High performance of carbon nanotubes/silver nanowires-PET hybrid flexible transparent conductive films via facile pressing-transfer technique

To obtain low sheet resistance, high optical transmittance, small open spaces in conductive networks, and enhanced adhesion of flexible transparent conductive films, a carbon nanotube (CNT)/silver nanowire (AgNW)-PET hybrid film was fabricated by mechanical pressing-transfer process at room temperature. The morphology and structure were characterized by scanning electron microscope (SEM) and atomic force microscope (AFM), the optical transmittance and sheet resistance were tested by ultraviolet-visible spectroscopy (UV-vis) spectrophotometer and four-point probe technique, and the adhesion was also measured by 3M sticky tape. The results indicate that in this hybrid nanostructure, AgNWs form the main conductive networks and CNTs as assistant conductive networks are filled in the open spaces of AgNWs networks. The sheet resistance of the hybrid films can reach approximately 20.9 to 53.9 Ω/□ with the optical transmittance of approximately 84% to 91%. The second mechanical pressing step can greatly reduce the surface roughness of the hybrid film and enhance the adhesion force between CNTs, AgNWs, and PET substrate. This process is hopeful for large-scale production of high-end flexible transparent conductive films.     

Flexible and Highly Conductive AgNWs/PEDOT:PSS Functionalized Aramid Nonwoven Fabric for High-Performance Electromagnetic Interference Shielding and Joule Heating

High-performance multifunctional textiles are highly demanded for human health-related applications. In this work, a highly conductive nonwoven fabric is fabricated by coating silver nanowires (AgNWs)/poly(3,4-ethyl enedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on a poly(m-phenylene isophthalamide) (PMIA) nonwoven fabric through a multistep dip coating process. The as-prepared PMIA/AgNWs/PEDOT:PSS composite nonwoven fabric shows an electrical resistance as low as 0.92 ± 0.06 Ω sq⁻¹ with good flexibility. The incorporation of the PEDOT:PSS coating layer improves the adhesion between AgNWs and PMIA nonwoven fabric, and also enhances the thermal stability of the composite nonwoven fabric. Electromagnetic interference (EMI) shielding and Joule heating performances of the PMIA/AgNWs/PEDOT:PSS composite nonwoven fabric are also investigated. The results show that the average EMI shielding effectiveness (SE) of the single-layer nonwoven fabric in X-band is as high as 56.6 dB and retains a satisfactory level of SE after being washed, bended, and treated with acid/alkali solution and various organic solvents. The composite nonwoven fabric also exhibits low voltage-driven Joule heating performance with reliable heating stability and repeatability. It can be envisaged that the multifunctional PMIA/AgNWs/PEDOT:PSS nonwoven fabric with reliable stability and chemical robustness can be used in EMI shielding devices and personal thermal management products.     

Hybrid transparent electrodes of silver nanowires and carbon nanotubes: a low-temperature solution process

ABSTRACT: Hybrid transparent electrodes with silver nanowires (AgNWs) and single-walled carbon nanotubes (SWCNTs) were fabricated on plastic films by a low-temperature solution process. The hybrid transparent electrodes exhibited a sheet resistance of 29.2 Ω/sq with a transparency of 80% when 6 wt.% of SWCNTs was mixed with AgNWs. This sheet resistance was less than one-fourth that of the AgNW transparent electrodes that were prepared using the same method. This reduction in sheet resistance is because the SWCNTs formed bridges between the AgNWs, thus, resulting in high conductivity of the hybrid transparent electrodes. The hybrid electrodes formed on plastic films exhibited high conductivity as well as excellent stability in sheet resistance when tested using a repeated bending test.PACS: 62.23.Hj; 61.48.De; 81.15.-z.     

