铁氧体多层结构电波吸收体的研究

用三种不同磁导率μｉ的铁氧体基复合电波吸收材料制成双层结构电波吸收体，在７～１２ＧＨｚ频段吸收量Ａ与频率ｆ关系曲线与单层基本相似，存在两个吸收峰，但第二峰移向高频，Ａ由２０ｄＢ增至３７ｄＢ；在吸收介质与反射板之间以及在两个介质层之间涂以介电型介质膜，使第一吸收峰移向高频，Ａ分别增至２９ｄＢ和２７ｄＢ。对其作用机理进行了探讨。     

磁性材料、超导材料和器件

TMZ(),TB323 98060037结构型铁砂墓复合电波吸收体研究/娄明连,阐涛,谢玉荣(安徽大学)11电子元件与材料.一1 998,17(3).一18一20由天然尖晶石铁氧体(铁砂)为基制备的复合电波吸收材料,在7一12GHz,吸收率A为12一27dB,匹配厚度d为1 .4mm。将几种铁砂基复合吸收材料制成双层结构电     

磁性材料、超导材料和器件

TM27 02040083添加稀土对吸波材料性能的影响/阚涛,娄明连(安徽大学) 磁性材料及器件。-2001,32(6)。-18-21在铁砂、铁氧体和铁磁-铁电等复合电波吸收材料中掺入微量稀土氧化物能全面大幅度提高材料的吸波特性。最大吸收量可提高54 ％～125％ 10dB带宽扩展近一倍。匹配厚度也有所降低。还发现,稀土氧化物的掺入量存在极值,添加混合稀土氧化物比添加高纯度稀土氧化物能获得更好的效果。因此添加稀土复合物是提高吸波材料性能的一种途径。图1表2参4(午)     

12GHz GaAs单片混频器

分析研究了一种新型１２ＧＨｚＧａＡｓＭＥＳＦＥＴ单片混频器，这种混频器采用级联ＦＥＴ作为混频元件。射频（ＲＦ）和本振（ＬＯ）信号分别通过各自的匹配网络进入混频电路，在中频输出端用中频缓冲放大器代替通常的中频匹配电路。电路在厚０．２ｍｍ，面积１．５ｍｍ×１．２ｍｍ的ＧａＡｓ基片上实现。设计的ＭＭＩＣ混频器在本振１１ＧＨｚ，射频１１．７～１２．２ＧＨＺ频率范围内的最大变频增益１．８ｄＢ。这一结果使进一步研究单片微波接收机成为可能。     

8～16GHzGaAs单片宽带分布放大器

报道了８～１６ＧＨｚＧａＡｓ单片宽带分布放大器的设计与制作。单级ＭＭＩＣ电路采用三个栅宽为２８０μｍ的ＧａＡｓＭＥＳＦＥＴ作为有源器件，芯片尺寸为１．１ｍｍ×１．６ｍｍ。在８～１６ＧＨｚ频率范围，用管壳封装的两级级联放大器增益Ｇ＿ａ，为１１．３±１ｄＢ，噪声系数Ｆ＿ｎ＜６ｄＢ，输出功率Ｐ＿（１ｄＢ）＞１６ｄＢｍ。     

宽带GaAsFET微波单片集成单刀双掷开关

本文报道了一种采用串、并联ＦＥＴｓ结构的ＧａＡｓＭＭＩＣ单刀双掷开关。芯片尺寸为０．９７＊１．２３ｍｍ．在ＤＣ－１０ＧＨＺ频率范围内，插入损耗小于２．２ｄＢ，隔离度大于３２ｄＢ，反射损耗大于１２ｄＢ，并关时间小于１ｎｓ，在５ＧＨＺ下的功率处理能力大于２０ｄＢｍ。此开关具有极低的直流功率耗散。     

2～12GHz GaAs单片行波放大器

报道了一个全平面超宽带ＧａＡｓ单片行波放大器的研究结果。该单片电路的核心部件是四个３００μｍ栅宽的ＭＥＳＦＥＴ，整个电路拓扑结构简单，芯片面积为３．０ｍｍ×１．８ｍｍ。电路经优化设计后在２～１２ＧＨｚ范围内，小信号增益为５±１ｄＢ，输入输出电压驻波比≤１．７５。上述频率范围内输出功率≥１６ｄＢｍ，噪声系数≤８ｄＢ。采用全离子注入、全平面工艺，均匀性、一致性良好。实验结果与设计预计值十分一致。     

C频段内匹配砷化镓功率场效应晶体管

采用离子注入、多层欧姆接触金属结构、干法刻蚀、г形栅、空气桥、通孔接地和电镀热沉等先进技术，在直径５０ｍｍＧａＡｓ片上制作了总栅宽为９．６ｍｍ的功率场效应晶体管芯片。用４枚这种芯片并联，在其输入端和输出端分别加入内匹配电路，制成了Ｃ频段内匹配功率场效应晶体管。在大于５００ＭＨｚ的带宽内，１ｄＢ增益压缩输出功率达１８Ｗ，１ｄＢ压缩增益为８．３ｄＢ，功率附加效率达３０％。     

