共查询到19条相似文献,搜索用时 109 毫秒
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聚苯胺导电纤维对电磁屏蔽效能的影响 总被引:1,自引:0,他引:1
张瑞刚 《电子材料与电子技术》2009,(1)
本文介绍了聚苯胺导电纤维对电磁屏蔽效能的影响。聚苯胺(PANI)是最重要的导电聚合物之一,金属材料与导电聚苯胺复合形成屏蔽组分有效提高了复合电磁屏蔽材料的高频电磁屏蔽效能,从而扩展了屏蔽材料的屏蔽带宽。本文分析了复合电磁屏蔽材料中聚苯胺导电纤维对屏蔽效能的贡献及作用机理。结果表明聚苯胺与基体树脂相溶形成基体导电网络,有效阻碍了高频电磁波的穿透,是提高高频电磁屏蔽效能的主要原因。 相似文献
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点胶成形导电橡胶在电磁屏蔽技术中的应用 总被引:2,自引:0,他引:2
点胶成形导电橡胶是一种新型的高性能电磁屏蔽复合材料,被专门设计成流体状态,以满足自动化生产中,金属或塑料外壳上应用导电弹性体的大批量、高速度增长需求.相比于传统模压或挤出工艺制备的导电橡胶材料,其独特的使用方式、准确的安装定位性能和高屏蔽性能,非常适用于具有精细和复杂结构壳体的电磁屏蔽和环境密封.在现有的抑制EMI的应用中,点胶成形导电橡胶技术因总成本最低而得到越来越多的应用.介绍了点胶成形导电橡胶的特点、使用方法、设计安装要点和国内外的研究及应用现状. 相似文献
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RayBorgersen 《今日电子》2002,(5):36-37
在通信、计算机、自动化、医疗等商用电子设备上选择最有效的电磁屏蔽衬垫时,通常可以考虑以下三种衬垫类型:导电橡胶、导电布、铍铜指簧。依据设备的不同需要,这几种类型的衬垫可提供不同程度的电磁屏蔽,适合不同的形状和环境密封的要求。 在设计和选择电磁屏蔽衬垫时,应主要考虑以下因素: ●衬垫形状; ●机械耐久性; ●衰减水平,多数商用设备要求衰减量达到60~100分贝,最高至120分贝。 ●压缩量,多数商用设备考虑低闭合力设计。压缩量对导电橡胶的屏蔽效能有很大影响。由于导电橡胶所采用的填料不同,其导电性有高有低,所以导电橡胶可达到屏蔽效能范围较宽。 相似文献
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Yasuyuki Hirakawa Yoshitomo Ohno Toyohiko Gondoh Tetsuo Mori Kei Takeya Masayoshi Tonouchi Hideyuki Ohtake Tomoya Hirosumi 《Journal of Infrared, Millimeter and Terahertz Waves》2011,32(12):1457-1463
Rubber compounds were investigated by terahertz time-domain spectroscopy. Terahertz absorption spectra of crude rubbers and
additives were measured as well as those of acrylonitrile-butadiene rubber compounds, which included the additives. It was
found that carbon black, which is one of the additives and serves as a filler, dominates the terahertz absorption owing to
its metallic characteristics. Thus, terahertz spectroscopy is a useful method for rapid nondestructive inspection during the
rubber production. 相似文献
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Electromagnetic shielding of nylon-66 composites applied to laser modules was studied experimentally and theoretically. The
effects of conductive carbon fiber length and weight percentage upon the shielding effectiveness (SE) of nylon composites
were investigated. The SE of long carbon fiber filled nylon-66 composites was found to be higher than short carbon fiber composites
under the same weight percentage of carbon fibers. In addition, higher electromagnetic shielding was obtained for the composite
with higher carbon fibers contents at the same length. The SE of conductive carbon fiber filled nylon-66 composites was measured
to be 42 dB at a low frequency of 30 MHz and 50 dB at a high frequency of 1 GHz. The SE predicted by theoretical models and
measured by experiments were in good agreement for filled nylon-66 composites with different length fiber. 相似文献
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Multiwall carbon nanotubes (MWCNTs) reinforced magnesium matrix (MWCNTs/Mg) composites were successfully fabricated by friction stir processing (FSP). Microstructure and microwave-absorption properties of WCNTs/Mg composites are studied. The results show that with increasing the MWCNTs content to 7.1% in volume fraction, the agglomeration of MWCNTs is found in the WCNTs/Mg composites. The addition of MWCNTs has little effect on microwave-absorption properties. With increasing the frequency from 2 GHz to 18 GHz, the microwave absorption of the composites decreases. Compared with the absorption loss of the MWCNTs, the reflection loss of base material takes the most part of the loss of the microwave, and the increase of the reflection loss can promote electromagnetic shielding properties of the composites. Moreover, the electromagnetic shielding properties of the composites are less than ?85 dB in the lower frequency range from 0.1 MHz to 3 GHz. With increasing the content of MWCNTs, the electrical conductivity of the composites is decreased, and the electromagnetic shielding properties is slightly enhanced. 相似文献
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Jiacheng Wang Changshu Xiang Qian Liu Yubai Pan Jingkun Guo 《Advanced functional materials》2008,18(19):2995-3002
A series of novel, dense, and interesting ordered mesoporous carbon (OMC)/fused silica composites with different carbon contents has been prepared by a controllable but simple sol‐gel method followed by hot‐pressing. In the as‐sintered OMC/fused silica composites the carbon particles still exist in the form of perfectly ordered carbon nanowires. Conductivity measurements on the composites indicate that these novel composites are electrically conductive and have a typical percolation threshold of 3.5–5 vol% OMC. The electromagnetic interference (EMI) shielding efficiency (SE) of an OMC/fused silica composite containing 10 vol% OMC is as high as 40 dB in the X band which is higher than that of a carbon nanotube (CNT)/ fused silica composite with the same carbon content (~30 dB). This indicates that these conductive OMC/fused silica composites are very suitable for an application as EMI shielding materials. Upon increasing the volume content of OMC in the composite the overall contribution as well as the increase rate of the microwave absorption are larger than those of the microwave reflection, which suggest that OMC/fused silica composites may also be promising electromagnetic (EM) wave absorbing materials. Based on the promising properties of these composites this work will hopefully lead to the development of new low‐cost and highly efficient EMI shielding or EM wave absorbing materials. 相似文献
