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| 1 | Microwave electromagnetic and absorbing properties of Dy^(3+) doped MnZn ferrites显示文摘Dy3+ doped Mn-Zn ferrites Mn0.3Zn0.7Fe2-xDyxO4(x=0,0.01,0.02,0.03,0.04)were prepared by the conventional solid-state reaction.The crystal structure,surface morphology and electromagnetic properties of the calcined samples were characterized by X-ray diffraction analysis(XRD),scanning electron microscopy(SEM) and network analyzer(Agilent 8722ET).All the XRD patterns showed the single phase of the spinel-type ferrite without other intermediate when x≤0.03.The average crystallite size was about 44?56 nm.The microwave electromagnetic properties of the samples were studied at the frequency range from 2 GHz to 18 GHz.It was shown that small amounts of Dy3+ substitution could adjust microwave electromagnetic parameters magically.The tan δ exhibited a maximal peak when x=0.03,and the peak value was 0.56.It indicated that the microwave electromagnetic loss properties were excellent when x=0.03.Furthermore,the reasons were also discussed using electromagnetic theory.The reflection loss(RL) increased with the Dy3+ content when x<0.04.The Mn0.3Zn0.7Fe1.97Dy0.03O4 ferrite displayed excellent microwave absorption properties.The frequency(with respect to-10 dB) started from 11.9 GHz,and the bandwidth reached about 3.5 GHz.The peak value of RL was about-20.5 dB at a matching thickness of 2.7 mm. | 宋杰 王丽熙 许乃岑 张其土 | 2010 | Journal of Rare Earths2010，28，3： | 11 |
| 2 | Microwave metamaterials显示文摘Metamaterials are artificial structures with tailored meta-atoms at subwavelength scales to control electromagnetic waves at will.Usually,metamaterials are described by effective medium parameters(e.g.index of refraction,permittivity and permeability)due to the subwavelength nature of meta-atoms.When the meta-atom is comparable to the wavelength,the effective medium | Tie Jun Cui | 2018 | National Science Review2018，5，2： | 6 |
| 3 | Targeted Double Negative Properties in Silver/Silica Random Metamaterials by Precise Control of Microstructures显示文摘Te mechanism of negative permittivity/permeability is still unclear in the random metamaterials,where the precise control of microstructure and electromagnetic properties is also a challenge due to its random characteristic.Here silver was introduced into porous SiO_(2) microsphere matrix by a self-assemble and template method to construct the random metamaterials.Te distribution of silver was restricted among the interstices of SiO_(2) microspheres,which lead to the precise regulation of electrical percolation(from hoping to Drude-type conductivity)with increasing silver content.Negative permittivity came from the plasma-like behavior of silver network,and its value and frequency dispersion were further adjusted by Lorentz-type dielectric response.During this process,the frequency of epsilon-near-zero(ENZ)could be adjusted accordingly.Negative permeability was well explained by the magnetic response of eddy current in silver micronetwork.Te calculation results indicated that negative permeability has a linear relation with ω^(0.5),showing a relaxation-type spectrum,diferent from the“magnetic plasma”of periodic metamaterials.Electromagnetic simulations demonstrated that negative permittivity materials and ENZ materials,with the advantage of enhanced absorption(40dB)and intelligent frequency selection even in a thin thickness(0.1 mm),could have potentials for electromagnetic attenuation and shielding.Tis work provides a clear physical image for the theoretical explanation of negative permittivity and negative permeability in random metamaterials,as well as a novel strategy to precisely control the microstructure of random metamaterials. | Peitao Xie Zidong Zhang Zhongyang Wang Kai Sun Runhua Fan | 2019 | Research2019，，1： | 6 |
