焦炭-水泥基复合材料电磁屏蔽性能的研究

研究了焦炭和碳纤维的掺量,焦炭细度,减水剂,样品厚度对材料电磁屏蔽性能的影响。分别利用两电极法和同轴电缆法测试了材料的电阻和电磁屏蔽效能。研究结果表明,增加焦炭的掺量对水泥基材料导电性能的影响不显著,但增加焦炭细度能明显提高水泥基材料的导电性能;而样品厚度对水泥基材料的电磁屏蔽性能影响不大;焦炭-水泥基材料掺入碳纤维后能使材料的导电性能和电磁屏蔽性能明显提高。     

纤维增强树脂基吸波复合材料的研究进展

简述了吸波材料的电磁屏蔽机制、吸波剂的分类和损耗机制以及微波波段的划分与应用,并从材料的选择、结构的设计以及获得的吸波效果等方面对目前纤维增强树脂基吸波复合材料的研究进行了对比总结,重点阐述了单层结构、多层结构、多层夹心结构以及频率选择表面的主要特点和研究现状。最后提出了纤维增强树脂基吸波复合材料目前存在的问题,并对今后的发展进行了展望。     

铁尾矿在电磁吸波建筑材料中的研究进展

铁尾矿是我国大宗工业固废的主要组成部分，库存量大，若不加以处理，将会造成环境污染风险和二次资源浪费，如何高效资源化利用铁尾矿是安全消纳大宗工业固废的重要保障。本文基于铁尾矿的基本性质和利用途径，以及电磁吸波原理，主要介绍了铁尾矿及其改性电磁吸波材料研究，以及铁尾矿在水泥基吸波混凝土和地质聚合物吸波胶凝材料中的研究，着重阐述了铁尾矿在水泥基混凝土中的吸波性能和机理研究进展，探讨了通过地质聚合反应制备铁尾矿基地质聚合物吸波混凝土的可行性及其性能，可为铁尾矿基地质聚合物在多功能建筑材料方面的应用提供借鉴，为提高铁尾矿固废资源的综合利用率，解决尾矿堆积、环境污染等问题提供解决思路。本文旨在总结铁尾矿在吸波建筑材料的研究进展并进一步推动地质聚合物吸波建筑材料的发展。     

聚噻吩基吸波材料研究进展

简单介绍了电磁屏蔽的机理,简述了聚噻吩及其衍生物类吸波材料的分类,综述了近几年国内外有关聚噻吩单元、二元及多元复合材料的吸波性能研究,展望了聚噻吩及其衍生物作为新型微波吸收材料的发展前景。     

聚苯胺和聚吡咯导电高分子吸波材料进展

介绍了吸波材料的吸波机理及分类,总结了近年来导电高分子在电磁屏蔽领域的研究进展。重点概述了基于聚苯胺(PANI)、聚吡咯(PPy)的两大类导电高分子复合吸波材料,着重强调导电高分子组分的引入在一定程度上增强材料的介电损耗与电阻损耗,提高匹配阻抗,极大地改善材料吸波性能,最后指出导电高分子吸波材料的发展趋势。     

纳米吸波剂改性水泥基材料研究进展

水泥基吸波材料可以有效缓解电磁波辐射对人们日常生活的影响。传统吸波剂所制备的水泥基吸波材料因其有效带宽窄、吸波效率低和体积厚重等缺点，限制了其在工程中的应用。与之相比，纳米吸波剂具有量子尺寸效应、宏观量子隧道效应和界面效应等特点，因此纳米吸波剂改性水泥基材料为电磁辐射防护提供了一个新途径。根据纳米吸波剂种类的不同，从碳纳米管水泥基吸波材料、石墨烯水泥基吸波材料和磁性纳米颗粒水泥基吸波材料3个方面总结了国内外相关研究成果，并对未来该领域的发展进行了展望。     

碳纳米管填充聚合物基电磁屏蔽复合材料的研究进展

对碳纳米管填充聚合物基电磁屏蔽复合材料的研究进展进行了综述。在阐述研究电磁屏蔽材料必要性的基础上,介绍了复合材料的电磁屏蔽机理,重点论述了碳纳米管填充量、长径比及管径、屏蔽体的厚度、复合材料的加工方式等对复合材料电磁屏蔽性能的影响。最后对碳纳米管填充聚合物基复合电磁屏蔽材料的研究进行了展望,指出低成本填料与碳纳米管协同作用、可提高碳纳米管分散性的制备工艺的研究以及复合材料电磁屏蔽机理的研究等为未来的研究方向。     

电磁屏蔽橡胶复合材料的研究进展

介绍电磁屏蔽橡胶复合材料及其所用胶种(天然橡胶、丁苯橡胶、三元乙丙橡胶、丁基橡胶和硅橡胶等)及电磁屏蔽填料[导电填料(金属和镀金属填料、导电炭黑、碳纤维、碳纳米管、石墨烯等)和吸波填料(铁氧体和羰基铁粉等)]的研究状况,并概述新型立体导电骨架结构电磁屏蔽复合材料的特征,指出电磁屏蔽橡胶复合材料的导电和吸波机理、结构以及橡胶与填料之间的界面作用等是今后的研究重点。     

