“三明治”型超材料吸波体及其设计优化的研究现状

超材料吸波体因其独特的性质,自出现以来一直是吸波材料研究的热点。主要介绍了三明治型超材料吸波体的结构类型和研究现状,对三明治型超材料吸波体的设计原则和优化方法进行了概述,并对三明治型超材料吸波体的发展进行了总结和展望。     

基于超材料设计的钡铁氧体吸波涂层研究

本工作设计了一种基于超材料结构的钡铁氧体吸波涂层,分析了超材料的结构设计对钡铁氧体涂层吸波性能的影响,并对涂层的吸波机理进行了研究和讨论。通过仿真发现,钡铁氧体涂层经超材料设计改进后,吸波性能得到大幅增强,改进后的钡铁氧体涂层存在最佳的匹配厚度2.5mm和电阻膜方块电阻值70Ω/,此时涂层的吸收带宽最大,并存在两个吸收峰,在8～18GHz频段内反射损耗都小于-10dB。钡铁氧体通过超材料设计改进后,吸波性能得到极大改善。     

超材料在宽频微波衰减吸收材料中的应用研究进展

主要对不同吸波机理扩展超材料微波吸收体衰减吸收频带的研究现状进行了综述,包括基于谐振吸收、加载集总元件、加载电阻材料的频带扩展方法以及通过可调超材料实现超材料吸波体的智能化吸收和宽频吸收的方法,重点讨论了分形学曲线在超材料设计中的应用,分析了其能通过小的尺寸实现低频谐振吸收的优点以及分形学图案自带的频带扩展能力,提出了分形学曲线和图案是未来超材料吸波体发展的一个重要途径。     

基于有源超材料的可调超薄雷达吸波体研究

在超材料结构中引入电阻和有源变容二极管,通过合理设计微结构型式以及微结构之间的连线方式,实现吸波频带的动态可调,研究电阻、电容和入射波极化方向对吸波特性的影响。结果表明:通过改变外加电压调整超材料的吸收频段,在3.7倍频带范围内实现吸波频段的主动自调节;吸波体的总厚度仅为波长的1/181,相比于传统吸波材料,在同等吸波性能条件下,表现出了优异的超薄特性;TE和TM极化电磁波表现出相同的吸波效果,即吸波特性对入射波的极化方向不敏感。     

基于电阻膜与超材料的超薄宽频吸波体设计

设计了一种基于多层电阻膜和超材料的超薄宽频吸波体模型。该吸波体由两层含介质基板的电阻膜片和一层一阶Minkowski分形双方环(minkowski fractal double square loop,MFDSL)电谐振器结构组成,各层电阻膜片阻值相同,但外形不同。仿真分析结果表明,该吸波体对1.2~20GHz频段内垂直入射的电磁波的吸收率均大于90%;同时对于45°角入射的TE和TM波仍能保持良好的吸收性能,具有宽入射角特性和极化不敏感的特点,且厚度仅有1mm。另外,对不同电阻膜片阻值得分析结果表明,随着电阻膜片阻值的增大,该吸波体的吸波效果更好,吸波性能更加稳定。     

新型全介质谐振表面二元超材料吸波体

基于干涉理论,利用低介电材料全介质谐振表面(All-dielectric resonance surface,ADRS)设计并制备了一种新型二元结构超材料吸波体(Binary-structural metamaterial absorber,BMA)。优化后的BMA分别在13. 332 GHz、16. 722 GHz和17. 34 GHz处有强吸收。通过阻抗分析、能量损耗分布及场分析的方法解释了BMA的谐振与吸波机理,并研究了ADRS结构参数对吸波性能的影响。分析表明,BMA的三频谐振来源于ADRS的电谐振响应; ADRS的结构决定谐振峰处磁场分布,进而影响吸波性能。仿真结果与实测结果吻合较好。本工作提出的采用低介电材料ADRS代替传统金属谐振表面及难以制备的高介电常数ADRS,极大地简化了超材料吸波体的设计。     

超材料结构单元轮廓法对吸波材料衰减吸收频带的拓宽与优化

设计了一个由金属谐振单元、FR4基板和金属背板构成的超材料吸波体,通过数值仿真软件对该吸波体在2~8GHz范围内的S参数以及吸收率特征进行了计算;对这个模型进行了取轮廓化的处理,通过计算发现这种处理对其谐振吸收基本上没有影响;在此基础上,通过在这个轮廓模型中加入其他谐振单元,实现了双频带范围的微波衰减吸收。通过激光刻蚀的方法,对所设计的模型进行了实验验证,发现计算结果和实验结果有很好的一致性,这就验证了超材料轮廓法拓宽吸波材料的技术思路,为宽频带超材料吸波体的研究提供了一个可行的技术途径。     

