电磁屏蔽材料用银包玻璃微珠核-壳粒子的制备及其性能

采用自组装化学镀银技术制备了银包玻璃微珠核-壳粒子,并且运用X射线衍射仪、扫描电镜和电子能谱仪等对该核-壳粒子的物相和形貌等进行了表征.分析了该核-壳粒子的介电性能与结构的关系,并以此为屏蔽填料,研究了电磁屏蔽涂料的相关性能.结果表明,银粒子在玻璃微珠的表面包覆均匀且致密,该粒子的介电常数较包覆前大幅度提高.该电磁屏蔽涂料的导电性能随着填料的体积分数(下同)的增加而增加,达到25%时,其表面电阻率为0.050 7Ω/cm2.同时,在电磁波的频率范围为30～1 500MHz时,屏蔽效能达40～65 dB,并且该材料具有较好力学性能和耐环境性能.     

具有电磁屏蔽功能聚苯硫醚复合材料的制备与性能研究

本文采用粉末浸渍工艺制得连续玄武岩纤维和不锈钢纤维增强聚苯硫醚预浸料,预浸料的编织物经层压成型制备了聚苯硫醚复合材料,对复合材料的力学和电磁屏蔽性能进行了研究。结果表明:不锈钢纤维/聚苯硫醚预浸料与玄武岩纤维/聚苯硫醚预浸料层压所形成的复合材料其力学性能和电磁屏蔽性能均优于铝箔与玄武岩纤维/聚苯硫醚预浸料层压所形成的复合材料;当电磁波频率小于200 MHz时,复合材料的电磁屏蔽效能较高,不锈钢纤维/聚苯硫醚预浸料中不锈钢纤维质量分数(含量)为30%时,复合材料的电磁屏蔽效果达到较高值,当电磁波频率在200～1 500 MHz范围内,材料的屏蔽效能在20～30dB间波动。     

抗静电涤纶屏蔽性能的研究

在自制抗静电涤纶的基础上,均匀掺杂一些新的导电粒子,如碳纳米管(CNTs)、银粉和铁粉,研究其抗静电及屏蔽性能的变化。结果表明:自制抗静电涤纶的比电阻为5.6×10~9Ω·cm,在电磁波频率为30～100 MHz时,屏蔽效率小于10 dB。掺入铁粉和银粉后,其比电阻增大,屏蔽效果提高。当抗静电母粒和含CNTs质量分数为6%的PA6母粒质量比为7:3时,所得纤维的比电阻为2.1×10~9Ω·cm,在电磁波频率为30～100 MHz时屏蔽效率为20 dB以上,进一步涂敷自制导电涂料后,比电阻为1.9×10~9Ω·cm,屏蔽效率为25～30 dB,屏蔽性能良好。     

电磁屏蔽织物的制备及性能表征

采用真空磁控溅射在涤纶织物上镀上金属镍,然后电镀上金属铜和镍。测试了样品的表面电阻、耐磨性、附着力及其在1kHz~40GHz频率范围内的电磁屏蔽性能。结果表明,样品具有良好的导电性、耐磨性和附着力,在30MHz~1.5GHz内的屏蔽效能大于70dB,在1.5GHz~40GHz内的屏蔽效能大于60dB,可以满足各种条件下的电磁屏蔽要求。     

Electroless silver plating on the PET fabrics modified with 3‐mercaptopropyltriethoxysilane

The feasibility of adherent silver layers onto PET fabrics by electroless plating was explored and its optimal technology for modification and electroless plating was investigated. Morphology, structure, and thermal stability of silver plating PET fabrics were characterized by scanning electric microscope (SEM), X‐ray diffraction (XRD) and thermogravitric (TG) analysis. As the silver weight on the modified fabric is 25 g/m², the electromagnetic shielding effectiveness (SE) of silver plating PET fabric is more than 30dB at the frequency ranging from 1MHz to 5000 MHz. The results show that the silver plating PET fabric has good electrical conductivity and electromagnetic shielding property. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

热处理温度对铁镍合金膜层微观结构和镀膜玻璃性能的影响

为了研究不同热处理温度下铁镍合金薄膜的形貌结构以及镀膜玻璃的性能,本文采用真空电子束加热蒸发镀膜技术在玻璃基片上镀铁镍合金薄膜,通过多晶X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)分析结构,测试镀膜玻璃的光学性能、电磁性能以及电磁屏蔽性能。结果表明:随着热处理温度的升高,薄膜的结晶性能变好,逐渐析出体心立方晶相,在(110)方向具有择优取向,当热处理温度过高时薄膜中出现孔隙;热处理温度对镀膜玻璃雾度的影响小于1%,但镀膜玻璃的可见光透过率、表面方块电阻和相对磁导率会随热处理温度变化呈现一定规律变化;铁镍合金镀膜玻璃在30 MHz以下的低频电磁波频段内的屏蔽效能大于30 dB,在14 kHz时最高达到55 dB,是一种低频电磁屏蔽的优选材料。     

