Nanotube Composite Fibers Research Articles

Mechano-Electrochemical Energy Harvesting for Self-Powered Sensors

Recent developments in mechano-electrochemical technology show tremendous promise for creating autonomous sensors that are instrumental in energy harvesting and health monitoring. This innovative energy conversion mechanism principally transforms the mechanical energy from stretching carbon nanotube composite fibers along their length into electrical energy. This transformation is facilitated by a combination of physical deformation and electrochemical processes.State-of-the-art mechano-electrochemical energy harvesters are incorporating new fiber configurations, such as coiled and buckled structures made from carbon nanotubes. These fibers, when extended within an electrolyte, undergo structural modifications at the microscale, which increase the electrochemically active surface area. These modifications consequently alter capacitance and the voltage across open circuits.The fiber described here, notable for its low Young’s modulus (0.2 MPa) and its ability to stretch up to 400%, surpasses traditional materials used for energy harvesting. It achieves a gravimetric current density of 121 A/kg and a power density of 16 W/kg through an optimal combination of macroscopic coiling and microscopic buckling. This design significantly expands the area accessible to ions, boosting electrical output.This technology has been practically implemented in a pig bladder, proving its effectiveness as a self-powered sensor that can adaptively respond to organ volume changes. Such functionality is essential for real-time health monitoring systems, offering new ways to manage medical conditions impacting bladder functions and movements of other organs.

Collagen composite fibers with various functionalized carbon nanotubes fabricated via microfluidic spinning

AbstractCollagen (Col) composite fibers containing various functionalized multiwalled carbon nanotubes (MWNTs) were prepared via microfluidic spinning, and the influences of MWNT content and type on the performances of the composite fibers were investigated by transmission electron microscope, UV–vis, SEM, Fourier Transform Infrared Spectrometer, differential scanning calorimetry, X‐ray diffraction, and tensile testing. The Col composite fibers showed tightly packed bundle structures on surfaces originated from the high shear rates in the microfluidic channels, and MWNT facilitates the self‐assembly of Col molecules, leading to the ordered arrangement of Col fibrils along the fiber axis. When the loading of carboxylated MWNT (cMWNT) was 0.5 wt%, the tensile strength of Col/cMWNT achieved the maximum of 1.94 cN/dtex owing to the excellent hydrogen bond and electrostatic interactions between the carboxyl groups in cMWNT and amino groups in Col molecules, which is significantly higher than those composite fibers made from unfunctionalized and hydroxylated MWNT. Moreover, with the incorporation of MWNT the thermal stability and water resistance of Col fibers were improved due to the enhanced interfacial interactions between Col and MWNT. The fabrication method in this work enables the controlled formation of Col fibers and demonstrates huge potential for use in Col‐based biomaterials.Highlights Novel collagen (Col)/multiwalled carbon nanotube (MWNT) composite fibers were prepared via microfluidic spinning. The Col composite fibers showed tightly packed bundle surface structures. Col/carboxylated MWNT achieved the maximum tensile strength of 1.94 cN/dtex. MWNT enhanced thermal stability and water resistance of Col fibers.

Sodium alginate/guar gum/multi-walled carbon nanotubes-based hydrophobic Joule thermal textiles for enhanced body thermal management and dehumidification

A sodium alginate (SA), guar gum, and multi-walled carbon nanotube composite solution was prepared using a simple blending method, followed by the construction of alginate/guar gum/multi-walled carbon nanotube fibers and fabrics through complexation with various metal ions (zinc, copper, calcium), featuring multiple hydrogen bonds and ionic complex structures. Specifically, the sodium alginate zinc/guar gum/multi-walled carbon nanotube (SA/GG/Zn2+/MWCNTs) composite fibers exhibited a significant Joule heat effect. By integrating with electronic components such as a temperature control switch, a wearable device capable of operating in cold and humid environments for dehumidification and warming was fabricated. The SA/GG/Zn2+/MWCNTs composite fabric demonstrated excellent hydrophobicity, with a contact angle reaching 145.4°, significantly enhancing its resistance to droplet penetration. Under a 5V voltage, the composite fabric rapidly generated Joule heat, increasing the surface temperature by 5∼7 °C (sensible heat) within just 40 s. Additionally, part of its energy (latent heat) transformed the tiny droplets adhering to the fabric's surface from liquid to gas, achieving dehumidification. This research provides an important theoretical and practical foundation for enhancing the performance and energy efficiency of personal thermal management textiles.

