Flexible Nanocomposite Conductors for Electromagnetic Interference Shielding

With the extensive use of electronic communication technology in integrated circuit systems and wearable devices, electromagnetic interference(EMI) has increased dramatically. The shortcomings of conventional rigid EMI shielding materials include high brittleness, poor comfort, and unsuitability for conforming and deformable applications. Hitherto, flexible(particularly elastic) nanocomposites have attracted enormous interest due to their excellent deformability. However, the current flexible shielding nanocomposites present low mechanical stability and resilience, relatively poor EMI shielding performance, and limited multifunctionality. Herein, the advances in low-dimensional EMI shielding nanomaterials-based elastomers are outlined and a selection of the most remarkable examples is discussed. And the corresponding modification strategies and deformability performance are summarized. Finally, expectations for this quickly increasing sector are discussed, as well as future challenges.

Flexible Polydimethylsiloxane Composite with Multi-Scale Conductive Network for Ultra-Strong Electromagnetic Interference Protection

Highly conductive polymer composites(CPCs) with excellent mechanical flexibility are ideal materials for designing excellent electromagnetic interference(EMI) shielding materials,which can be used for the electromagnetic interference protection of flexible electronic devices.It is extremely urgent to fabricate ultra-strong EMI shielding CPCs with efficient conductive networks.In this paper,a novel silver-plated polylactide short fiber(Ag@PL ASF,AAF) was fabricated and was integrated with carbon nanotubes(CNT) to construct a multi-scale conductive network in polydimethylsiloxane(PDMS) matrix.The multi-scale conductive network endowed the flexible PDMS/AAF/CNT composite with excellent electrical conductivity of 440 S m-1and ultra-strong EMI shielding effectiveness(EMI SE) of up to 113 dB,containing only 5.0 vol% of AAF and 3.0 vol% of CNT(11.1wt% conductive filler content).Due to its excellent flexibility,the composite still showed 94% and 90% retention rates of EMI SE even after subjected to a simulated aging strategy(60℃ for 7 days) and 10,000 bending-releasing cycles.This strategy provides an important guidance for designing excellent EMI shielding materials to protect the workspace,environment and sensitive circuits against radiation for flexible electronic devices.

Flexible Large-Area Graphene Films of 50-600 nm Thickness with High Carrier Mobility

Bulk graphene nanofilms feature fast electronic and phonon transport in combination with strong light-matter interaction and thus have great potential for versatile applications,spanning from photonic,electronic,and optoelectronic devices to charge-stripping and electromagnetic shielding,etc.However,large-area flexible close-stacked graphene nanofilms with a wide thickness range have yet to be reported.Here,we report a polyacrylonitrile-assisted’substrate replacement’strategy to fabricate large-area free-standing graphene oxide/polyacrylonitrile nanofilms(lateral size~20 cm).Linear polyacrylonitrile chains-derived nanochannels promote the escape of gases and enable macro-assembled graphene nanofilms(nMAGs)of 50-600 nm thickness following heat treatment at 3,000℃.The uniform nMAGs exhibit 802-1,540 cm^(2)V-1s-1carrier mobility,4.3-4.7 ps carrier lifetime,and>1,581 W m^(-1)K^(-1)thermal conductivity(n MAG-assembled 10μm-thick films,mMAGs).nMAGs are highly flexible and show no structure damage even after 1.0×10^(5)cycles of folding-unfolding.Furthermore,n MAGs broaden the detection region of graphene/silicon heterojunction from near-infrared to mid-infrared and demonstrate higher absolute electromagnetic interference(EMI)shielding effectiveness than state-of-the-art EMI materials of the same thickness.These results are expected to lead to the broad applications of such bulk nanofilms,especially as micro/nanoelectronic and optoelectronic platforms.

Recent Advances in Design Strategies and Multifunctionality of Flexible Electromagnetic Interference Shielding Materials

With rapid development of 5G communication technologies,electromagnetic interference(EMI)shielding for electronic devices has become an urgent demand in recent years,where the development of corresponding EMI shielding materials against detrimental electromagnetic radiation plays an essential role.Meanwhile,the EMI shielding materials with high flexibility and functional integrity are highly demanded for emerging shielding applications.Hitherto,a variety of flexible EMI shielding materials with lightweight and multifunctionalities have been developed.In this review,we not only introduce the recent development of flexible EMI shielding materials,but also elaborate the EMI shielding mechanisms and the index for"green EMI shielding"performance.In addition,the construction strategies for sophisticated multifunctionalities of flexible shielding materials are summarized.Finally,we propose several possible research directions for flexible EMI shielding materials in near future,which could be inspirational to the fast-growing next-generation flexible electronic devices with reliable and multipurpose protections as offered by EMI shielding materials.

