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.     

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.     

Biodegradable PLA/CNTs/Ti3C2Tx MXene nanocomposites for efficient electromagnetic interference shielding

Environment friendly electromagnetic interference (EMI) shielding materials with excellent EMI-shielding efficiency (SE) are urgently required to deal with the increasing electromagnetic wave and environmental pollution. In this work, biodegradable poly(lactic acid) (PLA)/carbon nanotubes (CNTs)/Ti₃C₂T_x MXene nanocomposites are prepared via co-coagulation and compression molding techniques. The distribution state of Ti₃C₂T_x MXene or CNTs, the excellent conductivity and EMI-shielding properties of the nanocomposites are confirmed by scanning electron microscopy (SEM), four-probe conductivity tester and vector network analyzer, respectively. The PLA/CNTs/Ti₃C₂T_x nanocomposites show efficient EMI SE of 24.4 dB for 7 wt% CNTs/8 wt% Ti₃C₂T_x at the thickness of 0.5 mm. By increasing the thickness of the film, the EMI SE of PLA/CNTs/Ti₃C₂T_x nanocomposites can be increased to 39.6 dB at 1.9 mm, nearly 99.989% of electromagnetic wave is shielded. The EM wave reflection is the main shielding mechanism of the PLA/CNTs/Ti₃C₂T_x nanocomposites. Considering future environmental issues, this work provides a novel way for fabricating MXene-based biodegradable EMI shielding materials.

     

Hydrophobic,Flexible, and Lightweight MXene Foams for High‐Performance Electromagnetic‐Interference Shielding

Ultrathin, lightweight, and flexible electromagnetic‐interference (EMI) shielding materials are urgently required to manage increasingly serious radiation pollution. 2D transition‐metal carbides (MXenes) are considered promising alternatives to graphene for providing excellent EMI‐shielding performance due to their outstanding metallic electrical conductivity. However, the hydrophilicity of MXene films may affect their stability and reliability when applied in moist or wet environments. Herein, for the first time, an efficient and facile approach is reported to fabricate freestanding, flexible, and hydrophobic MXene foam with reasonable strength by assembling MXene sheets into films followed by a hydrazine‐induced foaming process. In striking contrast to well‐known hydrophilic MXene materials, the MXene foams surprisingly exhibit hydrophobic surfaces and outstanding water resistance and durability. More interestingly, a much enhanced EMI‐shielding effectiveness of ≈70 dB is achieved for the lightweight MXene foam as compared to its unfoamed film counterpart (53 dB) due to the highly efficient wave attenuation in the favorable porous structure. Therefore, the hydrophobic, flexible, and lightweight MXene foam with an excellent EMI‐shielding performance is highly promising for applications in aerospace and portable and wearable smart electronics.     

Versatile Electronic Textile Enabled by a Mixed-Dimensional Assembly Strategy

Electronic textiles (e-textiles) hold great promise for serving as next-generation wearable electronics owing to their inherent flexible, air-permeable, and lightweight characteristics. However, these e-textiles are of limited performance mainly because of lacking powerful materials combination. Herein, a versatile e-textile through a simple, high-efficiency mixed-dimensional assembly of 2D MXene nanosheets and 1D silver nanowires (AgNWs) are presented. The effective complementary actions of MXene and AgNWs endow the e-textiles with superior integrated performances including self-powered pressure sensing, ultrafast joule heating, and highly efficient electromagnetic interference (EMI) shielding. The textile-based self-powered smart sensor systems obtained through the screen-printed assembly of MXene-based supercapacitor and pressure sensor are flexible and lightweight, showing ultrahigh specific capacitance (2390 mF cm⁻²), robust areal energy density (119.5 µWh cm⁻²), excellent sensitivity (474.8 kPa⁻¹), and low detection limit (1 Pa). Furthermore, the interconnected conductive MXene/AgNWs network enables the e-textile with ultrafast temperature response (10.4 °C s⁻¹) and outstanding EMI shielding effectiveness of ≈66.4 dB. Therefore, the proposed mixed-dimensional assembly design creates a multifunctional e-textile that offers a practical paradigm for next-generation smart flexible electronics.     