| 4 | Microfluidic temperature sensor based on temperature-dependent dielectric property of liquid显示文摘We propose a low-cost compact microfluidic temperature sensor by virtue of the temperature-dependent permittivity of liquid.The sensor is composed of a coplanar waveguide(CPW)transmission line loaded with three resonators and a microfluidic plate with three channels.The resonant frequency of each resonator relies on the temperature-dependent dielectric property of liquid in corresponding channel,which therefore can be used to extract the temperature.The proposed sensor features a compact size and low cost since it requires only micro fluid volume instead of additional electronic components to produce significant frequency shift with changing temperature.Moreover,it exhibits decent accuracy and stability in a temperature sensing range from 30℃ to 95℃.A theoretical analysis of the sensor is provided,followed by the detailed characterization method,and a prototype is designed,manufactured,and measured to verify the theoretical analysis. | 刘琦 俞钰峰 赵文生 李慧 | 2020 | Chinese Physics B2020，29，1： | 3 |
| 5 | Microwave absorption of magnesium/hydrogen-treated titanium dioxide nanoparticles显示文摘Interactions between materials and electromagnetic irradiations in the microwave frequency are critical for many civil and military applications, such as radar detection, communications, information processing and transport et al. Dipole rotations or magnetic domain resonance are the mainly traditional mechanisms for microwave absorption. The recent finding of the excellent microwave absorption from hydrogenated TiO2 nanoparticles provides us an alternative approach for achieving such absorption, by manipulating the structural defects inside nanoparticles through hydrogenation. In this study, we demonstrate that the microwave absorption can be not only achieved but fine-tuned with TiO2 nanoparticles thermally treated in a Mg/H2 environment. Their position and efficiency can be effectively controlled by the treating temperature. Specifically, the microwave absorption position shifts to the lower frequency region as the treating temperature increases, and there seems to exist an optimal treating temperature to obtain the maximum efficiency, as the absorbing efficiency first increases, and then decreases, with the increase in treatment temperature. Therefore, this study enriches our knowledge and understanding microwave absorption from TiO2-based nanomaterials which may inspire new ideas on other systems to enhance their performance as well. | Michael Green Anh Thi Van Tran Russell Smedley Adam Roach James Murowchick Xiaobo Chen | 2019 | Nano Materials Science2019，1，1： | 3 |
| 6 | The Comprehensive Retrieval Method of Electromagnetic Parameters Using the Scattering Parameters of Metamaterials for Two Choices of Time-Dependent Factors显示文摘The electromagnetic parameters (permittivity and permeability) method,retrieved from the reflection and transmission coefficients of a slab,is presented.Improvements over existing methods,including the determination of the permittivity,permeability and impedance of the slab,are expressed as explicit functions of the S parameters for both the time-dependent factors,e^(iwt) and e^(-iwt) (ω is the angular frequency of the incident electromagnetic wave),and the proper selection of the sign of impedance and the real part of the refractive index.Moreover,based on the retrieving method,the calculations of the electromagnetic parameters of the conventional-material teflon slab standard sample through the experimental data of the S parameters are performed,which confirm the validity of the technique for the retrieval of electromagnetic parameters. | 侯志灵 孔令宝 金海波 曹茂盛 李笑 祁欣 | 2012 | Chinese Physics Letters2012，29，1： | 2 |
| 7 | Sensing grain and seed moisture and density from dielectric properties显示文摘The importance of moisture measurement in grain and seed is discussed,and a brief history of the development of moisture sensing instruments,based on sensing of dielectric properties of these materials,is presented.Data are presented graphically on the permittivities or dielectric properties of grain and seed showing their variation with frequency,moisture content,temperature,and bulk density,and references are cited for further information.More recent developments on microwave measurements for moisture content and bulk density sensing are briefly described,and numerous studies are cited providing sources of information on these newer techniques. | Stuart O.Nelson D.Sc.Samir Trabelsi | 2011 | International Journal of Agricultural and Biological Engineering2011，4，1： | 2 |