B4C/NRL flexible films for thermal neutron shielding

Boron carbide/natural rubber latex(B_4 C/NRL)flexible films were prepared via dip-molding with B_4 C content in the range of 5–55 wt% for thermal neutron(0.0253 e V) shielding. B_4 C was well dispersed in NRL according to microscopic observation. Both the inside and outside surfaces of the film were smooth. For B_4 C/NRL flexible films, the minimum elongation at break was greater than 600%, the minimum tensile strength was greater than 12 MPa, and the hardness was in the range of 35–55 HA,which were suitable for preparing flexible wearable products. The attenuation efficiencies of the B_4 C/NRL flexible films for thermal neutrons were also calculated. The B_4 C/NRL flexible films exhibit good attenuation effect for thermal neutrons.

Highly Flexible Fabrics/Epoxy Composites with Hybrid Carbon Nanofillers for Absorption-Dominated Electromagnetic Interference Shielding

Epoxy-based nano-composites can be ideal electromagnetic interference(EMI)-shielding materials owing to their lightness,chemical inertness,and mechanical durability.However,poor conductivity and brittleness of the epoxy resin are challenges for fast-growing portable and flexible EMI-shielding applications,such as smart wristband,medical cloth,aerospace,and military equipment.In this study,we explored hybrid nanofillers of single-walled carbon nanotubes(SWCNT)/reduced graphene oxide(rGO)as conductive inks and polyester fabrics(PFs)as a substrate for flexible EMI-shielding composites.The highest electrical conductivity and fracture toughness of the SWCNT/rGO/PF/epoxy composites were 30.2 S m^(−1)and 38.5 MPa m^(1/2),which are~270 and 65%enhancement over those of the composites without SWCNTs,respectively.Excellent mechanical durability was demonstrated by stable electrical conductivity retention during 1000 cycles of bending test.An EMI-shielding effectiveness of~41 dB in the X-band frequency of 8.2-12.4 GHz with a thickness of 0.6 mm was obtained with an EM absorption-dominant behavior over a 0.7 absorption coefficient.These results are attributed to the hierarchical architecture of the macroscale PF skeleton and nanoscale SWCNT/rGO networks,leading to superior EMI-shielding performance.We believe that this approach provides highly flexible and robust EMI-shielding composites for next-generation wearable electronic devices.

Enhancing the Interaction of Carbon Nanotubes by Metal-Organic Decomposition with Improved Mechanical Strength and Ultra-Broadband EMI Shielding Performance

The remarkable properties of carbon nanotubes(CNTs)have led to promising applications in the field of electromagnetic inter-ference(EMI)shielding.However,for macroscopic CNT assemblies,such as CNT film,achieving high electrical and mechanical properties remains challenging,which heavily depends on the tube-tube interac-tions of CNTs.Herein,we develop a novel strategy based on metal-organic decomposition(MOD)to fabricate a flexible silver-carbon nanotube(Ag-CNT)film.The Ag particles are introduced in situ into the CNT film through annealing of MOD,leading to enhanced tube-tube interactions.As a result,the electrical conductivity of Ag-CNT film is up to 6.82×10^(5) S m^(-1),and the EMI shielding effectiveness of Ag-CNT film with a thickness of~7.8μm exceeds 66 dB in the ultra-broad frequency range(3-40 GHz).The tensile strength and Young’s modulus of Ag-CNT film increase from 30.09±3.14 to 76.06±6.20 MPa(~253%)and from 1.12±0.33 to 8.90±0.97 GPa(~795%),respectively.Moreover,the Ag-CNT film exhibits excellent near-field shield-ing performance,which can effectively block wireless transmission.This innovative approach provides an effective route to further apply macroscopic CNT assemblies to future portable and wearable electronic devices.