Lightweight multi-walled carbon nanotube buckypaper/glass fiber–epoxy composites for strong electromagnetic interference shielding and efficient microwave absorption

Multi-walled carbon nanotube buckypaper (BP) reinforced glass fiber–epoxy (GF/EP) composites were selected to fabricate electromagnetic interference (EMI) shielding and microwave absorbing materials. Six different composite configurations with 3.0 mm thick have been conceived and tested over the X-band (8.2–12.4 GHz). Flexible and low-density (0.29 g/cm³) BP provided a high specific EMI SE of 76 dB with controlled electrical conductivity. GF/EP/BP₁₁₁ and GF/EP/BP₁₀₁ composites possess EMI SE as high as of 50–60 dB, which can be attributed to the number of BP inserted and variation in the wave-transmitting layer of the laminates. Furthermore, the shielding mechanism was discussed and suggested that the absorption was the dominant contribution to EMI SE. GF/EP/BP₁₁₀ laminate demonstrated suitable EMI performance (~?20 dB), whereas GF/EP/BP₀₁₁ composite revealed excellent microwave performance, achieving an effective ? 10 dB bandwidth of 3.04 GHz and minimum reflection loss (RL) value of ? 21.16 dB at 10.37 GHz. On the basis of these results, GF/EP/BP composites prepared in this work have potential applications as both EMI shielding and microwave absorber materials given their facile preparation and lightweight use.

     

Multifunctional Nanocrystalline-Assembled Porous Hierarchical Material and Device for Integrating Microwave Absorption,Electromagnetic Interference Shielding,and Energy Storage

Multifunctional applications including efficient microwave absorption and electromagnetic interference (EMI) shielding as well as excellent Li-ion storage are rarely achieved in a single material. Herein, a multifunctional nanocrystalline-assembled porous hierarchical NiO@NiFe₂O₄/reduced graphene oxide (rGO) heterostructure integrating microwave absorption, EMI shielding, and Li-ion storage functions is fabricated and tailored to develop high-performance energy conversion and storage devices. Owing to its structural and compositional advantages, the optimized NiO@NiFe₂O₄/15rGO achieves a minimum reflection loss of −55 dB with a matching thickness of 2.3 mm, and the effective absorption bandwidth is up to 6.4 GHz. The EMI shielding effectiveness reaches 8.69 dB. NiO@NiFe₂O₄/15rGO exhibits a high initial discharge specific capacity of 1813.92 mAh g⁻¹, which reaches 1218.6 mAh g⁻¹ after 289 cycles and remains at 784.32 mAh g⁻¹ after 500 cycles at 0.1 A g⁻¹. In addition, NiO@NiFe₂O₄/15rGO demonstrates a long cycling stability at high current densities. This study provides an insight into the design of advanced multifunctional materials and devices and provides an innovative method of solving current environmental and energy problems.     

Effect of silver incorporation into PVDF-barium titanate composites for EMI shielding applications

Composites of polyvinylidene fluoride (PVDF) with micron and nano sized BaTiO₃ powders were developed for electromagnetic interference (EMI) shielding applications in the X band. PVDF-nano BaTiO₃ composites show better shielding property compared to PVDF-micron sized BaTiO₃ composites. The composite of PVDF with 40 vol% of nano BaTiO₃ showed the best EMI shielding effectiveness and is about 9 dB. The contributions from reflection and absorption to the total EMI shielding effectiveness is same for the PVDF-BaTiO₃ composites. Addition of small amount of silver particles improved the shielding properties of these composites due to the increased conductivity. An EMI shielding effectiveness of about 26 dB is obtained in the measured frequency range for the PVDF-20 vol% nano BaTiO₃-10 vol% Ag composite of thickness 1.2 mm. Novel three phase composite combining the advantages of metal, nano ceramic and polymer is obtained with the potential for effective EMI shielding applications.     