Ultraviolet-protective thin film based on PVA–melanin/rod-coated silver nanowires and its application as a transparent capacitor

Melanin is a biopigment in many organisms with interesting intrinsic properties suitable for emerging and sustainable technologies. In this work, we report the fabrication of transparent ultraviolet (UV)-protective thin films based on synthetic melanin in poly(vinyl alcohol) (PVA) matrixes. Melanin was synthesized through the auto-oxidation of l -3,4-dihydroxyphenylalanine (l -DOPA) under oxygen pressure, resulting in excellent solubility in water. A thin film with a composition of 3 wt % melanin (synthesized at 6 atm oxygen pressure) and silver nanowires (AgNWs) deposited on the surface has good transparency in visible light and 100% UV irradiation photoprotection. Encapsulated PVA–melanin/AgNW films dipped in water for 7 days retained 98% of their UV irradiation photoprotection. Moreover, using a transparent conductive oxide substrate, this UV-protective system can be simultaneously used as a transparent capacitor. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47805.     

Fabrication of high-quality flexible transparent conductive thin films with a Nb2O5/AgNWs/Nb2O5 sandwich structure

Different sandwich structures of flexible transparent conductive thin film (TCFs) composed of Nb₂O₅ layers and Ag nanowires (AgNWs) have been prepared onto flexible polyethylene terephthalate (PET) substrate at room temperature to develop an indium-free TCF. The AgNWs are synthesized by a modified polyol method and inserted into the Nb₂O₅ layers that are prepared by radio frequency magnetron sputtering. The optical and electrical properties can be modified by changing the number of spin-coating cycle of AgNW suspension. At optimized condition, we achieve a flexible Nb₂O₅/AgNWs/Nb₂O₅ sandwich thin film with a low sheet resistance of 9.61 Ω/square and a high optical transmittance of 84.3%. Meanwhile, the resistance remains nearly constant after 30 tape tests, suggesting a strong adhesion to the PET substrate. The sandwich thin films show high long-term stability to oxidation, humid heat, and chemicals compared with that of AgNW networks, which can be attributed to the effective covering of Nb₂O₅ layer on the AgNWs. In addition, the Nb₂O₅/AgNWs/Nb₂O₅ sandwich thin films show good stability after repeated bending. This Nb₂O₅/AgNWs/Nb₂O₅ sandwich thin film can therefore serve as a high-performance transparent conductive electrode for numerous flexible electronic devices.     

Novel Insights into Inkjet Printed Silver Nanowires Flexible Transparent Conductive Films

Silver nanowire (AgNWs) inks for inkjet printing were prepared and the effects of the solvent system, wetting agent, AgNWs suspension on the viscosity, surface tension, contact angle between ink droplet and poly(ethylene) terephthalate (PET) surface, and pH value of AgNWs ink were discussed. Further, AgNWs flexible transparent conductive films were fabricated by using inkjet printing process on the PET substrate, and the effects of the number printing layer, heat treatment temperature, drop frequency, and number of nozzle on the microstructures and photoelectric properties of AgNWs films were investigated in detail. The experimental results demonstrated that the 14-layer AgNWs printed film heated at 60 °C and 70 °C had an average sheet resistance of 13 Ω∙sq⁻¹ and 23 Ω∙sq⁻¹ and average transparency of 81.9% and 83.1%, respectively, and displayed good photoelectric performance when the inkjet printing parameters were set to the voltage of 20 V, number of nozzles of 16, drop frequency of 7000 Hz, droplet spacing of 15 μm, PET substrate temperatures of 40 °C and nozzles of 35 °C during printing, and heat treatment at 60 °C for 20 min. The accumulation and overflow of AgNWs at the edges of the linear pattern were observed, which resulted in a decrease in printing accuracy. We successfully printed the heart-shaped pattern and then demonstrated that it could work well. This showed that the well-defined pattern with good photoelectric properties can be obtained by using an inkjet printing process with silver nanowires ink as inkjet material.     