The Effective Surface Metallization of Hollow Glass Microspheres for Flexible Electromagnetic Shielding Film

The surface of hollow glass microspheres (HGMs) was roughened by a HCl+NH_(4)F strategy,which achieved a broken ratio as 16.10%,and then metallized by electroless plating by Co nanoparticles up to 90 wt% (abbreviated as Co-HGMs).The average grain size of Co was measured to range from 0.4 to 0.5 μm.Then Co-HGMs were mixed with liquid silicone rubber and xylene,and cured on a perspex plate applicable for flexible electromagnetic shielding.By attentive parameter optimization,a film about 0.836 mm in thickness was obtained with a density of 0.729 g/cm^(3),showing a shielding effectiveness of 15.2 dB in the X-band (8.2-12.4 GHz) at room temperature,which was ascribed to the formation of a conductive network of Co-HGMs inside the film.Simultaneously,the tensile strength of 0.89 MPa at an elongation ratio of 194.5% was also obtained,showing good mechanical properties and tensile strength.

Regulating the Electrical and Mechanical Properties of TaS_(2) Films via van der Waals and Electrostatic Interaction for High Performance Electromagnetic Interference Shielding

Low-dimensional transition metal dichalcogenides(TMDs) have unique electronic structure, vibration modes, and physicochemical properties, making them suitable for fundamental studies and cutting-edge applications such as silicon electronics, optoelectronics, and bioelectronics. However, the brittleness, low toughness,and poor mechanical and electrical stabilities of TMD-based films limit their application. Herein, a TaS_(2) freestanding film with ultralow void ratio of 6.01% is restacked under the effect of bond-free van der Waals(vdW) interactions within the staggered 2H-TaS_(2) nanosheets.The restacked films demonstrated an exceptionally high electrical conductivity of 2,666 S cm^(-1), electromagnetic interference shielding effectiveness(EMI SE) of 41.8 dB, and absolute EMI SE(SSE/t) of 27,859 dB cm^(2) g^(-1), which is the highest value reported for TMD-based materials. The bond-free vdW interactions between the adjacent 2H-TaS_(2) nanosheets provide a natural interfacial strain relaxation, achieving excellent flexibility without rupture after 1,000 bends. In addition, the TaS_(2) nanosheets are further combined with the polymer fibers of bacterial cellulose and aramid nanofibers via electrostatic interactions to significantly enhance the tensile strength and flexibility of the films while maintaining their high electrical conductivity and EMI SE.This work provides promising alternatives for conventional materials used in EMI shielding and nanodevices.

环保型钆硼柔性热中子吸收材料特性研究

本文以聚苯乙烯-乙烯-丁二烯-苯乙烯(SEBS)为基体、以Gd_(2)O_(3)、B_(4)C为功能填料,研制了一种柔性热中子吸收材料。SEM测试结果表明,不同含量的材料中Gd_(2)O_(3)和B_(4)C微米颗粒分布相对均匀;XRD和FT-IR测试结果表明,Gd_(2)O_(3)、B_(4)C与基体SEBS未发生化学反应,属于物理性混合。通过实验和蒙特卡罗模拟进行热中子屏蔽性能验证,对照组材料的实验透射率为31.97%~35.35%,实验组材料的实验和模拟透射率分别为32.11%~36.54%和26.26%~31.31%。对实验组进行了热中子面透射率均匀性测试,结果表明,(10%Gd_(2)O_(3)+40%B_(4)C)/SEBS和(30%Gd_(2)O_(3)+40%B_(4)C)/SEBS材料的平均透射率分别为34.34%和31.60%,所有采样点的绝对偏差在±0.5%以内,标准差为0.33%和0.26%,离散系数为0.0096和0.0082。该柔性材料有效弥补了传统刚性射线屏蔽材料的不足,在核设施异形复杂结构表面包覆防护和可穿戴辐射防护服领域具有潜在应用价值。

纳米纤维素/MXene多功能电磁干扰屏蔽复合材料的研究进展

电磁干扰(EMI)屏蔽材料在日益密集的电磁环境中显得尤为重要。纳米纤维素具有低密度、优异的力学性能、高度的结构稳定性和热稳定性等特点;MXene具有类金属的高电导率、大纵横比、高比表面积及优良的电化学特性等优点。因此,将纳米纤维素与MXene复合能够制备高性能EMI屏蔽复合材料。本文对不同维度纳米纤维素/MXene EMI屏蔽复合材料的制备方法进行综述,包括宏观复合纤维、薄膜和气凝胶复合材料,重点总结了纳米纤维素/MXene EMI屏蔽复合材料的多功能性应用,包括光热转化、储能和柔性传感等,并对其发展进行了展望。