Functional and structural modification of polyvinyl alcohol/carbon nanotubes composite fibers

This research was based on the synthesis of new materials with capacitive properties and low cost, seeking efficient energy storage, through the manufacture and characterization of composite materials of polyvinyl alcohol (PVA)/multiwalled carbon nanotubes with carboxyl group (MWCNTs-COOH) (1 %) for electrodes. Forcespinning and electrospinning techniques were used to develop composite fiber films and compare the physical structure of the fibers and its influence on their capacitive properties. These samples were characterized by SEM, FESEM, FT-IR, XRD, TGA, Raman spectroscopy and electrochemical techniques. The characterization of the composites makes evident the structural modification that the material underwent after the treatments. The electrochemical parameters were measured by electrochemical impedance spectroscopy (EIS), with the samples immersed in H2SO4 1 M as electrolyte. The PVA/MWCNTs-COOH composites with thermal treatment (340 °C) showed a considerable decrease in total impedance of up to 6 orders of magnitude (124 Ω) with respect to the blank sample (2.3 × 108 Ω), as a function of the immersion time in the acid solution. As well as, an increase in the specific capacitance of up to 8 orders of magnitude (1.01×10−2 F cm−2) with respect to the blank sample (5.07 × 10−10 F cm−2) for the composite manufactured by the electrospinning technique. The obtaining of fibers with directionality as a result of the forcespinning technique, the highly crossed network observed by electrospinning and the electrochemical properties shown by the structural modification of PVA/MWCNTs-COOH composite, make it, a material with potential technological applications such as electrode in electrochemical capacitors.

Spacesuit Textiles from Extreme Fabric Materials: Aromatic Amide Polymer and Boron Nitride Nanotube Composite Fiber for Neutron Shielding and Thermal Management

Spacesuit Textiles from Extreme Fabric Materials: Aromatic Amide Polymer and Boron Nitride Nanotube Composite Fiber for Neutron Shielding and Thermal Management

Highly conductive and mechanically strong metal-free carbon nanotube composite fibers with self-doped polyaniline

Individual carbon nanotubes (CNTs) have gained popularity as lightweight wire materials due to their high electrical conductivity and low density than that of copper wires. Despite intensive research on light-weight and highly conductive CNT fibers, the bulk properties of CNT assemblies are inferior to those of metal wires in terms of electrical conductivity. Herein, we propose a method to increase the specific electrical conductivity of CNT fibers with polyaniline (PANI). The structure and physical properties of the CNT fibers are precisely controlled by optimizing the PANI content through a simple and effective solution process. PANI is considered to enhance CNT orientation, decrease voids, and dope the CNT fibers, resulting in a better electron flow in the fibers. The developed composite fiber with 5 wt% PANI demonstrated remarkable specific electrical conductivity of 6,200 ± 160 S m2/kg (11.9 MS/m) (max: 6,360 S m2/kg), an improvement of 16% above as-spun CNT fiber. Simultaneously, the mechanical properties increased by 27%, yielding a high specific tensile strength of 2.63 ± 0.10 N/tex (5.05 GPa). Furthermore, the toughness improved to 79.5 J/g, approximately a 1.8 times improvement over that of the CNT fiber. The addition of a small amount of PANI to CNT fibers has led to significant improvements in electrical and mechanical properties, which can provide insights into research on the CNT fiber field.

