicators after 3 months of treatment.Furthermore,the survival rates of 1 and 2 years after surgery of the observation group were all higher than those of the control group(P<0.05).Conclusion:TACE combined with CT-guided MWA is more effective in treating primary liver cancer compared to TACE alone.Besides,it resulted in better improvement of liver function and long-term survival rate.Therefore,this treatment regime should be popularized.展开更多
Cobalt ferrite(CoFe_(2)O_(4)),with good chemical stability and magnetic loss,can be used to prepare composites with a unique structure and high absorption.In this study,CoFe_(2)O_(4)@mesoporous carbon hollow spheres(M...Cobalt ferrite(CoFe_(2)O_(4)),with good chemical stability and magnetic loss,can be used to prepare composites with a unique structure and high absorption.In this study,CoFe_(2)O_(4)@mesoporous carbon hollow spheres(MCHS)with a core-shell structure were prepared by introducing CoFe_(2)O_(4)magnetic particles into hollow mesoporous carbon through a simple in situ method.Then,the microwave absorption performance of the CoFe_(2)O_(4)@MCHS composites was investigated.Magnetic and dielectric losses can be effectively coordinated by constructing the porous structure and adjusting the ratio of MCHS and CoFe_(2)O_(4).Results show that the impedance matching and absorption properties of the Co Fe_(2)O_(4)@MCHS composites can be altered by tweaking the mass ratio of MCHS and CoFe_(2)O_(4).The minimum reflection loss of the Co Fe_(2)O_(4)@MCHS composites reaches-29.7 dB at 5.8 GHz.In addition,the effective absorption bandwidth is 3.7 GHz,with the thickness being 2.5 mm.The boosted microwave absorption can be ascribed to the porous core-shell structure and introduction of magnetic particles.The coordination between the microporous morphology and the core-shell structure is conducive to improving the attenuation coefficient and achieving good impedance matching.The porous core-shell structure provides large solid-void and CoFe_(2)O_(4)-C interfaces to induce interfacial polarization and extend the electromagnetic waves’multiple scattering and reflection.Furthermore,natural resonance,exchange resonance,and eddy current loss work together for the magnetic loss.This method provides a practical solution to prepare core-shell structure microwave absorbents.展开更多
Two-dimensional transition metal carbides and nitrides(MXene)have emerged as promising candidates for microwave absorption(MA)materials.However,they also have some drawbacks,such as poor impedance matching,high self-s...Two-dimensional transition metal carbides and nitrides(MXene)have emerged as promising candidates for microwave absorption(MA)materials.However,they also have some drawbacks,such as poor impedance matching,high self-stacking tendency,and high density.To tackle these challenges,MXene nanosheets were incorporated into polyacrylonitrile(PAN)nanofibers and subsequently assembled into a three-dimensional(3D)network structure through PAN carbonization,yielding MXene/C aerogels.The 3D network effectively extends the path of microcurrent transmission,leading to enhanced conductive loss of electromagnetic(EM)waves.Moreover,the aerogel’s rich pore structure significantly improves the impedance matching while effectively reducing the density of the MXenebased absorbers.EM parameter analysis shows that the MXene/C aerogels exhibit a minimum reflection loss(RL_(min))value of−53.02 dB(f=4.44 GHz,t=3.8 mm),and an effective absorption bandwidth(EAB)of 5.3 GHz(t=2.4 mm,7.44–12.72 GHz).Radar cross-sectional(RCS)simulations were employed to assess the radar stealth effect of the aerogels,revealing that the maximum RCS reduction value of the perfect electric conductor covered by the MXene/C aerogel reaches 12.02 dB m^(2).In addition to the MA performance,the MXene/C aerogel also demonstrates good thermal insulation performance,and a 5-mm-thick aerogel can generate a temperature gradient of over 30℃ at 82℃.This study provides a feasible design approach for creating lightweight,efficient,and multifunctional MXene-based MA materials.展开更多
Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents.Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently req...Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents.Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently required.Herein,utilizing the low boiling point of Zn,porous N-doped carbon was fabricated by carbonization of ZIF-8(Zn)at different temperature,and the microwave absorption performance was investigated.The porous N-doped carbon inherits the high porosity of ZIF-8 precursor.By increasing the carbonization temperature,the contents of Zn and N elements are decreased;the graphitization degree is improved;however,the specific surface area and porosity are increased first and then decreased.When the carbonization temperature is 1000°C,the porous N-doped carbon behaves enhanced microwave absorption.With an ultrathin thickness of 1.29 mm,the ideal RL reaches-50.57 dB at 16.95 GHz and the effective absorption bandwidth is 4.17 GHz.The mechanism of boosted microwave absorption is ascribed to the competition of graphitization and porosity as well as N dopants,resulting in high dielectric loss capacity and good impedance matching.The porous structure can prolong the pathways and raise the contact opportunity between microwaves and porous carbon,causing multiple scattering,interface polarization,and improved impedance matching.Besides,the N dopants can induce electron polarization and defect polarization.These results give a new insight to construct lightweight carbon-based microwave absorbents by regulating the graphitization and porosity.展开更多
This work aims at investigating the microwave absorption and mechanical properties of short-cutted carbon fiber/glass fiber hybrid veil reinforced epoxy composites.The short-cutted carbon fibers(CFs)/glass fibers(GFs)...This work aims at investigating the microwave absorption and mechanical properties of short-cutted carbon fiber/glass fiber hybrid veil reinforced epoxy composites.The short-cutted carbon fibers(CFs)/glass fibers(GFs)hybrid veil were prepared by papermaking technology,and composites liquid molding was employed to manufacture CFs/GFs hybrid epoxy composites.The microstructure,microwave absorbing properties and mechanical properties of the hybrid epoxy composites were studied by using SEM,vector network analyzer and universal material testing,respectively.The reflection coefficient of the composites were calculated by the measured complex permittivity and permeability in the X-band(8.2-12.4 GHz)range.The optimum microwave absorption properties can be obtained when the content of CFs in the hybrid veil is 6 wt%and the thickness of the composites is 2 mm,the minimum reflection coefficient of-31.8 dB and the effective absorption bandwidth is 2.1 GHz,which is ascribed to benefitting impedance matching characteristic and dielectric loss of the carbon fiber.Simultaneously the tensile strength and modulus can achieve 104.0 and 2.98GPa,demonstrating that the CFs/GFs hybrid epoxy composites can be a promising candidate of microwave absorbing materials with high mechanical properties.展开更多
基金supported by the National Magnetic Confinement Fusion Energy Program of China(No.2019YFE03020001)the Collaborative Innovation Program of Hefei Science Center,CAS(No.2021HSC-CIP010)the Fundamental Research Funds for the Central Universities。
文摘Interpreting experimental diagnostics data in tokamaks,while considering non-ideal effects,is challenging due to the complexity of plasmas.To address this challenge,a general synthetic diagnostics(GSD)platform has been established that facilitates microwave imaging reflectometry and electron cyclotron emission imaging.This platform utilizes plasma profiles as input and incorporates the finite-difference time domain,ray tracing and the radiative transfer equation to calculate the propagation of plasma spontaneous radiation and the external electromagnetic field in plasmas.Benchmark tests for classical cases have been conducted to verify the accuracy of every core module in the GSD platform.Finally,2D imaging of a typical electron temperature distribution is reproduced by this platform and the results are consistent with the given real experimental data.This platform also has the potential to be extended to 3D electromagnetic field simulations and other microwave diagnostics such as cross-polarization scattering.
基金supported, in part, by the United States Department of Agriculture National Institute of Food and Agriculture Hatch Act Fundingthe University of Arkansas Grain and Rice Processing Program, USA
文摘As rice consumption increases,ensuring its safety has become a priority for the food industry.To address this concern,the industry is exploring a single-pass microbial inactivation treatment at the rough rice stage.In this study,a long-grain rice variety,RT7321[21.2%wet basis(WB)and a 20 mm bed thickness]was exposed to microwave radiation(915 MHz frequency)at powers of 16,18,and 20 kW for durations of 1,2,and 3 min.We found that the highest microwave power(20 kW)and the longest exposure duration(3 min)produced the greatest reduction in total aerobic count and total fungal count,reducing them by up to 1.21 and 5.01 log(CFU/g),respectively.Our findings provided insights into the used to high-power,shortduration 915 MHz microwave technology for decontamination purposes in rough rice to help improve the microbial safety of rice.The aim is to develop a single-pass drying approach for microbial inactivation in rice processing facilities while ensuring that the yield and quality is not compromised.