采煤弓形柔性掩护支架沿空留巷技术分析

以山西A矿3062工作面大倾角煤层为例,设计了弓形柔性掩护支架沿空留巷技术方案。首先,介绍了大倾角煤层的基本情况,以此为基础,分析了弓形柔性掩护支架结构设计的内容与安装流程,并根据大倾角煤层特点,探讨了弓形柔性掩护支架的受力情况;其次,通过案例分析的方式验证了该技术的应用效果;最后,确定了利用弓形柔性掩护支架沿空留巷技术后,可以提高煤层顶底板的稳定性,减小变形量,有利于煤矿开采工作的开展。

煤矿急倾斜煤层柔性掩护支架采煤法开采参数分析

以神角煤矿为例,介绍了1种煤矿急倾斜煤层柔性掩护支架采煤法。通过对煤矿的生产技术条件进行分析,进而计算出作业面主要参数、巷道支护参数、回采工艺参数,确定了最佳的柔性掩护支架采煤技术方案,为煤矿急倾斜煤层的开采提供了支持,明确了根据柔性掩护支架采煤法的开采参数进行煤矿设计,可以提高煤矿的生产效率和经济效益。

柔性碳/三聚氰胺复合泡沫的电磁屏蔽与传感特性

智能可穿戴设备不断发展,对柔性传感与电磁屏蔽提出了更高的要求。以三聚氰胺泡沫为基底,通过一种低成本、短周期的浸渍-化学镀镍工艺,将纳米碳质颗粒等物质包覆于三聚氰胺泡沫骨架,制备了兼具电磁屏蔽与柔性传感的复合泡沫材料。采用扫描电子显微镜(SEM)、万能试验机、电化学工作站和矢量网络分析仪研究了碳/三聚氰胺复合泡沫的微观结构、循环压缩、应力传感特性及电磁屏蔽效能。结果表明,碳/三聚氰胺复合泡沫呈三维开孔网状结构,压缩韧性良好;镀镍后,复合泡沫的最大应力为2.75 MPa,循环压缩前两圈吸收能量为22.17 MJ·cm^(-3)。碳/三聚氰胺复合泡沫呈压阻式传感特性,在低应力区传感准确性良好,测试范围较宽,灵敏度为(0.62±0.06) kPa^(-1);镀镍后,响应电流增大,复合泡沫在高应力区传感准确性良好,灵敏度为(3.38±1.0) kPa^(-1)。碳/三聚氰胺复合泡沫的电磁屏蔽以吸收屏蔽效能为主。镀镍前,电磁屏蔽效能与密度呈正相关,当密度为0.168 g·cm^(-3)时,复合泡沫的比电磁屏蔽值最优,为182.86 dB·cm3·g^(-1);镀镍后,复合泡沫的绝对电磁屏蔽值最佳,为178.61 dB·cm^(2)·g^(-1)。

Flexible liquid metal electromagnetic shielding materials

The demand for flexible shielding has been rapidly growing in recent years.Shielding materials using solid metals,carbon materials,or MXenes as shielding units usually have difficulty in combining high shielding and flexibility(stretching and bending characteristics),and thus they gradually fail to meet the shielding needs of flexible electronics.Therefore,shielding materials with both flexibility and high conductivity are urgent to fill this gap.Gallium-based room temperature liquid metal(LM)is an emerging functional material with a low melting point,low viscosity,low modulus,and easy modification.However,due to wettability and compatibility issues,it is difficult to apply bulk LMs directly in the field of electromagnetic shielding(EMS).The article reviews the fabrication methods,performance,and applications of LMs EMS materials from three perspectives:Macroscopic LMs,micro/nano-LMs,and LM-based composites.The gallium-based liquid EMS materials demonstrate the characteristics of high shielding performance with stretchability and a wide shielding band.In this review,different types of gallium-based LM materials are described from macroscopic to microscopic,from liquid to semi-solid,from high density to low density,from room temperature to ultra-low temperature,and from monolayer structure to multilayer structure.The prospect of LM materials as amorphous high-performance EMS materials is demonstrated in various applications,such as mobile communication,astronomical observation,radar,and medical detection,showing tremendous potential in the EMS field.

