在塑料表面用磁控溅射制备电磁屏蔽膜的研究

随着电磁污染的日益严重以及塑料在电子产品封装上的广泛应用,对电子产品进行电磁屏蔽设计已成为必然趋势.本文采用磁控溅射的方法在PET塑料基底上沉积多种膜系的金属屏蔽膜层,并对金属膜层的制备工艺进行了研究,最后采用波导法对金属膜层的屏蔽效能进行测试.研究表明,采用Cu/1Cr18Ni9Ti双层金属膜层结构,可以获得良好的表面性能以及结合力,结合力达到500 kPa以上;总厚度仅为764nm的Cu/1Cr18Ni9Ti在2.5 GHz时可获得60 dB以上的屏蔽效能;在总厚度相等的情况下,双面金属层比单面金属层具有更高的效果.     

PDP电磁屏蔽膜的特性测试及其研究

等离子体显示器面板的电磁屏蔽膜,既要满足对规定的电磁辐射波段进行屏蔽的要求,又需要有良好的可见光透过率和对非三基色波段的光的吸收能力,以提高图象画面的显示质量.本文通过实验的方法,在某商品屏和样品屏上分别采用进口与国产EMI屏蔽膜进行测量对比,结果表明二者的EMI屏蔽膜对电磁辐射的屏蔽效果相当,基本都能将规定的不同频段的电磁辐射降到限值以下,而对于非三基色波段的光的吸收能力,进口EMI屏蔽膜的吸收效果要好于国产EMI屏蔽膜的吸收效果.     

碳化细菌纤维素的电磁屏蔽效能

细菌纤维素在不同的温度下进行碳化处理,将得到一系列网状结构的碳纤维。利用X射线衍射仪(XRD)、拉曼光谱仪和透射电子显微镜(TEM)对制备的碳纤维晶体结构和微观形貌进行了表征;通过矢量网络分析仪在频率600MHz～14GHz范围内对其进行了电磁参数测试;应用电磁屏蔽理论计算获得碳纤维的电磁屏蔽效能。结果表明,1200℃碳化得到的碳纤维在频率为6～14GHz之间的屏蔽效能都大于30dB,在14GHz时最高可以达到41dB,该碳纤维密度低、屏蔽效果好,在电磁屏蔽领域有较好的应用前景。     

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。     

防辐射聚酯布的化学镀制备与表征

采用化学镀方法在聚酯布表面沉积1层Ni-P合金,用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、热重分析仪(TG)对镀层形貌、结构和性能进行表征。结果表明:聚酯布表面化学镀Ni-P合金由大小为0.1～1μm的微粒组成;镀层为非晶结构、热稳定性好、与聚酯布之间的结合力好;表面化学镀Ni-P合金后的聚酯布对频率20GHz的电磁波屏蔽效能可达到60dB,具有较好的电磁屏蔽效果。     

纳米透明电磁屏蔽玻璃的制备及性能研究

迄今为止,国内现有的电磁屏蔽视窗不能很好兼具高透光率和高电磁波屏蔽效能.为此,本工作采用电子束蒸发法以ITO膜作为电磁波屏蔽层,探讨了纳米透明电磁屏蔽玻璃的制备及性能.为得到高屏蔽效能并保证较高的透光度,研究了膜厚、成膜速率、透光率、方电阻、屏蔽效能之间的关系,找到了最佳工艺参数.另一方面,通过对屏蔽膜进行原位高纯氧气氛下的后续热处理,改变ITO材料微结构,获得微纳晶团簇化显微结构,进一步降低方电阻,有效地提高了屏蔽效能.结果表明,厚度在500～1000nm之间,蒸镀速率为0.23nm,并经过400℃40min原位后处理可得到方电阻为5～3Ω/□,透光率76.3%～71.6%,屏蔽效能54.8～63.2dB的高性能ITO膜.另外,通过对玻璃基片采用预先热处理增强或将镀有屏蔽膜的玻璃和另外一块普通白玻进行复合制成夹层玻璃的方式,制得符合要求的特种安全玻璃.     