基金This work was financially supported by the National Natural Science Foundation of China(52130510,62071120,52075097,52205454,52375413)the Natural Science Foundation of Jiangsu Province(BE2022066,BZ2023043,BK20202006,BK20211562)Science and Technology Program of Suzhou,Jiangsu Province,China(SYG202302).
文摘High-performance microwave absorption(MA) materials must be studied immediately since electromagnetic pollution has become a problem that cannot be disregarded. A straightforward composite material, comprising hollow MXene spheres loaded with C–Co frameworks, was prepared to develop multiwalled carbon nanotubes(MWCNTs). A high impedance and suitable morphology were guaranteed by the C–Co exoskeleton, the attenuation ability was provided by the MWCNTs endoskeleton, and the material performance was greatly enhanced by the layered core–shell structure. When the thickness was only 2.04 mm, the effective absorption bandwidth was 5.67 GHz, and the minimum reflection loss(RLmin) was-70.70 d B. At a thickness of 1.861 mm, the sample calcined at 700 ℃ had a RLmin of-63.25 d B. All samples performed well with a reduced filler ratio of 15 wt%. This paper provides a method for making lightweight core–shell composite MA materials with magnetoelectric synergy.
基金financial support from the National Natural Science Foundation of China(52203070)the Open Fund of State Key Laboratory of New Textile Materials and Advanced Processing Technologies(FZ2022005)+2 种基金the Open Fund of Hubei Key Laboratory of Biomass Fiber and Ecological Dyeing and Finishing(STRZ202203)the financial support provided by the China Scholarship Council(CSC)Visiting Scholar Programfinancial support from Institute for Sustainability,Energy and Resources,The University of Adelaide,Future Making Fellowship。
文摘Urea holds promise as an alternative water-oxidation substrate in electrolytic cells.High-valence nickelbased spinel,especially after heteroatom doping,excels in urea oxidation reactions(UOR).However,traditional spinel synthesis methods with prolonged high-temperature reactions lack kinetic precision,hindering the balance between controlled doping and highly active two-dimensional(2D)porous structures design.This significantly impedes the identification of electron configuration-dependent active sites in doped 2D nickel-based spinels.Herein,we present a microwave shock method for the preparation of 2D porous NiCo_(2)O_(4)spinel.Utilizing the transient on-off property of microwave pulses for precise heteroatom doping and 2D porous structural design,non-metal doping(boron,phosphorus,and sulfur)with distinct extranuclear electron disparities serves as straightforward examples for investigation.Precise tuning of lattice parameter reveals the impact of covalent bond strength on NiCo_(2)O_(4)structural stability.The introduced defect levels induce unpaired d-electrons in transition metals,enhancing the adsorption of electron-donating amino groups in urea molecules.Simultaneously,Bode plots confirm the impact mechanism of rapid electron migration caused by reduced band gaps on UOR activity.The prepared phosphorus-doped 2D porous NiCo_(2)O_(4),with optimal electron configuration control,outperforms most reported spinels.This controlled modification strategy advances understanding theoretical structure-activity mechanisms of high-performance 2D spinels in UOR.
基金financial support from the National Natural Science Foundation of China (52203070)the Open Fund of State Key Laboratory of New Textile Materials and Advanced Processing Technologies (FZ2022005)+2 种基金the Open Fund of Hubei Key Laboratory of Biomass Fiber and Ecological Dyeing and Finishing (STRZ202203)the financial support provided by the China Scholarship Council (CSC)Visiting Scholar Programfinancial support from Institute for Sustainability,Energy and Resources,The University of Adelaide,Future Making Fellowship,Australia。
文摘The incorporation of partial A-site substitution in perovskite oxides represents a promising strategy for precisely controlling the electronic configuration and enhancing its intrinsic catalytic activity.Conventional methods for A-site substitution typically involve prolonged high-temperature processes.While these processes promote the development of unique nanostructures with highly exposed active sites,they often result in the uncontrolled configuration of introduced elements.Herein,we present a novel approach for synthesizing two-dimensional(2D)porous GdFeO_(3) perovskite with A-site strontium(Sr)substitution utilizing microwave shock method.This technique enables precise control of the Sr content and simultaneous construction of 2D porous structures in one step,capitalizing on the advantages of rapid heating and cooling(temperature~1100 K,rate~70 K s^(-1)).The active sites of this oxygen-rich defect structure can be clearly revealed through the simulation of the electronic configuration and the comprehensive analysis of the crystal structure.For electrocatalytic oxygen evolution reaction application,the synthesized 2D porous Gd_(0.8)Sr_(0.2)FeO_(3) electrocatalyst exhibits an exceptional overpotential of 294 mV at a current density of 10 mA cm^(-2)and a small Tafel slope of 55.85 mV dec^(-1)in alkaline electrolytes.This study offers a fresh perspective on designing crystal configurations and the construction of nanostructures in perovskite.
