化学共沉淀法制备的纳米Ni0.5Zn0.5CexFe2-xO4铁氧体微波吸收特性研究

采用化学共沉淀法制备了纳米Ni0.5Zn0.5CexFe2-xO4(x=0,0.005,0.01,0.015)铁氧体吸波材料,用AV3618型微波矢量网络分析仪测试了样品在8.2～12.5GHz范围内的微波吸收特性,实验结果表明:稀土元素铈的含量影响材料的吸波性能,当x=0.01时, 纳米Ni0.5Zn0.5CexFe2-xO4铁氧体的吸波性能最佳.对于Ni0.5Zn0.5Ce0.01Fe1.99O4铁氧体吸波材料,当涂层厚度为1mm时,在测试频段内有三个吸收峰,在8.8GHz处,其最大吸收衰减量为15.4dB,10 dB以上带宽达3.8GHz,适量掺杂稀土元素铈是提高镍锌铁氧体吸波材料性能的一种有效途径.     

溶胶-凝胶法制备空心微珠表面钡铁氧体包覆层的研究

铁氧体是微波吸收材料的主要成分之一,应用非常广泛,但由于铁氧体比重较大,制成吸波材料难以满足吸收频带宽、质量轻、厚度薄的要求,因此实际使用的铁氧体吸波涂层往往不是单一的铁氧体涂层,而是通过复合制备成复合铁氧体吸波涂层.以质量轻、化学性能稳定的热电厂粉煤灰空心微珠为基体,以硝酸铁、硝酸钡和柠檬酸为原料,用溶胶-凝胶法在空心微珠表面包覆钡铁氧体涂层,并用差热分析仪(DTA)、X射线衍射仪(XRD)、能谱仪(EDX)和扫描电镜(SEM)对其进行了分析表征,结果表明用溶胶-凝胶法在空心微珠表面能均匀地包覆一层薄的M-型钡铁氧体涂层.     

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。     

宽频段雷达表面波衰减特征规律研究

目标物体上表面波的衰减吸收对目标的隐身起到很大的作用.研究了雷达吸波涂层对宽频段雷达表面波衰减吸收的规律以及频率选择表面与吸波涂层相结合的复合吸波涂层对宽频段表面波衰减吸收的规律.实验结果表明,低厚度的雷达吸波涂层就可以实现高频表面波的强衰减吸收,而频率选择表面与低厚度雷达吸波涂层相结合的复合涂层与雷达吸波涂层共同交替使用可以实现宽频段表面波的强衰减吸收,有望实现目标物体在宽频段范围内的高性能均衡雷达隐身.     

天然尖晶石型铁氧体(铁砂)基复合吸波涂料特性研究

天然尖晶石型铁氧体（铁砂）与聚氨脂粘结剂制成的吸波涂料在7～12GHz频段有两个吸收峰，涂层厚度1．25mm时，吸收量5．2～8．5dB，在基础吸波材料(铁砂)中添加尖晶石型铁氧体、顺磁性稀土材料和六角铁氧体制成复合吸波涂料，使其吸收量达18～25aB，匹配厚度1．1～1．2mm，两吸收峰间距＞4．4GHz，它加工简单，价格低廉。     

生物型吸波微粒的制备

电磁波吸收微粒对于电磁防护和雷达波的吸收起着关键的作用.采用微生物作为模板,通过溶胶-凝胶处理,在微生物表面包覆了一层Fe3O4,制备了相应的生物吸波微粒,研究了产物的形貌、成份、微波磁参数.实验表明生物吸波微粒表面形成厚度<3μm的尖晶石型铁氧体Fe3O4.包覆铁氧体的螺旋形生物吸波微粒性能良好.采用硅橡胶作为粘结剂制备了1.2mm厚的参杂螺旋形生物吸波微粒的涂层,结果显示该涂层在10～16GHz内反射损失>-10dB.     

