石墨烯/聚苯胺复合材料的电磁屏蔽性能

采用直流电弧放电法制备高结晶性石墨烯, 利用乙醇助溶分散法得到石墨烯/聚苯胺电磁屏蔽复合材料, 研究不同掺杂比例的石墨烯/聚苯胺复合材料的电磁屏蔽性能。拉曼光谱分析表明: 由于石墨烯与聚苯胺之间的相互作用, 复合材料中聚苯胺特征峰比纯聚苯胺特征峰稍弱或向低频方向移动。复合物的电导率随石墨烯掺杂量的增加而增大, 当掺杂质量分数为25%时, 其电导率达到19.4 S/cm, 接近纯石墨烯电导率(20.1 S/cm)。频率为2~18 GHz时, 复合材料的电磁屏蔽效能随着石墨烯掺杂量和频率的增大而增强; 当石墨烯掺杂质量分数为25%时, 总屏蔽效能在2~18 GHz范围内由19.8 dB增至34.2 dB, 增加了约42%, 其中吸收部分占总屏蔽效能的比例为66%~81%, 这表明石墨烯/聚苯胺复合材料的电磁屏蔽性质是以电磁波吸收为主; 同时也说明了拥有特殊结构与特性的石墨烯是一种较好的聚苯胺填料, 在微波屏蔽与微波吸收领域将会有广阔的应用前景。     

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。     

非织造基网格型碳纤维复合材料的屏蔽性能分析

在PET非织造基材表面,采用等间距排列连续碳纤维的方式制备网格型单层和双层碳纤维复合材料,测试分析具有不同排列间距、重叠层数和重叠角的复合材料,在30 MHz~1.5GHz频段内的电磁屏蔽性能,从而为制备低成本、高性能的电磁屏蔽复合材料提供一定的理论指导。结果表明:对单层网格型复合材料,在碳纤维排列间距为6mm时,其最优屏蔽效能特征峰值为46.66dB,对应频率1.05GHz;对双层网格型复合材料,以0°-0°角重叠、排列间距为6mm时,其屏蔽效能特征峰值达到51.31dB,对应频率1.15GHz;相比于单层复合材料,双层复合材料的屏蔽性能提高了10%,其有效频宽提高了42%。     

化学镀镍碳纤维/环氧树脂复合材料电磁屏蔽性能

采用化学镀方法对碳纤维进行表面镀镍, 采用SEM、 EDX、 XRD分析了镀镍碳纤维的微观形貌、 镀层成分和镀层结构, 通过电阻测试研究了镀镍碳纤维的导电性。将体积分数为2.5%、 5%、 7.5%、 10%的镀镍碳纤维作为导电填料制备镀镍碳纤维/环氧树脂复合材料, 并用屏蔽室法测试了不同频段复合材料的屏蔽效能。结果表明: 碳纤维化学镀镍后, 表面形成了一层均匀的复合镀层, 镀层中镍的质量分数高达94%, 镀镍碳纤维的电阻值仅为碳纤维原丝的1/54。镀镍碳纤维/环氧树脂复合材料的电磁屏蔽能力较碳纤维原丝有所提高。复合材料的屏蔽效能随镀镍碳纤维添加量的增加而升高。在低频频段(kHz频段), 复合材料的屏蔽能力主要决定于材料的本征参数, 不同镀镍碳纤维含量的镀镍碳纤维/环氧树脂复合材料的屏蔽能力相差不大; 在中高频频段(MHz、 GHz频段), 镀镍碳纤维/环氧树脂复合材料屏蔽效能主要决定于材料的电阻率。     

化学镀镍碳纤维/环氧树脂复合材料电磁屏蔽性能

采用化学镀方法对碳纤维进行表面镀镍,采用SEM、EDX、XRD分析了镀镍碳纤维的微观形貌、镀层成分和镀层结构,通过电阻测试研究了镀镍碳纤维的导电性.将体积分数为2.5％、5％、7.5％、10％的镀镍碳纤维作为导电填料制备镀镍碳纤维/环氧树脂复合材料,并用屏蔽室法测试了不同频段复合材料的屏蔽效能.结果表明:碳纤维化学镀镍后,表面形成了一层均匀的复合镀层,镀层中镍的质量分数高达94％,镀镍碳纤维的电阻值仅为碳纤维原丝的1/54.镀镍碳纤维/环氧树脂复合材料的电磁屏蔽能力较碳纤维原丝有所提高.复合材料的屏蔽效能随镀镍碳纤维添加量的增加而升高.在低频频段(kHz频段),复合材料的屏蔽能力主要决定于材料的本征参数,不同镀镍碳纤维含量的镀镍碳纤维/环氧树脂复合材料的屏蔽能力相差不大;在中高频频段(MHz、GHz频段),镀镍碳纤维/环氧树脂复合材料屏蔽效能主要决定于材料的电阻率.     