基金jointly supported by the National Key Research and Development Program of China(Grant No.2022YFC3004002)the Fengyun Application Pioneering Project(FY-APP-2021.0201)FY-3 Meteorological Satellite Ground Application System Project[FY-3(03)-AS-11.08]。
文摘The three-orbit constellation can comprehensively increase the spatial coverage of polar-orbiting satellites,but the polar-orbiting satellites currently in operation are only mid-morning-orbit and afternoon-orbit satellites.Fengyun-3E(FY-3E)was launched successfully on 5 July 2021 in China.As an early-morning-orbit satellite,FY-3E can help form a complete three-orbit observation system together with the mid-morning and afternoon satellites in the current mainstream operational system.In this study,we investigate the added benefit of FY-3E microwave sounding observations to the midmorning-orbit Meteorological Operational satellite-B(Met Op-B)and afternoon-orbit Fengyun-3D(FY-3D)microwave observations in the Chinese Meteorological Administration global forecast system(CMA-GFS).The results show that the additional FY-3E microwave temperature sounder-3(MWTS-3)and microwave humidity sounder-2(MWHS-2)data can increase the global coverage of microwave temperature and humidity sounding data by 14.8% and 10.6%,respectively.It enables the CMA-GFS to achieve nearly 100% global coverage of microwave-sounding observations at each analysis time.Furthermore,after effective quality control and bias correction,the global biases and standard deviations of the differences between observations and model simulations are also reduced.Based on the Advanced Microwave Sounding Unit A and the Microwave Humidity Sounder onboard Met Op-B,and the MWTS-2 and MWHS-2 onboard FY-3D,adding the microwave sounding data of FY-3E can further reduce the errors of analysis results and improve the global prediction skills of CMA-GFS,especially for the southern-hemisphere forecasts within 96 hours,all of which are significant at the 95% confidence level.
文摘La_(0.8)A_(0.2)NiO_(3) (A=K,Ba,Y) catalysts supported on the microwave-absorbing ceramic heating carrier were prepared by the sol-gel method.The crystalline phase and the catalytic activity of the La_(0.8)A_(0.2)NiO_(3)catalysts were characterized by XRD and H_(2) temperature-programmed reduction (TPR).The effects of reaction temperature,oxygen concentration,and gas flow rate on the direct decomposition of nitric oxide over the synthesized catalysts were studied under microwave irradiation (2.45 GHz).The XRD results indicated that the La_(0.8)A_(0.2)NiO_(3) catalysts formed an ABO_(3) perovskite structure,and the H_(2)-TPR results revealed that the relative reducibility of the catalysts increased in the order of La_(0.8)K_(0.2)NiO_(3)>La_(0.8)Ba_(0.2)NiO_(3)>La_(0.8)Y_(0.2)Ni O_(3).Under microwave irradiation,the highest NO conversion amounted to 98.9%,which was obtained with the La_(0.8)K_(0.2)NiO_(3) catalyst at 400℃.The oxygen concentration did not inhibit the NO decomposition on the La_(0.8)A_(0.2)NiO_(3) catalysts,thus the N_(2) selectivity exceeded 99.8%under excess oxygen at 550℃.The NOconversion of the La_(0.8)A_(0.2)NiO_(3) catalysts decreased linearly with the increase in the gas flow rate.