原位聚合法制备铁氧体/聚苯胺吸波复合材料的研究进展

电磁污染已成为继空气污染、水污染和噪声污染之后的第四大污染, 吸波材料因其吸收和衰减特性, 可以作为解决电磁污染的有效手段。聚苯胺(PANI)作为一种电阻损耗型吸波材料, 可以满足吸波材料"厚度薄"、"质量轻"的发展理念, 但由于阻抗匹配度差, 吸波性能并不理想。铁氧体作为一类传统的磁损耗型吸波材料, 因其密度较高使其适用范围受到限制。高密度的铁氧体与低密度的聚苯胺复合制备的吸波材料, 不仅可以调整复合材料的密度, 而且还能改善复合材料的阻抗匹配, 提高铁氧体/聚苯胺复合材料的吸波性能。本文首先探讨了聚苯胺以及铁氧体/聚苯胺复合材料的制备方法, 其次阐述了铁氧体/聚苯胺复合材料的吸波机理。然后分别归纳了尖晶石型、磁铅石型、石榴石型铁氧体与聚苯胺制备的复合材料在吸波领域的研究进展。最后指出铁氧体/聚苯胺复合材料应趋向于电磁仿真和多元复合化的方向发展。     

吸波材料优化匹配的理论分析

为了研究电磁参数和涂层的厚度对单/双层吸波材料的吸收性能的影响,以期制备出具有良好的电磁匹配特征的吸波材料,利用通过单/双层吸波涂层内电磁波传播的理论机制,计算机模拟技术,分析了涂层厚度、电磁参数及频率变化对材料的电磁波吸收性能影响的规律.同时提出了双层吸波材料设计中厚度匹配和阻抗匹配等基本原则.结果显示,随着厚度的增加,吸波材料对电磁波的吸收峰向低频移动,并且相继出现多个吸收峰.当电磁匹配常数M=0.25时,涂层材料展现了很好的吸波性能.对于双层吸波材料,阻抗渐变原则和厚度匹配规律直接影响到其吸收性能.     

铁氧体/石墨复合吸波涂层的微波吸收性能

本文将固相法制备的磁损耗型Ba0.9Sm0.1Co2Fe16O27铁氧体与电损耗型石墨相结合,通过测试两者的电磁参数,采用YRcomputor软件模拟计算了双层复合吸波涂层的反射率。结果表明：铁氧体/石墨复合吸波涂层在2～8 GHz频段有较好的吸波性能;其中,下层为含量80 wt%的Ba0.9Sm0.1Co2Fe16O27,厚度1.5 mm,上层为10 wt%的石墨,厚度1.5 mm时,该复合涂层表现出优良的微波吸收特性,反射率损耗RL〈-10 dB时,带宽约为3 GHz（3.5～6.5 GHz）,最大吸收值约为-27 dB。     

天然尖晶石型铁氧化（铁砂）基复合吸波涂料特性研究

天然尖晶石型铁氧体（铁砂）与聚氨脂粘结剂制成的吸波涂料在７￣１２ＧＨｚ频段有两上吸收峰，涂层强度１．２５ｍｍ时，吸收量５．２￣８．５ｄＢ，在基础吸波材料（铁砂）中添加尖晶石型铁氧体、顺磁性稀土材料和六角铁氧体制成复合吸波涂料，使期吸收量达１８￣２５ｄＢ，匹配厚度１．１￣１．２ｍｍ，两吸收峰间距〉４．４ＧＨｚ，它加工简单，价格低廉。     

BaMnZnCoTi-W型铁氧体微波吸收剂的制备和特性研究

对用Ｃｏ２＋、Ｔｉ４＋部分置换Ｆｅ３＋的Ｂａ（ＭｎＺｎ）ａＣｏｂＦｅ１６－ｙＣｏ２＋０．５ｙＴｉ４＋０．５ｙＯ２７－Ｗ型平面六角晶系微波铁氧体吸收剂的制备和特性进行了研究,并对其复介电常数的实部ε′和虚部ε″、磁导率的实部μ′和虚部μ″、损耗随微波频率、Ｃｏ２＋、Ｔｉ４＋含量、涂层厚度的变化作了测试和分析,发现当ｙ＝１．０时铁氧体的吸收性能最佳,其最佳厚度为１．４０ｍｍ,吸收衰减最大达２７．５ｄＢ。     