Al颗粒夹层CFRP复合材料力学及电磁屏蔽性能EI北大核心

CFRP复合材料具有优异的力学性能,在航空航天装备中有广泛应用,但是因其单层铺层内部的结构各向异性,单向纤维铺层对于垂直极化波的电磁屏蔽效能较弱。为应对日益复杂的电磁环境,保护电子元器件不受干扰,增强复合材料的电磁屏蔽效能显得尤为重要,本工作利用非连续Al颗粒在层间面内紧密排列,构建了一种层间面内含连续Al屏蔽层的CFRP复合材料,并研究了不同Al颗粒含量对复合材料电磁屏蔽效能和力学性能的影响规律。结果表明,随着Al颗粒含量的增加,CFRP复合材料的导电性和电磁屏蔽效能也随之增加,当聚合物中Al颗粒质量分数达到33.3%时,复合材料的面内电导率提高了3个数量级,在垂直于纤维方向上对频率为3~17 GHz的电磁波的电磁屏蔽效能提高了10 dB以上。随着Al颗粒含量的增加,复合材料层间剪切强度与弯曲强度出现先上升后下降的变化规律,当树脂中Al质量分数为33.3%时,复合材料的层间剪切性能提高了5.2%达到80.5 MPa,当树脂中Al质量分数为50%时,复合材料的弯曲强度提高了20%至1441.0 MPa,弯曲模量提高了10.2%达到101.83 GPa。由此可见,Al颗粒夹层CFRP复合材料可以实现力学性能和电磁屏蔽效能的同步提升,是一种具有广泛应用前景的结构-电磁屏蔽一体化复合材料。     

水泥基纳米石墨复合材料的电磁屏蔽性能

以纳米石墨微片作为导电填料,水泥作为基体,制备高导电性复合材料,研究其电磁屏蔽等性能.探讨纳米石墨微片、含水量、龄期对复合材料的导电性及电磁屏蔽效能的影响.结果表明,质量分数为15%的纳米石墨微片制得的复合材料的性能为最佳,其体积电阻率为22.3Ω·cm,电磁屏蔽效能达到22.60dB(1.5GHz).     

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。     

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。     

单层宽频Ni基电磁波屏蔽复合材料模型建立及其性能研究

针对300KHz-1.5GHz频段电磁波屏蔽材料的要求,在大量研究电磁波屏蔽机理以及各个频段屏蔽效能影响因素的基础上,从微合金化多元复台的新思路出发,建立了单层宽频镍基电磁波屏蔽复合材料结构设计物理模塑.经测试,所制备的复合辅助填科/镍/丙烯酸树脂复合材料涂层厚度为02-0.4mm,在300KHz-1.5GHz须段屏蔽嫂能可达47-68dB,较镍/丙烯酸树脂复合材料涂层屏蔽效能提高了21-31%,达到了国军标GJB2604-96标准     

Dispersions of carbon nanotubes/polyhedral oligomeric silsesquioxanes hybrids in polymer: the mechanical,electrical and EMI shielding properties

A hybrid was synthesized by grafting polyhedral oligomeric silsesquioxane (POSS) to multiwalled carbon nanotubes (MWCNTs). The MWCNT/polymer composites produced using silsesquioxane grafted MWCNTs as a filler had a high electromagnetic interference shielding effectiveness. Homogeneous dispersion of silsesquioxane grafted MWCNTs occurred throughout the polymer without any aggregation, while a pristine MWCNT aggregate that integrated several nanotube domains existed in the polymer matrix. A comparative study of the optical transmittance, electrical, and electromagnetic interference shielding properties of poly(l-lactide) (PLLA)/MWCNT composites based on pristine MWCNTs and silsesquioxane grafted MWCNTs was carried out. A high electromagnetic interference shielding effectiveness (15–16 dB) was obtained in the 36–50 GHz range at a relatively low filler loading (4 wt%) in the PLLA/silsesquioxane grafted MWCNT composite.     

