碳化硅／手性体混凝土电磁屏蔽性能实验研究

实验研究了碳化硅．铁精矿砂组合比例改变对混凝土电磁屏蔽性能的影响，在0．3~500MHz频段，该组合获得的屏蔽效能均不超过7dB，在500MHz1．5GHz有7～15dB的屏蔽效果，并有屏蔽吸收峰出现；通过在碳化硅．铁精矿砂组合中引入手性体，在013～500MHz频段也获得了8～15dB的屏蔽效果。     

碳化硅／石墨混凝土的电磁屏蔽性能实验研究

通过实验研究，发现以普通磨料类碳化硅为骨料的混凝土也有一定的电磁屏蔽性能；通过加入石墨组分形成碳化硅。石墨吸收相，能进一步增强复合体的吸波性能。得出结论如下：碳化硅．石墨组合比例变化时，碳化硅，石墨=1：1的比例时综合性能较好，混凝土电磁屏蔽效能在0．3～1500MHz频带内达到22dB以上。     

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。     

多壁碳纳米管/聚乙烯醇复合材料电磁屏蔽性能研究

通过熔融共混、流延成膜法制备了多壁碳纳米管/聚乙烯醇(MWCNTs/PVA)复合材料,并研究了碳纤维作为增强体的作用。扫描电子显微镜、傅里叶变换红外光谱、热重分析表明:MWCNTs在PVA基体中均匀分散且形成了良好的空间导电网络;MWCNTs的加入会使吸收峰转移并与PVA发生键合反应;MWCNTs/PVA复合材料具有优异的热稳定性,热分解温度低于105℃时只有少量水分蒸发。导电性和电磁屏蔽测试表明,MWCNTs/PVA复合材料电磁屏蔽性能随其导电性的增强而提高,MWCNTs质量分数为1.2%的复合材料样品,在干扰电磁波频率为1~18GHz频段上具有良好的屏蔽性能,当干扰电磁波频率为13.3GHz时,其屏蔽效能为36.7dB。碳纤维可以增强MWCNTs/PVA复合材料的屏蔽性能,MWCNTs质量分数为0.6%的碳纤维增强MWCNTs/PVA复合材料样品,在干扰电磁波频率为1~18GHz频段时,其电磁屏蔽效能大于40dB。     

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%。     

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。     

镀银织物双层叠放模式与电磁屏蔽效能增量研究

电磁辐射是四大环境污染之一,通过不同电磁屏蔽体的叠加组合能够有效提高屏蔽效能。研究了镀银织物以紧密叠放、夹空气层和夹角叠放3种模式构造,采用小窗法屏蔽效能测试系统实测了0～18 GHz宽频段内双层织物的电磁屏蔽效能的增量问题。结果表明：镀银织物双层紧密叠加有利于电磁屏蔽效能提升,其屏蔽效能可达70 dB,明显高于单层织物,紧密叠放更有利于双层织物的屏蔽效能;夹空气层双层织物在0～6.5 GHz频段的屏蔽效能有所提高,而在其他频段其屏蔽效能呈下降趋势,尤其不利于高频电磁波的屏蔽;夹角叠放双层织物屏蔽效能均达到60 dB以上,大夹角叠放(90°)时使双层织物的屏蔽效能降低。建立了双层织物电磁屏蔽效能的增量模型,为电磁屏蔽效能分析提供了一个新的视角,通过结构优化方式探索屏蔽体构造的最佳配置,对电磁屏蔽体的设计、生产及使用具有一定的参考价值。     

超细镍粉／微米镍粉复合电磁屏蔽涂料的研究

在水溶液中制备了大量的直径约为0.5μm的超细镍粉,将其与微米镍粉以不同的比例进行复合作为导电填料制备电磁屏蔽涂料.结果表明当超细镍粉与微米镍粉的比例适当时(质量比=1:1),得到的涂料在130MHz～1.5GHz频段内具有比纯微米镍粉涂料更好的电磁屏蔽性能(40～55dB).     

ITO防电磁辐射玻璃屏蔽性能研究

采用直流磁控溅射技术在玻璃基板上沉积ITO薄膜,通过调整基板温度、薄膜厚度得到了最低方阻1．4Ω／□,薄膜透光率超过76％。对样品在150KHz到18GHz频段内电磁屏蔽效能采用屏蔽室法进行测试,1G频率点得到的屏蔽效能最好,达到了54dB,在屏蔽困难的低频段,150KHz频率点的屏蔽效能迟到24dB。     

La0．8Sr0．2Mn1-xCoxO3微波电磁特性与损耗机制

采用溶胶一凝胶法制备La0．8Sr0．2Mn1-xCoxO3（Y=0、12，0、14），用Hp8722型网络分析仪测定样品2—18GHz介电常数、复磁导率、损耗角正切及微波吸收特性曲线，发现y=0、14，样品厚度为1．8mm，收峰值达到了17dB，10dB以上吸收带宽达到了3．5GHz。对该材料的电磁损耗机理进行了研究，发现在频率11．2GHz附近有突变发生，2～11．2GHz频段损耗主要以介电损耗为主，11、2～18GHz频段损耗是介电损耗与磁损耗共同作用的结果，其中磁损耗更大一些。     

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.     

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.

     

石墨烯负载氧化铁在电磁屏蔽中的应用研究

研究了石墨烯负载氧化铁的制备工艺条件和电磁性能,并对石墨烯负载氧化铁复合材料的电磁屏蔽性能进行了测试,结果表明,石墨烯负载氧化铁后,磁性能获得提升,复合粒子材料具有较好的电磁屏蔽性能.     

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.     

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.     

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。     

塑料表面溅射电磁屏蔽膜的研究

电磁干扰(EMI)日益严重,在产品表面镀覆电磁屏蔽膜成为抗EMI主要措施之一.本文采用磁控溅射技术在聚酯塑料(PET)上制备出附着力大于5 MPa、2 GHz～4 GHz频率范围内屏蔽效能大于60 dB的复合结构的电磁屏蔽膜,并研究了导电膜、导磁膜及其复合膜层的电磁屏蔽特性.有关数据表明:镀覆500 nm Cu+300 nm 1Cr18Ni9Ti的复合屏蔽膜可以获得屏蔽效果、成膜速率和结合力的综合好效果.溅射功率、膜层厚度对电磁屏蔽特性和结合力有一定影响.     

Electromagnetic interference shielding behavior of poly(trimethylene terephthalate)/multi-walled carbon nanotube composites

Poly(trimethylene terephthalate) [PTT]/multiwalled carbon nanotube [MWCNT] composites having varying amounts of MWCNTs were fabricated with an aim to investigate the potential of such composites as an effective light weight electromagnetic interference (EMI) shielding material in the frequency range of 12.4-18 GHz (Ku-band). PTT/MWCNT composite with shielding effectiveness (SE) of 36-42 dB was obtained at 10% (w/w) MWCNT loading. Shielding mechanism was studied by resolving the total SE into absorption (SE_A) and reflection loss (SE_R). PTT/MWCNT composite showed absorption dominated shielding; thus it can be used as microwave, radar absorbing and stealth material. The effect of MWCNT loadings on electrical conductivity (σ) and dielectric properties of PTT and the correlation among conductivity, tan δ, absorption loss and reflection loss were also studied.