基金supported by the Fundamental Research Funds for the Central Universities(Grant Nos.D5000210522 and D5000210517)China Postdoctoral Science Foundation(Grant No.2021M702665)+2 种基金Natural Science Foundation of Shaanxi Province(Grant Nos.2022JQ-482 and 2023-JC-QN-0380)Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2021A1515111155,2022A1515111200 and 2022A1515011191)Basic Research Programs of Taicang(Grant Nos.TC2021JC01,TC2021JC21,and TC2022JC08)。
文摘The well-designed composite with satisfactory electromagnetic microwave absorption at high temperatures remains a serious challenge.Herein,we fabricated a resorcinol-formaldehyde/silica dioxide composite aerogel(RF/SiO_(2))with a three-dimensional network structure using sol-gel,atmospheric pressure drying technique as well as heat-treated processes to achieve enhanced microwave absorption capabilities in the low frequency range.The pristine RF/SiO_(2)aerogel presented a typical micropores structure with a surface area,porous volume,and density of 146.82 m^(2)/g,62.40%,and 0.28 cm^(3)/g,respectively.Remarkably,the RF/SiO_(2)aerogel showed an effective absorption bandwidth of 3.56 GHz and a minimum reflection loss value of-46.10 d B at 2.25 mm after being heat-treated at 1500°C,while the maximum effective absorption bandwidth was 3.60 GHz at 2.30 mm.The intricate three-dimensional networks possessed remarkable impedance matching,multiple attenuation mechanisms,interfacial polarization,and dielectric loss,which were attributed to the exceptional ability to absorb electromagnetic microwaves.It offered a fresh approach to creating adaptable and effective microwave absorption materials in military defense.
文摘Sea surface temperature(SST)is one of the important parameters of global ocean and climate research,which can be retrieved by satellite infrared and passive microwave remote sensing instruments.While satellite infrared SST offers high spatial resolution,it is limited by cloud cover.On the other hand,passive microwave SST provides all-weather observation but suffers from poor spatial resolution and susceptibility to environmental factors such as rainfall,coastal effects,and high wind speeds.To achieve high-precision,comprehensive,and high-resolution SST data,it is essential to fuse infrared and microwave SST measurements.In this study,data from the Fengyun-3D(FY-3D)medium resolution spectral imager II(MERSI-II)SST and microwave imager(MWRI)SST were fused.Firstly,the accuracy of both MERSIII SST and MWRI SST was verified,and the latter was bilinearly interpolated to match the 5km resolution grid of MERSI SST.After pretreatment and quality control of MERSI SST and MWRI SST,a Piece-Wise Regression method was employed to correct biases in MWRI SST.Subsequently,SST data were selected based on spatial resolution and accuracy within a 3-day window of the analysis date.Finally,an optimal interpolation method was applied to fuse the FY-3D MERSI-II SST and MWRI SST.The results demonstrated a significant improvement in spatial coverage compared to MERSI-II SST and MWRI SST.Furthermore,the fusion SST retained true spatial distribution details and exhibited an accuracy of–0.12±0.74℃compared to OSTIA SST.This study has improved the accuracy of FY satellite fusion SST products in China.
基金financially supported by the National Natural Science Foundation of China (No.51964046)。
文摘The preparation process of sodium molybdate has the disadvantages of high energy consumption,low thermal efficiency,and high raw material requirement of molybdenum trioxide,in order to realize the green and efficient development of molybdenum concentrate resources,this paper proposes a new process for efficient recovery of molybdenum from molybdenum concentrate and preparation of sodium molybdate by microwave-enhanced roasting and alkali leaching.Thermodynamic analysis indicated the feasibility of oxidation roasting of molybdenum concentrate.The effects of roasting temperature,holding time,and power-to-mass ratio on the oxidation product and leaching product sodium molybdate (Na_(2)MoO_(4)·2H_(2)O) were investigated.Under the optimal process conditions:roasting temperature of 700℃,holding time of 110 min,and power-to-mass ratio of 110 W/g,the molybdenum state of existence was converted from MoS_(2) to Mo O3.The process of preparing sodium molybdate by alkali leaching of molybdenum calcine was investigated,the optimal leaching conditions include a solution concentration of 2.5 mol/L,a liquid-to-solid ratio of 2 mL/g,a leaching temperature of 60℃,and leaching solution termination at pH 8.The optimum conditions result in a leaching rate of sodium molybdate of 96.24%.Meanwhile,the content of sodium molybdate reaches 94.08wt%after leaching and removing impurities.Iron and aluminum impurities can be effectively separated by adjusting the pH of the leaching solution with sodium carbonate solution.This research avoids the shortcomings of the traditional process and utilizes the advantages of microwave metallurgy to prepare high-quality sodium molybdate,which provides a new idea for the highvalue utilization of molybdenum concentrate.