Optically transparent polymer composites: A study on the influence of filler/dopant on electromagnetic interference shielding mechanism

Composite materials made of polymers and carbon-based ferromagnetic filler are attractive for electromagnetic interference shielding through a combination of reflection and microwave absorption. It is possible to enhance their shielding properties by controlling electrical conductivity, dielectric, and magnetic properties. In this work, the aforementioned properties are tailored to achieve optically transparent films with microwave absorbing properties. Nanocarbon materials, namely carbon nanotubes, graphene nanoribbons (GNR) and their ferromagnetic nanocomposites with Fe₃O₄ and cobalt in PVA-PEDOT:PSS matrix were made and tested in X-band. The highest shielding effectiveness for PVA films with nanocarbon filler was observed for 0.5 wt% GNR − Fe₃O₄ at 16.36 dB (9.7 GHz) with 79.8% transmittance.     

Simple approach to fabricate MXene/cellulose paper for electromagnetic interference shielding applications

A simple approach was developed to fabricate high-performance MXene/cellulose (MC)-based electromagnetic interference (EMI) shielding papers. The oriented MXene sheets located on one side of cellulose filter paper construct a continuous conductive layer, endowing the MC paper with high electrical conductivity (240.1 S/m) and excellent EMI shielding effectiveness (29.3 dB for 0.192-mm thickness) at an MXene content of 0.72 vol%. Moreover, the EMI shielding effectiveness of four stacked MC papers reached 40.5 dB. This result means that 99.9911% of the microwave radiation is attenuated, and 0.0089% is transmitted, through the four-piece MXene/cellulose filter papers. Therefore, MC paper has promising properties for excellent EMI shielding materials in current electronic devices.     

木材单板表面化学镀镍

以杨木单板为原料,利用化学镀法在其表面镀覆N i-P合金镀层,以此来制备具有电磁屏蔽功能的木材-金属复合材料。用扫描电镜(SEM)、能谱分析仪(EDS)和X射线衍射仪(XRD)分析了镀层形貌、成分和镀层结构,研究了经表面化学镀N i-P合金后杨木单板的电磁屏蔽性能和表面导电性能。SEM分析表明,杨木单板经表面化学镀N i-P合金后,表面完全被镀层覆盖,金属感增强。EDS分析表明,镀层为N i-P合金镀层,其中磷含量较低,主要成分为镍。XRD分析结果表明,镀层为晶态结构。镀后杨木单板的表面电阻率很低,而电磁屏蔽效能较高,在9 kHz~1.5 GHz,可达到60 dB左右。     

New porous carbon materials,Woodceramics: Development and fundamental properties

Woodceramics are new porous carbon materials obtained by carbonizing wood or woody material impregnated with thermosetting resin such as phenol resin in a vacuum furnace. During the carbonizing process, thermosetting resin changes into glassy carbon, which has superior corrosion resistance and mechanical strength, reinforces the material and suppresses the fissures and warps (caused by the porous structure specific to wood) that develop during thermoforming. The dimension, weight decrease rate, and electrical characteristics depend on the thermoforming temperature. The manufacturing method of Woodceramics is introduced in this paper and various industrial uses, such as electromagnetic shields, are discussed.     

CuxS/PAN 3D Nanofiber Mats as Ultra‐Lightweight and Flexible Electromagnetic Interference Shielding Materials

Shielding materials are becoming increasingly important, but present materials suffer from either insufficient mechanical stability or limited shielding properties. In this study, 3D flexible copper sulfide (Cu_xS)/polyacrylonitrile (PAN) nanofiber mats are developed via air spinning followed by chemical reaction with copper salt. The Cu_xS/PAN nanofiber mats exhibit an ultra‐lightweight density of 0.044 g cm^?3 and a thickness of 0.423 mm. Stable electromagnetic interference (EMI) shielding effectiveness (SE) (29–31 dB) of the Cu_xS/PAN composite is achieved in the frequency range of 500–3000 MHz. EMI SE per unit surface density of 16 655.92 dB cm² g^?1 is several orders of magnitude higher than most copper sulfide containing EMI shielding materials reported in literature. In addition, the introduction of the Cu_xS improves the thermal stability and launderability of the PAN mats giving the mats thermal, mechanical, and aqueous stability. Finally, the shielding mechanism of the Cu_xS/PAN nanofiber mats for electromagnetic waves is proposed     

