铁氧体、石墨及碳纤维水泥基复合材料的电磁屏蔽性能研究

通过设计正交实验的方式研究了复掺铁氧体、石墨和碳纤维水泥基复合材料材料的电磁屏蔽效能.结果表明:在30～1500 MHz频率范围内,影响电磁屏蔽效能的主次因素分别为碳纤维、铁氧体和石墨.铁氧体、石墨和碳纤维最佳掺量为占水泥质量比34.4％、25％和1.9％,其平均电磁屏蔽效能达到33.51 dB,且电磁屏蔽效能随着试样厚度的增加而线性增大.在200～1500 MHz范围内,掺入铁氧体和碳纤维的平均屏蔽效能在37 dB左右,而掺入石墨和碳纤维的平均屏蔽效能在31 dB左右,复掺铁氧体和碳纤维试样的电磁屏蔽效能要比复掺石墨和碳纤维的屏蔽效果好.     

铁氧体、石墨及钢纤维水泥复合砂浆电磁屏蔽性能的实验研究

利用同轴平面夹具-频谱分析仪法研究了掺铁氧体、石墨及钢纤维的水泥复合砂浆在100 kHz～1500 MHz频率范围内的电磁屏蔽效能.结果表明:同时掺加铁氧体、石墨及钢纤维的水泥基复合材料低频段的电磁屏蔽性能有明显提高,当钢纤维掺量为0.5％时,在200 ～ 1000 MHz频段内最低电磁屏蔽效能为13 dB,1000～ 1500 MHz屏蔽效能均大于20 dB,最大的屏蔽效能达到35 dB左右;复掺铁氧体-钢纤维或石墨-钢纤维均比单掺铁氧体、石墨或钢纤维试样的屏蔽效能有所改善,其中复掺锰锌铁氧体和钢纤维水泥基复合材料的屏蔽效能在钢纤维掺量为1％时达到45 dB左右.     

焦炭-水泥基复合材料电磁屏蔽性能的研究

研究了焦炭和碳纤维的掺量,焦炭细度,减水剂,样品厚度对材料电磁屏蔽性能的影响。分别利用两电极法和同轴电缆法测试了材料的电阻和电磁屏蔽效能。研究结果表明,增加焦炭的掺量对水泥基材料导电性能的影响不显著,但增加焦炭细度能明显提高水泥基材料的导电性能;而样品厚度对水泥基材料的电磁屏蔽性能影响不大;焦炭-水泥基材料掺入碳纤维后能使材料的导电性能和电磁屏蔽性能明显提高。     

炭纤维增强水泥基复合材料的导电性研究

通过向水泥基材料中添加炭纤维制备炭纤维增强水泥基复合材料(CFRC),研究了炭纤维掺量、硅粉掺量、养护龄期等因素对其导电性能的影响。结果表明,CFRC复合材料的电阻率随着炭纤维掺量的增加而减小;掺入10%的硅粉能够显著降低CFRC复合材料的电阻率;CFRC复合材料中的炭纤维掺量低于0.6%时,电阻率随着养护龄期的延长而迅速增大,炭纤维掺量高于0.6%时电阻率增加不明显。     

铁粉/聚丙烯复合材料的电磁屏蔽性能

研究铁粉含量、粒度及偶联剂对铁粉/PP复合材料导电性和电磁屏蔽性能的影响.结果表明:铁粉/PP复合材料的体积电阻率随铁粉质量含量的增加而降低,在20%时出现渗滤值,当铁粉质量含量超过30%之后,继续增大铁粉含量复合材料的体积电阻率和屏蔽效能变化不明显.铁粉含量一定时,随着铁粉目数增大,复合材料的屏蔽效能有所提高;在100MHz～1 GHz低频区域,复合材料最大电磁屏蔽效能达到了40dB.钛酸酯偶联剂为铁粉质量的4%时,能很好地改善铁粉/PP材料的导电性和屏蔽性能.     

石墨–碳纤维水泥基复合材料的电磁屏蔽效能

采用同轴法兰–网络分析仪法研究了石墨–碳纤维水泥基材料在100kHz～1.5GHz频率范围内的电磁屏蔽性能。结果表明:水泥中石墨掺量接近渗滤阈值时,材料的屏蔽效能可获得明显改善。胶体石墨的屏蔽效能要明显好于鳞片石墨的,石墨的细度以25μm为宜,超过25μm对进一步改善屏蔽效果作用不大。碳纤维能显著提高材料的屏蔽效能,复掺石墨及碳纤维可使水泥基材料的屏效值进一步提高,其屏效值在测试频段内最高可达24dB。     

