镀铜／镍聚丙烯腈纤维填充复合材料电磁波屏蔽性能的研究

研究了镀铜／镍的聚丙烯腈纤维填充ＡＢＳ树脂制得的复合材料的导电性及电磁波屏蔽性能，复合材料的导电性主要与导电纤维的填加量有关，导电纤维与基体树脂间的相容状况、复合加工时某些工艺条件等对复合材料的导电性也有较大的影响，电磁波屏蔽性能随导电纤维填加量的增加而提高，加入适当的偶联剂有助于改善和复合材料的电磁波屏蔽性能。     

三维碳化硅纳米线增强碳化硅陶瓷基复合材料的电磁屏蔽性能

碳化硅纳米线具有优异的电磁吸收性能, 三维网络结构可以更好地使电磁波在空间内被多次反射和吸收。通过抽滤的方法制备得到体积分数20%交错排列的碳化硅纳米线网络预制体。然后采用化学气相渗透工艺制备热解炭界面和碳化硅基体, 并通过化学气相渗透和前驱体浸渍热解工艺得到致密的SiCNWs/SiC陶瓷基复合材料。甲烷和三氯甲基硅烷分别是热解炭和碳化硅的前驱体, 随着热解碳质量分数从21.3%增加到29.5%, 多孔SiCNWs预制体电磁屏蔽效率均值在8~12 GHz (X)波段从9.2 dB增加到64.1 dB。质量增重13%的热解碳界面修饰的SiCNWs/SiC陶瓷基复合材料在X波段平均电磁屏蔽效率达到37.8 dB电磁屏蔽性能。结果显示, SiCNWs/SiC陶瓷基复合材料在新一代军事电磁屏蔽材料中具有潜在应用前景。     

聚苯胺性状及其含量对镍粉/聚苯胺涂层屏蔽性能的影响

系统分析了金属粉末/聚苯胺复合电磁屏蔽材料中导电聚苯胺的性状,体积分数对微观结构和电磁屏蔽效能的影响.从二次掺杂的导电聚苯胺的电磁性能讨论了聚苯胺对电磁屏蔽效能的贡献.研究了二次掺杂聚苯胺性状对电磁屏蔽涂层微观结构形貌以及与金属粉末的复合效应对电磁屏蔽效能的贡献.研究的结果表明导电聚苯胺的加入有利于增加电磁屏蔽材料对于高频电磁波的电磁屏蔽效能,但是对低频部分的电磁波的屏蔽效能与纯金属粉末电磁屏蔽材料相比有所降低,这可能是由于聚苯胺加入导致的导电组分分布不均匀所引起的.实验结果表明胶状体聚苯胺和粉末状聚苯胺在电磁屏蔽涂料基体树脂中具有完全不同的形态,分析了对电磁屏蔽效能的影响.     

电磁屏蔽复合材料电磁屏蔽效能探讨

电磁屏蔽材料目前向着薄、轻、宽、高的方向发展,复合材料已逐渐取代单一材料成为电磁屏蔽研究的主要方向.以机械复合材料为基础,研究高导电材料+高导磁2层复合材料与高导电材料+高导电材料+高导磁材料3层复合材料电磁屏蔽效能的差别.研究结果表明,2层复合材料高导电材料一侧增加1层高导电材料对电磁屏蔽性能的提高非常有限.     

表面改性和复合工艺对金属纤维/聚合物复合材料性能的影响

以不锈钢纤维为导电填料,分别与ABS和PP复合,制得了电磁屏蔽用导电高分子复合材料。考察了表面改性和复合工艺对金属纤维／聚合物复合材料性能的影响。结果表明,用不同表面处理剂处理不锈钢纤维后,随纤维表面张力增加,复合材料的电阻率增加。使用母料法工艺可以有效地改善金属纤维在聚合物基体中的分散,从而提高复合材料的导电性能和电磁屏蔽性能。     

铁镍合金对复合电磁屏蔽材料性能的影响

在导电组分中添加磁性合金粉末,利用复合效应增加电磁屏蔽材料的吸收损耗,以获得较好的屏蔽效能。通过在12%体积分数的金属镍粉中添加不同体积分数的FeNi合金,研究了复合材料中FeNi合金对电磁屏蔽效能的影响。实验结果表明,当加入4%体积分数的FeNi合金时,屏蔽效能最好。分析得出FeNi合金粉末的加入能够增加材料的磁导率,增加材料对电磁波的吸收,在提升屏蔽效能的同时达到低二次污染的目的。     

