电磁屏蔽泡沫混凝土的性能研究

研究了不同密度泡沫混凝土的电磁屏蔽性能,结果表明孔径较大时泡沫混凝土具有电磁屏蔽能。在泡沫混凝土制备过程中加入石墨和碳纤维,改善了泡沫混凝土的电磁屏蔽能。研究了石墨和碳纤维掺量对泡沫混凝土电磁屏蔽能的影响。结果表明,石墨不能增加泡沫混凝土电磁屏蔽能;碳纤维泡沫混凝土在0~100MHz频率范围内,屏蔽效能SE随着频率增加而迅速降低,在100~1500MHz频率范围内,屏蔽效能SE随着频率增加而增加,在100MHz附近,碳纤维电磁屏蔽砂浆的SE最小。     

泡沫铝/环氧树脂复合材料电磁屏蔽及力学性能实验

以环氧树脂填充泡沫铝.制备了具有一定结构性能及电磁屏蔽功能的结构和功能一体化复合材料试件,泡沫铝的孔径设计为1.0 mm和2.0 mm,厚度为5.0mm、10.0 mm和15.0 mm.通过法兰同轴测试法,分别测试了这6组试件的电磁屏蔽效能,研究发现:泡沫铝厚度一定,频率为10～300 MHz时,随着孔径的增大屏蔽效能增强;频率为300 MHz～1.5 GHz时,孔径对屏蔽效能的影响不明显.泡沫铝孔径一定,频率为10～300 MHz时,随着厚度的增大屏蔽效能增强;频率为300 MHz～1.5 GHz时,厚度对屏蔽效能影响不大.同时,通过拉伸和弯曲实验测试了复合材料中泡沫铝孔径不同的试件的强度和弹性模量等力学性能.结果表明,泡沫铝孔径小的复合材料的抗拉和抗弯性能比孔径大的更好.     

泡沫铝材料电磁屏蔽效能的优化研究

选取渗流法制备的泡沫铝材料,测试其内部连通性、表面结构和孔径对其电磁屏蔽效能的影响。结果表明:小孔径泡沫铝材料具有较高的屏蔽效能,平均孔径为0.3mm的泡沫铝的屏蔽幅值在70~110dB之间;增大泡沫铝的表面反射面积可以提高材料对低频电磁波(f1000 MHz)的屏蔽效能;提高泡沫铝的内部连通性可以提高材料对中频电磁波(1000 MHzf2000 MHz)的屏蔽效能。     

掺石墨/碳纤维电磁屏蔽砂浆的研究

以石墨和碳纤维为电磁屏蔽功能基元材料,将其添加到砂浆中,部分取代砂浆中的砂,调节电磁屏蔽功能材料的含量,使砂浆对电磁波具有屏蔽和吸收功能。研究了电磁屏蔽功能基元材料含量对砂浆电磁屏蔽效能的影响。结果表明添加石墨和碳纤维电磁屏蔽功能基元材料的电磁屏蔽砂浆,在30～200MHz频率范围内,电磁屏蔽效能SE较大,随着频率增加,屏蔽效能SE迅速降低。在200MHz～1.8GHz频率范围内,电磁屏蔽效能SE值趋于平缓,屏蔽效能较低。在1.8GHz附近,碳纤维电磁屏蔽砂浆的SEmin最大,为10dB。     

金属手性材料复合水泥砂浆的电磁屏蔽性能

电磁屏蔽建筑材料在当今信息化社会中具有重要的应用价值。在水泥砂浆中添加金属螺旋圈材料,在10kHz～1500MHz范围内进行电磁屏蔽性能测试。结果显示,随着频率的增加,屏蔽性能一般逐渐增强,在550MHz、1050MHz附近都有2个明显的拐点;在10kHz～550MHz范围,屏蔽效能都小于4dB;但在900～1050MHz频率范围内,最大屏蔽效能都能够超过10dB。     

