含电路模拟结构陷阱式吸波复合材料研究

研究了电路屏材质、电路屏尺寸、介质层电磁参数等对“陷阱”式结构吸波复合材料吸波性能的影响,总结了改变参数后吸波性能的变化规律。研究结果表明：通过合理的结构设计,使得吸波复合材料的吸波／承载综合性能得以提高。     

含Minkowski活性碳毡电路屏复合材料的吸波性能研究

研究了含Minkowski活性碳毡电路屏复合材料的微波吸收特性,并对电路屏的吸波机理进行了初步的探讨。结果表明,含Minkowski活性碳毡电路屏复合材料的吸波性能与电路屏阵列单元的尺寸密切相关,经合理设计,复合材料在5.3～18GHz频率范围内有-10dB以下的吸收,有效带宽达12.7GHz。复合材料对电磁波的主要吸收机制是电磁波在电路屏和反射板之间的多次反射、衰减。     

含同轴线活性碳毡电路屏复合材料的吸波性能研究

研究了含同轴线活性碳毡电路屏复合材料的微波吸收特性,并对电路屏的吸波机理进行了初步探讨.结果表明,含同轴线活性碳毡电路屏复合材料的吸波性能与电路屏阵列单元的尺寸和间距密切相关,经合理设计,复合材料在7～18GHz频率范围内有-10dB以下的吸收,有效带宽达11GHz.复合材料对电磁波的主要吸收机制是电磁波在电路屏和反射板之间的多次反射、衰减.     

含电路模拟结构吸波复合材料

研究了电路模拟结构材质、电路模拟结构尺寸、介质层电磁参数等对电阻渐变型和"陷阱"式结构吸波复合材料的吸波性能和力学性能的影响。结果表明:通过合理的结构设计,在其它条件相同的情况下含电路模拟结构电阻渐变吸波复合材料的吸波性能在8~18 GHz范围内有3~5 dB的提高;含电路模拟结构"陷阱"式吸波复合材料在厚度≤4 mm条件下,实现了吸波性能在8~18 GHz频率范围内吸收率≥12 dB。在提高吸波复合材料吸波性能的同时,电路模拟结构的引入使复合材料力学性能有一定的提高,有利于实现吸波复合材料的吸波/承载一体化。      

碳毡电路模拟吸波复合材料的研究

分别研究了含矩形碳毡电路屏和“十”字形碳毡电路屏吸波复合材料的微波吸收特性，并对碳毡电路屏的吸波机理做了初步的探讨。结果表明，碳毡电路模拟吸波材料的吸波性能与电路屏阵列单元的结构和尺寸密切相关。矩形电路屏阵列单元中矩形缝隙的长或宽增大，材料的吸波性能提高；矩形缝隙之间的距离增加，材料的吸波性能降低。本实验条件下当矩形缝隙的长、宽和间距分别为24、12和6mm时，材料可获得8．56GHz的有效带宽和-25dB的最大反射衰减。“十”字形电路屏阵列单元中“十”字形缝隙的臂长或臂宽增大，材料的吸波性能提高；“十”字形缝隙之间的距离增加，材料的吸波性能降低。“十”字形缝隙的臂长、臂宽和“十”字形缝隙之间的距离分别为16、8和6mm时，材料的有效带宽7．2GHz，最大反射衰减-26．2dB。     

活性碳纤维结构对电路屏复合材料吸波性能影响研究

采用二次活化活性碳纤维(activated carbon fiber,ACF)设计交错结构频率选择表面(FSS),并制备了吸波复合材料,采用SEM对碳纤维表面微观形貌进行观察,采用矢量网络分析仪对其微波反射和吸收性能进行了测试。结果表明,随着活化温度的升高,ACF的比表面积及孔径逐渐增大,孔深也逐渐增加。吸波性能随着活化温度的升高呈先增大后降低的趋势,当活化温度为750℃时的电路屏制备的复合材料吸波效果最好:在5.2~9.9 GHz有-10 d B以下的反射,最低反射衰减为-21.1 d B;ACF内部π电子的极化弛豫及纤维微观形貌对电磁波的散射损耗能够提高ACF电路屏复合材料吸波性能。     