Highly Conductive Ti3C2Tx MXene Hybrid Fibers for Flexible and Elastic Fiber‐Shaped Supercapacitors

Fiber‐shaped supercapacitors (FSCs) are promising energy storage solutions for powering miniaturized or wearable electronics. However, the scalable fabrication of fiber electrodes with high electrical conductivity and excellent energy storage performance for use in FSCs remains a challenge. Here, an easily scalable one‐step wet‐spinning approach is reported to fabricate highly conductive fibers using hybrid formulations of Ti₃C₂T_x MXene nanosheets and poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate. This approach produces fibers with a record conductivity of ≈1489 S cm^?1, which is about five times higher than other reported Ti₃C₂T_x MXene‐based fibers (up to ≈290 S cm^?1). The hybrid fiber at ≈70 wt% MXene shows a high volumetric capacitance (≈614.5 F cm^?3 at 5 mV s^?1) and an excellent rate performance (≈375.2 F cm^?3 at 1000 mV s^?1). When assembled into a free‐standing FSC, the energy and power densities of the device reach ≈7.13 Wh cm^?3 and ≈8249 mW cm^?3, respectively. The excellent strength and flexibility of the hybrid fibers allow them to be wrapped on a silicone elastomer fiber to achieve an elastic FSC with 96% capacitance retention when cyclically stretched to 100% strain. This work demonstrates the potential of MXene‐based fiber electrodes and their scalable production for fiber‐based energy storage applications.     

Construction of 1D Heterogeneous Co/C@Ag Nws With Tunable Electromagnetic Wave Absorption And Shielding Performance

In this study, silver nanowires (Ag NWs) are synthesized at first, and then the 1D heterogeneous Co/C@Ag NWs with a kebab- and popsicle-like microstructures are constructed by in situ growth ZIF-67 on Ag NWs combined with calcination. Results show that the EM wave prevention performance of composites depends on the loading of Co/C particles threaded on the Ag NWs. The popsicle-like structure with high Co/C loading gives Co/C@Ag NWs excellent EM wave absorption performance, which achieved a minimum reflection loss (RL_min) of −44.5 dB with a low filling of 30 wt.% in paraffin; while the kebab-like structure with low Co/C loading shows good electromagnetic interference (EMI) shielding effectiveness (SE_T) of 30.2 dB at the same filler ratio. The enhanced EM wave absorption performance is attributed to the synergy of multiple energy dissipation mechanisms including dielectric loss, magnetic loss, polarization loss, eddy-current loss, multiple reflection loss, as well as proper impedance matching; the good EMI shielding performance is mainly due to the conduction loss brought by the Ag NWs with ultrahigh conductivity. This work provides a reference for the design of electromagnetic wave prevention material with tuned absorption and shielding performance.     

Complex permittivity and electromagnetic interference shielding properties of Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript>/polyaniline composites

Ti₃SiC₂/insulating polyaniline (Ti₃SiC₂/PANI) composites were prepared by solution blending and subsequently by hot-pressing process. The dielectric permittivity and electromagnetic interference (EMI) shielding effectiveness (SE) of the composites were determined in the frequency range of 8.2–12.4 GHz (X-band). Both real and imaginary permittivities increase with the increasing Ti₃SiC₂ content, and which are attributed to the enhanced displacement current and conduction current. The EMI SE of the composites can be greatly improved by addition of Ti₃SiC₂ filler, which may be ascribed to the increase of electrical conductivity of the composites. It is also found that the reflection of electromagnetic radiation is a dominant mechanism for EMI shielding of the composite. An average EMI SE of 23 dB can be achieved in the X-band range for the composite with 25 wt% Ti₃SiC₂ content, which shows the potential of the Ti₃SiC₂/PANI composites as EMI shielding materials for commercial applications.     