文摘BACKGROUND Microwave endometrial ablation(MEA)is a minimally invasive treatment method for heavy menstrual bleeding.However,additional treatment is often required after recurrence of uterine myomas treated with MEA.Additionally,because this treatment ablates the endometrium,it is not indicated for patients planning to become pregnant.To overcome these issues,we devised a method for ultrasound-guided microwave ablation of uterine myoma feeder vessels.We report three patients successfully treated for heavy menstrual bleeding,secondary to uterine myoma,using our novel method.CASE SUMMARY All patients had a favorable postoperative course,were discharged within 4 h,and experienced no complications.Further,no postoperative recurrence of heavy menstrual bleeding was noted.Our method also reduced the myoma’s maximum diameter.CONCLUSION This method does not ablate the endometrium,suggesting its potential appli-cation in patients planning to become pregnant.
文摘BACKGROUND Transarterial chemoembolization(TACE)combined with microwave ablation(MWA)is an effective treatment strategy for patients with advanced gastric cancer and liver metastasis.However,it may cause severe postoperative pain and inflammatory responses.The paravertebral block(PVB)is a regional anesthetic technique that provides analgesia to the thoracic and abdominal regions.AIM To evaluate the effect of PVB on postoperative analgesia and inflammatory response in patients undergoing TACE combined with MWA for advanced gastric cancer and liver metastasis.METHODS Sixty patients were randomly divided into PVB and control groups.The PVB group received ultrasound-guided PVB with 0.375%ropivacaine preoperatively,whereas the control group received intravenous analgesia with sufentanil.The primary outcome was the visual analog scale(VAS)score for pain at 6 h,12 h,24 h,and 48 h after the procedure.Secondary outcomes were the dose of sufentanil used,incidence of adverse events,and levels of inflammatory markers(white blood cell count,neutrophil percentage,C-reactive protein,and procalcitonin)before and after the procedure.RESULTS The PVB group had significantly lower VAS scores at 6 h,12 h,24 h,and 48 h after the procedure compared with the control group(P<0.05).The PVB group also had a significantly lower consumption of sufentanil and a lower incidence of nausea,vomiting,and respiratory depression than did the control group(P<0.05).Compared with the control group,the PVB group had significantly lower levels of inflammatory markers 24 h and 48 h after the procedure(P<0.05).CONCLUSION PVB can effectively reduce postoperative pain and inflammatory responses and improve postoperative comfort and recovery in patients with advanced gastric cancer and liver metastasis treated with TACE combined with MWA.
基金the National Natural Science Foundation of China(grant No.62174013,92265111)Central Government Guides Local Funds for Science and Technology Development(No.YDZJSX2022A021)the funding Program of BIT(grant No.3180012212214 and 3180023012204).
文摘Two-dimensional(2D)transition metal chalcogenides(TMCs)hold great promise as novel microwave absorption materials owing to their interlayer interactions and unique magnetoelectric properties.However,overcoming the impedance mismatch at the low loading is still a challenge for TMCs due to the restricted loss pathways caused by their high-density characteristic.Here,an interface engineering based on the heterostructure of 2D Cr_(5)Te_(8) and graphite is in situ constructed via a one-step chemical vapor deposit to modulate impedance matching and introduce multiple attenuation mechanisms.Intriguingly,the Cr_(5)Te_(8)@EG(ECT)heterostructure exhibits a minimum reflection loss of up to−57.6 dB at 15.4 GHz with a thin thickness of only 1.4 mm under a low filling rate of 10%.The density functional theory calculations confirm that the splendid performance of ECT heterostructure primarily derives from charge redistribution at the abundant intimate interfaces,thereby reinforcing interfacial polarization loss.Furthermore,the ECT coating displays a remarkable radar cross section reduction of 31.9 dB m^(2),demonstrating a great radar microwave scattering ability.This work sheds light on the interfacial coupled stimulus response mechanism of TMC-based heterogeneous structures and provides a feasible strategy to manipulate high-quality TMCs for excellent microwave absorbers.