Sustainability of Multiwall Carbon Nanotube Fibers and Their Cellulose Composite

Nowadays, the research community envisions smart materials composed of biodegradable, biocompatible, and sustainable natural polymers, such as cellulose. Most applications of cellulose electroactive materials are developed for energy storage and sensors, while only a few are reported for linear actuators. Therefore, we introduce here cellulose-multiwall carbon nanotube composite (Cell-CNT) fibers compared with pristine multiwall carbon nanotube (CNT) fibers made by dielectrophoresis (DEP) in their linear actuation in an organic electrolyte. Electrochemical measurements (cyclic voltammetry, square wave potential steps, and chronopotentiometry) were performed with electromechanical deformation (EMD) measurements. The linear actuation of Cell-CNT outperformed the main actuation at discharging, having 7.9 kPa stress and 0.062% strain, making this composite more sustainable in smart materials, textiles, or robotics. The CNT fiber depends on scan rates switching from mixed actuation to main expansion at negative charging. The CNT fiber-specific capacitance was much enhanced with 278 F g−1, and had a capacity retention of 96% after 5000 cycles, making this fiber more sustainable in energy storage than the Cell-CNT fiber. The fiber samples were characterized by scanning electron microscopy (SEM), BET (Braunauer-Emmett-Teller) measurement, energy dispersive X-ray (EDX) spectroscopy, FTIR, and Raman spectroscopy.

Lightweight Copper–Carbon Nanotube Core–Shell Composite Fiber for Power Cable Application

The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO2 emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss in copper cables resulting in a decrease in coal and gas consumption, and ultimately diminishing the carbon footprint. In this work, we created a lightweight Cu–CNT composite fiber through a multistep scalable process, including spinning, densification, functionalization, and double-layer copper deposition. The characterization and testing of the fabricated fiber included surface morphology, electrical conductivity, mechanical strength, crystallinity, and ampacity (current density). The electrical conductivity of the resultant composite fiber was measured to be 0.5 × 106 S/m with an ampacity of 0.18 × 105 A/cm2. The copper-coated CNT fibers were 16 times lighter and 2.7 times stronger than copper wire, as they revealed a gravimetric density of 0.4 g/cm3 and a mechanical strength of 0.68 GPa, suggesting a great potential in future applications as lightweight power transmission cables.

Boost Up the Mechanical and Electrical Property of CNT Fibers by Governing Lyotropic Liquid Crystalline Mesophases with Aramid Polymers for Robust Lightweight Wiring Applications

Monofilament type of polyaromatic amide (PA) and carbon nanotube (CNT) composite fibers is presented. A concept of a lyotropic liquid crystal (LLC) constructed via a spontaneous self-assembly is introduced to mitigate the extremely low compatibility between PA and CNT. These approaches provide an effective co-processing route of PA and CNT simultaneously to fabricate the uniform, continuous, and reliable composite fibers through a wet-spinning. Interestingly, the addition of a small amount PA into the dope solution of CNT governs the LLC mesophase not only in a spinneret stage but also in a coagulant region. Thus, the developed PA/CNT composite fibers have the high uniaxial orientational order and the close interfacial packing compared to the pure CNT fibers. The PA/CNT composite fibers achieve the outstanding tensile strength, electrical conductivity, and electrochemical response, while maintaining a lightweight. They also exhibit the chemical, mechanical, and thermal robustness. All of these advantages can make flexible, sewable, and washable PA/CNT composite fibers ideal nanocomposite materials for use in next-generation information and energy transporting system by replacing conventional metal electrical conductors.Graphical The lyotropic liquid crystal self-assembly governed by doping the aramid polymers shows the ability to construct mechanically strong and continuous carbon nanotube-based composite fibers that can be used in the lightweight and robust electrical wiring for extreme environmental applications.