Multifunctional MoSe2@MXene Heterostructure-Decorated Cellulose Fabric for Wearable Thermal Therapy

A booming demand for wearable electronic devices urges the development of multifunctional smart fabrics. However, it is still facing a challenge to fabricate multifunctional smart fabrics with satisfactory mechanical property, excellent Joule heating performance, highly efficient photothermal conversion, outstanding electromagnetic shielding effectiveness, and superior anti-bacterial capability. Here, a MoSe₂@MXene heterostructure-based multifunctional cellulose fabric is fabricated by depositing MXene nanosheets onto cellulose fabric followed by a facile hydrothermal method to grow MoSe₂ nanoflakes on MXene layers. A low-voltage Joule heating therapy platform with rapid Joule heating response (up to 230 °C in 25 s at a supplied voltage of 4 V) and stable performance under repeated bending cycles (up to 1000 cycles) is realized. Besides, the multifunctional fabric also exhibits excellent photothermal performance (up to 130 °C upon irradiation for 25 s with a light intensity of 400 mW cm⁻²), outstanding electromagnetic interference shielding effectiveness (37 dB), and excellent antibacterial performances (>90% anti-bacterial rate toward Escherichia coli, Bacillus subtilis, and Staphylococcus aureus). This work offers an efficient avenue to fabricate multifunctional wearable thermal therapy devices for mobile healthcare and personal thermal management.     

Electromagnetic interference (EMI) shielding of single-walled carbon nanotube epoxy composites

Single-walled carbon nanotube (SWNT)-polymer composites have been fabricated to evaluate the electromagnetic interference (EMI) shielding effectiveness (SE) of SWNTs. Our results indicate that SWNTs can be used as effective lightweight EMI shielding materials. Composites with greater than 20 dB shielding efficiency were obtained easily. EMI SE was tested in the frequency range of 10 MHz to 1.5 GHz, and the highest EMI shielding efficiency (SE) was obtained for 15 wt % SWNT, reaching 49 dB at 10 MHz and exhibiting 15-20 dB in the 500 MHz to 1.5 GHz range. The EMI SE was found to correlate with the dc conductivity, and this frequency range is found to be dominated by reflection. The effects of SWNT wall defects and aspect ratio on the EMI SE were also studied.     

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.     

Bath Electrospinning of Continuous and Scalable Multifunctional MXene‐Infiltrated Nanoyarns

Electroactive yarns that are stretchable are desired for many electronic textile applications, including energy storage, soft robotics, and sensing. However, using current methods to produce these yarns, achieving high loadings of electroactive materials and simultaneously demonstrating stretchability is a critical challenge. Here, a one‐step bath electrospinning technique is developed to effectively capture Ti₃C₂T_x MXene flakes throughout continuous nylon and polyurethane (PU) nanofiber yarns (nanoyarns). With up to ≈90 wt% MXene loading, the resulting MXene/nylon nanoyarns demonstrate high electrical conductivity (up to 1195 S cm^?1). By varying the flake size and MXene concentration, nanoyarns achieve stretchability of up to 43% (MXene/nylon) and 263% (MXene/PU). MXene/nylon nanoyarn electrodes offer high specific capacitance in saturated LiClO₄ electrolyte (440 F cm^?3 at 5 mV s^?1), with a wide voltage window of 1.25 V and high rate capability (72% between 5 and 500 mV s^?1). As strain sensors, MXene/PU yarns demonstrate a wide sensing range (60% under cyclic stretching), high sensitivity (gauge factor of ≈17 in the range of 20–50% strain), and low drift. Utilizing the stretchability of polymer nanofibers and the electrical and electrochemical properties of MXene, MXene‐based nanoyarns demonstrate potential in a wide range of applications, including stretchable electronics and body movement monitoring.     