| 8 | Synthesis and characterization of MoS2/Fe@Fe3O4 nanocomposites exhibiting enhanced microwave absorption performance at normal and oblique incidences显示文摘Herein,we attempted to prepare MoS2/Fe@Fe3O4 nanocomposites capable of strongly absorbing broadband incident electromagnetic(EM)radiation and probed the effects of their composition on complex permittivity and permeability at 2-18 GHz.Calculations of normal-incidence reflection losses(RLs)based on EM parameters revealed that the Fe@Fe3O4 to MoS2 mass ratio strongly influenced the absorption peak intensity and bandwidth.Specifically,an RL peak of-31.8 dB@l5.3 GHz and a bandwidth(RL<-lOdB)of4.8 GHz(13.2-18 GHz)were achieved at a thickness of 1.52 mm and a Fe@Fe3O4 to M0S2 mass ratio of 60:40.Further,RL and bandwidth were investigated for oblique incidence,in which case two kinds of EM waves(TE-electric field perpendicular to plane of incidence;TM-electric field in the plane of incidence)were considered.The absorption peaks of TE and TM waves did not exceed-2 0 dB when the incidence angle increased to 3 0,and the bandwidth(R L<-10 dB)reached 4.2 GHz(TE wave)and 4.0 GHz(TM wave)when this angle was further increased to 40.0°and 50.4,respectively.Finally,the mechanism of microwave absorption was discussed in detail. | Peng Wang Junming Zhang Guowu Wang Benfang Duan Donglin He Tao Wang Fashen Li | 2019 | Journal of Materials Science & Technology2019，35，9： | 2 |
| 9 | A rocky hill on the continuous ejecta of Ziwei crater revealed by the Chang’e-3 mission显示文摘The Chinese Chang’e-3 mission landed close to the eastern rim of the ~450 m diameter Ziwei crater. Regional stratigraphy of the landing site and impact excavation model suggest that the bulk continuous ejecta deposits of the Ziwei crater are composed by Erathothenian-aged mare basalts. Along the traverse of the Yutu rover, the western segment features a gentle topographic uplift(~0.5 m high over ~4 m), which is spatially connected with the structurally-uplifted crater rim. Assuming that this broad topographic uplift has physical properties discontinuous with materials below, we use data returned by the high-frequency lunar penetrating radar onboard the Yutu rover to estimate the possible range of relative permittivity for this topographic uplift. Only when the relative permittivity is ~9 is the observed radar reflection consistent with the observed topography, suggesting that the topographic uplift is composed of basaltic blocks that were excavated by the Ziwei crater. This result is consistent both with the impact excavation model that predicts deeper basaltic materials being deposited closer to the crater rim, and with observation of numerous half-buried boulders on the surface of this hill. We note that this study is the first to use topography and radargram data to estimate the relative permittivity of lunar surface uplifts, an approach that has had many successful applications on Mars. Similar approaches can apply other ground penetrating radar data for the Moon, such as will be available from the ongoing Chang’e-4 mission. | ChunYu Ding YuZhen Cai ZhiYong Xiao Yan Su | 2020 | Earth and Planetary Physics2020，4，2： | 2 |
| 10 | Improved dielectric and electro-optical parameters of nematic liquid crystal doped with magnetic nanoparticles显示文摘This study investigates the effect of magnetic nanoparticles(NPs) on the weakly polar nematic liquid crystal(NLC).Different parameters of dielectric data were measured for both the homeotropic and planar aligned samples as a function of frequency and temperature and the substantial changes have been noticed for the doped systems. Dielectric permittivity has been increased after the dispersion of magnetic NPs in the pure NLC. Dielectric anisotropy has also been influenced by incorporating the magnetic NPs with the NLC molecules. These results were attributed to the