活性碳毡电路屏(直立碳纤维)/树脂复合吸波材料

研究了含活性碳毡电路屏和直立碳纤维吸波复合材料的微波吸收特性。结果表明: 含碳毡电路屏吸波材料的吸波性能与电路屏的种类(感性、容性) 和尺寸密切相关。含感性屏的吸波材料, 当毡条间距、宽度分别为7 mm、5 mm 时, 材料在整个雷达波段(8～18 GHz) 有- 10 dB 以下的反射衰减。含容性屏的吸波材料, 随电路屏中碳毡块间距和边长的减小, 吸波性能提高。含直立碳纤维材料的吸波性能与纤维间距有关, 间距为4 mm 时可获得有效带宽7. 6 GHz 的吸波材料。用分块设计的思想设计吸波材料, 可提高其吸波性能。分块中心对称的感性电路屏(毡条宽5 mm , 间距10 mm) 和直立碳纤维(间距8 mm) 混杂吸波体在11. 8～18 GHz 频带内有低于- 20 dB 的反射衰减, 最大吸收峰值- 30 dB。     

吸收剂颗粒界面效应对电磁波吸收性能影响的理论研究

针对含夹杂颗粒的电磁吸波复合材料,探讨了颗粒界面对电磁波吸波性能的影响.首先给出了表征电磁波吸收层吸波性能的场强反射率及其功率反射率的计算公式,在此基础上结合颗粒夹杂复合吸波材料含界面效应的等效介电常数和等效磁导率的预测公式与电磁波吸波层的功率反射率的基本理论,给出了电磁波吸收层的功率反射率与颗粒尺寸,以及颗粒界面效应之间的关系.进而从数值角度展示了颗粒界面效应与电磁波吸收的最佳频率和电磁波吸收层厚度的影响,以及颗粒界面对电磁波功率反射率的尺度效应等.分析结果表明,当电磁波吸收剂的颗粒尺寸较小时,颗粒界面效应对电磁波功率反射率的影响是明显的.     

“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。     

电磁屏蔽机理及涂敷/结构型吸波复合材料研究进展

电子产品和通讯技术快速发展造成的电磁污染日益严重,既危害人体健康和仪器仪表精度,又会造成信息泄露、失去安全保障等.因此,电磁屏蔽技术为直接有效的防控措施之一,通过衰减甚至完全消除电磁波来阻止电磁波的传递.电磁屏蔽机理包括电磁波反射和电磁波吸收两个方面,科学地设计制备出高性能的吸波复合材料已成为研究的热点问题之一.研究结果表明,电磁波衰减不仅需要吸波材料自身较好的电磁损耗性能,更需电磁波能够基于自由空间与基体材料间具有阻抗匹配特性,有效进入吸波材料内部,使电磁波能被吸波剂高效吸收.通常,按照制备工艺划分,吸波复合材料可分为涂敷型和结构型吸波复合材料两大类.前者是将吸波剂与涂料、粘合剂等充分混合后涂敷于元件表面作为吸波涂层,而后者则是以吸波剂作为功能载体,具有优良物理化学特性的材料作为基体,并与功能载体产生协同或增强作用的新型吸波复合材料.本文通过对电磁屏蔽理论及吸波材料的本征特性进行系统的总结归纳,并基于相关理论基础对涂敷/结构型吸波复合材料进行简要综述,对比不同类型吸波材料的吸波性能,探讨涂敷/结构型吸波复合材料未来发展的制约因素及今后发展前景,为开发新型吸波复合材料提供理论支撑和研究思路.     

Effect of short carbon fibers and MWCNTs on microwave absorbing properties of polyester composites containing nickel-coated carbon fibers

Multiphase composite materials filled with multiwall carbon nanotubes (MWCNTs), short nickel-coated carbon fibers and millimeter-long carbon fibers with various weight fractions and compositions are developed and used for the design of wide-band thin radar-absorbing screens. The effective complex permittivity of several composite samples is measured in the frequency range from 8 GHz to 18 GHz. The obtained results show that the addition of the MWCNTs into the mixture allows tuning the EM properties of the composite filled with the short nickel-coated fibers. Numerical simulations are also performed in order to design new radar-absorbing shields. Single-layer and bi-layer thin dielectric Salisbury screens are designed to exhibit minimum reflection coefficient at 10 GHz and at 15 GHz, and maximum bandwidth at −10 dB. It results that the total thickness of the screen can be reduced below 2 mm by using a lossy sheet made with the composite filled with MWCNTs and nickel-coated carbon fibers, whereas the bandwidth at −10 dB can exceed 6 GHz in a bi-layer structure.     

