Carbon Nanotube Fibers Research Articles

Temperature and rate-dependent plastic deformation mechanism of carbon nanotube fiber: Experiments and modeling

High-performance carbon nanotube (CNT) fibers inevitably encounter complicated thermal environments while used in aerospace structures and intelligent actuators. Catastrophic damage is unavoidably induced due to the loss of their mechanical properties. Herein, a modified Hopkinson bar and an in-situ SEM tensile equipment were introduced to study the high-temperature time-dependent mechanical behaviors and microstructure evolution of individual CNT fibers. It was found that the interaction between CNTs was weakened by thermal expansion and defects were introduced into CNTs by thermal oxidation. In addition, the effects of temperature on the viscoplastic strain transition and durability of CNT fibers were studied through a series of relaxation experiments. A shear-lag unit cell and a three-level mathematical model were developed for describing the hierarchical structure evolution of CNT fibers. These models clarified the mechanism of strength loss of CNT fibers at high temperatures and characterized the effect of thermal expansion on their microstructure and mechanical properties. The overlap length and the distance between tubes as a function of temperature were discussed. According to the modeling, an effective strategy was proposed to improve the mechanical properties of CNT fibers at high temperatures by restraining thermal expansion and thermal oxidation. This work would provide crucial theoretical and experimental guidance for the improvement of the thermal dynamic stability of CNT fibers and their composites in extremely high-temperature operating conditions.

Temperature-dependent pseudocapacitive behaviors of polyaniline-based all-solid-state fiber supercapacitors

The work temperatures have a crucial influence on the performance of supercapacitors. However, temperature effects on pseudocapacitive behaviors are rarely studied for flexible high-performance fiber supercapacitors. Herein, we systematically investigated the electrochemical responses of all-solid-state fiber-based supercapacitors composed of carbon nanotube fiber (CNF) electrodes decorated with porous carbon nanotubes (CNTs)/polyaniline (PANI) and gel electrolyte at various ambient temperatures between −5 °C and 55 °C. The results show that the capacitance of the supercapacitor first enhances with the rising temperature under 40 °C and declines at 55 °C. The internal resistance presents a gradual downward trend and the self-discharge behavior accelerates at high operating temperatures. CNTs/PANI-modified flexible fiber supercapacitors are also far from unsatisfactory for cycling stability tests in a high-temperature environment. After experiencing 5000 charge–discharge cycles at 55 °C, the capacitance retains only 43.86 %, far below the counterpart at low temperatures. This study provides a fundamental comprehension of the temperature dependence of pseudocapacitive behaviors of PANI-based fiber supercapacitors.

A flexible carbon nanotube electrode array for acute in vivo EMG recordings.

Executing complex behaviors requires precise control of muscle activity. Our understanding of how the nervous system learns and controls motor skills relies on recording electromyographic (EMG) signals from multiple muscles that are engaged in the motor task. Despite recent advances in tools for monitoring and manipulating neural activity, methods for recording in situ spiking activity in muscle fibers have changed little in recent decades. Here, we introduce a novel experimental approach to recording high-resolution EMG signals using parylene-coated carbon nanotube fibers (CNTFs). These fibers are fabricated via a wet spinning process and twisted together to create a bipolar electrode. Single CNTFs are strong, extremely flexible, small in diameter (14-24 µm), and have low interface impedance. We present two designs to build bipolar electrode arrays that, due to the small size of CNTF, lead to high spatial resolution EMG recordings. To test the EMG arrays, we recorded the activity of small (4 mm length) vocal muscles in songbirds in an acute setting. CNTF arrays were more flexible and yielded multiunit/bulk EMG recordings with higher SNR compared with stainless steel wire electrodes. Furthermore, we were able to record single-unit recordings not previously reported in these small muscles. CNTF electrodes are therefore well-suited for high-resolution EMG recording in acute settings, and we present both opportunities and challenges for their application in long-term chronic recordings.NEW & NOTEWORTHY We introduce a novel approach to record high-resolution EMG signals in small muscles using extremely strong and flexible carbon nanotube fibers (CNTFs). We test their functionality in songbird vocal muscles. Acute EMG recordings successfully yielded multiunit recordings with high SNR. Furthermore, they successfully isolated single-unit spike trains from CNTF recordings. CNTF electrodes have great potential for chronic EMG studies of small, deep muscles that demand high electrode flexibility and strength.