A review on carbon/magnetic metal composites for microwave absorption

At present,developing high-efficiency microwave absorption materials with properties including light-weight,thin thickness,strong absorbing intensity and broad bandwidth is an urgent demand to solve the electromagnetic pollution issues.An ideal microwave absorber should have excellent dielectric and magnetic loss capabilities,thereby inducing attenuation and absorption of incident electromagnetic radiation.Recently,various carbon/magnetic metal composites have been developed and expected to become promising candidates for high-performance microwave absorbers.In this review,we introduce the mechanisms of microwave absorption and summarize the recent advances in carbon/magnetic metal composites.Preparation methods and microwave absorption properties of carbon/magnetic metal com-posites with different components,morphologies and microstructures are discussed in detail.Finally,the challenges and future prospects of carbon/magnetic metal absorbing materials are also proposed,which will be useful to develop high-performance microwave absorption materials.     

碳基材料吸波性能研究进展

随着雷达探测技术的迅猛发展和电磁波辐射污染的日益加剧,新型吸波材料的研究和开发成为各国研究的热点。单一吸收剂存在吸波频带窄和吸收强度低等缺点,无法满足新型吸波材料频带宽、厚度薄、质量轻、吸收强的要求。碳材料具有密度低和吸波性能好等优点,通过与其他吸收剂的双组分、多组分复合,或对复合材料的微观结构进行设计,碳系复合材料表现出优异的吸波性能。简要介绍了吸波材料的工作机理,然后分别从炭黑、碳纤维、碳纳米管、石墨烯和其他碳系材料等5个方面综述了碳系材料在电磁波吸收中的应用和发展,归纳了碳系材料吸波性能的最新研究进展,最后提出了当前研究中存在的不足并明确了研究方向。     

Untersuchung zur Schichtfolge eines Multilayerschichtsystems NiZn Ferrit / Si bzw. SiO2 für Höchstfrequenzleiterplatten im Frequenzbereich größer 1000 MHz

Simulation of Layer – Sequence of Ni‐Zn Ferrite Thin Films and Multilayers for EMC Applications > 1000 MHz NiZn ferrite multilayer have attracted much attention as materials with unique properties. One of these properties is enhanced microwave absorption. This gives a possibility to product absorption electromagnetic covers ( EMC ) with ultrathin thickness. The Electromagnetic Compatibility absorption of NiZn Ferrite polycristalline sample is 0,6 dB in the rf‐ range.     

D-xylose-derived carbon microspheres modified by CuFe2O4 nanoparticles with excellent microwave absorption properties

In this work, we studied the preparation and microwave absorption properties of D-xylose-derived carbon materials modified by CuFe₂O₄ nanoparticles and discussed the influence of the addition amount of carbon materials. It was prepared with a simple hydrothermal method, and various methods are used to characterize its microscopic morphology, chemical structure and microwave absorption properties.Results show that the modification of copper ferrite nanoparticles is effective in mitigating polarization and magnetic losses, enhancing the microwave absorption properties of the samples and absorption curves of the composite materials change from a single peak to double peaks. Comparing all samples it can be concluded that the effective absorption bandwidth of CuFe₂O₄ composite materials containing carbon microspheres (CuFe₂O₄/CMs-0.3) is 6.24 GHz. The minimum reflection loss (RL) is???50.4 dB at 14.64 GHz. The thickness of the above corresponds to 2.5 mm. This work not only provides a reference method for the preparation of microwave absorbing materials but also contributes to the understanding of absorption mechanisms.