The Research on Surface Technology and Structures for Camouflage Net

This paper is about how to improve camouflage net protecting effect from radar detection, by introducing the layer-composite technology of radar-absorbing materials and optimizing radar-absorbing structure. In the layer-composite technology, materials choices and parameters setting, especially the relation between the content of Phosphor and radar absorption on the Ni-P electroless plating technology, are mentioned. Moreover, four superficial structures, are compared. A conclusion is got that jungle-two structure can do the best to attenuate 5.7 dB over the whole frequency ranges. In addition, according to the theory of the interaction of electromagnetic wave, the study applies physical optics to the RCS computation for optimizing technological parameters and structure by the computing software.     

Development of the composite RAS (radar absorbing structure) for the X-band frequency range

Since the EM properties of fiber reinforced polymeric composites can be tailored effectively by adjusting its composition, they are plausible materials for fabricating the radar absorbing structure (RAS) of desired performance. In this study, the composite RAS which has superior load bearing capacity and EM absorption characteristics has been developed by blending the conductive carbon black with the binder matrix of the E-glass/polyester composite, and its EM absorption characteristics has been measured by the free space method in the X-band frequency range (8.2–12.4 GHz). The composite RAS was designed so as to have the optimal performance for the X-band centered at 10 GHz. From the investigation, it was found that the composite RAS of 2.93 mm thickness with the conductive carbon black absorbed more than 90% of incident EM wave throughout the entire X-band frequency range.     

Preparation of Metal-Coated Carbon Fiber Reinforced Composites and Their Electromagnetic Properties

Medium temperature curing by infrared radiation was used to prepare electromagnetic wave absorbing multilayered plastic matrix composite materials containing metal-coated carbon fibers (MCFs). The electromagnetic properties of the materials were investigated by frequency scanning tests with microwave vector network analyzer. It is found that the electromagnetic parameters, mainly permittivity of the composites increase significantly with the addition of MCFs, which gives the composites good designability as thin, light-weight EM wave absorbers. It is also shown that MCFs can improve on the EM wave energy attenuating property of the composites by widening the work frequency band width and raising the absorptive peak     

碳基复合吸波材料研究进展分析

碳基材料由于具有优异的介电性能、良好的复合特性、特殊的微观结构、较低的密度、较强的化学稳定性以及使用便捷、维护简单等优点,在雷达吸波领域有着广阔的应用前景,已逐渐成为学界与工业界所追逐的热点研究对象与应用方向。本文在梳理总结分析国内外碳基材料雷达吸波应用研究成果的基础上,提出依据微观结构,按照形状维数划分归类,将材料分为零维(0D)、一维(1D)、二维(2D)和三维(3D)结构,进而以此为主线梳理碳基复合材料在雷达吸波隐身领域的研究进展,总结对比分析近年来国内外在碳基吸波材料方面的研究成果,指出未来材料将以"薄、轻、宽、强"为基础要求,朝着组成复合化、结构多样化、机理协同化和电磁参数可调化方向发展。     

Novel optimization method of single square FSS impinged and cascaded radar absorbing composites

It is well known that radar absorbing potentiality of existing magneto-dielectric composites can be significantly enhanced by the application of frequency selective surface (FSS) and cascaded electromagnetic (EM) structures. But the optimization of such complex EM structures and validation of the adopted optimization strategy is still a very challenging task for the researchers. Therefore, in this study, an effective effort has been made for the optimization and the corresponding validation for Single Square FSS (SS-FSS) impinged and cascaded radar wave absorbers using advanced computational EM software’s like FEldberechnung fur Korper mit beliebiger Oberflache – a German acronym (FEKO) and high frequency structure simulator (HFSS). In addition, a critical analysis of dielectric constant (ε′) has been carried out to select the best combination of composites for the development of efficient radar wave absorbers. A comparison between optimized and simulated results have been carried out to examine the effect of advanced EM approaches over reflection loss (RL) characteristics of composite radar absorbing materials (CRAMs). A rapid change in radar absorption properties of composites has been observed after the application of SSFSS and cascading. A SS-FSS impinged composite has been found to provide a wide absorption bandwidth of 3.6 GHz at X-band. A cascaded absorber having layer thickness 1.8 mm provides a peak RL of ?42.6 dB at 10.6 GHz with an absorption bandwidth of 2.5 GHz. The strong agreement between mathematical model, HFSS and FEKO results clearly reflects the efficiency of adopted approach for distinct practical EM applications.     