Cyclic heat-generation and storage capabilities of self-heating cementitious composite with an addition of phase change material

This study explored the efficiency of the phase-change materials (PCM) to improve the heat storage capacity of carbon nanotube (CNT) and carbon fiber (CF) based self-heating cementitious composites. Composites were prepared with 0.8 wt% CNT and 0.2 wt% CF as conductive fillers, and five different PCM contents (0, 5, 10, 20, and 30 wt%), and their electrical conductivities, thermal conductivities, and compressive strengths were measured. To determine the self-heating capability, the heat-generation and heat-storage capabilities of the composites were investigated using monotonic and cyclic heating/cooling tests. The results of these tests were analyzed through a differential scanning calorimetry and micro-computed tomography, which showed that the PCM particles with high latent heat were well dispersed in the composites, improving the heat storage capacity. Therefore, it can be said that the addition of PCM may improve heat storage capacity and enhance energy efficiency of the cement-based self-heating composites.

Understanding Mode I interlaminar toughening of unidirectional CFRP laminates interleaved with aligned ultrathin CNT fiber veils: Thickness and orientation effects

Ultrathin CNT fiber veils (100–300 nm thick) were used as interleaves to improve the interlaminar fracture toughness of unidirectional carbon fiber reinforced polymer composites. These veils, drawn from vertically aligned CNT forests, were directly deposited at the mid-plane of CFRPs either longitudinally or transversely to the carbon fiber. The results revealed that triggering multiple toughening mechanisms is the key to achieve high toughness FRP composites. When the veils were oriented parallelly to the carbon fiber, the crack propagates in a “zig-zag” manner, not only interacting with more CNTs, but also triggering more carbon fiber bridgings, leading to a steeply “rising” R-curve. The superiority and effectiveness of this technique is exemplified by the extremely thin toughening layers (about 300 nm thick) needed to remarkably improve the propagation value of Mode I interlaminar fracture toughness of the CFRP by approximately 107%. The Mode I toughening factor (ηI), defined as the change in Mode I interlaminar fracture toughness per interleaf-to-ply thickness ratio, comes out as high as 713, which is far outweigh the state-of-the-art. However, transversely-placed CNT veils will seriously block the formation of carbon fiber bridgings, remarkably degrading the Mode I interlaminar toughness of the laminates.

Scalable Structural Coloration of Carbon Nanotube Fibers via a Facile Silica Photonic Crystal Self-Assembly Strategy

The coloration of carbon nanotube (CNT) fibers (CNTFs) is a long-lasting challenge because of the intrinsic black color and chemically inert surfaces of CNTs, which cannot satisfy the aesthetic and fashion requirements and thus significantly restrict their performance in many cutting-edge fields. Recently, a structural coloration method of CNTFs was developed by our group using atomic layer deposition (ALD) technology. However, the ALD-based structural coloration method of CNTFs is expensive, time-consuming, and not suitable for the large-scale production of colorful CNTFs. Herein, we developed a very simple and scalable liquid-phase method to realize the structural coloration of CNTFs. A SiO2/ethanol dispersion containing SiO2 nanospheres with controllable sizes was synthesized. The SiO2 nanospheres could self-assemble into photonic crystal layers on the surface of CNTFs and exhibited brilliant colors. The colors of SiO2 nanoparticle-coated CNTFs could be easily changed by tuning the sizes of SiO2 nanospheres. This method provides a simple, effective, and promising way for the large-scale production of colorful CNTFs.