Silver nanowire network embedded in polydimethylsiloxane as stretchable,transparent, and conductive substrates

Highly stretchable transparent conductors where Ag nanowire networks (AgNWs) are reliably embedded into a polydimethylsiloxane (PDMS) substrate are presented. In spite of the weak physical and chemical interaction between Ag nanowires and PDMS, a significantly high transfer efficiency and uniform embedding of AgNW percolation mesh electrodes into PDMS was achieved by simply coating aerogels onto the AgNWs and using water‐assisted transfer. By the failure‐free transfer and reliable bonding with the substrate, the conductive PDMS with embedded AgNWs that exhibits a sheet resistance (R_s) of 15 Ω/sq and 80% optical transmittance (T) are reported here. The PDMS films accommodate tensile strains up to 70% and a cyclic strain of 25% for more than 100 cycles, with subsequent R_s values as low as 90 and 27 Ω/sq, respectively. The T of this conductive PDMS is more than 25% higher than that of networks of CNTs, Cu nanowires, and hybrid composites of CNTs and graphene embedded in elastomer films such as PDMS, polyurethane, and Ecoflex. The simple and reproducible fabrication allows the extensive study and optimization of the stretchability of the meanders in terms of humidity, thickness, and substrate. The results provide new insights for designing stretchable electronics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43830.     

The Sintering Behavior of Electrically Conductive Adhesives Filled with Surface Modified Silver Nanowires

Electrically conductive adhesives (ECAs) filled with sintered silver nanowires were prepared and the effect of different curing conditions on the electrical property of the ECAs was discussed. Silver nanowires with a diameter of 50–60 nm and a length of 2–3 μm were successfully synthesized through a polyol process and surface functionalized with dicarboxylic acid. Morphology studies showed that surface modified silver nanowires began to sinter at 200°C and became shorter and thicker, and eventually formed large chunks at higher temperatures. The conductive adhesives filled with 75 wt% of silver flakes and nanowires (3:2 weight ratio) were cured at different temperatures using two kinds of catalysts. The volume resistivity of the conductive adhesives cured at 300°C without a catalyst reached 5.8 × 10 ^–6 Ω cm. The dramatic improvement in the conductivity of the ECA is due to the sintering of silver nanowires and the high solid content resulting from the partial evaporation of polymer components.     

High conductivity of isotropic conductive adhesives filled with silver nanowires

As an alternative to lead-bearing solder, isotropic conductive adhesives (ICA) have been utilized for many years in microelectronic packaging. In this study, silver nitrate (AgNO₃) as precursor, N-N-dimethylformamide (DMF) as solvent and reducing agent, preparing silver (Ag) nanowires in the nanoporous templates formed by the controlled hydrolysis and condensation of butyl titanate (Ti(OC₄H₉)₄). The Ag nanowires were characterized by X-ray diffraction and transmission electron microscopy. An isotropic conductive adhesive (ICA) has been developed by adding Ag nanowires as conductive filler. Bulk resistivity and shear strength of the ICA are measured and compared with those of conventional ICA filled with micrometer-sized Ag particles (about 1 μm) and nanometer-sized Ag particles (about 100 nm). It is found that the ICA filled with lower content of Ag nanowires exhibits lower bulk resistivity and higher shear strength than ICA filled with micrometer-sized Ag particles and nanometer-sized Ag particles. Possible conductive mechanisms of the ICA are discussed.     

Silver nanowire-based transparent,flexible, and conductive thin film

The fabrication of transparent, conductive, and uniform silver nanowire films using the scalable rod-coating technique is described in this study. Properties of the transparent conductive thin films are investigated, as well as the approaches to improve the performance of transparent silver nanowire electrodes. It is found that silver nanowires are oxidized during the coating process. Incubation in hydrogen chloride (HCl) vapor can eliminate oxidized surface, and consequently, reduce largely the resistivity of silver nanowire thin films. After HCl treatment, 175 Ω/sq and approximately 75% transmittance are achieved. The sheet resistivity drops remarkably with the rise of the film thickness or with the decrease of transparency. The thin film electrodes also demonstrated excellent flexible stability, showing < 2% resistance change after over 100 bending cycles.     