高密度聚乙烯/低密度聚乙烯共混材料的模压发泡

用模压发泡法制备了高密度聚乙烯(HDPE)/低密度聚乙烯(LDPE)共混发泡材料,研究了偶氮二甲酰胺(AC)发泡剂)、HDPE的用量及模压发泡工艺对于HDPE/LDPE共混泡沫的表观密度、力学性能的影响。结果表明,随着HDPE用量增加,共混发泡材料的表观密度、撕裂强度和拉伸强度均逐渐增加。在一定范围内,AC发泡剂用量增加,泡沫材料的表观密度和力学性能先下降后增加。发泡时间为10min时泡沫表观密度较低,再延长发泡时间,泡沫表观密度变化较小。在0MPa~10MPa范围,模压压力增加,泡沫表观密度缓慢下降。在温度为170℃~180℃范围内,温度升高,泡沫密度逐渐下降。电镜扫描图显示,HDPE/LDPE共混发泡材料泡孔均匀,且多为闭孔。     

高密度聚乙烯/低密度聚乙烯共混材料的模压发泡EI北大核心CSCD

用模压发泡法制备了高密度聚乙烯(HDPE)/低密度聚乙烯(LDPE)共混发泡材料,研究了偶氮二甲酰胺(AC)发泡剂)、HDPE的用量及模压发泡工艺对于HDPE/LDPE共混泡沫的表观密度、力学性能的影响。结果表明,随着HDPE用量增加,共混发泡材料的表观密度、撕裂强度和拉伸强度均逐渐增加。在一定范围内,AC发泡剂用量增加,泡沫材料的表观密度和力学性能先下降后增加。发泡时间为10min时泡沫表观密度较低,再延长发泡时间,泡沫表观密度变化较小。在0MPa^10MPa范围,模压压力增加,泡沫表观密度缓慢下降。在温度为170℃~180℃范围内,温度升高,泡沫密度逐渐下降。电镜扫描图显示,HDPE/LDPE共混发泡材料泡孔均匀,且多为闭孔。     

碳化细菌纤维素的电磁屏蔽效能

细菌纤维素在不同的温度下进行碳化处理,将得到一系列网状结构的碳纤维。利用X射线衍射仪(XRD)、拉曼光谱仪和透射电子显微镜(TEM)对制备的碳纤维晶体结构和微观形貌进行了表征;通过矢量网络分析仪在频率600MHz～14GHz范围内对其进行了电磁参数测试;应用电磁屏蔽理论计算获得碳纤维的电磁屏蔽效能。结果表明,1200℃碳化得到的碳纤维在频率为6～14GHz之间的屏蔽效能都大于30dB,在14GHz时最高可以达到41dB,该碳纤维密度低、屏蔽效果好,在电磁屏蔽领域有较好的应用前景。     

生物质多孔炭的电磁屏蔽性能研究

以思茅松锯末为原料,固体氯化铵为造孔剂,酚醛树脂为粘结剂,采用现有的固化烧结技术,制备多孔炭材料。利用法兰同轴法测试其电磁屏蔽效能。结果表明,在130～1800MHz内,多孔炭的屏蔽效能在38.8～56.2dB之间,屏蔽效果较好,并优于无孔炭材料。其中,在130～716MHz内,多孔炭的屏蔽效能随着频率的增加而减小;但在716～1800MHz内,多孔炭的屏蔽效能随频率的增加而增加。多孔炭的孔径越大,其电磁屏蔽效能越好,但是随着频率的增加,0.35mm和0.13mm两种孔径的多孔炭屏蔽效能差距越来越小。当孔径和厚度一定时,多孔炭的屏蔽效能随着孔隙率的增加而增大。     

颗粒增强铝合金基泡沫铝材料压缩性能的研究

利用熔体发泡法制备了颗粒增强铝合金基闭孔泡沫铝,进行了准静态压缩和动态压缩实验,并且与铝合金基泡沫铝的相关性能进行了比较.研究了不同相对密度的泡沫铝准静态压缩和动态压缩性能.添加颗粒能增强基体合金性能,改善泡沫压缩效果.结果表明,在动态压缩和准静态压缩中,随着密度增加,颗粒增强基泡沫铝的平台应力和弹性模量逐渐增大;动态情形下的能量吸收能力要高于准静态情形下的能量吸收能力.向熔体中添加适当比例的粉煤灰颗粒可产生显著的基体增强效果,有效提高泡沫铝的压缩性能.     