Hybrid polyaniline/nanomagnetic particles composites: High performance materials for EMI shielding

In this work, two types of hybrid composite materials were elaborated. The first based on polyaniline (PANI) doped Camphor Sulfonic acid (CSA), Carbon‐Coated Cobalt (CCo), and FeNi nanoparticles dispersed in polyurethane. A value of 10⁴ S/m of conductivity and a 90 dB of shielding effectiveness in multilayer structure were obtained over the 8–18 GHz frequency band. The second type, based on PANI doped para‐toluene sulfonic acid (PTSA), dispersed in epoxy resin with FeNi nanoparticles. A thick material with moderate conductivity and high attenuation of electromagnetic waves was obtained. It was found that a PANI‐PTSA/FeNi/epoxy resin composite with thicknesses of 9.7 and 6.5 mm had, respectively, reflection loss values of ?22 dB at 9.52 GHz, and ?20.7 dB at 14.7 GHz. The electromagnetic properties of the elaborated structure hybrid materials can be optimized to increase the electromagnetic reflection–absorption properties. Thus, the obtained structure can be used in shielding and radar absorbing materials applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

导电银胶在电磁屏蔽材料上的研究与应用

以片状银粉作为导电介质,以环氧树脂、固化剂、促进剂混合为成膜剂制备出可用于电磁屏蔽,具有良好力学性能的导电银胶。讨论了银粉在银胶中质量分数为75％、81％时,固化后银胶在100kHz～18GHz波段的电磁屏蔽性能,银含量越高对15M～18GHz高频率波段电磁屏蔽效能越好,可达到17～51dB。分析了银胶导电性与电磁屏蔽功效之间的关系;通过扫描电镜的观察,从微观上进一步验证其电磁屏蔽作用;当银含量为81％时其拉伸强度为1．20MPa。     

High electromagnetic interference shielding effectiveness in MgO composites reinforced by aligned graphene platelets

Graphene has been considered as an excellent filler to reinforce ceramics with enhanced properties. However, the uniform dispersion and controlled orientation of graphene sheets in a ceramic matrix have become major challenges toward higher performance. In this paper, we prepared MgO matrix composites with parallel graphene layers through the intercalation of the precursor into expandable graphite. We obtained a high electromagnetic interference (EMI) shielding effectiveness of ~30 dB, due to the multiple reflections and absorptance of electromagnetic waves between the parallel graphene layers. The hardness and strength of the MgO composite were also increased by introducing parallel graphene layers. All these properties suggest that the graphene/MgO composite represents a promising electromagnetic shielding material.     

Preparation of lightweight and high-strength polypropylene-based ternary conductive polymer foams by in situ microfiber reinforcement

Conductive polymer composites (CPCs) have demonstrated significant potential in the aerospace, electronics, and communications industries. In this study, polypropylene (PP)/multiwalled carbon nanotubes (MWCNTs) binary composites and in situ fiber reinforced multicomposites made from PP/MWCNTs were fabricated by microcellular injection molding. In addition to crystallization behavior, foam morphology, mechanical properties, dielectric properties, and electromagnetic shielding properties of the composites were analyzed. According to the results, microporous structures can facilitate the distribution of conductive fillers, thereby enhancing the electromagnetic shielding performance and mechanical properties of the composite. In situ microfiber networks display a heterogeneous nucleation effect, resulting in an increase in foam density, which improves composite performance. In situ fiber-reinforced microporous multicomposites are capable of exhibiting higher elongation at break and electromagnetic shielding properties than binary systems, and the multicomposites can achieve greater electromagnetic shielding effectiveness (SE) with fewer conductive fillers. Ultimately, fiber-reinforced microporous composites with an elongation at break of 194.40%, an electromagnetic shielding effect of >20 dB, and an absorption mechanism are produced. A feasible method is presented in this study for preparing CPCs that produce light weight, excellent mechanical properties, and high electromagnetic SE at low filler levels.     