生物质衍生碳基吸波材料研究新进展

综述了生物质衍生碳基吸波材料的最新研究进展,简要介绍了电磁吸波材料对电磁波的吸收机理和评价吸波材料性能的物理参数,总结了近期报道的几种生物质为碳源,通过不同方法制备的独特结构和性能优异的衍生碳及其镍、铁和钼复合材料,阐述了生物质为碳源制备衍生碳材料的优点和固有结构对吸波材料影响,以及金属的引入可以提升吸波性能的原因,为设计优化多种结构的吸波材料,进而改善和提升材料的阻抗匹配,调控电磁参数,实现吸波性能的提高提供参考,并展望了未来生物质以及衍生碳基吸波材料的应用前景。     

吸波/防弹复合材料的研发

采用玻璃纤维布/改性环氧树脂、碳纤维布/环氧树脂以湿法手糊成型工艺制备透波层和反射层,并与吸波浆料浸渍后的芳纶蜂窝芯复合制成电磁屏蔽材料。将电磁屏蔽材料与芳纶防弹板复合制成吸波/防弹一体化材料,该材料可满足GA 141—2010防弹标准要求,在频率2～18 GHz范围的最大反射率可达-25 dB,具有较好的吸波性能。     

Enhanced electromagnetic shielding property of cf/mullite composites fabricated by spark plasma sintering

Aiming to prepare high-performance electromagnetic interference (EMI) shielding materials, chopped carbon fibers were incorporated into mullite ceramic matrix via rapid prototyping process of spark plasma sintering (SPS). Results indicate that C_f/mullite composites with only 1 wt% of carbon fibers exhibit highest shielding effectiveness (SE_T) over 40 dB at a small thickness of 2.0 mm, showing great advantages both in terms of performance and thickness compared with many mature carbon/ceramic composites. The high EMI shielding properties mainly depend on two mechanisms of absorption and reflection in this present work. The enhanced absorption and reflection of electromagnetic wave are ascribed to the promotional electrical conductivity arising from the formation of conductive network by introduction of carbon fibers. Regarding enhanced electrical conductivity, notable intensified interfacial polarization on a large number of interfaces between mullite matrix and carbon fibers is also the key factor to the improved absorption, which makes absorption play a dominant role in the significant improvement of EMI SE_T. The C_f/mullite composites with excellent EMI shielding properties and thin thickness show great potential application as EMI materials.     

Asymmetrically structured polyvinylidene fluoride composite for directional high absorbed electromagnetic interference shielding

In the face of electromagnetic pollution issues caused by the advancement of communication technology, it is of great significance to develop materials with high electromagnetic interference (EMI) shielding capability as well as high absorption efficiency. The nickel-coated silicon carbide whiskers (Ni@SiCw)/graphene nanosheets (GNP)/polyvinylidene fluoride (PVDF) EMI shielding composites with the asymmetric structure are constructed by simple solution mixing and multiple hot pressing. Specifically, the Ni@SiCw in the top layer is prepared by simple electroless plating, and the saturation magnetization intensity reaches 12.50 emu/g. The combination of dielectric and magnetic losses provides reliable electromagnetic wave absorption performance with a reflection coefficient less than 0.35. GNP is selectively enriched in the bottom layer with a maximum conductivity of 85.43 S/m. The composite shows an EMI shielding performance of 36.83 dB when the GNP content is just 4 wt%, which means 99.98% of microwaves can be shielded. Furthermore, due to the distinct structure, the composites display various shielding mechanisms when electromagnetic waves are incident from different faces. Without a doubt, this asymmetric structure offers a novel approach to the preparation of directional EMI shielding materials.     

高性能聚酰亚胺电磁屏蔽材料的研究进展

电磁信号之间的干扰和混乱已成为当今5G无线通信时代的首要挑战，研发有效、屏蔽高、低频电磁干扰的高性能电磁屏蔽材料已成为当前的研究热点。未来电磁屏蔽材料将朝着超薄、柔性化、轻质化、宽频高效吸收、耐高温、力学性能好等方向发展。聚酰亚胺（PI）因其具有质量轻、可柔化、机械性能好、热学稳定性好等特点，常被用作高性能电磁屏蔽复合材料的基体材料。该文介绍了PI电磁屏蔽材料的屏蔽机理，重点总结了其屏蔽性能的影响因素及研究进展，并阐述了高性能PI电磁屏蔽材料未来的发展趋势。     

Review on Shielding Mechanism and Structural Design of Electromagnetic Interference Shielding Composites

Conductive polymer composites (CPCs) for electromagnetic interference shielding have received significant attention and shown rapid development. According to the electromagnetic wave interface conduction theory of Schelkunoff, excellent conductive performance and perfect conductive network structure are prerequisites for high shielding efficiency of electromagnetic interference shielding composites. Effective multiple interface reflection absorption, dielectric loss, and hysteresis loss characteristics of the materials are crucial for realizing the regulation of the electromagnetic interference shielding performance of CPCs. Therefore, the structural design of conductive and magnetic network for CPCs is crucial for achieving high shielding performance. In this study, it is established that an electromagnetic shielding composite with a uniform structure is widely used because of its simple preparation process, but its inefficient conductive network causes a high percolation threshold. The inefficiency can be solved by designing a composite structure and improving the efficiency of the conductive network. Currently, common structural designs include segregated structural, layered structural, and foam structural designs. These structural designs effectively solve the problem of high percolation threshold of CPCs and coordinate the contradiction between the performance of electromagnetic interference shielding and other advantages.     