碳纤维对水泥基复合材料电磁屏蔽性能的影响

本文根据电磁屏蔽原理,对掺有短切碳纤维(CF)的水泥基复合材料的电磁屏蔽性能进行了实验研究.结果表明:碳纤维水泥基复合材料在频率为9KHz～1.5GHz范围内具有良好的屏蔽效果.同时分析了碳纤维对水泥基复合材料屏蔽性能的影响机制.     

电磁屏蔽涂料制备的新进展

从导电填料的种类、复合工艺及其对涂料导电性能的影响等方面,综述了近五年来掺和型电磁屏蔽涂料制备的最新进展.金属、石墨和复合导电填料等都具有良好的导电性,尤以复合导电填料应用效果最好;原位插层复(聚)合法是制备电磁屏蔽材料的一种较新复合工艺,可获得低逾渗阀值和高导电率,具有良好的发展前景;同时,导电填料的用量、性状、分散效果以及分散助剂等对电磁屏蔽涂料的导电性能都有较大影响.     

电磁屏蔽层设计及其磁控溅射制备的研究

通过传输线模型推导出多层无限大平板的屏蔽效能的计算公式,并根据公式设计了双层屏蔽层,通过多靶直流溅射制备了多种金属屏蔽膜.研究结果表明衰减损耗是各层屏蔽效果线性相加的结果,反射损耗与各层相对位置关系无关,层数多或各屏蔽层的反射越大,则屏蔽效果越好.采用Cu/1Cr18Ni9Ti的金属屏蔽层结构,可获得良好的屏蔽效能及耐候性,单纯用表面阻抗来评估多层金属膜的电磁屏蔽效果并不合适.     

膨胀石墨基纳米镍、铁、钴化学镀制备复合吸波材料

为了获得薄、轻、宽、强等性能理想的吸波材料,采用化学镀的方法在膨胀石墨表面镀覆纳米镍、镍钴、镍铁钴,制备了复合吸波材料.SEM和EDs分析证实,膨胀石墨表面镍层、镍钴层、镍铁钴层的镀覆厚度约为70～150 nm.采用HP8722ES矢量网络分析仪测量了复合吸波材料在2～18 GHz内的复介电常数(ε=ε'-jε")和复磁导率(μ=μ'-jμ").用吸收屏理论公式计算了反射率损耗(R.L)、匹配频段(fm)及匹配厚度(dm).结果表明,当dm=0.3 mm时,镀覆镍铁钴层的复合吸波材料最低的反射损耗达-28 dB,对应的fm=13.5 GHz,R>L<-10 dB时频宽达7.5 GHz.本法制备的复合吸波材料符合"轻、薄、宽、强"的现代要求.     

Electromagnetic Shielding of Monolayer MXene Assemblies

Miniaturization of electronics demands electromagnetic interference (EMI) shielding of nanoscale dimension. The authors report a systematic exploration of EMI shielding behavior of 2D Ti₃C₂T_x MXene assembled films over a broad range of film thicknesses, monolayer by monolayer. Theoretical models are used to explain the shielding mechanism below skin depth, where multiple reflection becomes significant, along with the surface reflection and bulk absorption of electromagnetic radiation. While a monolayer assembled film offers ≈20% shielding of electromagnetic waves, a 24-layer film of ≈55 nm thickness demonstrates 99% shielding (20 dB), revealing an extraordinarily large absolute shielding effectiveness (3.89 × 10⁶ dB cm² g⁻¹). This remarkable performance of nanometer-thin solution processable MXene proposes a paradigm shift in shielding of lightweight, portable, and compact next-generation electronic devices.     

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.     