Graphene Interlocking Carbon Nanotubes for High-Strength and High-Conductivity Fibers

Carbon nanotubes (CNTs) are promising building blocks for the fabrication of novel fibers with structural and functional properties. However, the mechanical and electrical performances of carbon nanotube fibers (CNTFs) are far lower than the intrinsic properties of individual CNTs. Exploring methods for the controllable assembly and continuous preparation of high-performance CNTFs is still challenging. Herein, a graphene/chlorosulfonic acid-assisted wet-stretching method is developed to produce highly densified and well-aligned graphene/carbon nanotube fibers (G/CNTFs) with excellent mechanical and electrical performances. Graphene with small size and high quality can bridge the adjacent CNTs to avoid the interfacial slippage under deformation, which facilitates the formation of a robust architecture with abundant conductive pathways. Their ordered structure and enhanced interfacial interactions endow the fibers with both high strength (4.7 GPa) and high electrical conductivity (more than 2 × 106 S/m). G/CNTF-based lightweight wires show good flexibility and knittability, and the high-performance fiber heaters exhibit ultrafast electrothermal response over 1000 °C/s and a low operation voltage of 3 V. This method paves the way for optimizing the microstructures and producing high-strength and high-conductivity CNTFs, which are promising candidates for the high-value fiber-based applications.

Wet-spinning of continuous hyaluronic-based MXene/CNTs hybrid fibers for flexible supercapacitor applications

Carbon nanotube (CNTs) fibers with high conductivity and excellent electrochemical properties are the most promising candidate materials for flexible supercapacitor electrodes. Utilizing the high energy storage characteristics of MXene materials, this paper designed and prepared the novel MXene/CNTs/HA hybrid fibers by wet spinning methods with sodium hyaluronate (HA) as the dispersant, and MXene and CNTs powder as main materials. The volumetric capacitance of obtained MXene/CNTs/HA hybrid fibers can reach 13.95 ± 2.45 F/cm3 and the retention rate of capacitance could remain 82 % after 1000 charge–discharge cycles. These results indicate that MXene/CNTs/HA hybrid fibers have great potential application in flexible supercapacitors and multi-functional electronic devices.

Multicolored structural coloration of carbon nanotube fibers

AbstractCarbon nanotube fibers (CNTFs) are endowed with excellent mechanical, electrical, and thermal properties and are considered promising candidates in numerous cutting‐edge fields. However, the inherent black color of CNTFs hinders their practical application in fields with high aesthetic requirements such as wearable devices and smart textiles. Due to the smooth surface and chemical inertness, CNTFs are hard to be dyed by conventional chemical dyes or colorful inks. Herein, we realize a structural coloration of CNTFs by coating them with two metal oxide layers via atomic layer deposition. The three elements of color, that is, hue, saturation, and brightness, can be controlled by adjusting the types and thickness of each oxide layer. Colorful CNTFs with wide color gamut and high saturation are achieved through different combinations. A film interference model is also established to reveal the mechanism of the structural coloration, which is a comprehensive result of thin‐film interference and surface roughness briefly. The calculated reflectance well fits the measured results by introducing surface roughness parameters. Moreover, the colored CNTFs are not iridescent because of retinal signal delay, which will further expand their applications.

Facile Construction of Three-Dimensional Architectures of a Nanostructured Polypyrrole on Carbon Nanotube Fibers and Their Effect on Supercapacitor Performance