聚氨酯掺杂铜粉涂层的电磁特征及其涂层织物的吸波性能

将掺杂了不同含量微米铜粉的聚氨酯（PU）涂料通过涂层工艺涂敷在棉织物上制成吸波涂层织物,并利用扫描电子显微镜、红外光谱和矢量网络分析仪等测试了不同铜粉含量聚氨酯涂层的介电常数、磁导率和电磁损耗等电磁性能,同时还探讨不同铜粉含量涂料对涂层织物电磁吸收性能的影响。结果表明,在 8~13 GHz 的频段范围内,随着涂层中铜粉含量增加,涂层介电常数实部与虚部均增大,铜粉具有良好的介电性能,在外加电场的作用下产生极化,对电磁波产生介电损耗;铜粉不属于磁损耗材料,对电磁波产生磁损耗较小;当铜粉的含量较低（3 %,质量分数,下同）时,涂层材料的吸波与电磁屏蔽性能较弱,当含量由5 %增加至11 %时,在9.0、10.5、12.8 GHz处反射损耗最低分别为-20.4、-28.3、-25.6 dB,有效吸收带宽分别为0.2、1.3、1.1 GHz,电磁屏蔽效能分别由12.24、16.59、21.1 dB增加至25.92 dB。     

窗用电磁屏蔽波导玻璃

通过对电磁屏蔽玻璃屏蔽性能和截至波导理论的研究,制造了一种窗用电磁屏蔽波导玻璃。该玻璃是一种既能屏蔽电磁波,又能保持通风且具有防止信息泄露及情报泄密的绿色建材产品。     

Electromagnetic shielding performance of SiC/graphitic carbon-SiCN porous ceramic nanocomposites derived from catalyst assisted single-source-precursors

In this work, SiC nanowires and graphitic carbon (GC) including 2D reduced graphene oxide and graphene-liked ribbons modified polymer derived SiCN (SiC/GC-SiCN) porous ceramic monoliths were prepared via catalyst assisted single-source-precursor derived ceramic route. The inclusion of absorbents (e.g. graphitic carbon and SiC nanowires) significantly improved the electrical conductivity of the materials from 1.77 × 10^?8 S/cm (pristine SiCN) to 0.56 S/cm. In turn, the electromagnetic interference shielding effectiveness (EMI SE) of the ceramic increased significantly from 4.0 dB to 19.2 dB. At the highest absorbent content, the SiC/GC-SiCN ceramics exhibit a high absorption power of 0.3 nW and an SE of 48.5 dB at thickness of 2 mm, which means more than 99.998 % of the EM wave is blocked. This work finds new avenue for the design of advanced electromagnetic shielding materials possessing strong absorption capability.     

Electromagnetic interference shielding mechanisms of CNT/polymer composites

The electromagnetic interference (EMI) shielding mechanisms of multi-walled carbon nanotube (MWCNT)/polymer composites were analyzed experimentally and theoretically. For the experimental analysis, EMI shielding effectiveness (SE) of MWCNT/polypropylene (PP) composite plates made in three different thicknesses and at four different concentrations were studied. A model based on the shielding of electromagnetic plane wave was used to theoretically study the EMI shielding mechanisms. The experimental results showed that absorption is the major shielding mechanism and reflection is the secondary shielding mechanism. The modeling results demonstrated that multiple-reflection within MWCNT internal surfaces and between MWCNT external surfaces decrease the overall EMI SE. The EMI SE of MWCNT/PP composites increased with increase in MWCNT content and shielding plate thickness.     

Carbon fiber reinforced composites from industrial waste for microwave absorption and electromagnetic interference shielding applications

Lightweight materials with hybrid microstructures are getting great attention in the area of electromagnetic wave absorption. In the present study, carbon fiber and fly ash reinforced composites are prepared by mixing them with ground granulated blast furnace slag, followed by compaction and sintering at 1000 °C under an argon atmosphere. Akermanite-gehlenite was observed to be the primary crystalline phase present in the prepared samples. Porous composites are obtained with the addition of fly ash and carbon fiber as they inhibit densification. The resultant microstructure has homogeneous carbon fiber dispersion and uniform fly ash anchoring on the matrix phase. This enhanced interface polarization, defect polarization, electron transportation, and impedance matching characteristics of the composites. Hence, the developed composites' microwave absorption and electromagnetic interference shielding properties exhibited an outstanding performance at low thickness with a reflection loss value of ?41.24 dB and total shielding effectiveness of 42.29 dB at the X-band.