铁氧体电波吸收板透射和反射特性研究

用三种不同磁导率 (μr1 、μr2 、μr3 )的铁氧体电波吸收剂 ,制成 10 0 m m× 10 0 mm双层结构的电波吸收板 ,在 8～ 12 GHz频段测得其透射吸收特性为 :涂层厚度 1.80 mm,吸收量 At=12 .2 d B;涂层厚度 1.15～ 1.85mm,吸收量 At>9d B。反射吸收特性为 :吸收量 Af=2 3d B,10 d B带宽 4GHz,匹配厚度 1.17mm。     

C波段单片有源环行器

报道了一种源耦合反馈单片有源环行器的研究结果、该单片电路采用实测ＦＥＴ的Ｓ参数进行微波ＣＡＤ优化设计，内部包含有３个３００μｍ栅宽的ＦＥＴ，芯片面积１．７ｍｍ×１．９ｍｍ。采用ＧａＡｓ的离子注入平面工艺，芯片电路具有良好的均匀性、一致性。在３．５～４．５ＧＨｚ内，电路插入损耗约７．５ｄＢ，隔离度为２１～２６ｄＢ，驻波比基本小于２。     

基于熔融沉积成型的多层石墨烯吸波体的快速制备及其性能

在制备石墨烯/聚乳酸(PLA)复合材料的基础上,利用熔融沉积成型技术快速制备了单层均质样件,研究了石墨烯含量对其电磁参数的影响规律,并基于传输线理论计算分析了其吸波效果;选择石墨烯含量较低的复合材料作为透波层的打印材料,石墨烯含量较高的复合线材作为吸收层和再次吸收层的打印材料,并基于四分之一波长匹配理论确定了吸收层、再次吸收层的匹配厚度范围。设计制造了由不同石墨烯/PLA复合材料组合而成的三层吸波体,测试结果表明:三层吸波体的吸波效果远优于单层均质吸波体,且当选取石墨烯质量分数分别为5%、7%、8%的复合材料作为透波层、吸收层和再次吸收层打印材料时,可以获得最佳的吸收效果,此吸波体在13.3~18GHz频段内的反射率均小于-10dB,在17GHz时有-30dB的最大吸收峰值。     

Simultaneous Manipulation of Interfacial and Defects Polarization toward Zn/Co Phase and Ion Hybrids for Electromagnetic Wave Absorption

Rational manipulation of multimetal hybrid materials (HMs) with tunable substitution or phases is evolving as an effective strategy to meet the controllable electromagnetic (EM) properties and EM wave (EMW) absorption. Herein, a new thermodynamic and kinetic cocontrol strategy is proposed to construct Zn/Co bimetal HMs with tuning ion and phase hybridization for synergistic effect on EM properties for the first time. Auxiliary chelating agent triethanolamine (TEA) dominates the phase separation by stepwise Zn/Co deposition in metal–organic frameworks, then the pyrolysis process under gradient temperature give rise to controllable ion hybridization products due to thermal motion. Benefiting from the tunable collaboration between defects polarization and interfacial polarization, the 700 °C HMs exhibit ultrahigh EM parameters and EMW absorption, of which products with no TEA deliver the effective absorbing bandwidth of 4.80 GHz (1.6 mm) and minimum reflection loss of −45.85 dB. The results indicated that synergistic effect of ion and phase hybridization can improve the defects induced “polarization centers” and coherent interfaces induced interfacial polarization. Furthermore, the comprehensive research and deep understanding on respective contribution of hybridization forms provide a precise inspiration in developing bimetal and even multimetal ferrite with tunable hybridization structure.     

热处理对羰基铁粉磁性能和吸波性能的影响

为了改善羰基铁粉的微观结构和吸波性能,对羰基铁粉吸收剂在氮气氛下进行了热处理,热处理温度为300℃,热处理时间为30 h,研究了羰基铁粉的磁性能和在2～18 GHz的吸波性能。以热处理前后羰基铁粉作为吸收剂制备了单层吸波涂层,涂层的厚度为1.2 mm时,热处理羰基铁粉吸波涂层在10.2～15.4 GHz反射率R小于-10 dB,反射率小于-10 dB的频宽为5.2 GHz,反射率小于-5 dB的频宽为10 GHz;最大吸收峰在12.8 GHz,反射率R为-22.68 dB。磁性能研究表明,热处理后随着矫顽力的增加,在2～18 GHz羰基铁粉的微波吸收峰向高频移动,而且吸收峰变宽,吸波性能得到大幅提高。     