金属纤维填充聚合物复合材料的导电性能和电磁屏蔽性能

以不锈钢纤维作为填料,分别与ＡＢＳ和ＰＰ两种聚合物复合制得了电磁屏蔽用导电性高分子复合材料。通过研究复合材料导电性能和电磁屏蔽性能与纤维含量的关系,发现结晶性的ＰＰ基体比无定形ＡＢＳ基体所需的纤维临界填充量低,同时ＳＳＦ／ＰＰ的屏蔽效果高于ＳＳＦ／ＡＢＳ复合材料;此外,结果还表明这类复合材料对电磁波的屏蔽效果以吸收损耗为主,反射损耗量较小。     

石墨—MDF水泥基复合材料屏蔽电磁波性能

研究了石墨、聚合物（ＰＶＡ）及材料厚度对石墨－ＭＤＦ（Ｍａｃｒｏ－Ｄｅｆｅｃｔ－Ｆｒｅｅ）水泥基复合材料屏蔽电磁性能的影响及其机理。结果表明：当石墨添加量超过１８ｖ．％时，材料对２００１６００ＭＨｚ的电磁波有１０－４０ｄＢ的衰减效果，屏蔽效率Ｓ随材料中聚合物增加而降低，随材料厚度增加而升高，随电磁波的频率ｆ的增加有升高的趋势。当石墨在水泥基体里形成导电网络时，材料的电阻率ｐｖ发生显著变化，即出现渗     

3D编织碳纤维复合材料的制备及其屏蔽性能的研究

用三维五向3D编织技术和模压成型工艺制备了碳纤维增强环氧树脂基电磁屏蔽复合材料,测试结果表明,三维五向编织结构可形成良好的导电网络,基于该结构制成的碳纤维复合材料屏蔽效能最高可达85dB,编织体整体化学镀镍可使材料的屏蔽效能提高约15dB,镀镍后的复合材料在14kHz～18GHz频段内具有较高的屏蔽效能,最高可达95dB。同时发现,该材料的屏蔽性能显示各向异性,这与编织体的纤维取向和电磁波的极化方向有关。     

镀镍PET纤维/环氧树脂复合材料的性能

以PET纤维经超声波化学镀镍制成的导电PET/Ni纤维作填料,与环氧树脂共混,制得导电环氧树脂复合材料.对纤维表面镀层的形态结构及复合材料的导电性、电磁屏蔽性及力学性能进行了深入的研究.结果表明,填充适量(1%～5%,质量分数,下同)的纤维就可以得到导电性能良好的复合材料,同时也具有较好的电磁屏蔽性能,当纤维含量为3%时材料的力学性能也得到改善.     

Lightweight multi-walled carbon nanotube buckypaper/glass fiber–epoxy composites for strong electromagnetic interference shielding and efficient microwave absorption

Multi-walled carbon nanotube buckypaper (BP) reinforced glass fiber–epoxy (GF/EP) composites were selected to fabricate electromagnetic interference (EMI) shielding and microwave absorbing materials. Six different composite configurations with 3.0 mm thick have been conceived and tested over the X-band (8.2–12.4 GHz). Flexible and low-density (0.29 g/cm³) BP provided a high specific EMI SE of 76 dB with controlled electrical conductivity. GF/EP/BP₁₁₁ and GF/EP/BP₁₀₁ composites possess EMI SE as high as of 50–60 dB, which can be attributed to the number of BP inserted and variation in the wave-transmitting layer of the laminates. Furthermore, the shielding mechanism was discussed and suggested that the absorption was the dominant contribution to EMI SE. GF/EP/BP₁₁₀ laminate demonstrated suitable EMI performance (~?20 dB), whereas GF/EP/BP₀₁₁ composite revealed excellent microwave performance, achieving an effective ? 10 dB bandwidth of 3.04 GHz and minimum reflection loss (RL) value of ? 21.16 dB at 10.37 GHz. On the basis of these results, GF/EP/BP composites prepared in this work have potential applications as both EMI shielding and microwave absorber materials given their facile preparation and lightweight use.