CNT基木塑复合材料的力学性能、电磁屏蔽性能

采用碳纤维(CF)和碳纳米管(CNT)通过模压工艺制备出具有电磁屏蔽功能的丙烯酸酯木塑复合材料。借助材料试验机、动态热机械分析仪、微欧计和电磁屏蔽测量仪等详细研究CNT质量分数对丙烯酸酯木塑复合材料弯曲性能、动态力学性能、电阻率和电磁屏蔽效能的影响。结果表明,添加质量分数为2%的CNT,使得复合材料的弯曲强度和弯曲弹性模量分别增加了10%和16%。复合材料的储能模量也在CNT质量分数为2%时达到最大值,之后储能模量随着CNT的增加而逐渐下降,损耗因子在CNT质量分数多于2%时也逐渐增加。复合材料的吸水率和导电性能随着CNT含量的增加而增加。同时复合材料的电磁屏蔽效能也随着CNT含量增加而递增。在30~1 500 MHz范围内,电磁屏蔽效能从27 d B增加到40 d B。结果证明,当CNT质量分数在2%时,丙烯酸酯木塑复合材料具有较佳的力学性能和较好的电磁屏蔽效能(30 d B),能满足商业要求。     

基于煤沥青基MCMB的C/Cu复合材料的制备及性能研究

以煤沥青基MCMB为前驱体,采用模压烧结的方法制备了C/Cu复合材料,研究了材料组分对C/Cu复合材料性能的影响.结果表明,C/Cu复合材料的电阻率随着Cu纤维含量的增加而减小,摩擦系数随着石墨添加量的增加而减小,当石墨添加量大于15％时摩擦系数趋于稳定.     

镀镍石墨/杜仲橡胶复合材料的制备及性能

用硅烷偶联剂对镀镍石墨(NCG)进行湿法处理,采用机械共混法制备了镀镍石墨/杜仲橡胶(EUG)复合材料,考察了NCG用量对NCG/EUG复合材料导电性能、电磁屏蔽效能和力学性能的影响。结果表明,随着NCG质量分数的增加,NCG/EUG复合材料的电导率和电磁屏蔽效能逐渐增大,拉伸强度先增大后减小,扯断伸长率逐渐降低,邵尔A硬度逐渐增大。当NCG质量分数为50%时,NCG/EUG复合材料的电导率可达到2.59 S/cm,电磁屏蔽效能最高可达到47.50 dB。     

炭纤维增强水泥基复合材料(CFRC)的电磁性能

炭纤维增强水泥基复合材料(Carbon Fiber Reinforced Cement Composites,CFRC)是新发展起来的一种电磁屏蔽材料,它是防止电磁污染的防护性功能材料之一。本文阐述了炭纤维增强水泥基复合材料的制备成型工艺;分析了炭纤维掺入量和长度、水灰比和密实成型制备工艺、炭纤维分散性、养护龄期、外加剂、炭纤维表面化学气相沉积(CVD)处理等因素对CFRC力学性能、导电性能、压敏性能及电磁性能的影响。合适的炭纤维掺入量和长度、炭纤维的均匀分散、合理的水灰比和炭纤维表面处理是影响CFRC导电性能和电磁性能的主要因素。CFRC对电磁波的屏蔽效果除利用屏蔽效能从反射电磁波角度衡量外,亦可从吸收电磁波角度利用反射率进行评价。     

炭黑对ASA/天然石墨复合材料的电磁屏蔽性能影响

通过熔融共混方法制备导电高分子复合材料丙烯腈-苯乙烯-丙烯酸酯共聚物(ASA)/天然石墨(NGR)/炭黑(CB),采用电磁屏蔽测量仪、四探针电阻率测量仪和动态热机械分析仪对复合材料的电性能和力学性能进行详细研究.结果 表明,ASA/NGR复合材料的体积电阻率随着炭黑含量增加而增加;同时在30 MHz～1500 MHz范...     

Electromagnetic interference shielding of graphite/acrylonitrile butadiene styrene composites

Dispersion of graphite within the acrylonitrile butadiene styrene matrix demonstrates enhanced electromagnetic interference shielding of composites through the use of tumble mixing technique. A shielding effectiveness of 60 dB with 15 wt % of graphite has been achieved. D shore hardness data revealed a little decrease in hardness of composites with rise in graphite content. DC conductivity measurements revealed a fairly low percolation threshold at 3 wt % of graphite. The conductivity exhibited by 15 wt % composite is 1.66 × 10⁻¹ S/cm. These composites are fit for use as an effective and convenient EMI shielding material because of easy processing, better hardness, light weight, and, reasonable shielding efficiency. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Colloidal graphite as an admixture in cement and as a coating on cement for electromagnetic interference shielding

A water-based colloid of submicron graphite particles is an effective admixture for enhancing the EMI shielding effectiveness of cement paste, though it is ineffective for lowering the electrical resistivity. As an admixture, it is more effective for shielding than 15-μm-diameter discontinuous carbon fibers, though it is less effective than 0.1-μm-diameter discontinuous carbon filaments. A shielding effectiveness of 22 dB at 1 GHz is reached by cement paste at a solid graphite content of 0.92 vol.%, compared to a value of 11 dB for a coating made from the graphite colloid and a value of 14 dB for graphite-colloid-coated cement paste (without admixture).     