Facile synthesis and excellent electromagnetic wave absorption properties of flower-like porous RGO/PANI/Cu<Subscript>2</Subscript>O nanocomposites

Novel porous ternary nanocomposite systems containing reduced graphene oxide (RGO)/polyaniline (PANI)/cuprous oxide (Cu₂O) were prepared via one-step in situ redox method. The RGO/PANI/Cu₂O nanocomposites present a flower-like structure with an average size of 2.0 μm in diameter. The morphologies and properties of the products can be controlled by adjusting the molar ratios of aniline to Cu²⁺. When the molar ratio of aniline to Cu²⁺ is 1:1, the product exhibits excellent microwave absorption property in the frequency range of 2–18 GHz. It can be seen that the maximum reflection loss (RL) of the ternary composite is up to ?52.8 dB at 2.7 GHz with a thickness of only 2 mm, and the absorption bandwidth corresponding to ?10 dB (90% of EM wave absorption) is 13.2 GHz. The microwave absorption property of ternary RGO/PANI/Cu₂O composite is significantly improved due to its special flower-like porous structure, dielectric loss property and well impedance matching characteristics, which is 8.12 times than that of pure RGO and 5.28 times than that of pure PANI. Therefore, our study paves a new way to prepare the promising lightweight and high-performance composite materials combined with the characteristics of three components for electromagnetic absorption.     

三维夹芯层连织物透波复合材料性能研究

考察了玻璃纤维三维夹芯层连织物/氰酸酯(CE)复合材料的透波性能, 并与夹芯层连织物/环氧树脂复合材料和蜂窝夹层结构复合材料进行了对比。研究发现: 实验频段范围内三维夹芯层连织物/氰酸酯复合材料的平均透波率高于蜂窝夹层结构复合材料和夹芯层连织物/环氧树脂复合材料; 夹芯层连织物/氰酸酯复合材料的透波率受电磁波入射角度影响较小, 并且在芯柱高度为8 mm时有最大值, 平行经向入射的透波率略大于平行纬向入射的透波率, 8~12 GHz频率的透波率略大于12~18 GHz的透波率; 由于反射作用, 面板增强后夹芯层连织物/氰酸酯复合材料的透波率下降明显。      

Controllable synthesis of Ni/NiO@porous carbon hybrid composites towards remarkable electromagnetic wave absorption and wide absorption bandwidth

The reasonable design of the composition of the composite materials is of great significance to optimized the electromagnetic (EM) wave absorption performance.Herein,the Ni/NiO@C hybrid composites with tunable Ni proportion were successfully synthesized through a two-step process.With the assistance of X-ray diffraction with refinement treatment,the specific proportion of Ni of as-obtained hybrid com-posites could be obtained.Employing controlling calcination time to adjust the Ni content of Ni/NiO@C hybrid composites,it has been found that the composite carbonized at 500 ℃ exhibited remarkable EM wave absorption with the minimum reflection loss (RLmin) of-49.1 dB at 4.9 mm and the widest effective absorption bandwidth (EABmax) of 4.56 GHz at 2.1 mm.Moreover,by adjusting the Ni source,the optimal EM wave absorption performance could be achieved.Results illustrated that the N3PC with the Ni pro-portion of 13.17 ％ showed the RLmin as low as-51.1 d B at 2.4 mm and the EABmax was 5.12 GHz at 2.7 mm.It is worth noting that this work demonstrates the relevance of the composition and EM wave absorption performance of hybrid composites,which offers a feasible reference for the absorption mechanism of absorber.