     

Electromagnetic interference shielding of carbon nanotube/ethylene vinyl acetate composites

Single-walled carbon nanotube (SWCNT) and ethylene vinyl acetate (EVA) composites were synthesized in an internal mixer by melt mixing. The electrical conductivity as well as electromagnetic interference (EMI) shielding effectiveness (SE) over the X-band (8–12 GHz) and microwave (200–2,000 MHz) frequency ranges of these composites were investigated. It was observed that the electrical conductivity of composites increases with increasing SWCNT loading. A percolation threshold of about 3.5 wt.% was obtained and the electrical conductivity of EVA was increased by ten orders of magnitude, from 10⁻¹⁴ to 10⁻⁴ Ω⁻¹ cm⁻¹. The effect of sample thickness on SE was investigated. The correlation between SE and conductivity of the composites is discussed. The experimental data showed that the SE of the composites containing higher carbon nanotube loadings (above 10 wt.%) could be used as an EMI shielding material and lower SWCNT loadings could be used for the dissipation of electrostatic charge.     

Processing of graphene nanoribbon based hybrid composite for electromagnetic shielding

The advent of graphene heralded by the recent studies on carbon based conducting polymer composites has been a motivation for the use of graphene as an electromagnetic interference (EMI) shielding material. One of the variants of graphene, graphene nanoribbon (GNR) shows remarkably different properties from graphene. The EMI shielding effectiveness of the composite material mainly depends on fillers’ intrinsic conductivity, dielectric constant and aspect ratio. We have synthesized graphene nanoribbon (GNR) – Polyaniline (PANI) – epoxy composite film for effective shielding material in the X-band frequency range of 8.2–12.4 (GHz). We have performed detailed studies of the EMI shielding effect and the performance of the composite and found that the composite shows ∼−40 dB shielding which is sufficient to shield more than 95% of the EM waves in X Band. We checked the shielding effectiveness of the composite film by varying the GNR percentage and the thickness of the film. The strength properties of the synthesized composited were also studied with a aim to have a material having both high strength and EMI shielding properties.     

CNT纸/SiC对称梯度层状复合材料的高温电磁屏蔽性能和介电性能

将单层碳纳米管(CNT)纸浸渍酚醛树脂致密化,通过树脂碳层层焊接得到厚度约为2.6 mm的CNT纸/SiC层状梯度复合材料,由13个CNT纸/SiC复合材料结构层和12个膨胀石墨增韧树脂C界面层组成,SiC含量沿厚度方向由中心向两端呈递增的对称梯度分布。CNT纸/SiC层状梯度复合材料的体积密度为1.65 g/cm3,开气孔率为7.25%,在宏观尺度范围获得在SiC基体中均匀弥散分布的高含量的CNT。在X频段范围,CNT纸/SiC层状梯度复合材料600℃时的平均总屏蔽效率(37.19 dB)高于室温(35.00 dB)。较之室温时的屏蔽性能,CNT纸/SiC层状梯度复合材料600℃时的反射系数略有减小,但吸收系数明显增加,透射系数由0.0003减小至0.0002,展示了良好的在电磁屏蔽领域尤其是高温屏蔽领域的应用前景。在X频段范围,随温度由室温升高至600℃,CNT纸/SiC层状梯度复合材料的虚介电常数平均值由114.6增大至149.1;平均损耗正切值由1.62增大至1.79。      

Synergistic influence of barium hexaferrite nanoparticles for enhancing the EMI shielding performance of GNP/epoxy nanocomposites

Journal of Materials Science - In this work, the electromagnetic interference (EMI) shielding performance of epoxy composites containing barium hexaferrite (BaM) nanoparticles and graphene...     

Correlation between Young’s modulus and impregnation quality of epoxy-impregnated SWCNT buckypaper

Carbon nanotube (CNT) sheets, also known as buckypaper, have high potential for structural applications due to their high volume fraction of CNT, the strongest and stiffest materials known. In this work, two different techniques, one based on positive pressure and another based on vacuum infiltration, are utilized to impregnate single-walled carbon nanotube (SWCNT) buckypaper sheets of 50–70 μm in thickness, resulting in a Young’s modulus of up to 15.4 GPa. Scanning electron microscopy demonstrates that the vacuum-based technique results in more effective impregnation of the buckypaper than the positive pressure technique. Thermogravimetry analysis of vacuum-impregnated specimens indicated a void content ranging from 5% to 32%. An advanced Mori–Tanaka-based micromechanics technique is also utilized to predict the effect of SWCNT volume fraction and void content on Young’s modulus of nanocomposites. These calculations suggest a higher void content of around 40% for the vacuum-impregnated composites.     