Advanced Ti3C2Tx MXene-modified cement nanocomposites toward high efficiency electromagnetic functional materials for green buildings

The proliferation of electronic devices and wireless communication is leading to serious electromagnetic (EM) interference. In this work, Ti₃C₂/cement composites were developed as high efficiency EM functional materials by introducing exfoliated Ti₃C₂T_x MXene with cement for green buildings with EM shielding function. In the composites, few-layered Ti₃C₂ MXene were dispersed homogeneously throughout the cement matrix. The EM properties of the composites were studied as a function of the MXene content. With increasing MXene content, real and imaginary part of permittivity was significantly improved owing to the polarization and electrical conduction caused by the MXene phase. Composites with 15 wt.% MXene showed good EM absorbing properties with a maximum effective absorbing bandwidth of 2.67 GHz. Strong EM shielding can be achieved when MXene content increased to 25 wt.%. The EM shielding effectiveness of such composites was higher than 22.0 dB, and the dominating shielding mechanism was EM absorption. This work finds new materials for the development of advanced green buildings with EM shielding function.     

Electromagnetic interference properties of carbon nanofiber–reinforced acrylonitrile–styrene–acrylate/natural graphite composites

Acrylonitrile–styrene–acrylate/natural graphite/carbon nanofiber composites (ASA/NG/CNF) were prepared using a melting blending method. The effects of CNFs on the morphology, rheological properties, dynamical mechanical properties, electrical resistivity, and electromagnetic interference shielding effectiveness (EMI SE) were studied using a scanning electron microscope, a rotational rheometer, and dynamic mechanical analysis (DMA). The addition of CNFs changed the oriented and laminated structure of the ASA/NG composite. The flexural strength of the ASA composite reached a maximum at 6% CNF, and then it began to decrease. The addition of CNFs did not alter the glass‐transition temperature of ASA, but it largely increased the storage modulus of the composite in DMA tests. In the rheological measurements, the complex viscosity and storage modulus of the composite increased as CNF content increased, and the resistance to creep of the composites was significantly increased by the addition of CNFs. The electrical resistivity of the ASA composites decreased from 49.8 Ω cm to 2.3 Ω cm as the CNF content was increased from 0 to 12%. At the same time, the EMI properties of the composites rose from 15 dB to 30 dB in the frequency range 30–1500 MHz. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45455.     

Partial replacement of carbon fiber by carbon black in multifunctional cement-matrix composites

Cement reinforced with discontinuous carbon fiber is known for its piezoresistivity-based strain sensing ability, its electrical conductivity and the consequent multifunctionality. The high cost of carbon fiber is disadvantageous. Both carbon fiber and carbon black (used with silica fume in the amount of 15% by mass of cement) increase the DC conductivity and the EMI shielding effectiveness of cement, but carbon fiber is more effective than carbon black. Partial (50%) replacement of carbon fiber by carbon black lowers the cost, in addition to increasing the workability, while the electrical conductivity and the electromagnetic interference shielding effectiveness are maintained. However, the partial replacement reduces the strain sensing effectiveness. Total replacement of carbon fiber by carbon black diminishes both the conductivity and the shielding effectiveness, further reduces the strain sensing effectiveness, decreases the compressive modulus and increases the compressive strain at failure, while the compressive strength is maintained. The increased workability due to the partial replacement enables a higher total conductive admixture content to be attained. The maximum total conductive admixture content is 3.5% by mass of cement. In contrast to fiber replacement, the addition of carbon fiber to cement with carbon black decreases the compressive strength, strain at failure and density.     

导电炭黑/杜仲胶复合材料电磁屏蔽性能的研究

采用机械共混法制备了导电炭黑/杜仲胶复合材料,研究炭黑用量对复合材料电性能和电磁屏蔽性能的影响。结果表明：随着炭黑用量的增加,复合材料的导电率增大,当炭黑用量为25份时,导电率达到3.3S/cm,导电率遵循导电逾渗规律;复合材料的Payne效应越来越大,有利于形成稳定的导电网络;复合材料的拉伸强度逐渐增大后略微降低,断裂伸长率先增加后逐渐下降。复合材料的屏蔽效能增大,当炭黑用量为20份时,屏蔽效能最高能达到33.2dB,可以满足一般工业或者商业用电子设备的要求。     

Electromagnetic wave shielding and microwave absorbing properties of hybrid epoxy resin/foliated graphite nanocomposites

The aim of this study is to prepare and characterize foliated graphite nanosheets (FGNs) reinforced composites based on epoxy resin for the electromagnetic wave shielding and microwave absorbing applications. The microstructure of as prepared FGNs and epoxy reinforced with different content of foliated graphite was examined by means of scanning electron microscopy and transmission electron microscopy. The effect of FGNs on thermal stability of composites was examined by thermal gravimetric. It is found that the inclusion of FGNs into the epoxy resin matrix enhances the microstructure core of epoxy resin composites. Static electric properties such as electrical conductivity, carrier mobility, number of charge carriers, and thermoelectric power of composites were studied in details. Dielectric properties of epoxy/FGN composites were characterized as a function of composition and frequency in the range of 1–18 GHz. The electromagnetic wave shielding as a function of frequency of composites was examined and compared with theoretical values. The highest shielding effectiveness was obtained for high foliated graphite loading sample FG40 at frequency of 18 GHz it equals to 62 dB. Finally, the electromagnetic wave properties such as absorption loss and reflection loss as a function of frequency were investigated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013