Highly transparent low resistance ATO/AgNWs/ATO flexible transparent conductive thin films

Indium-free flexible transparent conductive thin films (TCFs) composed of silver nanowire (AgNW) networks and Sb doped SnO₂ (ATO) layers were prepared on polyethylene terephthalate (PET) substrates. The ATO layers were deposited via radio frequency (RF) magnetron sputtering at room temperature. The AgNWs were achieved via a modified polyol reduction method and embedded between the ATO layers. The effects of AgNW networks and ATO layers on electrical and optical properties of the ATO/AgNWs/ATO flexible tri-layer thin films are investigated. The ATO layers can improve the optical transmittance and reduce the resistivity of tri-layers, and the corresponding mechanisms are proposed. Typically, an ATO/AgNWs/ATO flexible tri-layers show a high figure of merit value (30.06 × 10^-3 Ω^-1) with a low sheet resistance of 7.1 Ω/sq. and a high transmittance of 85.7%. Meanwhile, the tri-layers present excellent mechanical flexibility, and the ATO layers acted as the protecting layers improve the adhesive and environmental stability at high temperature and humidity for the ATO/AgNWs/ATO flexible tri-layers. These results indicate that ATO/AgNWs/ATO flexible tri-layer thin films can be useful for the fabrication of wearable electronic devices.     

Growth of silver nanowires on carbon fiber to produce hybrid/waterborne polyurethane composites with improved electrical properties

One dimensional silver nanowires (AgNWs) were grown on carbon fiber (CF) by a facile polyol method. Fourier transform infrared spectrometer (FTIR), laser Raman spectrometer (Raman), field‐emission scanning electron microscopy (FESEM), X ray diffraction instrument (XRD), energy dispersive spectrometer (EDS), and X‐ray photoelectron spectrometer (XPS) were carried out to reveal the structure, morphology, and formation mechanism of the CF‐AgNWs. It was found that AgNO₃ concentration of 1.5 mM, reaction temperature of 160°C, and reaction time of 120 min were appropriate conditions for growth of AgNWs on CF. Moreover, a mechanism was suggested that the cysteamine on CF acted as nucleation centers for growth of silver nanoparticles and then small sized silver nanoparticles reduced from silver nitrate were grown on CF via the silver bonding to sulfur. Through an Ostwald ripening process, small sized silver nanoparticles were grown into larger particles. With the assistance of polyvinylpyrolidone (PVP), these larger particles were directed to grow in a definite direction to form nanowires. It was found that the resistance of CF‐AgNWs was decreased to 19.5 Ω, compared with that of CF (102.6 Ω) with the same quality. Thus, the CF‐AgNWs was added into waterborne polyurethane (WPU) to improve the electrical and dielectric properties of WPU. Results showed the WPU/CF‐AgNWs composite presented a lower percolation threshold than WPU/CF composite. When the content was 2.5 wt %, the volume resistivity of the WPU/CF‐AgNWs (1.90 × 10⁴ Ω cm^?1) was lower by approximately three orders of magnitude than that of WPU/CF (4.19 × 10⁷ Ω cm^?1). When the content was 2.5 wt %, the dielectric constant and dielectric loss of the WPU/CF‐AgNWs were improved to 15.24 and 0.21, which were 34.5 and 40.8% higher than that of WPU/CF. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43056.     

Flexible Sandwich Structural Strain Sensor Based on Silver Nanowires Decorated with Self‐Healing Substrate