超材料吸波体吸波特性研究

设计了一个强谐振超材料吸波体,它由电谐环振器(Electric ring resonator)和短导线组合而成.采用数值仿真法,在8～12GHz波段提取了这种超材料的s参数,并计算了其吸渡率.单层超材料吸波体在10.2GHz处达到吸收峰,吸波率达91.3%.多层组合吸渡体在9.72GHz处峰值吸波率接近100%.与传统吸波材料不同的是,该超材料吸波体完全由金属结构组成,通过对介电常数和磁导率的灵活调节,经优化设计即可实现对入射电磁波的高吸收.另外,通过尺寸变化的多层组合结构,利用不同吸波频段的叠加效应,实现了对吸波频带的拓宽.     

P波段吸波材料研究进展

吸波材料的出现极大改善了电磁环境,提升了武器装备的作战效能,但随着P波段探测技术的迅猛发展,研究具有"薄、宽、轻、强"特性的P波段吸波材料有着非常重要的意义。针对目前吸波材料存在的低频瓶颈,对传统吸波材料和超材料吸波体,从影响P波段吸收性能的因素及研究现状两方面进行了综述,并对未来P波段吸波材料的发展方向进行了总结与展望。     

低电导率超材料的吸波性能研究

本文研究了由低电导率材料制备的超材料的吸波性能,通过仿真软件计算了不同电导率超材料吸波性能,研究了其变化规律,在复合材料基材上采用喷涂法制备了电导率为2.3×10~4 S/M的超材料结构,探究了不同基板厚度时超材料吸波体的吸波性能变化规律.仿真结果表明,低电导率材料在一定基材厚度下可以实现电磁波的高吸收,并且基材的厚度有最优值,这说明电导率也可以成为设计超材料的参数.制备的超材料基底材料厚度为2 mm时,其在7.8 GHz处实现了-23.2 dB的深吸收,实验规律与仿真结果相吻合.采用喷涂法有助于解决超材料在大曲率、复杂外形等部位难以应用的问题,为超材料的制备以及其大规模应用开辟了一个新的方向.     

Tunable metamaterial absorber based on resonant strontium titanate artificial atoms

Dynamic control of the absorption frequency and intensity of metamaterial absorbers has attracted considerable attention,and many kinds of tunable metamaterial absorbers have been proposed.Unfortunately,due to the integration of separate resonant unit and tunable unit,these designed metamaterial absorbers suffer from complex structure and low sensitivity.We numerically and experimentally demonstrate a tunable metamaterial absorber composed of artificial dielectric atoms as both resonant and tunable unit arrayed periodically in the background matrix on the metallic plate.Polarization insensitive and wide incident angle absorption band with simulated and experimental absorptivity of 99%and 96%at 9.65 GHz are achieved at room temperature.The absorption frequency can be gradually modulated by temperature,however,the absorption intensity at working frequency remains near unity.The dielectric atoms based tunable metamaterial absorbers with simple structure have potential applications as tempe rature sensors and frequency selective thermal emitters.     

石墨/碳化硅/铁氧体涂层复合材料性能研究

为了开发具备良好介电性能和力学性能的多功能吸波复合材料,以涤纶针织物为基布,以环氧树脂为基体,在基布上进行石墨/碳化硅/铁氧体三层复合涂层整理,制备1.5 mm涂层厚度的柔性纺织涂层复合材料.采用介电谱仪研究了吸波剂的含量对吸波涂层材料介电常数和损耗角正切的影响.鉴于该材料多用于工程领域,采用万能材料实验机测试了该复合材料的拉伸、弯曲、剪切等力学性能.结果表明,该复合材料在低频段具备良好的介电性能,且具备一定的力学性能.     

Temperature tunable metamaterial absorber at THz frequencies

Dynamic or active control over the resonance frequency of the perfect metamaterial absorbers have attracted considerable attention, and many kinds of frequency tunable absorbers have been proposed. Unfortunately, these designed absorbers have drawbacks of very small frequency tuning range as well as complex unit structure. In this paper, a simple design and large frequency change range of terahertz metamaterial absorber is investigated. The absorber structure consists of only a patterned square metallic patch and an appropriate thickness of the dielectric spacing slab on top of a metallic board. Results show that the frequency tuning range of the metamaterial absorber can be up to 80.4%, which is much greater than that of the existing absorbers (no more than 30%). The continuous shift of the resonance frequency can be explained by the temperature dependent dielectric m. Besides, we also found that the presented design strategy is a genetic method and can apply to other types of structure designs. The simple design and wide frequency tuning range of the absorbers could find potential applications in materials detection, biological sensing, and frequency selective thermal emitters.     