dipole–dipole interaction between the magnetic nanoparticles and nematic liquid crystal molecules. Electro-optical study indicated the faster rise time and fall time of the doped systems as compare to pure NLC. Threshold voltage has been calculated and found to be decreased for the doped systems. Moreover, we have also calculated the rotational viscosity and the splay elastic constant for pure and the doped systems. Both the rotational viscosity and splay elastic constant of the doped systems are found to be considerably lower than those of pure NLC. Change in these properties has been explained on the basis of molecular disturbances created by the interaction between the magnetic nanoparticle and LC director. This study reveals that the inclusion of magnetic NPs in weakly polar NLC can be useful to enhance the basic properties of the weakly polar NLC and make it a promising material for many display applications. | Geeta Yadav Govind Pathak Kaushlendra Agrahari Mahendra Kumar Mohd Sajid Khan V S Chandel Rajiv Manohar | 2019 | Chinese Physics B2019，28，3： | 2 |
| 11 | Analytical model for the transient permittivity of uncured TiO_(2) whisker/liquid silicone rubber composites under an AC electric field显示文摘The electric field grading of dielectric permittivity gradient devices is an effective way of enhancing their insulation properties.The in situ electric field‐driven as-sembly is an advanced method for the fabrication of insulation devices with adaptive permittivity gradients;however,there is no theoretical guidance for design.In this study,an analytical model with a time constant is developed to determine the transient permittivity of uncured composites under an applied AC electric field.This model is based on optical image and dielectric permittivity monitoring,which avoids the direct processing of complex electrodynamics.For a composite with given components,the increased filler content and electric field strength can accelerate the transient process.Compared with the finite element method based on differential equations,this statistical model is simple but efficient,and can be applied to any low‐viscosity uncured composites,which may contain multiple fillers.More importantly,when a voltage is applied to an uncured composite insulating device,the proposed model can be used to analyse the spatiotemporal permittivity characteristics of this device and optimise its permittivity gradient for electric field grading. | Zikui Shen Zhenyu Xin Xilin Wang Xinyu Wei Zhidong Jia | 2021 | High Voltage2021，6，3： | 1 |
| 12 | Enhanced Microwave Absorption for High Filler Content Composite Molded from Polymer Coated Flaky Carbonyl Irons Modified by Silane Coupling Agents显示文摘A microwave absorbing sheet with a high complex permeability and a relatively low complex permittivity is obtained by molding of the densely coated flaky carbonyl iron particles(FCIPs)by styrenebutadiene-styrene block copolymer(SBS)in the assistance of coupling agent modification.Direct molding of the core-shell FCIPs without adding extra binder results in a large permeability due to the high filling ratio(55vol%)of absorbents.Importantly,the permittivity is well suppressed by the dense insulate polymer shell on the FCIPs,avoiding the severe impedance mismatch problem of the high filler content microwave absorbing materials.Investigations show that modifying the surface of FCIPs by proper amount of silane coupling agent is critical for the coating quality of the SBS shell,which is verified by resistivity and corrosion current density measurements,and can be interpreted by improved interfacial compatibility between the modified FCIPs and SBS.The obtained microwave absorbing sheet shows a minimum reflection loss of-38.74 dB at 1.57 GHz and has an effective absorption bandwidth from 1.1 to 2.3 GHz at a relatively small thickness of 2 mm. | 崔正明 MA Guoqing WANG Mengqi LUO Chuangyu CHEN Zhihong MA Huiru LI Qifan 李维 | 2023 | Journal of Wuhan University of Technology(Materials Science)2023，38，1： | 1 |