Preparation of Porous Silver Nanowires-Melamine Formaldehyde Hybrid Composite Materials and Their Electromagnetic Shielding and Flame-Retardant Properties

Along with the booming development of communication technology and electronic equipment, higher requirements of flame-retardant and EMI shielding performances for electromagnetic interference (EMI) shielding materials are put forward. Herein, the ultralight and porous silver nanowires (AgNWs)-melamine formaldehyde (MF) hybrid composite with unique micro-/nanostructure is developed by a facile dip-coating method, which uses the AgNWs as 1D conductive coating and MF foam (MF foam) as 3D skeleton template. Benefiting from the unique porous micro-/nanostructure, the resultant hybrid composite displays low density, excellent EMI shielding performances, and superior flame-retardant property. The EMI shielding effectiveness (SE) and specific EMI SE (SSEt) of the hybrid composite in X-band (8.2–12.4 GHz) can be up to 77 dB and 26971.4 dB cm⁻² g⁻¹, respectively. At the same time, the hybrid composite also passes the vertical burning test and shows an increased LOI value of 40.6%. The combination of flame-retardant and EMI shielding performances for EMI shielding materials makes the AgNWs-MF hybrid composite great application potential in civil and military fields. This work provides a new guide for the design of multifunctional high-performance EMI shielding materials.     

A mechanistic study on electromagnetic shielding effectiveness of polysulfone/carbon nanofibers nanocomposites

The present study aims to produce a light weight electromagnetic interference (EMI) shielding material from carbon nanofibers (CNFs)-based polysulfone (PSU) nanocomposites. EMI shielding effectiveness (EMI SE) was studied by analyzing the electromagnetic wave transmission, reflection, and absorption characteristics of nanocomposites. The electrical conductivity and EMI SE of the nanocomposite with different weight percentage of CNFs (3–10 wt%) were investigated at room temperature and the measurement of EMI SE was carried out in a frequency range of 8.2–12.4 GHz (X-band). The mechanism of EMI shielding of PSU/CNFs nanocomposite has been well explained by comparing the contribution of reflection and absorption to the total EMI SE. The state of dispersion of CNFs and PSU–CNFs interaction was studied by high resolution transmission electron microscopy and scanning electron microscopy. The thermal stability of nanocomposite studied from thermogravimetric analysis was increased after addition of CNFs to PSU matrix. Electrical conductivity of nanocomposite followed power law model of percolation theory having a percolation threshold Φ_c = 0.0079 vol% (0.9 wt%) and exponent t = 1.73. The EMI SE of nanocomposites with thickness of 1 mm was 19–45 decibel (dB) at 3–10 wt% CNFs loading. This high thermal stability and high EMI SE suggest the potential use of PSU/CNFs nanocomposite as effective lightweight EMI shielding material in different 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。      

Ultrahigh Conductive Copper/Large Flake Size Graphene Heterostructure Thin‐Film with Remarkable Electromagnetic Interference Shielding Effectiveness

To guarantee the normal operation of next generation portable electronics and wearable devices, together with avoiding electromagnetic wave pollution, it is urgent to find a material possessing flexibility, ultrahigh conductive, and superb electromagnetic interference shielding effectiveness (EMI SE) simultaneously. In this work, inspired by a building bricks toy with the interlock system, we design and fabricate a copper/large flake size graphene (Cu/LG) composite thin film (≈8.8 μm) in the light of high temperature annealing of a large flake size graphene oxide film followed by magnetron sputtering of copper. The obtained Cu/LG thin‐film shows ultrahigh thermal conductivity of over 1932.73 (±63.07) W m^?1 K^?1 and excellent electrical conductivity of 5.88 (±0.29) × 10⁶ S m^?1. Significantly, it also exhibits a remarkably high EMI SE of over 52 dB at the frequency of 1–18 GHz. The largest EMI SE value of 63.29 dB, accorded at 1 GHz, is enough to obstruct and absorb 99.99995% of incident radiation. To the best of knowledge, this is the highest EMI SE performance reported so far in such thin thickness of graphene‐based materials. These outstanding properties make Cu/LG film a promising alternative building block for power electronics, microprocessors, and flexible electronics.     

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。