Conducting polymer and carbon nanotube hybrids have been researched intensively in recent years for electrodes of fiber-shaped supercapacitors (FSSCs) toward flexible and wearable energy storage devices. Here, three-dimensional (3D) hierarchical polypyrrole (PPy)/carbon nanotube fiber (CNTF) architectures have been prepared by a facial electrodeposition method for flexible FSSC electrodes. PPy nanoparticles, vertically aligned nanowire arrays (VANAs), and nanowire networks were synthesized on CNTFs, respectively, to construct three types of 3D architectures by controlling the electrodeposition condition of PPy. The influence of the 3D architectures of PPy/CNTF electrodes on the performance of the assembled quasi-solid-state FSSCs has been carefully studied. The FSSCs with PPy VANAs showed a much higher specific capacitance than that with PPy nanoparticles because the hierarchical porous structure of PPy VANAs provides a higher accessibility of electrolytic ions and a higher Coulombic efficiency than that with the PPy nanowire network. The PPy VANA-/CNTF-based FSSCs displayed high flexibility, stability, and a specific capacitance of 178.14 F g–1 at 0.4 A g–1, which is much higher than that based on common PPy cauliflower-like film/CNTF electrodes (92.06 F g–1) and pure CNTF electrodes (8.48 F g–1) under the same conditions, demonstrating the great advantages of the 3D hierarchical structure.

One dimensional nickel phosphide polymorphic heterostructure as carbon-free functional support loading single-atom iridium for promoted electrocatalytic water oxidation

Although conducting materials such as carbon nanotube and carbon fiber paper (CFP) have been extensively employed as support of electrocatalytic active sites, most of them are of poor catalytic functionality by themselves and undesirable stability during strong acid/alkaline environments or oxidation process. Here we report a novel one-dimensional (1D) nickel phosphide polymorphic heterostructure (denoted as NPPH) to work as one effective carbon-free functional support for loading of single-atom Ir water oxidation electrocatalyst. Specifically, the NPPH composed of both Ni12P5 and Ni2P phases is not only active for robust alkaline water oxidation but also is of good stability and hydrophilicity for favorable loading of single-atom dispersed iridium. The NPPH supported single-atom Ir electrocatalyst (Ir/NPPH) is found to exhibit remarkably superior water oxidation activity with respect to the NPPH itself or CFP supported single-atom Ir catalyst (Ir/CFP), demonstrating the synergetic promotion effect between NPPH and single-atom Ir catalyst. Furthermore, the NPPH supported single-atom Ir catalyst can bear alkaline water oxidation for over 120 h at current density of 50 mA cm−2. The NPPH developed here is expected as functional support to composite with other water oxidation catalysts, as may be an alternative strategy of developing highly efficient carbon-free electrocatalysts.

Carbon Nanotube Fiber-Based Flexible Microelectrode for Electrochemical Glucose Sensors.

Electrochemical sensors are gaining significant demand for real-time monitoring of health-related parameters such as temperature, heart rate, and blood glucose level. A fiber-like microelectrode composed of copper oxide-modified carbon nanotubes (CuO@CNTFs) has been developed as a flexible and wearable glucose sensor with remarkable catalytic activity. The unidimensional structure of CNT fibers displayed efficient conductivity with enhanced mechanical strength, which makes these fibers far superior as compared to other fibrous-like materials. Copper oxide (CuO) nanoparticles were deposited over the surface of CNT fibers by a binder-free facile electrodeposition approach followed by thermal treatment that enhanced the performance of non-enzymatic glucose sensors. Scanning electron microscopy and energy-dispersive X-ray analysis confirmed the successful deposition of CuO nanoparticles over the fiber surface. Amperometric and voltammetric studies of fiber-based microelectrodes (CuO@CNTFs) toward glucose sensing showed an excellent sensitivity of ∼3000 μA/mM cm2, a low detection limit of 1.4 μM, and a wide linear range of up to 13 mM. The superior performance of the microelectrode is attributed to the synergistic effect of the electrocatalytic activity of CuO nanoparticles and the excellent conductivity of CNT fibers. A lower charge transfer resistance value obtained via electrochemical impedance spectroscopy (EIS) also demonstrated the superior electrode performance. This work demonstrates a facile approach for developing CNT fiber-based microelectrodes as a promising solution for flexible and disposable non-enzymatic glucose sensors.