| 13 | Enhanced electrocaloric effect at room temperature in Mn^(2+) doped lead-free(BaSr)TiO_(3) ceramics via a direct measurement显示文摘(Ba_(1-x)Sr_(x))(MnyTi1-y)O_(3)(BSMT)ceramics with x=35,40 mol%and y=0,0.1,0.2,0.3,0.4,0.5 mol%were prepared using a conventional solid-state reaction approach.The dielectric and ferroelectric properties were characterized using impedance analysis and polarization-electric field(P-E)hysteresis loop measurements,respectively.The adiabatic temperature drop was directly measured using a thermocouple when the applied electric field was removed.The results indicate that high permittivity and low dielectric losses were obtained by doping 0.1-0.4 mol%of manganese ions in(BaSr)TiO_(3)(BST)specimens.A maximum electrocaloric effect(ECE)of 2.75 K in temperature change with electrocaloric strength of 0.55 K·(MV/m)^(-1)was directly obtained at~21℃and 50 kV/cm in Ba_(0.6)Sr_(0.4)Mn_(0.001)Ti_(0.999)O_(3) sample,offering a promising ECE material for practical refrigeration devices working at room temperature. | Xiang NIU Xiaodong JIAN Xianyi CHEN Haoxuan LI Wei LIANG Yingbang YAO Tao TAO Bo LIANG Sheng-Guo LU | 2021 | Journal of Advanced Ceramics2021，10，3： | 1 |
| 14 | Conductivity Study of Polyaniline-Cobalt Ferrite(PANI-CoFe_2O_4) Nanocomposite显示文摘In this investigation,the structural and electrical properties of nanocomposites of polyaniline(PANI) and cobalt ferrite synthesized by hydrothermal route are reported for the first time(with weight ratios of CoFe_2O_4/PANI 1:2 and 2:1).Synthesized nanomaterials have been characterized by XRD,FT-IR,SEM and TEM techniques.FT-IR results confirm the presence of CoFe_2O_4 and PANI in the samples.Their detailed conductivity measurements have been investigated.It has been found that PANI has a more effective conducting mechanism in CoFe_2O_4-PANI composites.These results are also consistent with the change in AC conductivity orders in composites. | E.E.Tanriverdi A.T.Uzumcu H.Kavas A.Demir A.Baykal | 2011 | Nano-Micro Letters2011，3，2： | 1 |
| 15 | RECONSTRUCTION OF ONE DIMENSIONAL MULTI-LAYERED MEDIA BY USING A TIME DOMAIN SIGNAL FLOW GRAPH TECHNIQUE显示文摘A novel inverse scattering method to reconstruct the permittivity profile of one-dimensional multi-layered media is proposed in this paper.Based on the equivalent network ofthe medium,a concept of time domain signal flow graph and its basic principles are introduced,from which the reflection coefficient of the medium in time domain can be shown to be a series ofDirac δ-functions(pulse responses).In terms of the pulse responses,we will reconstruct both thepermittivity and the thickness of each layer will accurately be reconstructed.Numerical examplesverify the applicability of this | 崔铁军 梁昌洪 | 1993 | Journal of Electronics(China)1993，10，2： | 1 |
| 16 | Excellent energy storage performance of niobate-based glass-ceramics via introduction of nucleating agent显示文摘For glass-ceramics, how to realize the collaborative optimization of BDS and permittivity is the key toimprove the energy storage density. In this work, ZrO2 is introduced into BPKNAS glass-ceramics asnucleating agent to promote crystal development of glass-ceramics and then achieve high permittivity.When 1.5 mol% ZrO2 is added, the glass-ceramics have the highest permittivity (~128.59) and meanwhilepossess high BDS (1948.90 kV/cm) due to the dense microstructure. Therefore, BPKNAS-1.5ZrO2 glass-ceramics has the highest theoretical energy storage density (21.62 J/cm3). Moreover, the permittivityvariation of BPKNAS-1.5ZrO2 glass-ceramics is less than 6 % in the wide temperature range from 80 to300 C, showing excellent temperature stability. In addition, BPKNAS-1.5ZrO2 glass-ceramics possessesultrahigh power density, which reaches up to 382.40 MW/cm3 in overdamped circuit. The above evi-dence shows that BPKNAS-1.5ZrO2 glass-ceramics with ultrahigh energy storage density and powerdensity is very competitive in the field of energy storage applications. | Changshuai Liu Shufeng Xie Hairui Bai Fei Yan Tongtong Fu Bo Shen Jiwei Zhai | 2022 | Journal of Materiomics2022，8，4： | 1 |
