三层电磁屏蔽复合材料结构设计

随着信息和电子技术的飞速发展,对电磁屏蔽性能的要求越来越高,电磁屏蔽材料由单一材料向复合材料的方向发展。复合材料屏蔽效能不仅取决材料本身,还与复合材料的结构密切相关。本文以3层机械电磁屏蔽复合材料为基础,运用Schelkunoff的传输线理论研究电磁屏蔽复合材料的结构与电磁屏蔽效能的关系为以后电磁屏蔽结构设计提供基础。研究结果表明Cu＋非晶＋Cu3层复合结构电磁屏蔽性能在射频段明显优于Cu＋Cu＋非晶3层复合结构,但在0．1MHz以下的频率段和800MHz以上频率段差别并不大。     

电沉积FeNi合金电磁屏蔽性能研究

采用电沉积工艺在铜基体上得到了Fe21Ni79铁镍合金,通过XRD确定了电沉积铁镍合金的晶体结构,通过扫描电镜观察电沉积铁镍合金的表面形貌.运用低频磁场源和交变磁强计自制低频电磁屏蔽效能测试平台测量复合材料在0～1900Hz电磁屏蔽性能,运用Aligent信号源和矢量网络分析仪测量100 kHz～1.5 GHz电磁屏蔽...     

绿色建筑与电磁屏蔽材料

随着人类对工业化社会的反省和对后现代化社会的思考,人类寻求健康宜居的生存环境及追求社会可持续发展的欲望愈加强烈,绿色建筑成为当今热门话题。绿色建筑材料作为绿色建筑发展基石,是实现绿色建筑标准的核心和关键内容。系统地阐述了绿色建筑的内涵和绿色建筑材料的发展现状以及绿色建筑生态水泥材料、绿色建筑墙体砌筑材料、绿色建筑玻璃材料、绿色建筑屋顶材料、绿色建筑饰面涂料等绿色建筑材料的技术性能。同时阐述了人类宜居健康生活环境对于绿色建筑材料发展的需求,以及当今日益严重的电磁辐射污染对人类健康造成的侵害。重点论述了绿色建筑屏蔽材料的工作原理,提出了未来绿色建筑电磁屏蔽材料的发展策略,以及在绿色建筑电磁屏蔽生态水泥、绿色建筑电磁屏蔽墙体材料、绿色建筑电磁屏蔽门窗玻璃材料、绿色建筑电磁屏蔽屋顶饰面材料、绿色建筑电磁屏蔽饰面涂料等方面的实验研究成果,并对绿色建筑电磁屏蔽材料的研究进展和存在的主要问题进行了探讨。最后对绿色建筑电磁屏蔽材料的发展进行了预见和展望。     

超细镍纤维复合材料的电磁屏蔽研究

在外加磁场的诱导作用下,采用常压液相还原法,制备较大量直径约为250 nm、长度可达100 μm的超细镍纤维。分别将得到的镍纤维和商品微米镍粉作为填料制备树脂基导电复合材料,在130 MHz~1.5 GHz的频段范围内测定复合材料的电磁屏蔽性能与镍填料含量的关系。结果表明,跟微米镍复合材料相比,镍纤维复合材料具有更好的电磁屏蔽性能。镍纤维含量为33.3%（质量分数）的复合材料的平均电磁屏蔽效果为15.7 dB。     

基于磁控溅射技术的电磁屏蔽层研究

为了解决电子系统塑料机盒的抗EMI问题,提出了一种采用多靶磁控溅射技术对塑料内表面进行金属化的新环保工艺,利用屏蔽效能对电磁兼容性作了理论分析,并对金属化层的膜系结构、溅射工艺、附着强度等作了较为深入的研究.研究结果表明:衰减损耗是各层屏蔽效果线性相加的结果;反射损耗与各层相对位置关系无关;层数多或各屏蔽层的反射越大,则屏蔽效果越好.试验表明:采用Cu/1Cr18Ni9Ti的金属屏蔽层结构,可以获得良好的屏蔽效能及耐候性,其中500nm Cu 100nm 1Cr18Ni9Ti较宜.     

化学镀在电磁屏蔽中的应用

简述了电磁辐射的危害以及各国政府为减少和控制电磁辐射制定的一系列标准和规定.指出目前在生活中广泛应用的纺织品、塑料、木材等本身并无电磁防护性能,运用化学镀使上述材料表面金属化是电磁屏蔽复合材料发展的重要方向.详细介绍了目前化学镀在电磁屏蔽织物、碳纤维、木基复合材料、电磁屏蔽粉末填充料以及电磁屏蔽塑料的研究应用现状,并引出了化学镀在电磁屏蔽应用中的发展方向.     