Flexible and stretchable conducting composites that can sense stress or strain are needed for several emerging fields including human motion detection and personalized health monitoring. Silver nanowires (AgNWs) have already been used as conductive networks. However, once a traditional polymer is broken, the conductive network is subsequently destroyed. Integrating high pressure sensitivity and repeatable self‐healing capability into flexible strain sensors represents new advances for high performance strain sensing. Herein, superflexible 3D architectures are fabricated by sandwiching a layer of AgNWs decorated self‐healing polymer between two layers of polydimethylsiloxane, which exhibit good stability, self‐healability, and stretchability. For better mechanical properties, the self‐healing polymer is reinforced with carbon fibers (CFs). The sensors based on self‐healing polymer and AgNWs conductive network show high conductivity and excellent ability to repair both mechanical and electrical damage. They can detect different human motions accurately such as bending and recovering of the forearm and shank, the changes of palm, fist, and fingers. The fracture tensile stress of the reinforced self‐healing polymer (9 wt% CFs) is increased to 10.3 MPa with the elongation at break of 8%. The stretch/release responses under static and dynamic loads of the sensor have a high sensitivity, large sensing range, excellent reliability, and remarkable stability.     

Conductive sizing for improving electrical conductivity of carbon fiber/polyaryl ether ketone/AgNWs composites

The aim of this work is to enhance the electrical conductivity of PAEK/continuous carbon fiber (CF) composites while maintaining their mechanical properties. A conductive sizing was elaborated by mixing polyetherimide (PEI) with silver nanoplates (AgNpts) in suspension in dichloromethane. An aqueous PEI formulation was used as insulating sizing reference. The presence of AgNpts into the sizing enhances electrical conductivity up to 0.2 S.m⁻¹ for a silver content ∼ 0.2 vol % without any modification of mechanical properties. The influence of conductive sizing on PAEK–AgNWs/CF was observed. For low AgNWs content lower (<1 vol %); the conductive sizing increases the electrical conductivity of the composite by one decade. This result shows that both types of Ag particles participate to the conductive path. For higher AgNWs content, electrical conductivity (200 S.m⁻¹) is independent from the AgNpts content: the conductive path is only constituted by AgNWs. Mechanical properties of such composites show that the value of the conservative modulus is almost the same, while the dissipative modulus slightly increases. The global mechanical properties of the composite are preserved despite the addition of the CF, AgNWs, and AgNpts. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47872.     

细菌纤维素@Fe3O4/AgNWs复合薄膜的制备与电磁屏蔽性能

采用原位共沉淀法在高性能细菌纤维素（BC）表面负载磁性四氧化三铁（Fe3O4）纳米粒子得到BC@Fe3O4，进而采用两步真空辅助抽滤法制得具有磁性导电层级结构的BC@Fe3O4/AgNWs复合薄膜。通过扫描电镜（SEM）、透射电镜（TEM）、傅里叶红外光谱（FTIR）、X射线衍射（XRD）和矢量网络分析仪等对纳米材料和复合薄膜的微观结构与性能进行分析。结果表明：当AgNWs面积含量为1.8 g/m2时，复合薄膜的电磁屏蔽效能（EMI SE）可达56 dB。AgNWs与BC@Fe3O4基体之间具有良好的界面相互作用，使BC@ Fe3O4/AgNWs复合薄膜具有优异的力学性能，拉伸强度和断裂伸长率最高达到84.6 MPa和4.05%。所得柔性、高强且高电磁屏蔽效能细菌纤维素基电磁屏蔽复合薄膜在柔性可穿戴电子设备等领域具有良好的应用前景。     

Fabrication and characteristics of graphene‐reinforced silver nanowire/polybenzoxazine/epoxy copolymer composite thin films

In this study, composite thin films were fabricated by mixing one‐dimensional silver nanowires (AgNWs) with graphene, polybenzoxazine (PBZ) and epoxy. Their electrical and thermal properties under different environmental conditions were investigated. The AgNWs were prepared by a polyol reduction method using ethylene glycol as a reducing agent and polyvinylpyrrolidone as a soft template to reduce silver ions. High aspect ratio AgNWs were then mixed into polymer matrices to allow them to form electrical and thermal conductive paths. Next, a trace amount of graphene was added into the nanocomposites in order to enhance their electrical and thermal properties. The results showed that the addition of graphene and AgNWs improved the threshold leakage current, and a 33% increase in thermal diffusivity was observed. The water resistance and gas barrier properties of PBZ and graphene effectively improved the thermal oxidation stability, and a 200% increase in electrical conductivity was achieved after 120 h of thermal oxidation treatment. A considerable difference was observed between the moduli of epoxy and PBZ. Hardness and phase analyses using atomic force microscopy showed that material modulus mismatch occurred across the interface between the materials, triggering phonon scattering. However, the increase in thermal conductivity was not significant for either material. © 2018 Society of Chemical Industry     