Scalable Fabrication of Nacre-Structured Graphene/Polytetrafluoroethylene Films for Outstanding EMI Shielding Under Extreme Environment

In this work, inspired by the great advantage of the unique “brick-mortar” layered structure as electromagnetic interference (EMI) shielding materials, a multifunctional flexible graphene nanosheets (GNS)/polytetrafluoroethylene (PTFE) composite film with excellent EMI shielding effects, impressive Joule heating performance, and light-to-heat conversion efficiency is fabricated based on the self-emulsifying process of PTFE. Both PTFE microspheres and nanofibers are employed together for the first time as “sand and cement” to build unique nacre-structured EMI shielding materials. Such configuration can obviously enhance the adhesion of composites and improve their mechanical property for the application under extreme environment. Moreover, the simple and effective repetitive roll pressing method can be used for the scalable production in industrialization. The GNS/PTFE composite film shows a high EMI shielding effectiveness (SE) of 50.85 dB. Furthermore, it has a high thermal conductivity of 16.54 W (m K)⁻¹, good flexibility, and recyclable properties. The excellent fire-resistant and hydrophobic properties of GNS/PTFE film also ensure its reliability and safety in practical application. In conclusion, the GNS/PTFE film demonstrates the potential for industrial manufacturing, and outstanding EMI shielding performance with high stability and durability, which has a broad application prospect for electronic devices in practical extreme outdoor environments.     

Superhigh Electromagnetic Interference Shielding of Ultrathin Aligned Pristine Graphene Nanosheets Film

Ultrathin, lightweight, high-strength, and thermally conductive electromagnetic interference (EMI) shielding materials with high shielding effectiveness (SE) are highly desired for next-generation portable and wearable electronics. Pristine graphene (PG) has a great potential to meet all the above requirements, but the poor processability of PG nanosheets hinders its applications. Here, efficient synthesis of highly aligned laminated PG films and nacre-like PG/polymer composites with a superhigh PG loading up to 90 wt% by a scanning centrifugal casting method is reported. Due to the PG-nanosheets-alignment-induced high electrical conductivity and multiple internal reflections, such films show superhigh EMI SE comparable to the reported best synthetic material, MXene films, at an ultralow thickness. An EMI SE of 93 dB is obtained for the PG film at a thickness of ≈100 µm, and 63 dB is achieved for the PG/polyimide composite film at a thickness of ≈60 µm. Furthermore, such PG-nanosheets-based films show much higher mechanical strength (up to 145 MPa) and thermal conductivity (up to 190 W m⁻¹ K⁻¹) than those of their MXene counterparts. These excellent comprehensive properties, along with ease of mass production, pave the way for practical applications of PG nanosheets in EMI shielding.     

Scalable Manufacturing of Free-Standing,Strong Ti3C2Tx MXene Films with Outstanding Conductivity

Free-standing films that display high strength and high electrical conductivity are critical for flexible electronics, such as electromagnetic interference (EMI) shielding coatings and current collectors for batteries and supercapacitors. 2D Ti₃C₂T_x flakes are ideal candidates for making conductive films due to their high strength and metallic conductivity. It is, however, challenging to transfer those outstanding properties of single MXene flakes to macroscale films as a result of the small flake size and relatively poor flake alignment that occurs during solution-based processing. Here, a scalable method is shown for the fabrication of strong and highly conducting pure MXene films containing highly aligned large MXene flakes. These films demonstrate record tensile strength up to ≈570 MPa for a 940 nm thick film and electrical conductivity of ≈15 100 S cm⁻¹ for a 214 nm thick film, which are both the highest values compared to previously reported pure Ti₃C₂T_x films. These films also exhibit outstanding EMI shielding performance (≈50 dB for a 940 nm thick film) that exceeds other synthetic materials with comparable thickness. MXene films with aligned flakes provide an effective route for producing large-area, high-strength, and high-electrical-conductivity MXene-based films for future electronic applications.     