High rate and ultralong cyclelife fiber‐shaped sodium dual‐ion battery based on bismuth anodes and polytriphenylamine cathodes

AbstractFiber‐shaped sodium dual‐ion batteries (FSDIBs) have attracted considerable attention in wearable electronics because of their low cost and natural abundance and intrinsic flexibility, as well as high working voltage and energy density. Thus, exploration of an electrode material with good flexibility and more accommodative spaces for the reversible shuttle of large anions and Na+ cations is quite necessary but challenging. Herein, Bi nanoparticles anchored on a carbon nanotube fiber are homogeneously fabricated and used as anodes to assemble FSDIBs with carbon fiber‐coated polytriphenylamine cathodes. A series of in situ/ex situ characterizations are conducted to investigate the corresponding battery reaction mechanism of anodes, revealing a reversible reaction process of mixed insertion‐alloying behavior. Owing to excellent electrochemical properties and electrode match, the FSDIBs show ultralong cycle stability for 5000 cycles at 5 A g−1 and remarkable rate capability ranging from 2.5 to 20 A g−1. Moreover, the FSDIBs also show good flexibility under different bending deformations. This work paves the way for development of flexible energy storage devices for wearable devices.

An all-solid-state potentiometric microsensor for real-time monitoring of the calcification process by Bacillus subtilis biofilms

A robust all-solid-state potentiometric microsensor using carbon nanotube fibers was designed. The ion-selective microelectrodes provide a simple and versatile tool for real-time monitoring of the calcification process by Bacillus subtilis biofilms.

Continuous Preparation of High-performing Carbon Nanotube Fibers Based on Cycloalkane/ethanol Mixing Carbon Source

Continuous Preparation of High-performing Carbon Nanotube Fibers Based on Cycloalkane/ethanol Mixing Carbon Source

Vibrations of axially travelling CNT reinforced beams with clamped-clamped boundary condition and an elastic support

Vibrational analysis in engineering systems of axially travelling beams has attracted noticeable attention due to the many applications, such as in robotic manipulators, cable tramways, textile fibres, and in general when there is the axial mass transport of a continuous structure. This article studies the vibrational response of axially-travelling, functionally-graded, carbon nanotube-(CNT)-reinforced beam structures, by investigating linear gyroscopic aspects, such as Argand diagrams. The distribution of CNT fibres is assumed to vary along the thickness of the beam. The Hamilton principle is employed to obtain the coupled axial and transverse behaviour of the beam, subjected to clamped-clamped boundary condition and additionally supported by a spring. These equations of motion are then solved using the modal decomposition technique for the Coriolis-dependent axial and transverse frequencies. For verification, the results are compared to the simplified case in the literature for CNT strengthened beams with zero axial velocity, the dynamics of axially travelling beams, studies of the clamped-clamped boundary condition, and the effects on the Argand diagrams, which have been performed. The Argand diagrams are plotted to examine the effects of varying axial speed on the different linear characteristics of vibration. Variation of the volume fraction of the CNT and the spring support, has also been considered, to understand its effects on the vibration characteristics. Results produced in this article are important in assisting in the future design of engineering devices involving axially travelling systems.

Hierarchical Fermat helix-structured electrochemical sensing fibers enable sweat capture and multi-biomarker monitoring.

Wearable electrochemical sensors have shown potential for personal health monitoring due to their ability to detect biofluids non-invasively at the molecular level. Smart fibers with high flexibility and comfort are currently ideal for fabricating electrochemical sensors, but little research has focused on fluid transport at the human-machine interface, which is of great significance for continuous and stable monitoring and skin comfort. Here, we report an electrochemical sensing fiber with a special core-sheath structure, whose outer layer is wound by nanofibers with a hierarchical Fermat helix structure which has excellent moisture conductivity, and the inner layer is based on CNT fibers covered by three-dimensional reduced graphene oxide folds which have good sensing properties after modification of active materials such as enzymes and selective membranes. This kind of fiber enables efficient sweat capture, and thus only 0.1 μL of sweat is required to activate the device, and it responds very quickly (1.5 s). The fibers were further integrated into a garment to build a wireless sweat detection system, enabling stable monitoring of six physiological markers in sweat (glucose, lactate, Na+, K+, Ca2+, and pH). This work provides a feasible proposal for future personalized medicine and the construction of "smart sensing garments".