Flexible thermoregulatory microcapsule/polyurethane-MXene composite films with multiple thermal management functionalities and excellent EMI shielding performance

The development of miniaturized,flexible,and portable electronic devices has led to an increasing demand for multifunctional flexible films that can provide temperature regulation,electromagnetic interference(EMI)shielding,and thermal management.In this study,a novel hierarchical multifunctional flexible composite film is presented.The first step involves the synthesis of phase change microcapsule(PCMC)latex through in-situ polymerization.Next,PCMC and waterborne polyurethane(WPU)latex were mixed and dried using a binary colloidal approach to produce a flexible composite phase change film(WPU/PCMC)with complete anti-leakage and satisfying melting enthalpy(147.86 J g^(-1)).To enhance the EMI performance and mechanical strength,a thin layer of antioxidant MXene@poly tannin acid(PTA)was directly sprayed onto the surface of WPU/PCMC,resulting in the WPU/PCMC/MXene@PTA film(WPM).Consequently,the WPM displays exceptional thermal management performance for multiple drives and outstanding EMI performance(56.86 dB),making it an ideal candidate for future multifunctional products.

110 kV干式柔性户外电缆终端常见问题分析

干式柔性电缆终端广泛应用于110 kV电缆线路。针对110 kV干式柔性电缆终端,分别介绍有尾管和无尾管两种类型终端的结构特点,然后通过典型现场案例,从制作和吊装两个角度,分析易引起缺陷或故障的常见问题,并针对性地制定防范措施,为110 kV干式柔性终端的运维、除缺、故障分析和处理工作提供参考。

Printable Aligned Single-Walled Carbon Nanotube Film with Outstanding Thermal Conductivity and Electromagnetic Interference Shielding Performance

Ultrathin,lightweight,and flexible aligned single-walled carbon nanotube(SWCNT)films are fabricated by a facile,environmentally friendly,and scalable printing methodology.The aligned pattern and outstanding intrinsic properties render“metal-like”thermal conductivity of the SWCNT films,as well as excellent mechanical strength,flexibility,and hydrophobicity.Further,the aligned cellular microstructure promotes the electromagnetic interference(EMI)shielding ability of the SWCNTs,leading to excellent shielding effectiveness(SE)of~39 to 90 dB despite a density of only~0.6 g cm^(−3) at thicknesses of merely 1.5-24μm,respectively.An ultrahigh thickness-specific SE of 25693 dB mm^(−1) and an unprecedented normalized specific SE of 428222 dB cm^(2)g^(−1) are accomplished by the freestanding SWCNT films,significantly surpassing previously reported shielding materials.In addition to an EMI SE greater than 54 dB in an ultra-broadband frequency range of around 400 GHz,the films demonstrate excellent EMI shielding stability and reliability when subjected to mechanical deformation,chemical(acid/alkali/organic solvent)corrosion,and high-/low-temperature environments.The novel printed SWCNT films offer significant potential for practical applications in the aerospace,defense,precision components,and smart wearable electronics industries.

碳纤维/聚苯硫醚复合纸的电磁屏蔽性能研究

为制备高性能碳纤维纸基材料,用短切碳纤维(CFs)和聚苯硫醚(PPS)浆粕通过湿法抄造和高温热处理的方法制备了CFs/PPS复合纸。在复合纸中,PPS浆粕经高温热处理后成为球形焊接点,将三维空间中混乱无序的碳纤维连接在一起形成三维导电碳纤维网络通路。结果表明:CFs/PPS复合纸的电磁屏蔽效能最高可达53 dB;制备的CFs/PPS复合纸表现出优异的柔韧性、导电性能、电磁屏蔽性能、超疏水性能以及阻燃性能。为制备柔性高性能电磁屏蔽碳纤维纸提供了新的方法;制备的CFs/PPS复合纸可以适应极端恶劣环境。

静电纺丝导电纳米纤维膜的研究进展

由于具有电导率可调、比表面积大、自支撑、柔性等优点,导电纳米纤维膜材料的研究日益受到关注。静电纺丝技术结合涂层包覆法、超声包覆法、原位聚合包覆法等化学方法是制备导电纳米纤维膜材料最简单、有效的工艺。首先简单介绍了静电纺丝技术,然后按照导电材料的种类对导电纳米纤维膜的制备工艺进行了归纳总结,最后综述了近几年导电纳米纤维膜材料在生物工程、电磁屏蔽防护和柔性传感器等领域的探索进展。