文摘Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature. Next, we propose an empirical equation for the fine-structure constant. Considering the compatibility among these empirical equations, the CMB temperature (T<sub>c</sub>) and gravitational constant (G) were calculated to be 2.726312 K and 6.673778 × 10<sup>−11</sup> m<sup>3</sup>∙kg<sup>−1</sup>∙s<sup>−2</sup>, respectively. Every equation could be explained in terms of the Compton length of an electron (λ<sub>e</sub>), the Compton length of a proton (λ<sub>p</sub>) and a. Furthermore, every equation could also be explained in terms of Avogadro’s number and the number of electrons in 1 C. However, the ratio of the gravitational force to the electric force cannot be uniquely determined when the unit of the Planck constant (Js) is changed. In this study, we showed that every equation can be described in terms of Planck constant. From the assumption of minimum mass, the ratio of gravitational force to electric force could be elucidated.
文摘Previously, we presented several empirical equations using the cosmic microwave background (CMB) temperature that were mathematically connected. Next, we proposed an empirical equation for the fine-structure constant. Considering the compatibility among these empirical equations, the CMB temperature (T<sub>c</sub>) and gravitational constant (G) were calculated to be 2.726312 K and 6.673778 × 10<sup>-11</sup> m<sup>3</sup>·kg<sup>-1</sup>·s<sup>-2</sup>, respectively. Every equation can be explained in terms of the Compton length of an electron (λ<sub>e</sub>), the Compton length of a proton (λ<sub>p</sub>) and α. However, these equations are difficult to follow. Using the correspondence principle with the thermodynamic principles in solid-state ionics, we propose a canonical ensemble to explain these equations in this report. For this purpose, we show that every equation can be explained in terms of Avogadro’s number and the number of electrons in 1 C.
文摘Objective:To explore the effect of transarterial chemoembolization(TACE)+CT-guided microwave ablation(MWA)on treating patients with primary liver cancer.Methods:78 primary liver cancer cases were enrolled and divided into groups according to their assigned surgical plans.The control group was treated with TACE alone,and the observation group was treated with TACE+CT-guided MWA.The efficacy of the treatment and the liver function indicators and follow-up results of the patients of the two groups were compared.Results:The efficacy of the treatment received by the observation group was higher than that of the control group.Besides,the patients in the observation group exhibited better improvement in liver function indicators after 3 months of treatment.Furthermore,the survival rates of 1 and 2 years after surgery of the observation group were all higher than those of the control group(P<0.05).Conclusion:TACE combined with CT-guided MWA is more effective in treating primary liver cancer compared to TACE alone.Besides,it resulted in better improvement of liver function and long-term survival rate.Therefore,this treatment regime should be popularized.
基金supported by the National Natural Science Foundation of China(No.51407134)the Sichuan Science and Technology Program(No.2021108)+1 种基金the Natural Science Foundation of Shandong Province(No.ZR2019YQ24)the Taishan Scholars and Young Experts Program of Shandong Province。
文摘Cobalt ferrite(CoFe_(2)O_(4)),with good chemical stability and magnetic loss,can be used to prepare composites with a unique structure and high absorption.In this study,CoFe_(2)O_(4)@mesoporous carbon hollow spheres(MCHS)with a core-shell structure were prepared by introducing CoFe_(2)O_(4)magnetic particles into hollow mesoporous carbon through a simple in situ method.Then,the microwave absorption performance of the CoFe_(2)O_(4)@MCHS composites was investigated.Magnetic and dielectric losses can be effectively coordinated by constructing the porous structure and adjusting the ratio of MCHS and CoFe_(2)O_(4).Results show that the impedance matching and absorption properties of the Co Fe_(2)O_(4)@MCHS composites can be altered by tweaking the mass ratio of MCHS and CoFe_(2)O_(4).The minimum reflection loss of the Co Fe_(2)O_(4)@MCHS composites reaches-29.7 dB at 5.8 GHz.In addition,the effective absorption bandwidth is 3.7 GHz,with the thickness being 2.5 mm.The boosted microwave absorption can be ascribed to the porous core-shell structure and introduction of magnetic particles.The coordination between the microporous morphology and the core-shell structure is conducive to improving the attenuation coefficient and achieving good impedance matching.The porous core-shell structure provides large solid-void and CoFe_(2)O_(4)-C interfaces to induce interfacial polarization and extend the electromagnetic waves’multiple scattering and reflection.Furthermore,natural resonance,exchange resonance,and eddy current loss work together for the magnetic loss.This method provides a practical solution to prepare core-shell structure microwave absorbents.
基金supported by the National Natural Science Foundation of China(52171033)the Natural Science Foundation of Jiangsu Province(No.BK20201283).