Electromagnetic interfering shielding of aluminum alloy–cenospheres composite

Fly-ash cenosphere particles were used as mixture in aluminum matrix composite by squeeze casting method [1]. The electromagnetic interfering shielding effectiveness (EMISE) was investigated in the frequency range from 0.03 MHz to 1.5 GHz. It showed the SE value of Al2024/cenospheres composite (ACC) is higher than that of aluminum alloy, and comparative to traditional material 1J50. Unlike 1J50, the mechanism of EMI shielding for ACC is reflection and multiple reflections. Analyzed by XRD and SEM, chemical reactions may occur between the matrix and cenosphere particles during the casting procedure, but it affects the shielding effectiveness little.     

合成纤维复合夹层屏蔽结构改性及其电磁特性研究

提出具有复合介质夹层屏蔽结构模型的设想,利用铜箔-聚四氟乙烯为原材料,设计了单层屏蔽结构与复合夹层屏蔽结构的对比实验,测试了复合夹层屏蔽结构的电磁屏蔽效能增量,并用Ватолцн多层电磁屏蔽理论公式进行了验证。具有复合夹层屏蔽结构材料的电磁屏蔽效能明显优于单层屏蔽结构材料的电磁屏蔽效能。继而以涤纶无纺布、锦纶合成纤维为研究对象,采用电化学改性的方法,制备了具有复合夹层屏蔽结构的柔性电磁屏蔽材料。结果表明,通过对研究对象的选择和优化电化学改性的工艺,可以制备出1 MHz~1000 MHz入射电磁波频段范围内,满足不同要求的合成纤维复合夹层屏蔽结构改性材料,其SE值最高可达98 dB。     

水性镍基电磁屏蔽涂料的研究

叙述了水性镍基电磁屏蔽涂料的制作及涂层的有关性能,探讨了水、温度、涂层厚度等因素对屏蔽涂层的电阻率及电磁屏蔽效能的影响规律。试验表明,在频率为9KHz-1000MHz范围内,屏蔽效能为45-60dB。     

Electromagnetic interference (EMI) shielding of single-walled carbon nanotube epoxy composites

Single-walled carbon nanotube (SWNT)-polymer composites have been fabricated to evaluate the electromagnetic interference (EMI) shielding effectiveness (SE) of SWNTs. Our results indicate that SWNTs can be used as effective lightweight EMI shielding materials. Composites with greater than 20 dB shielding efficiency were obtained easily. EMI SE was tested in the frequency range of 10 MHz to 1.5 GHz, and the highest EMI shielding efficiency (SE) was obtained for 15 wt % SWNT, reaching 49 dB at 10 MHz and exhibiting 15-20 dB in the 500 MHz to 1.5 GHz range. The EMI SE was found to correlate with the dc conductivity, and this frequency range is found to be dominated by reflection. The effects of SWNT wall defects and aspect ratio on the EMI SE were also studied.     