金属纤维电磁屏蔽材料的研究进展

描述电磁辐射的危害及电磁屏蔽材料的屏蔽机制,重点阐述金属纤维制备电磁屏蔽织物、电磁屏蔽聚合物材料及电磁屏蔽建筑与装饰材料的应用及研究进展,并对未来电磁屏蔽材料的发展趋势作预测,指出开发具有高吸收率、低反射率与低透射率的高性能、低消耗兼绿色环保的新型电磁屏蔽材料是未来的研究重点,同时对材料内部组织与结构进行优化,改进成型工艺,提高其电磁屏蔽效能     

ZnO/泡沫炭复合材料的制备及其电磁屏蔽性能

为进一步提高泡沫炭材料的电磁屏蔽性能,本文以泡沫炭为基体,以ZnO纳米颗粒为增强体,构建了ZnO/泡沫炭复合材料,研究了ZnO纳米颗粒的引入对泡沫炭电磁屏蔽性能的影响。实验结果表明,ZnO/泡沫炭复合材料在X波段内的总电磁屏蔽效能可达24 dB,明显优于泡沫炭材料。这主要归因于引入的ZnO纳米颗粒增强了泡沫炭材料的介电损耗。此外,研究了复合材料的衰减常数和趋肤深度,发现与泡沫炭材料相比,复合材料的衰减常数得到显著提升,趋肤深度明显降低。     

高性能电磁屏蔽方舱低温钎焊技术研究

对于大板式电磁屏蔽方舱，有效解决各大板之间的电气连接性是其制造过程中的关键技术。通过对电刷镀铜和低温钎焊技术的综合研究，制造出了屏蔽效能较高的大板式方舱产品，有效地解决了其各大板间的电气连接问题，并保证了方舱结构上的完整性。     

高性能电磁屏蔽方舱低温钎焊技术研究

对于大板式电磁屏蔽方舱,有效解决各大板之间的电气连接性是其制造过程中的关键技术。通过对电刷镀铜和低温钎焊技术的综合研究,制造出了屏蔽效能较高的大板式方舱产品,有效地解决了其各大板间的电气连接问题,并保证了方舱结构上的完整性。     

电磁屏蔽涂料用银基粉体材料研究

采用机械合金化等技术,制备了导电性能优异的Ag系、Ag/Cu系、Ag/Ni系粉体材料和电磁屏蔽涂料.粉体材料微细,呈片状;涂料表面电阻、电阻率低,满足使用要求.优异的导电性能使得涂料具有良好的电磁屏蔽性能,复合涂料的电磁屏蔽效能在100 kHz～1.5 GHz频段范围内可达到30 dB～90 dB.对电磁屏蔽涂料的屏蔽效能进行了理论分析.     

Enhanced Electromagnetic Interference Shielding of Mg–Zn–Zr Alloy by Ce Addition

The effects of Ce addition on microstructure and electromagnetic interference(EMI) shielding response of Mg–6Zn–0.5Zr(ZK60) alloy have been investigated.Ce addition resulted in grain refinement and higher density of Mg–Zn–Ce and Mg Zn2 intermetallic particles in the alloy.In particular,this was substantially remarkable as the addition of Ce was up to 1.0 wt%.It is interesting to note that as-extruded ZK60 alloy with 1.0 wt% Ce addition exhibited an EMI shielding effectiveness(SE) exceeding 70 d B at the frequency range of 30–1,500 MHz,which was significantly higher than that of ZK60 alloy without Ce addition and reached the requirement of high protection.The superior SE was probably related to the increased reflection and multiple reflection of electromagnetic radiation induced by Ce addition.Direct artificial aging at 150 °C for 25 or 50 h led to a further increase of 7–10 d B in the SE of the alloy with 1.0 wt% Ce addition.The advantages of excellent shielding capacity and favorable mechanical strength make the Mg–Zn–Zr–Ce alloy an attractive shielding candidate material for a variety of technological applications.     

Effect of Alloying Element on Electromagnetic Interference Shielding Effectiveness of Binary Magnesium Alloys

The microstructure,electrical conductivity and electromagnetic interference shielding effectiveness of Mg-X(X=Al,Sn,Y and Gd)alloys in as-cast and solution states were systematically investigated in this study.The electrical conductivity and electromagnetic shielding capacity of binary magnesium alloys decrease linearly with alloying element content.The electromagnetic shielding effectiveness of the binary magnesium alloys with the same alloying element content is as follows:Mg-GdMg-SnMg-YMg-Al.The main reason for the differences in electromagnetic interference shielding of the binary magnesium alloys is the change in conductivity,which is mainly affected by volumetric difference of solute atoms and magnesium atoms,solute atomic valence and configuration of extranuclear electron.     