Preparation of Porous Silver Nanowires-Melamine Formaldehyde Hybrid Composite Materials and Their Electromagnetic Shielding and Flame-Retardant Properties

Along with the booming development of communication technology and electronic equipment, higher requirements of flame-retardant and EMI shielding performances for electromagnetic interference (EMI) shielding materials are put forward. Herein, the ultralight and porous silver nanowires (AgNWs)-melamine formaldehyde (MF) hybrid composite with unique micro-/nanostructure is developed by a facile dip-coating method, which uses the AgNWs as 1D conductive coating and MF foam (MF foam) as 3D skeleton template. Benefiting from the unique porous micro-/nanostructure, the resultant hybrid composite displays low density, excellent EMI shielding performances, and superior flame-retardant property. The EMI shielding effectiveness (SE) and specific EMI SE (SSEt) of the hybrid composite in X-band (8.2–12.4 GHz) can be up to 77 dB and 26971.4 dB cm⁻² g⁻¹, respectively. At the same time, the hybrid composite also passes the vertical burning test and shows an increased LOI value of 40.6%. The combination of flame-retardant and EMI shielding performances for EMI shielding materials makes the AgNWs-MF hybrid composite great application potential in civil and military fields. This work provides a new guide for the design of multifunctional high-performance EMI shielding materials.     

孔隙率对三维针刺C/C复合材料电磁屏蔽性能的影响

通过多次重复先驱体浸渍裂解(PIP)工艺过程,改变材料的孔隙率和体密度,制备不同孔隙率的三维针刺碳/碳(C/C)复合材料,并研究了在8.2~12.4GHz频率范围内(X波段)不同孔隙率C/C复合材料的电磁屏蔽效能。结果表明:适当降低孔隙率有利于提高C/C复合材料的总电磁屏蔽效能和电磁吸收屏蔽效能,当开气孔率为33.4%时,C/C复合材料具有最大的电磁屏蔽效能(40dB),且电磁吸收屏蔽效能(30dB)远大于电磁反射屏蔽效能(12dB),是极具潜力的高吸收低反射电磁屏蔽材料。     

微纳米材料在电磁屏蔽方面的应用研究进展

信息技术的迅速发展和电子设备的大量使用,在环境中产生了如电子噪声、电磁波(EM)、电磁干扰(EMI)、射频干扰等电子污染。综述了EMI屏蔽微纳米材料相关方面的研究进展,简要分析了EMI屏蔽的基本机理和比较了纳米EMI屏蔽复合材料的制备方法,同时对比了金属和碳纳米填料EMI屏蔽复合材料,得到金属纳米EMI屏蔽复合材料,虽具有良好效果,但是存在质量大、成本高和耐腐蚀性弱等缺点。因碳系纳米材料具有质量轻,耐腐蚀性,优异的电学、电介质、热学、机械和磁性等独特特性,可替代金属作为EMI屏蔽填料,且EMI屏蔽效果优良。如多层纳米管(MWCNT)和石墨烯/聚苯胺(GN/PANI)纳米复合材料,并且两者材料的混杂可以协同改善复合材料的屏蔽效果。     

多壁巴基纸/环氧复合材料拉伸性能的影响因素

采用抽滤法制备了多壁碳纳米管(MWCNTs)纸(又称巴基纸), 研究了巴基纸增强不同环氧基体复合材料(巴基纸复合材料)的拉伸性能及其断口形貌, 分析了MWCNT含量、 树脂基体拉伸性能以及巴基纸与树脂的界面黏附作用对复合材料拉伸性能的影响。结果表明: 在MWCNT质量分数小于39.1%范围内, 增加碳纳米管含量, 可显著提高巴基纸/环氧复合材料的拉伸性能; 巴基纸/环氧复合材料的拉伸强度和模量与树脂基体的性能密切相关, 其拉伸破坏形式受基体的脆韧性影响显著; 相比较而言, 巴基纸与树脂间的黏附功对巴基纸/环氧复合材料拉伸性能的影响不明显。