Ultrahigh strength and modulus of polyimide-carbon nanotube based carbon and graphitic fibers with superior electrical and thermal conductivities for advanced composite applications

Development of carbon fibers (CFs) with high strength and high modulus for structural applications in CF-reinforced polymer (CFRP) industry has been a challenge. Herein, we propose a method for manufacturing highly oriented polymer–carbon nanotube (CNT) composite fibers having high strength (4.8 ± 0.2 GPa), modulus (390 ± 48 GPa), and electrical conductivity (5.75 ± 0.84 MS m-1) by a liquid crystalline wet-spinning process. The use of chlorosulfonic acid (CSA) as a solvent for CNTs and polyimide (PI) promotes dispersion and enables the production of high-performance composite fibers. In addition, the functional groups of PI in composite fibers improve the interfacial shear strength with epoxy resin without sizing additives by 72% compared to that of CNT fibers. Carbonization and graphitization of the composite fibers with an optimal ratio of PI (30%) and CNT cause significant improvement in their mechanical (tensile strength; 6.21 ± 0.3 GPa and modulus; 701 ± 47 GPa) and thermal properties (496 ± 38 W m−1 K−1) by reducing voids and improving orientation. We believe that the polymer–CNT composites and their CFs with high strength and high modulus would be the next-generation CFs for aerospace and defense industry.

Styrene-ethylene-butadiene-styrene copolymer/carbon nanotubes composite fiber based strain sensor with wide sensing range and high linearity for human motion detection

Flexible strain sensors have attracted extensive attention due to their potential applications in wearable electronics and health monitoring. However, it is still a challenge to obtain flexible strain sensors with both high stretchability and wide linear strain sensing range. In this study, styrene-ethylene-butadiene-styrene copolymer/carbon nanotubes (SEBS/CNTs) composite fiber which showed both electrical conductivity and high stretchability was fabricated through a scalable wet spinning method. The effect of CNTs content on the strain sensing behavior of the SEBS/CNTs fiber based strain sensor was investigated. The results showed that when the CNTs content reached 7 wt%, the SEBS/CNTs composite fiber was capable of sensing strains as high as 500.20% and showed a wide linear strain sensing range of 0-500.2% with a gauge factor (GF) of 38.57. Combining high stretchability, high linearity and reliable stability, the SEBS/CNTs composite fiber based strain sensor had the ability to monitor the activities of different human body parts including hand, wrist, elbow, shoulder and knee.

Wet-spun PEDOT:PSS/CNT composite fibers for wearable thermoelectric energy harvesting

Fiber-based thermoelectric materials have received increased attention as they are light weight and can be sewn and woven for portable and wearable thermoelectric generators. In this work, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)/single-walled carbon nanotube (SWCNT) composite fibers were fabricated by a continuous wet spinning process using concentrated sulfuric acid as a coagulation bath, which could effectively remove the excess PSS and result in improved electric conductivity. With a SWCNT content of 50 wt%, the PEDOT:PSS/SWCNT composite fibers show a high electric conductivity of 2982 S cm−1 and a Seebeck coefficient of 27.1 μV K−1, leading to a promising power factor of 219 μW m−1 K−2. By further treated with sodium hydroxide aqueous solution, the PEDOT:PSS/SWCNT fibers exhibit an enhanced Seebeck coefficient of 36.4 μV K−1 and a power factor of 280 μW m−1 K−2, which is higher than most PEDOT:PSS-based thermoelectric fibers. The mechanism of the enhancement of thermoelectric properties for the composite fibers was discussed. A flexible thermoelectric generator with five pairs of PEDOT:PSS/SWCNT fibers and copper wires were assembled and the electrical power generation capability were evaluated, demonstrating its potential application in wearable electronic devices.