P-GN/Ni复合材料的制备及其微波吸收性能研究

本文采用一步溶剂热法成功制备了磷掺杂石墨烯/Ni纳米复合材料(P-GN/Ni),并系统研究了其微纳结构和微波吸收性能。透射电镜(TEM)结果显示Ni纳米颗粒呈海胆状,并均匀地负载在半透明褶皱的磷掺杂石墨烯(P-GN)上。相比单独的海胆状Ni纳米颗粒,P-GN/Ni纳米材料表现出优异的微波吸收能力。在厚度仅为1.5 mm时,复合材料在17.3 GHz下反射损耗值(RL)达到了-34.8 dB且有效吸收带宽(RL<-10 dB)为3.7 GHz。复合材料的厚度为1.5-5.0 mm时,其有效吸收带宽为14.9 GHz(3.1-18 GHz),覆盖S波段到X波段,在微波吸收领域具有潜在的应用价值。微波吸收机制研究表明P-GN的引入,一方面利用磁损材料与电损材料的协同效应优化了阻抗匹配,另一方面极大地增加了材料的电导率和界面极化能力,提高了复合材料对电磁波的衰减能力。     

Lightweight Ni Foam-Based Ultra-Broadband Electromagnetic Wave Absorber

Skin effect and high density are the main reasons that restrict the search of lightweight and high-performance metal-based electromagnetic (EM) wave absorbing materials. Although nanostructured metal materials have been fabricated to solve above problems, poor dispersibility and chemical stability issues brought about by high surface energy due to existing nano-size effect. In this work, lightweight Ni foam with NiO/NiFe₂O₄ in situ growth composites are fabricated by a facile and universal route as an effective alternative to high-performance metal-based EM wave absorber. Impressively, it is found that the foam structure and NiO/NiFe₂O₄/Ni components can synergistically boost EM wave absorption capacity. In detail, impedance matching from foam structure and energy dissipation from interfacial polarization and defect induced polarization provided by NiO/NiFe₂O₄ mainly contributes to its ultra-broadband EM wave absorption performance. As a result, the as-prepared sample (0.06 g·cm⁻³) delivers a wide absorption bandwidth of 14.24 GHz and thin thickness of 0.6 mm, as well as, high specific effective absorption bandwidth of 19444.4 GHz·g⁻¹·cm⁻². This work sheds light on the novel view on the synergistic effect of structure and components on EM wave absorption behaviors and demonstrates a new pathway for preparation of lightweight and high-performance metal-based EM wave absorbers.     

Application of Ferrite to Electromagnetic Wave Absorber and its Characteristics

An electromagnetic wave absorber utilizing ferrite or rubber ferrite composed of ferrite powder and rubber is described. In our investigation, the existence of a matching frequency f/sub m/ and a matching thickness t/sub m/ has been found. The terms f/sub m/ and t/sub m/ mean that the ferrite which is backed with a conducting plate can be a perfect absorber only under the conditions that the frequency of the incident wave is f/sub m/ and that the thickness of the ferrite is t/sub m/.Each ferrite has two matching frequencies f/sub m1/, f/sub m2/, (f/sub m1相似文献   

漂珠/钡铁氧体/聚苯胺复合材料的制备及吸波性能研究

以溶胶–凝胶自蔓延燃烧法与原位掺杂聚合法相结合的方式制备了漂珠/钡铁氧体/聚苯胺复合材料。利用扫描电镜(SEM)、X射线衍射仪(XRD)和傅立叶红外光谱仪(FTIR)等表征了材料的微观形貌、晶体结构及组成。采用矢量网络分析仪在2~18 GHz频段内测定了复合材料的电磁参数。结果表明:所制材料的介质损耗和磁损耗最大值分别为0.30和0.52;当样品吸波层厚度为3.0 mm时,在电磁波频率为7.1 GHz时样品的反射损耗峰值为–33.74dB,在–20 dB的吸收带宽为3.2 GHz。     

(Zn_(0.3)Co_(0.7))_2-W型钡铁氧体电磁特性及吸波性能

采用sol-gel法合成了Ba(Zn0.3Co0.7)2Fe16O27六方铁氧体样品。通过XRD、SEM和Agilent8722ET网络分析仪等表征手段,研究了样品的显微结构、电磁特性及吸波性能。结果表明:在1250℃下制得的样品基本为单一相的Ba(Zn0.3Co0.7)2Fe16O27铁氧体。样品在14GHz附近出现介电损耗峰,在8～12GHz和15～17GHz内出现很宽的磁损耗。当吸波涂层厚度为1.85mm时,在15.3GHz左右反射损耗峰值可达到–23dB,并且在9～18GHz内反射损耗RL小于–10dB,具有优异的微波吸收性能。     

Fundamental investigation on a weakly magnetized ferrite absorber

Investigated are the matching characteristics of a magnetized ferrite absorber, which applies a weakly static magnetic field H_dc perpendicular to the sintered ferrite surface. Applying a static magnetic field to the ferrite enables the matching thickness of the absorber to be reduced from 8 mm in the absence of H_dc to 3 mm under 750 gauss. The matching frequency can also be changed broadly from 0.1 to 0.9 GHz by controlling ferrite thickness and H_dc, simultaneously. These are well explained in terns of an nonsaturated permeability rather than tensor permeability. A thin magnetized ferrite absorber is realized using a ferrite with a large value of imaginary part of permeability when real part takes the value near 1.0. Matching frequency characteristics, whether broad or narrow, correlates closely with the slant of the curve for real part of permeability taking the value near 1.0 in the present frequency