     

配比及热处理气氛对纳米Fe/石墨复合材料微波吸收性能的影响

利用氧化石墨层间可吸附大量离子的特性使Fe3+吸附到氧化石墨层间,再通过还原法制备了纳米Fe/石墨复合材料.采用元素分析、电磁参数测定等手段系统考察了硝酸铁与氧化石墨的配比及热处理气氛对纳米Fe/石墨复合材料分子组成和微波吸收性能的影响.结果表明,纳米Fe/石墨复合材料属于典型的软磁性材料;FeGO31H600的最大反射损耗为-6dB,而FeGO21H600的最大反射损耗达到了-9dB,故FeGO21H600的微波吸收效果最好;当厚度为1mm时,FeGO21600反射损耗大于6dB的频段范围为14～18GHz,而FeGO21H600反射损耗大于6dB的频段范围为11～18GHz,比FeGO21600低且宽,故FeGO21H600的微波吸收效果比FeGO21600的好.     

Microwave Absorption Properties of Cobalt-Zirconium Doped Strontium Hexaferrites in Ku-Frequency Band

In this article, microwave electromagnetic properties of doped strontium hexaferrites have been investigated in Ku microwave frequency band (12.4–18 GHz), along with their performance as microwave absorbing materials. Vector network analyzer has been used for characterization of cobalt-zirconium substituted strontium hexaferrites Sr(CoZr)_xFe_(12?2x)O₁₉ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0), synthesized using sol-gel method. Real parts of permittivity and permeability have shown very small variations up to 16 GHz. There has been a dip in spectrum of real part of permittivity and a peak in spectrum of real part of permeability at the same frequency in 16–18 GHz range for every composition. Regarding the electromagnetic wave absorption, all the six prepared compositions have potential (≥90% absorption) for usage in suppressing electromagnetic pollution. The composition with x = 1.0 has achieved the highest ?10 dB absorption bandwidth from 15 to 18 GHz frequency. The realization of absorbing materials with maximum absorption is related to the phenomenon of impedance matching and high electromagnetic losses. The correlation of absorption peaks with attenuation constant, wave impedance and complex thickness has also been studied.     

Multiphase Molybdenum Carbide Doped Carbon Hollow Sphere Engineering: The Superiority of Unique Double-Shell Structure in Microwave Absorption

In order to achieve excellent electromagnetic wave (EMW) absorption properties, the microstructure design and component control of the absorber are critical. In this study, three different structures made of Mo₂C/C hollow spheres are prepared and their microwave absorption behavior is investigated. The Mo₂C/C double-shell hollow spheres consisting of an outer thin shell and an inner rough thick shell with multiple EMW loss mechanisms exhibit good microwave absorption properties. In order to further improve the microwave absorption properties, MoC_1-x/C double-shell hollow spheres with different crystalline phases of molybdenum carbide are prepared to further optimize the EMW loss capability of the materials. Finally, MoC_1-x/C double-shell hollow spheres with α-phase molybdenum carbide have the best microwave absorption properties. When the filling is 20 wt.%, the minimum reflection loss at 1.8 mm is −50.55 dB and the effective absorption bandwidth at 2 mm is 5.36 GHz, which is expected to be a microwave absorber with the characteristics of “thin, light, wide, and strong”.     

Foam structure to improve microwave absorption properties of silicon carbide/carbon material

Foam structure materials are well known for their lightweight,efficient,and broadband microwave absorption properties compared to bulk material.However,little has been understood about the effect of a foam structure on the absorption performance of the foam material.In this study,the role of foam structure properties of the silicon carbide/carbon(SiC/C) foam material on microwave absorption is explored using experiment and simulation.We find that the foam structure of SiC/C foam material causes diffraction,multiple reflections,improves the interfacial polarization,and compatibilization.The absorption performance of SiC/C foam material is also studied.The-10 dB effective absorption bandwidth can be adjusted from 4.0 GHz to 18 GHz by tuning SiC/C foam material thickness to 3-7 mm.Therefore,the foam structure design is an effective way to improve the absorption performance of the SiC/C foam material.