多功能聚吡咯/聚酰亚胺电磁屏蔽复合膜的制备与性能研究

目的 开发具有优异屏蔽效率、轻质且热稳定性良好的电磁屏蔽材料。方法 以聚酰亚胺(PI)为聚合物基体,聚吡咯(PPy)为添加相,采用静电纺丝-低温原位聚合技术制备PPy/PI电磁屏蔽复合膜。通过在薄膜内部的多孔结构中构建致密的导电网络,赋予复合膜优异的导电性和高效的电磁屏蔽效能。结果 在聚合PPy浓度为0.1 mol/L时,复合膜的电导率和电磁屏蔽效能分别为2.23 S/cm和26.04 dB,且其单位厚度电磁屏蔽效能可达到110.81 dB/mm,展现出优异的电磁屏蔽性能。结论 PPy/PI复合纤维膜表现出良好的力学性能(拉伸强度为11.73 MPa)、优异的热稳定性(>400 ℃)和力学传感性能,具备在恶劣环境下广泛应用的潜力。     

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%.     

Electromagnetic interference shielding of composites consisting of a polyester matrix and carbon nanotube-coated fiber reinforcement

We investigated the electromagnetic interference shielding effectiveness (EMI SE) of composites consisting of an unsaturated polyester matrix containing woven glass or carbon fibers that had been coated with multiwalled carbon nanotubes (MWCNTs). Composite panels consisting of fiber fabrics with various combinations of fabric type and stacking sequence were fabricated. Their EMI SE was measured in the frequency range of 30 MHz–1.5 GHz. The underlying physics governing the EMI shielding mechanisms of the materials, namely, absorption, reflection, and multiple reflections, was investigated and used in analytical models to predict the EMI SE. Simulation and experimental results showed that the contributions of reflection and absorption to EMI shielding is enhanced by sufficient impedance mismatching, while multiple reflections have a negative effect. For a given amount of MWCNTs in the glass-fiber–reinforced composite, coating the outermost, instead of intermediate, glass fiber plies with MWCNTs was found to maximize the conductivity and SE.     

The effect of multi-wall carbon nanotubes on electromagnetic interference shielding of ceramic composites

Multi-wall carbon nanotubes (MWCNTs)-3?mol% yttria-stabilized zirconia (3Y-TZP) (MWCNTs-3Y-TZP) composite was prepared by spark plasma sintering. The complex permittivities of the composite have been measured in the Ku-band range (12.4-18?GHz) and it is found that both the real and imaginary permittivities of the composite increase with the increasing content of MWCNTs. The effect of the content of MWCNTs on the electromagnetic interference (EMI) shielding effectiveness (SE) of the composite has been evaluated, and it is found that the EMI SE of the composite increases with the increasing content of MWCNTs. An EMI SE value as high as 25-30?dB has been achieved in the Ku-band range for the composite with 9?wt% content of MWCNTs, indicating that the MWCNTs-3Y-TZP composite can be used as an effective EMI shielding material.     

镀银玻璃微珠/炭纤维填充导电硅橡胶的电磁屏蔽性能

分别研究了用镀银玻璃微珠,炭纤维和镀银玻璃微珠/炭纤维复合填料填充的硅橡胶的电磁屏蔽效能。结果表明,在2.6 GHz~3.95 GHz频段内,镀银玻璃微珠填充量越大,导电硅橡胶的电磁屏蔽效能越高,镀银玻璃微珠填充量为180份时,样品的屏蔽效能的峰值为-115.2 dB。添加少量炭纤维能够提高镀银玻璃微珠/炭纤维复合填料填充橡胶的电磁屏蔽性能,当炭纤维添加量增加到20份时,镀银玻璃微珠/炭纤维复合填料填充硅橡胶(镀银玻璃微珠填充量120份)的电磁屏蔽效能峰值达到-82.0 dB,高于填充量为150份的单纯镀银玻璃微珠填料样品的电磁屏蔽效能,并且能够提高导电硅橡胶的力学性能并降低成本。     

Synergistic effects of micro-/nano-fillers on conductive and electromagnetic shielding properties of polypropylene nanocomposites