“超材料”结构吸波复合材料技术研究

研究了"超材料"结构吸波复合材料的制备技术及其力学性能与电性能。通过突破不同尺寸金属周期结构单元制备、金属周期结构单元转移、含金属周期结构单元吸波复合材料工艺参数优化等关键技术,制备出电性能和力学性能批次间稳定性良好的含多层金属周期结构单元的"超材料"结构吸波复合材料,"超材料"结构吸波复合材料在2~18GHz频率范围具有宽频高吸收的特性。     

聚苯胺复合材料的介电性能研究

首先探讨了掺杂剂种类、掺杂剂用量对聚苯胺/聚酰胺纤维复合材料介电常数实部、虚部、损耗角正切、表面电阻的影响;其次研究了其外观形貌。结果表明:掺杂剂种类、掺杂剂用量对聚苯胺/聚酰胺纤维复合材料介电常数实部、虚部、损耗角正切、表面电阻影响较大;制备的聚苯胺复合材料具备良好的介电性能和导电性。     

聚吡咯/聚酯纤维复合材料吸波性能的探讨

聚吡咯是含有π电子共扼体系的高聚物,经掺杂反应电导率发生变化,当其电导率处于半导体状态时,具有良好的吸波性能.本文采用原位聚合法以聚酯纤维为基布,以吡咯为单体,制备具有良好吸波性能的柔性聚吡咯/聚酯纤维复合材料.首先探讨了吡咯浓度,温度,时间对复合材料吸波性能和表面电阻的影响;其次研究了其外观形貌和强力.结果表明:制备的聚吡咯复合材料具有良好的吸波性能;在0~106Hz频率内,吡咯浓度0.8 mol/L实验组,介电常数的实部、虚部均最大;1.0 mol/L实验组的损耗角正切最大;吡咯浓度0.8 mol/L实验组表面电阻最小;室温实验组的介电常数实部、虚部、损耗角正切最大,且明显优于其他组.反应时间150 min实验组的各项介电性能都明显优于其他组,且其电阻最小,导电率最好.     

Microwave absorption properties of double-layer absorbers based on spindle magnetite nanoparticles and flower-like copper sulfide microspheres

In this work, the spindle magnetite nanoparticles (SMNPs) and flower-like copper sulfide microspheres (FCSMSs) were synthesized via hydrothermal method. The structures, chemical composition and morphologies of samples were analyzed and characterized in detail. The microwave absorption properties of single-layer and double-layer absorbers were investigated based on the electromagnetic transmission line theory in the frequency range from 2 to 18 GHz. The results show that the double-layer absorbers consisting of FCSMSs as matching layer and SMNPs as absorbing layer display superior microwave absorbing performance compared to the single-layer ones due to the proper combination of magnetic loss of SMNPs and dielectric loss of FCSMSs, and the improved impedance matching characteristics. When the thicknesses of the absorbing layer and the matching layer are 1.6 and 0.4 mm, respectively, the minimum reflection loss reaches ??74.3 dB at 10.9 GHz, and the efficient absorption bandwidth is up to 5.34 GHz (8.46–13.8 GHz). The optimal SMNPs/FCSMSs double-layer absorbers can become a novel microwave absorption material with strong-absorption and broad-band.     

Study on preparation of the core-nanoshell composite absorbers by high-energy ball milling at room temperature

Electromagnetic (EM) wave pollution has become the chief physical pollution for environment. In recent years, some researches have been focused on the preparation of nano-composite absorbers at low temperatures or even at room temperature. In this letter, preparation of nanocomposite by using high-energy ball milling at room temperature is reported. The core-nanoshell composite absorbers with magnetic fly-ash hollow cenosphere (MFHC) as nuclear and nanocrystalline magnetic material as shell were prepared by high-energy ball milling and vacuum-sintering in this paper. The pre-treatment of MFHC, the sintering process and the mol ratio of starting chemicals had a significant impact for property of composite absorbers. The results of X-ray diffraction analysis (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) analysis indicated that perfect-crystalline nanomagnetic material coating was gotten with a particle size of 12 nm after ball milling. The results show the MFHC is dielectric loss and magnetic loss too; the exchange-coupling interaction happened between ferrite of the MFHC and nanocrystalline magnetic material coating. The exchange-coupling interaction enhances magnetic loss of composite absorbers. They have a perfect EM parameters at low microwave frequency. The core-nanoshell composite absorbers have a higher magnetic loss at low frequencies, and it is consistent with requirements of the microwave absorbing material at the low-frequency absorption. The microwave absorptivity of the core-nanoshell composite absorbers is better than single material.