| 17 | Production of composites with high relative permittivity using the spouted bed technique显示文摘This contribution presents a new application of the spouted bed technique. The developed production process involves coating fine copper particles with a polymer in a spouted bed plant and then hot pressing the produced granules to form a compact consisting of a copper–polymer composite with a high filling degree. The fabricated composites possess high relative permittivity, which is advantageous for the production of effective capacitors. With increasing filling degree of copper, the relative permittivity of the composites increased, with a maximum relative permittivity of 214 obtained for the composite containing 78.1 vol% copper. Such a high filling degree can be achieved with conductive particles without obtaining a conductive composite by using the spouted bed technology in the production process. The high relative permittivity results from the high filling degree of particles isolated by a polymer coating. | E. Eichner P.-K. Fischer S. Heinrich GA Schneider | 2019 | Particuology2019，17，1： | 0 |
| 18 | Poling Effects of Dielectric and Optical Properties on Pb(Zn1/3Nb2/3)1-xTixO3 Crystal显示文摘Dipolar relaxation and dielectric/piezoelectric resonance in a (001)-cut Pb(Zn1/3Nb2/3)0.9Ti0.1O3 (PZNT10%) single crystal before and after electric (E)-field poling were presented. Dielectric permittivities were measured as functions of temperature, frequency and poling E-field strength. Frequency-dependent dielectric spectroscopy in the poled sample exhibits multiple piezoelectric resonances between 0.1 and 1 MHz, which can be described by the forced-damped-oscillator model. The resonant spectra show significant changes while phase transitions are taking place. The unpoled crystal shows almost no optical birefringence, indicating that the average structure symmetry is isotropic. Birefringence of the crystal is significantly enhanced by a prior E-field poling. | Tu Chi Shun Wang Fu Tang Chien R R Hugo Schmidt V Chew L L | 2006 | Journal of Rare Earths2006，24，z1： | 0 |
| 19 | Studies of permittivity and permeability of dielectric matrix with cuboid metallic inclusions in different orientations显示文摘In this paper,we investigate the possibility of using the heterogeneous materials,with cuboid metallic inclusions inside a dielectric substrate(host)to control the effective permittivity.We find that in the gigahertz range,such a material demonstrates a significantly larger permittivity compared to the pure dielectric substrate.Three principal orientations of microscale cuboid inclusions have been taken into account in this study.The highest permittivity is observed when the orientation provides the largest polarization(electric dipole moment).The detrimental side effect of the metallic inclusion,which leads to the decrease of the effective magnetic permeability,can be suppressed by the proper choice of shape and orientation of the inclusions.This choice can in fact reduce the induced current and hence maximize the permeability.The dissipative losses are shown to be negligible in the relevant range of frequencies and cuboid dimensions. | W.M.Wu C.C.Njoku W.G.Whittow A.M.Zagoskin F.V.Kusmartsev J.C.Vardaxoglou | 2014 | Journal of Advanced Dielectrics2014，4，4： | 0 |
| 20 | CH ARACTERIZATION OF LA YERED Na_(2-x-y)LixKyTi_(3)O_(7) CERAMICS BY DIELECTRIC-SPECTROSCOPIC INV ESTIG ATIONS显示文摘In this paper,we present detailed investigations on the dielectric properties of Lithium(x=0.10)and Potassium(y=0.01,0.02,0.04,0.05)mixed Sodium trititanate,Na_(2-x-y)LixKyTi_(3)O_(7) poly-crystalline ma terials synthesized by solid-state reaction.The characteristics of the pelletized samples have been studied in the temperature range from 350 to 725 K and on the frequency in the range from 10kHz to 1 MHz.The studies reveal that the chain structured Na_(2-x-y)LixKyTi_(3)O_(7) layered compound posses electronic,ionic,dipolar,and space charge polarization mechanisms over the respective temperature regions in the entire temperature range of study. | SHRIPAL RAKESH SINGH GEETIKA RAVI K.SHUKLA K.K.RAINA | 2011 | Journal of Advanced Dielectrics2011，1，4： | 0 |
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