Fabrication of electrically conductive poly(styrene-b-ethylene-ran-butylene-b-styrene)/multi-walled carbon nanotubes composite fiber and its application in ultra-stretchable strain sensor

Although flexible polymer composites based strain sensors have been widely studied, it is still a challenge to obtain flexible strain sensors with large working range, high sensitivity and reliable stability. In this research, a flexible strain sensor based on poly(styrene-b-ethylene-ran-butylene-b-styrene) (SEBS)/multi-walled carbon nanotubes (MWCNTs) composite fiber was prepared through the wet spinning method. In particular, the effects of MWCNTs content and aspect ratio (L/D) on the morphology, and mechanical, electrical and electromechanical properties of the composite fiber were studied. The results showed that with the increase of MWCNTs content, the tensile strength and elongation at break of the composite fiber decreased, while the electrical conductivity and the strain sensing range increased. For the same MWCNTs content, the composite fiber filled with MWCNTs of the lowest L/D ratio (1.25/15) showed the highest tensile strength and elongation at break; whereas the composite fiber filled with MWCNTs of the highest L/D ratio (20/15) showed the highest electrical conductivity, strain sensing range (0–506%) and sensitivity (gauge factor of 58.274 at 0%–275% strain, and of 197.944 at 275%–506% strain). The fabricated composite fiber could be formed into a knitted fabric and had the ability of detecting various human motions.

A study on mechanical properties and thermal properties of UHMWPE/MWCNT composite fiber with MWCNT content and draw ratio

In this study, the mechanical properties and thermal properties of ultra-high molecular weight polyethylene (UHMWPE)/multi wall carbon nanotubes (MWCNT) composite fiber were investigated with different weight percent of the MWCNT contents and draw ratio. To verified the thermal properties of the MWCNT/UHMWPE composite fiber, DSC and TGA analysis were performed. The addition of MWCNT and the higher draw ratio improved the thermal properties of the UHMWPE composite fiber by improving the crystallinity of the polymer. By adding 2 wt% MWCNT, UHWMPE fibers with tensile strengths of 3.85 GPa and young’s modulus of 27.43 GPa could fabricated. In comparison with the pristine UHMWPE fiber with same draw ratio conditions, there values shows increases of 21% in tensile strength and 16% in young’s modulus value. However, in the case of the specimens in which the MWCNT content of 6wt% and 10wt% was added to the UHMWPE fiber, the tensile strength and tensile modulus gradually decreased. We proved by experimentally that the mechanism of strengthening the tensile strength of UHMWPE fibers with MWCNT content of 2wt% is to block craze stretching and reduce defects inside the amorphous region by improving the crystalline region. However, the MWCNT contents is increased by 6wt% or more, the nanofillers start to agglomerate and act as impurities and stress concentration factors, thereby reducing the mechanical properties of the UHMWPE composite fiber.

SiO2 hollow nanotubes composite aramid fiber interlayer for absorbtion of polysulfides in highly stable lithium-sulfur batteries

The shuttle effect and poor conductivity of the sulfur are the major obstacles to the commercialization of lithium-sulfur batteries. In this paper, hollow SiO2 nanotubes (SNTs) were prepared to combine with the aramid fiber paper (AP) as a multifunctional interlayer (SNTs-AP) in the Lithium-sulfur battery. SNTs-AP interlayer could efficiently suppress the polysulfide shuttle effect through polarization sites of SiO2 and enhance the electrical conductivity of lithium-sulfur batteries by forming conductive network. Moreover, the SNTs could accelerate the conversion process of long-chain polysulfides to short-chain polysulfides. The lithium-sulfur batteries with SNTs-AP interlayer exhibits a stable cycling performance with initial specific capacity of 1018mAh/g and average coulombic efficiency of 97.5% at 0.2C. Furthermore, the battery with the SNTs-AP interlayer exhibits a low cyclic decay rate of 0.073% after 350 cycles at 1 C. The above results proves that the SNTs-AP interlayer could provide a strategy for preparing high-stability lithium-sulfur batteries.