钢纤维混凝土电磁屏蔽性能实验研究

实验研究了纤维体积掺量相同情况下，4种不同纤维长度的钢纤维混凝土电磁屏蔽性能，并对其屏蔽规律进行了分析、比较。探讨了纤维长度对钢纤维混凝土电磁屏蔽性能的影响机理。当纤维体积掺量为2A％，纤维长度为18或12mm时，钢纤维混凝土电磁屏蔽效能在0-3～1000MHz频带内达到20dB以上。其中掺入长度为18mm钢纤维时，在0．3MHz最高达到65dB，掺入长度为6mm钢纤维时，在1．0GHz最高达到41dB。     

Electromagnetic interference shielding by carbon fibre-filled polychloroprene rubber composites

The electromagnetic interference (EMI) shielding effectiveness of short carbon fibre-filled polychloroprene composites was studied in the frequency ranges 100 to 1000 MHz and 8 to 12 GHz. It was observed that, at a particular frequency, the shielding effectiveness increases with increasing loading of carbon fibre in the composite. Results show that 30 to 40 phr (parts per hundred parts of rubber) loading of fibre makes the rubber composite a potential EMI shielding material for use in the electronics industry.     

Synergetic effect of conducting polymer composites reinforced E-glass fabric for the control of electromagnetic radiations

The use of fibril materials as substrate for reinforcing polymers has wide industrial applications. In this article, we discuss polyaniline and polypyrrole as conducting polymers to provide electronic conductivity in E-glass fabric reinforced conducting composite with varied degree of composition and conductivity using industrially important polymers polymethylmethacrylate and polyvinyl chloride as a host matrix. Aromatic sulphonic acids such as PXSA, OXSA, PSA, PDSA, RDSA, OCPSA and MCSA were used as a dopant. The influence of the aromatic ring substituents in these dopants over the conductivity and processibility due to various interactions has been studied. The study shows that due to bulk nature of conductivity, shielding effectiveness (SE) increases with increase in conductivity and thickness of a composite. The test samples were characterized by conductivity and electromagnetic shielding effectiveness (EMI SE). The electromagnetic shielding effectiveness was measured by co-axial transmission line method in the frequency range of 0.01–1000 MHz. These composites with both side shielded by polypyrrole offered a uniform shielding effectiveness of 69 dB.     

纤维复合材料电磁屏蔽效能分层多尺度计算

为建立复合材料宏细观尺度之间电磁响应的关联性,将分层多尺度计算方法应用于纤维复合材料电磁屏蔽效能计算。为准确描述复合材料宏细观之间的联系,以电磁屏蔽效能为衡量标准,确定了复合材料细观结构的代表性体积单元(RVE)。根据电磁场媒质本构方程计算了RVE的等效电磁参数。采用分层多尺度方法计算复合材料宏观构件的电磁屏蔽效能。结果表明工作频率越高则复合材料的RVE越小;所设计的纤维复合材料结构在工作频率2～18GHz范围内具有38dB以上的电磁屏蔽效能,且电磁屏蔽效能随工作频率增加而下降。研究方法适用于求解细观结构相分散均匀或分布有规律的任意形状复合材料宏观构件电磁屏蔽效能。     

Electromagnetic shielding effectiveness of thin film with composite carbon nanotubes and stainless steel fibers

Using the polymer blending method, conductive materials and waterborne polyurethane (WPU) were mixed to fabricate conductive composite films for application in electromagnetic shielding. First, nitric acid was used to purify the multi-walled carbon nanotubes (MWCNT). Second, sodium dodecyl sulfate (SDS) was utilized to disperse the carbon nanotubes, and then they were mixed with 8 microm diameter and 2 mm long stainless steel fibers (SSF) in the WPU by the polymer blending method. Finally, the thickness of 0.25 mm of conductive composite film was fabricated by means of coating. According to the ASTM D4935-99 standard, a coaxial transmission line was used to measure the electromagnetic shielding effectiveness (EMSE) of conductive composite film within the range of 50 MHz approximately 3.0 GHz. Moreover, the influence of the prior and posterior dispersion of carbon nanotubes dispersed on electromagnetic shielding was dealt with in the paper. Results demonstrated that the conductive composite film, within 50 MHz approximately 3.0 GHz, fabricated by the 15 wt% of the multi-walled carbon nanotubes and 30 wt% of the stainless steel fibers can achieve the maximum of the electromagnetic shielding effectiveness, 34.86 dB, and its shielding effect, 99.9%.