Flexible electromagnetic interference shields made of silver flakes,carbon nanotubes and nitrile butadiene rubber

The recent advances in portable and flexible electronic devices demand integration of flexibility into future electromagnetic interference shielding materials. Here we synthesized flexible adhesive shields made of microscale silver flakes (Ag flakes), multi-walled carbon nanotubes decorated with nanoscale silver particles (nAg-MWNTs), and nitrile butadiene rubber (NBR). The addition of nAg-MWNTs into the Ag flake–NBR mixture significantly enhanced both conductivity and shielding effectiveness. Long nanotubes electrically linked microscale Ag flakes embedded in the NBR matrix, and nanoscale silver particles further improved the contact interface. There was a logarithmic relationship between the conductivity and shielding effectiveness. The dominant mechanism of electromagnetic interference shielding was reflection. The achieved maximum shielding effectiveness was about ∼75 dB at 1 GHz. The flexible adhesive shield printed on a polyimide film was wrapped around a cylindrical rod with a radius of 4 mm. The shielding effectiveness decreased about 20% after 100 wrapping cycles. The conductivity and shielding effectiveness could be adjusted by changing the Ag flake concentration. There was an excellent agreement between the theoretically predicted shielding effectiveness and the experimental data.     

Probing the engineered sandwich network of vertically aligned carbon nanotube–reduced graphene oxide composites for high performance electromagnetic interference shielding applications

Herein, we developed a strategy for fabrication of iron oxide infiltrated vertically aligned multiwalled carbon nanotubes (MWCNT forest) sandwiched with reduced graphene oxide (rGO) sheets network for high performance electromagnetic interference (EMI) shielding application which offers a new avenue in this area. Such engineered sandwiched network exhibits enhanced shielding effectiveness compared to conventional EMI shielding materials. This network of exotic carbons demonstrates the shielding effectiveness value more than 37 dB (>99.98% attenuation) in Ku-band (12.4–18 GHz), which is greater than the recommended limit (∼30 dB) for techno-commercial applications.     

Electrical and Electromagnetic Interference (EMI) shielding properties of hexagonal boron nitride nanoparticles reinforced polyvinylidene fluoride nanocomposite films

The hexagonal boron nitride nanoparticles (h-BNNPs) reinforced flexible polyvinylidene fluoride (PVDF) nanocomposite films were prepared via a simple and versatile solution casting method. The morphological, thermal and electrical properties of h-BNNPs/PVDF nanocomposite films were elucidated. The electromagnetic interference (EMI) shielding properties of prepared nanocomposite films were investigated in the X-band frequency regime (8–12 GHz). The EMI shielding effectiveness (SE) was increased from 1 dB for the PVDF film to 11.21 dB for the h-BNNPs/PVDF nanocomposite film containing 25 wt% h-BNNPs loading. The results suggest that h-BNNPs/PVDF nanocomposite films can be used as lightweight and low-cost EMI shielding materials.     

Enhanced electromagnetic shielding property of cf/mullite composites fabricated by spark plasma sintering

Aiming to prepare high-performance electromagnetic interference (EMI) shielding materials, chopped carbon fibers were incorporated into mullite ceramic matrix via rapid prototyping process of spark plasma sintering (SPS). Results indicate that C_f/mullite composites with only 1 wt% of carbon fibers exhibit highest shielding effectiveness (SE_T) over 40 dB at a small thickness of 2.0 mm, showing great advantages both in terms of performance and thickness compared with many mature carbon/ceramic composites. The high EMI shielding properties mainly depend on two mechanisms of absorption and reflection in this present work. The enhanced absorption and reflection of electromagnetic wave are ascribed to the promotional electrical conductivity arising from the formation of conductive network by introduction of carbon fibers. Regarding enhanced electrical conductivity, notable intensified interfacial polarization on a large number of interfaces between mullite matrix and carbon fibers is also the key factor to the improved absorption, which makes absorption play a dominant role in the significant improvement of EMI SE_T. The C_f/mullite composites with excellent EMI shielding properties and thin thickness show great potential application as EMI materials.     

Electromagnetic shielding performance of SiC/graphitic carbon-SiCN porous ceramic nanocomposites derived from catalyst assisted single-source-precursors

In this work, SiC nanowires and graphitic carbon (GC) including 2D reduced graphene oxide and graphene-liked ribbons modified polymer derived SiCN (SiC/GC-SiCN) porous ceramic monoliths were prepared via catalyst assisted single-source-precursor derived ceramic route. The inclusion of absorbents (e.g. graphitic carbon and SiC nanowires) significantly improved the electrical conductivity of the materials from 1.77 × 10^?8 S/cm (pristine SiCN) to 0.56 S/cm. In turn, the electromagnetic interference shielding effectiveness (EMI SE) of the ceramic increased significantly from 4.0 dB to 19.2 dB. At the highest absorbent content, the SiC/GC-SiCN ceramics exhibit a high absorption power of 0.3 nW and an SE of 48.5 dB at thickness of 2 mm, which means more than 99.998 % of the EM wave is blocked. This work finds new avenue for the design of advanced electromagnetic shielding materials possessing strong absorption capability.