Research Progress of Electromagnetic Properties of MgB_2 Induced by Carbon-Containing Materials Addition and Process Techniques

For the high transition temperature(T_c) and low cost taking both raw materials and fabrication process into account,MgB_2 has been a competitive candidate to replace the conventional NiTi superconductor for high-temperature application in fault current limiters,transformers,motors,magnetic resonance imaging,adiabatic demagnetization refrigerators,generators,etc.The carbon-containing materials addition induced high critical current density(J_c) is reviewed based on their influences on the upper critical field(H_(c2)),flux pinning force,and connectivity.The doping effects were compared in the overview focusing on SiC,organic dopants,and graphene-related dopants.SiC doping is featured for the high-field critical current density,which is caused by the increased H_(c2) attributed to the substitution of carbon on boron site and the strong flux pinning force offered by the nanosized secondary phases in the MgB_2 matrix.Organic dopants have the advantage over SiC dopant for their relatively homogeneous distribution in the MgB_2 matrix based on wet mixing of the organics and the raw boron powders.Low doping level of two-dimensional materials can improve the superconducting properties in all measured fields because of the combined advantages of carbon substitution effect and grain connectivity.MgB_2 fabricated with carbon-encapsulated boron also introduces strong flux pinning centers in MgB_2,which show weak destruction of the connectivity of the MgB_2 grains as reflected by the low-magnetic-supercurrent behavior.High-pressure treatment and diffusion method can fabricate highdensity MgB_2 superconductors with better connectivity and increase the J_c compared with the in situ and ex situ methods.     

Research Progress of Metal-Based Shielding Materials for Neutron and Gamma Rays

The radiation generated by nuclear reaction is harmful to human body and equipment,thus the radiation shielding materials that employ the shielding ability from neutron and gamma rays are the best candidates according to application situations and radiation sources.In this paper,the researches of metal-based neutron and gamma rays or multiple purpose shield-ing materials are systematically summarized,and the respective and principal problems of these materials with respect to shielding effectiveness and other performances,such as corrosion,mechanical properties,manufacture,etc.,are discussed.Finally,the prospect of shielding materials is outlined,which suggests that the development of highly efficient and multiply functional radiation shielding materials with good environmental compatibility is one of the future development trends.     

开孔泡沫铝的电磁屏蔽性能

采用加压渗流法制备不同特征参数的开孔泡沫铝,在50～1050MHz电磁波频率内研究了开孔泡沫铝的屏蔽特性,并探讨了泡沫铝的孔径和厚度对其电磁屏蔽性能的影响。结果表明：在50～1050MHz频率范围内,泡沫铝具有较好的电磁屏蔽性能,其屏蔽效能为25～75dB。在50～850MHz频率内,泡沫铝的孔径增大,其电磁屏蔽效能上升;但当频率在850～1050MHz之间时,孔径变化对泡沫铝屏蔽效能的影响可以忽略不计。在50～700MHz频率之间时,随着泡沫铝厚度的增加,其屏蔽效能增大,但当频率在700～1050MHz之间时,厚度对屏蔽效能的影响可以忽略。     

电磁屏蔽涂料用非晶粉末偶联处理研究

非晶合金粉末作为电磁屏蔽涂料的填料应用的还较少。本文分别使用1％～10％的KH-550硅烷偶联剂对自制的钴基非晶合金粉末进行了偶联处理。通过SEM和TGA对偶联处理后的粉末分析后认为,偶联剂的较佳用量在2％左右。     

开孔泡沫铝的电磁屏蔽性能

采用加压渗流法制备不同特征参数的开孔泡沫铝,在50～1050MHz电磁波频率内研究了开孔泡沫铝的屏蔽特性,并探讨了泡沫铝的孔径和厚度对其电磁屏蔽性能的影响.结果表明:在50～1050MHz频率范围内,泡沫铝具有较好的电磁屏蔽性能,其屏蔽效能为25～75dB.在50～850MHz频率内,泡沫铝的孔径增大,其电磁屏蔽效能上升;但当频率在850～1050MHz之间时,孔径变化对泡沫铝屏蔽效能的影响可以忽略不计.在50～700MHz频率之间时,随着泡沫铝厚度的增加,其屏蔽效能增大,但当频率在700～1050MHz之间时,厚度对屏蔽效能的影响可以忽略.