Constructing metal-organic framework-derived carbon incorporated V2O5 nanowire-bundle arrays on carbon nanotube fiber as advanced cathodes for high-performance wearable zinc-ion batteries

Fiber-shaped energy storage devices with light weight, superflexibility, and weavability demonstrate promising prospects for application in wearable and portable electronics. Especially, fiber-shaped aqueous rechargeable zinc ion batteries (FARZIBs), which can facilitate the development of wearable electronic products owing to their high safety, low cost, environmental friendliness. Nevertheless, it is very challenging to achieve high rate capability, energy density, and cycling performance simultaneously for the FARZIBs. Herein, a high-performance FARZIB is created from vanadium-based metal-organic frameworks (MOFs) derived vanadic oxide (V2O5) nanowire-bundle arrays (NBAs) grown on highly conductive carbon nanotube fibers (CNTFs) directly as the binder-free cathode. Profiting from high specific area and porous structure of MOFs, as well as arrays structure and binder-free features, our as-assembled FARZIBs exhibited a high capacity of 0.71 mAh cm−2 at a current density of 2 mA cm−2, and demonstrated outstanding rate capability and prominent cycling performance. Moreover, the FARZIBs delivered an extremely high energy density of 215 mWh cm−3 at a power density of 600 mW cm−3. Therefore, our work brings new prospects for the next generation of wearable electronics.

Continuous intercalation compound fibers of bromine wires and aligned CNTs for high-performance conductors

This work presents macroscopic fibers of aligned double-walled carbon nanotubes (DWCNTs) intercalated with long-range ordered bromine, with a stoichiometry close to C17Br. Tribromide ions lie inside interstitial sites between hexagonally-packed DWCNTs and extend parallel to their axis as ordered supramolecular “wires”. First-principles simulations confirm this structure and a transfer of 0.13 electrons per Br atom. The structure of nested bundles of CNTs with a homogeneous distribution of bromine species in the interstitial sites of the superlattice is directly imaged by cross-sectional HRTEM, showing full intercalation of highly dense and aligned fibers. The presence of Br2 and Br3– is confirmed by Raman spectroscopy, and their supramolecular organization is resolved by 2D wide-angle X-ray scattering. Intercalation increases room-temperature longitudinal electrical conductivity by a factor of 8.4. Through low-temperature transport measurements in the longitudinal and transverse directions, we show that the intercalate reduces the tunneling-dominated resistance associated with transport between adjacent CNTs, rather than exclusively acting as a dopant that increases conductance of individual CNTs. By preserving the separation between CNTs, the exceptional mechanical properties of the CNT fiber host are retained. The combined tensile strength above 2.46 GPa and conductivity of 10.68 MS/m makes intercalated CNT fibers attractive lightweight conductors with combined properties superior to metals and graphite intercalation compounds.

Simultaneously enhanced tenacity, rupture work, and thermal conductivity of carbon nanotube fibers by raising effective tube portion.

Although individual carbon nanotubes (CNTs) are superior to polymer chains, the mechanical and thermal properties of CNT fibers (CNTFs) remain inferior to synthetic fibers because of the failure of embedding CNTs effectively in superstructures. Conventional techniques resulted in a mild improvement of target properties while degrading others. Here, a double-drawing technique is developed to rearrange the constituent CNTs. Consequently, the mechanical and thermal properties of the resulting CNTFs can simultaneously reach their highest performances with specific strength ~3.30 N tex-1 (4.60 GPa), work of rupture ~70 J g-1, and thermal conductivity ~354 W m-1 K-1 despite starting from low-crystallinity materials (IG:ID ~ 5). The processed CNTFs are more versatile than comparable carbon fiber, Zylon and Dyneema. On the basis of evidence of load transfer efficiency on individual CNTs measured with in situ stretching Raman, we find that the main contributors to property enhancements are the increasing of the effective tube contribution.