MXene基薄膜的有序组装及其在储能和电磁干扰屏蔽中的应用

5G电子消费产品日益普及,给人们的生活带来便利的同时也存在一些问题,如电磁干扰(EMI)风险大幅度提高,5G网络耗电速度快等。因此需要开发具有高EMI屏蔽性能的膜材料和高容量的电极材料来解决这些问题。作为一种新型二维材料,过渡金属碳化物、氮化物或氮碳化物(称为MXene)具有出色的导电性、低密度、亲水性表面、二维层状形态和可调节的表面化学性质等诸多优势。此外,由于MXene具有容易成膜的特点,在EMI屏蔽和储能设备等领域具有巨大的应用潜力。目前已经报道了很多基于MXene复合薄膜的工作,本文首先介绍了MXene纳米片的合成方法,然后讨论了MXene基复合薄膜的制备方法,目的是总结制备MXene复合薄膜的各种方法及其优缺点。其次,分别介绍了MXene在锂离子电池和超级电容器及EMI屏蔽膜中的应用,分析了目前的发展趋势,并且对目前主流的复合材料进行了对比,归纳了MXene复合薄膜在结构和性能上的特点和优势。最后,提出了目前MXene复合薄膜的发展所存在的问题,并对未来发展进行了展望。      

可用于包装的纤维素基电磁屏蔽材料研究进展

目的 为推动可用于包装的纤维素基电磁干扰(Electromagnetic Interference,EMI)屏蔽材料更深入的研究,综述一些具有包装材料潜质和EMI屏蔽功能的纤维素基薄膜、织物和气凝胶的最新研究进展。方法 主要介绍纤维素基薄膜、织物和气凝胶等3类EMI屏蔽材料的制备方法、EMI屏蔽性能、多功能性和在包装上应用的潜力。结果 当下纤维素基EMI屏蔽材料表现出令人满意的EMI屏蔽效能(EMI Shielding Effectiveness, EMI SE)和力学性能,有望作为包装材料。同时一些材料还显示出抗菌、隔热、抗冲击等特性,使得这些材料能在复杂的场景下应用。结论 通过合理的设计,纤维素基EMI屏蔽材料可拥有优异的EMI屏蔽性能、出色的力学性能和良好的耐用性。归因于上述优势和绿色可降解的特性,这类材料有望在未来取代传统的EMI屏蔽包装材料,然而这些材料通常需要精细的制备工艺,材料的量产和实际应用依然是亟待解决的问题。     

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 interference shielding of carbon nanotube-fluoropolymer elastomer composites with layered structure

Abstract

This paper presents carbon nanotubes-containing polymer composites with layered gradient structure having electromagnetic interference (EMI) shielding properties. Polymer composite films were obtained on metal surface by aerosol deposition of a dispersion of carbon nanotubes in the solution of a copolymer of vinylidene fluoride with hexafluoropropylene (SCF-26) in acetone. Single-wall TUBALL (OCSiAl) carbon nanotubes were used. Three-layer coatings were formed with a concentration of nanotubes decreasing in each subsequent deposited layer. The reflection coefficient of electromagnetic radiation in the range of 20–35?GHz was measured. Gradient samples had significantly better characteristics compared to samples with uniform concentration of carbon nanotubes: the reflection coefficient reached ?6dB at 35?GHz. The outer layer of gradient structure with 0.1?wt % CNT provides a better matching of the wave resistance with free space and a smooth entrance of an electromagnetic wave into the sample. The subsequent layers with an increasing concentration of single-walled carbon nanotubes (0.3 and 0.5%) absorb electromagnetic radiation. Polymer elastomer composite EMI shielding coatings with concentration gradient can be applied by aerosol deposition to the surfaces of any composition and shape. Our results could serve as a design tool in carbon nanotubes - based EMI shielding flexible polymer coatings.     

碳系填充型电磁屏蔽材料的研究进展

填充型电磁屏蔽材料在电磁屏蔽领域有着广阔的应用前景,而碳填料具有来源广、质量轻、成本低、导电性良好等优点,以其作为导电填料的填充型电磁屏蔽材料因具有较好的综合性能而受到越来越多的关注.对近年来国内外碳系填充型电磁屏蔽材料的发展情况进行了综合评述,着重介绍了碳系填充型电磁屏蔽材料的导电机理、填充方法、分类、掺杂及影响其屏蔽性能的主要因素.