文摘Two-dimensional transition metal carbides and nitrides(MXene)have emerged as promising candidates for microwave absorption(MA)materials.However,they also have some drawbacks,such as poor impedance matching,high self-stacking tendency,and high density.To tackle these challenges,MXene nanosheets were incorporated into polyacrylonitrile(PAN)nanofibers and subsequently assembled into a three-dimensional(3D)network structure through PAN carbonization,yielding MXene/C aerogels.The 3D network effectively extends the path of microcurrent transmission,leading to enhanced conductive loss of electromagnetic(EM)waves.Moreover,the aerogel’s rich pore structure significantly improves the impedance matching while effectively reducing the density of the MXenebased absorbers.EM parameter analysis shows that the MXene/C aerogels exhibit a minimum reflection loss(RL_(min))value of−53.02 dB(f=4.44 GHz,t=3.8 mm),and an effective absorption bandwidth(EAB)of 5.3 GHz(t=2.4 mm,7.44–12.72 GHz).Radar cross-sectional(RCS)simulations were employed to assess the radar stealth effect of the aerogels,revealing that the maximum RCS reduction value of the perfect electric conductor covered by the MXene/C aerogel reaches 12.02 dB m^(2).In addition to the MA performance,the MXene/C aerogel also demonstrates good thermal insulation performance,and a 5-mm-thick aerogel can generate a temperature gradient of over 30℃ at 82℃.This study provides a feasible design approach for creating lightweight,efficient,and multifunctional MXene-based MA materials.
基金financially supported by National Natural Science Foundation of China(Nos.51572218 and 11504293)Natural Science Foundation of Shaanxi Province(No.2019JM-138)+1 种基金Natural Science Foundation from Department of Science and Technology of Shaanxi Province(Nos.2021JQ-431,2021JM-304,and 2021JQ-427)Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0946)。
文摘Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents.Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently required.Herein,utilizing the low boiling point of Zn,porous N-doped carbon was fabricated by carbonization of ZIF-8(Zn)at different temperature,and the microwave absorption performance was investigated.The porous N-doped carbon inherits the high porosity of ZIF-8 precursor.By increasing the carbonization temperature,the contents of Zn and N elements are decreased;the graphitization degree is improved;however,the specific surface area and porosity are increased first and then decreased.When the carbonization temperature is 1000°C,the porous N-doped carbon behaves enhanced microwave absorption.With an ultrathin thickness of 1.29 mm,the ideal RL reaches-50.57 dB at 16.95 GHz and the effective absorption bandwidth is 4.17 GHz.The mechanism of boosted microwave absorption is ascribed to the competition of graphitization and porosity as well as N dopants,resulting in high dielectric loss capacity and good impedance matching.The porous structure can prolong the pathways and raise the contact opportunity between microwaves and porous carbon,causing multiple scattering,interface polarization,and improved impedance matching.Besides,the N dopants can induce electron polarization and defect polarization.These results give a new insight to construct lightweight carbon-based microwave absorbents by regulating the graphitization and porosity.
基金Funded by Key Research and Development Plan in Hubei Province of China(Nos.2022BCA082,2022BCA077,2021BCA153)Initial Scientific Research Fund for High-level Talents of Hubei University of Technology(No.GCRC2020017)。
文摘This work aims at investigating the microwave absorption and mechanical properties of short-cutted carbon fiber/glass fiber hybrid veil reinforced epoxy composites.The short-cutted carbon fibers(CFs)/glass fibers(GFs)hybrid veil were prepared by papermaking technology,and composites liquid molding was employed to manufacture CFs/GFs hybrid epoxy composites.The microstructure,microwave absorbing properties and mechanical properties of the hybrid epoxy composites were studied by using SEM,vector network analyzer and universal material testing,respectively.The reflection coefficient of the composites were calculated by the measured complex permittivity and permeability in the X-band(8.2-12.4 GHz)range.The optimum microwave absorption properties can be obtained when the content of CFs in the hybrid veil is 6 wt%and the thickness of the composites is 2 mm,the minimum reflection coefficient of-31.8 dB and the effective absorption bandwidth is 2.1 GHz,which is ascribed to benefitting impedance matching characteristic and dielectric loss of the carbon fiber.Simultaneously the tensile strength and modulus can achieve 104.0 and 2.98GPa,demonstrating that the CFs/GFs hybrid epoxy composites can be a promising candidate of microwave absorbing materials with high mechanical properties.