This study presents the synergistic effects of graphene nanosheets (GNSs) and carbon fibers (CFs) additions on the electrical and electromagnetic shielding properties of GNS/CF/polypropylene (PP) composites. These composites were fabricated by the melt blending of different ratios of GNSs and CFs (20:0, 15:5, 10:10, 5:15 and 0:20 wt/wt%) into a PP polymer matrix using a Brabender mixer. Besides, the chemical and crystalline structures and the thermal stability of the resultant GNS/CF/PP composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). FT-IR and XRD showed that with the addition of GNSs content, transmittances at 1373.4?cm^?1 and 1454.4?cm^?1 became smaller and the characteristic peak at 26.82° became stronger. TGA showed that the GNS/CF/PP composite can be used at high temperature below 456°C. Blending 10?wt% CFs and 10?wt% GNSs into the PP polymer resulted in excellent conductivity (0.397 S/cm), which indicated the occurrence of the critical percolation threshold phenomenon, and also reached the maximum electromagnetic shielding effectiveness (EMSE) of 20?dB at 1.28–2.00?GHz. Laminated with five layers of composites, its EMSE achieved 25–38?dB at 0.3–3.0?GHz, corresponding to blocking of 94.38–98.74% electromagnetic waves.     

Effect of carbon nanofiber reinforcement on electromagnetic interference shielding effectiveness of syntactic foam

A novel carbon nanofiber (CNF)-reinforced syntactic foam (CNFRSF) was fabricated. The electrical conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) of CNFRSF with various volume fraction of CNFs (0–2.0 vol%) were evaluated experimentally. The measurement of EMI SE was carried out in a frequency range of 30 MHz to 1.2 GHz. The experimental results showed that the SE of CNFRSF increases with increase of CNFs content and CNF is more effective in providing EMI shielding compared to chopped carbon fiber and long carbon fiber due to the larger aspect ratio. The CNFRSF having 2.0 vol% CNFs has a SE of 25 dB, which is good enough for most practical applications. Compared to CNFs composites, the EMI SE of CNFRSF has been enhanced by the presence of hollow carbon microspheres. The underlying mechanism is discussed in detail.     

Polypyrrole nanotube/ferrocene-modified graphene oxide composites: From fabrication to EMI shielding application

Polypyrrole nanotube/ferrocene-modified graphene oxide composites (PNT/GO-Fc, PNT/GO-Fc-GO, PNT/GO-EDA-Fc and PNT/GO-EDA-Fc-EDA-GO) were fabricated via in situ chemical oxidative polymerization. The prepared composites were characterized by FTIR, XRD, XPS, Raman, TGA, SEM, TEM and EDS. The electromagnetic interference shielding performance of the prepared composites was evaluated by a coaxial method within the frequency range of 1.0–4.5 GHz. The results demonstrated that the composite of PNT/GO-EDA-Fc-EDA-GO-7:1 exhibited the best electromagnetic interference shielding property with 28.73 dB (at the frequency of 1.0175 GHz with the thickness of 3.0 mm) of total shielding effectiveness by adding 50 wt% of the composite in the paraffin matrix. And the composite of PNT/GO-EDA-Fc-EDA-GO-7:1 exhibited good conductivity with a value of 1.320 S/cm. The relationship between the conductivities of prepared samples and the EMI shielding performance was investigated.

     

碳纤维/铁硅铝复合材料的低频吸波性能

为获得吸波性能良好的吸波材料,将电阻型吸波剂碳纤维和磁损耗型吸波剂FeSiAl片状磁粉复合,以石蜡为基体,利用模压法制备出复合材料。采用激光粒度分析仪、扫描电子显微镜(SEM)、X射线衍射仪(XRD)对单一吸波剂进行了测试分析。结果发现,片状FeSiAl磁粉的粒度在数十到几百微米之间;碳纤维表面留有活性物质,截面处能看到皮芯结构;XRD衍射图谱中,FeSiAl呈现出bcc结构。对复合吸波材料的电磁参数进行测量对比,结果表明,FeSiAl片状磁粉在1~3GHz内的最佳反射率达到-40.7dB,有效吸收频带宽度约为0.5GHz;当加入长度等于4mm,含量为0.4%(质量分数)的碳纤维时,碳纤维/铁硅铝复合材料吸波性能最佳,其反射率为-49.6dB,有效吸收频带宽度为1.0GHz;FeSiAl片状磁粉平行于吸波片表面排列时,材料的反射率减小,吸波性能增强。