A Highly Stretchable and Sensitive Strain Sensor Based on Dopamine Modified Electrospun SEBS Fibers and MWCNTs with Carboxylation

AbstractWearable flexible electronic strain sensor devices have developed rapidly in recent years due to their potential capacity to detect human motion in various situations. However, it still remains still a big challenge to fabricate strain sensors with high sensitivity over a wide workable strain range. In order to meet this challenge, a new type of strain sensor based on elastomer/carbon nanotube composite fiber is reported in this work. Elastomer fibers are initially prepared via the electrospinning of styrene ethylene butene styrene block copolymer (SEBS). The resultant SEBS fibers are then functionalized by sequentially coating with dopamine (DA) coating and carboxyl group (‐COOH) grafted multi‐walled carbon nanotubes (MWCNTs) under vacuum filtration and ultrasonication. Scanning electron microscopy (SEM) and thermogravimetric analysis reveals that a large amount of MWCNTs is firmly bonded onto the SEBS fibers and evenly distributed. SEBS@PDA/MWCNTs composite fibers based strain sensors exhibit excellent performance, including a high gauge factor of 3717 and large workable strain range up to 530%. Furthermore, the developed sensors demonstrate excellent washing fastness and superior sensitivity in monitoring both small strains (e.g., pulse beats and vocal cord vibrations) and large strains (e.g., finger, elbow, and knee bending).

Electrospun Polyacrylonitrile, Styrene–Acrylonitrile Copolymer and Carbon Nanotube Composite Fiber Based Oxygen Reduction Catalysts

An ever increasing worldwide energy demand drives the need for the development of more efficient and greener energy production and storage technologies.1 In recent years, one-dimensional nanofibrous materials (NFMs) have drawn a lot of attention and been widely studied to address these topical problems. For example, the electrospun NFMs can be employed as an oxygen reduction reaction (ORR) catalyst at the fuel cell cathode. The NFMs are appealing because of their attractive properties e.g. high specific surface area, high length/diameter ratio, specific porosities and multiple functionalities. For the preparation of NFMs, a simple and versatile technique called electrospinning can be applied.2 In our previous study of NFMs, we investigated pyrolyzed electrospun multiwall carbon nanotube (MWCNT) and styrene-acrylonitrile copolymer (SAN) fiber materials as ORR catalysts in alkaline solution. It was found that during the thermal decomposition of SAN, the ORR-active N-functionalities can be embedded into the carbon nanomaterial.3 For further optimization of the catalyst material ORR activity, another nitrogen-containing polymer (polyacrylonitrile, PAN) was incorporated into the NFM composition to study the ORR performance of three-component composite material (SAN/PAN/MWCNT) in our latest work regarding NFMs.4 The ORR performance of SAN/PAN/MWCNT-based catalysts was evaluated in 0.1 M KOH solution by rotating disk electrode and linear sweep voltammetry methods. The catalyst with the highest activity toward the ORR was prepared via pyrolysis at 1100 °C (SAN/PAN/MWCNT-1100) and this material outperformed the best electrospun two-component, SAN and MWCNT, composite fiber-based catalyst from our previous study.3 For physical characterization of the materials, scanning electron microscopy (SEM), X–ray photoelectron spectroscopy (XPS), Raman spectroscopy and N2 adsorption-desorption studies were performed. The structure of the catalysts is nanofibrous with visible MWCNTs according to the SEM images (Figure 1a). The high ORR activity of the catalysts prepared in this work is most likely attributed to the nitrogen species as determined by XPS. The catalyst SAN/PAN/MWCNT-1100 also showed good stability during long-term testing in 0.1 M KOH solution (Figure 1b).4 The material with the highest ORR performance used in the present study (SAN/PAN/MWCNT-1100) is a promising catalyst for the development of efficient cathode catalysts for low-temperature fuel cells.4

Multi-walled carbon nanotube composite fiber formation in a water coagulation bath and application as wire heater