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Wood-Hi Cheng Wen-Chi Hung Chien-Hui Lee Gan-Lin Hwang Wern-Shiang Jou Tzong-Lin Wu 《Lightwave Technology, Journal of》2004,22(9):2177-2183
The low-cost and low-electromagnetic-interference (EMI) packaging of optical transceiver modules employing housings of plastic composites are developed and fabricated. Optical transceiver modules fabricated by the plastic composites with transmission rates of 1.25 and 2.5 Gb/s are tested to evaluate the electromagnetic (EM) shielding against emitted radiation from the plastic packaging. The results show that these packaged optical transceiver modules with their high shielding effectiveness (SE) are suitable for use in low-cost and low-EMI Gigabit Ethernet lightwave transmission systems. By comparison of cost, weight, and shielding performance for optical transceiver modules fabricated by the housings of nylon and liquid-crystal polymer with carbon fiber filler composites, woven continuous carbon fiber (WCCF), and nanoscale hollow carbon nanocapulses (HCNCs) epoxy composites, the WCCF composite shows lower cost, lighter weight, and higher EM shielding than the other types of composites. Future studies may develop the low-cost and low-EMI optical transceiver modules using nanoscale HCNCs that have the combination of excellent physical and mechanical properties, light weight, and thinness compared with the conventional fabrication techniques. 相似文献
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为探索民用电磁屏蔽和军用隐形碳基高性能吸波材料的制备,研究了碳纳米管和磁性金属复合,碳纳〖JP2〗米管和铁氧体复合,碳纳米管/聚合物复合,碳、石墨基复合等碳基吸波材料的不同复合和制备方法,比较了其反射损耗等不同的特点、影响因素和性能特点及其相关应用。结果表明,多元复合、低维化、工艺优化是其制备的有效途径。 相似文献
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《Electromagnetic Compatibility, IEEE Transactions on》2005,47(4):872-879
Multiwalled carbon nanotubes (MWNTs) are chemically modified with respect to various different oxidative conditions, including the acid concentration, treatment time, and temperature. The conductivity of polyurethane (PU) composites filled with the MWNTs oxidized under optimal condition is measured as a function of frequency with the content of MWNTs and analyzed using percolation theory. Because the PU composites filled only with the MWNTs cannot satisfy the requirements for materials providing shielding against electromagnetic waves, conductive polymer composites are fabricated by the hybridization of MWNTs with Ag flakes. It is observed that a small amount of the MWNTs remarkably enhances the conductivity and shielding effectiveness of the MWNT/Ag flake/PU composites, by bridging the gap between the flaky Ag clusters. The electromagnetic interference shielding effectiveness of the composites can be controlled from about 60 dB to more than 80 dB at an extremely low loading level of both the MWNTs and the Ag flakes in the frequency range from 10 to 1000 MHz. 相似文献
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Tzong-Lin Wu Wern-Shiarng Jou Dai S.G. Wood-Hi Cheng 《Lightwave Technology, Journal of》2003,21(6):1536-1543
A low-cost plastic package of the standard 1 /spl times/ 9 type with effective electromagnetic (EM) shielding ability is developed. Optical transceiver modules with transmission rates of 155 Mb/s and 1.25 Gb/s are tested to evaluate the EM shielding against emitted radiation from the plastic packaging. The results show that the packaged optical transceiver modules exhibit shielding effectiveness (SE) of over 20 dB. The EM shielding properties of plastic materials consisting of nylon66 and liquid crystal polymer (LCP) with carbon fiber reinforced are investigated. The effects of weight percentage of fibers, carbon fiber length, and material thickness on the SE of the plastic composites are studied both from the plane-wave and near-field sources approaches. The packaged plastic optical transceiver modules with their good SE are suitable for use in low-cost and low electromagnetic interference (EMI) Gigabit Ethernet lightwave transmission systems. 相似文献
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Jana P.B. Mallick A.K. De S.K. 《Electromagnetic Compatibility, IEEE Transactions on》1992,34(4):478-481
The electromagnetic interference shielding effectiveness and return loss of short carbon-filled polychloroprene rubber composites of varying sample thickness and fiber aspect ratio were studied in the frequency range of 8 to 12 GHz (X -band). It was observed that composites prepared by the cement-mixed method with high fiber aspect ratio (L /D =100) show higher shielding effectiveness and lower return loss than the composites prepared by the mill-mixed method with low fiber aspect ratio (L /D =25). This indicates that loss due to absorption increases with increasing fiber aspect ratio. A similar effect has also been observed with increasing sample thickness 相似文献