Improved stability of volume resistivity in carbon black/ethylene-vinyl acetate copolymer composites by employing multi-walled carbon nanotubes as second filler

Semiconductive polymer shielding layers of power cable require stable volume resistivity to protect the insulation layer from stress enhancements when carbon black (CB)/polymer composite undergoes thermal cycles. For the CB-filled polymer composites, CB would often re-aggregate when temperature is close to the melting point of polymer matrix, so that the conductive network would be destroyed. Re-distribution of CB and re-formation of conductive CB network under thermal cycles might be the main reason for the instability of volume resistivity. In this work, the re-aggregation of CB in the CB/polymer composites was disclosed. Besides, a small amount of multi-walled carbon nanotubes (MWNTs) was employed as cofiller with CB to improve the stability of volume resistivity of the polymer composites under thermal cycles. The total weight fraction of conductive fillers (CB or CB cofilled with MWNTs) was set as 35 wt%. Compared with the polymer composites loaded with CB solely, the volume resistivity of the composites filled with CB-MWNTs was much more stable with changing temperature. This can be attributed to the enhancement of conductive networks when the MWNTs are employed as second conductive filler.     

Improvement in physical and electrical properties of poly(vinyl alcohol) hydrogel conductive polymer composites

With an aim to develop anti‐electrostatic discharge materials based on biodegradable polymers, poly(vinyl alcohol) films composited with two different conductive fillers (carbon black and aluminium) at various fillers contents (20?60%wt), were manufactured using solvent‐casting technique. The mechanical properties of such the films were investigated through tensile stress‐strain tests. Wettability and morphology of the composite films were performed by water contact angle measurement and SEM, respectively. Young's modulus of the composite films can be increased with the addition of conductive fillers. The surface of the composite films showed non‐homogeneous appearance, in which the phase boundary within the composites was clearly observed and the conductive fillers formed aggregation structure at high filler concentration. In addition, the composite films exhibited better hydrophobicity when higher conductive filler content was added. TGA results suggested that both carbon black and aluminum have proven their efficiency to enhance thermal stability of poly(vinyl alcohol). Investigation of cross‐cut adhesion performance of the prepared composite films revealed that carbon black‐filled composites exhibited excellent adhesion strength. The effect of conductive filler content on surface resistivity of the composite films was also examined. The experimental results confirmed that both the fillers used in this study can improve the electrical conductivity of poly(vinyl alcohol) hydrogel. The surface resistivity of the composite films was reduced by several orders of magnitude when the filler of its critical concentration was applied. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42234.     

Solution casting of transparent and conductive carbon nanotubes/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) films under a magnetic field

Transparent and conductive composite films of carboxyl functionalized single-walled carbon nanotubes and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) were deposited on various substrates under the influence of a magnetic field. It was demonstrated that the sample dewetting under the magnetic field enhances the conductivity of the dried films. Highly transparent films (∼88%) were obtained with a low sheet resistivity of ∼90 Ω/sq. The magnetic field assisted deposition method proposed here suggests scalable production of flexible and cost-effective transparent electronics.     

聚酰亚胺/导电石墨抗静电复合材料的制备与表征

采用原位聚合法制备了聚酰亚胺/导电石墨(PI/CG)抗静电复合材料薄膜,并探讨了复合膜的结构、微观形貌以及导电石墨用量对其表面电阻率、热性能以及力学性能的影响。结果表明:复合膜亚胺化完全、热性能得到提高;石墨的用量为15 phr时,复合膜表面电阻率的数量级为109Ω,达到抗静电的最佳要求范围。