A type of high-yield multi-walled carbon nanotubes (MWNTs) with a diameter of 4–13 nm was prepared by cracking propylene over Co-Mo/Al2O3-MgO catalyst. The pristine MWNTs were well dispersed in N-Methyl-Pyrrolidone (NMP) solution of an oil soluble non-ion surfactant. Then the MWNT dispersion was extruded out of a spinneret into a rotating water coagulation bath to form a free-standing gel fiber with ribbon shape. The surfactant was insoluble in water while NMP was miscible with water, which promoted the formation of gel fiber. When the gel fiber was dried, a solid MWNT-surfactant composite fiber was obtained. The composite fiber had certain flexibility. However, the tensile strength was only 15.6 ± 1.3 MPa, which was mainly limited by the weak orientation of MWNTs along the fiber and the lack of compactness of MWNTs inside the fiber. In addition, the electrothermal properties of the 3 cm MWNT-surfactant composite fiber as wire heater were also evaluated. The composite fiber possessed rapid temperature response under different voltages. The steady-state temperature reached 48.1 °C, 74.0 °C and 100.2 °C, respectively, at 10 V, 15 V and 17.5 V.

Ultralong Electrospun Copper–Carbon Nanotube Composite Fibers for Transparent Conductive Electrodes with High Operational Stability

Recent advances in nanotechnology have provided new materials which have the potential to surpass copper and aluminum alloys in electrical conductivity, weight and ampacity [2-6]. Among these carbon nanotubes (CNTs) stand out due to their remarkable thermal and electrical conductivity and ampacity (103 times of copper), low density, abundance of precursor materials and supreme mechanical properties. However, making these materials into a continuous fiber or macrostructures has remained the main obstacle. A promising approach to tackle this issue is employing CNTs as nanofillers in copper matrixes. Subramaniam et al. [5] combined several simple fabrication to produce high density CNT (45 vol%)-Cu composite films with specific conductivity 26% greater than copper. These results show that by improving the interfacial interactions between the CNTs and the copper matrix strong and highly conductive nanocomposites can be made. In this research continuous CNT-Cu nanocomposite is produced using electrospinning method. For improving the interfacial interaction the surface of the CNTs were first coated with a thin layer of copper using electroless deposition methods (the process is explained in details in [7]).

Supramolecular Structure and Mechanical Properties of Wet-Spun Polyacrylonitrile/Carbon Nanotube Composite Fibers Influenced by Stretching Forces

The effect of different elongation conditions on the crystalline structure and physical and mechanical properties of polyacrylonitrile/carbon nanotubes (PAN/CNT) microfibers during wet spinning process was studied. It turns out that the response of polymer chains in PAN/CNT and in PAN fibers to the stretching forces from jet stretching and steam drawing is different. The X-ray diffraction (XRD) results showed that crystalline domain size in steam drawn PAN/CNT fibers is 1.5 times larger than in PAN fibers. CNTs alter the optimum stretching conditions, as they improve the crystalline structure of the PAN/CNT fibers at lower steam drawing ratios than PAN fibers, through nucleation of crystals on their surface. Synchrotron radiation XRD studies revealed that the presence of CNTs improves the crystal orientation of PAN/CNT fibers significantly. In addition, steam drawing is more effective in improving the crystal orientation than jet stretching. Mechanical properties of PAN/CNT fibers have also been affected by steam drawing more than jet stretching. Multi-walled CNTs have the biggest impact on Young’s modulus. The Young’s modulus of PAN/CNT fibers could increase up to 19% higher than PAN fibers at specific stretching conditions, i.e. steam drawing ratio of 2.5. Better orientation of polymers and crystals in fiber direction is the reason for enhancement of Young’s modulus. To our knowledge, the differences between the response of PAN/CNT and PAN fibers to stretching forces inside coagulation bath and after fibers coagulation as well as the difference in evolution of crystalline structure at different stretching stages has not been reported elsewhere.