Carbon Nanotube Fibers Research Articles

Physicomechanical Properties of Carbon Nanotubes Reinforced Cementitious Concrete – A Review

Though concrete is one of the most widely used construction materials, there are some concerns and shortcomings associated with it. Cementitious materials' quasi-brittle behavior, which leads to cracking and a loss of durability, is a major concern in structural applications. In this review, the latest research on reinforcing cementitious concrete with carbon nanotubes (CNTs) is reviewed, with an emphasis on the material's structural performance in building and a comparison of CNTs to other reinforcing fibers. The improvement of the macro mechanical properties of carbon nanotube-reinforced composite structures has been discussed in the form of functionally graded carbon nanotubes reinforced composites (FG-CNTRC). Several researches have, in the past, used other forms of reinforcements to enhance the properties of concrete till the implementation of nanotechnology in concrete production by incorporating CNTs into the concrete mixes. Concrete's crucial mechanical properties as a structural material and the durability of conventional cement-based building materials can both be improved by CNTs. They have drawn a lot of interest because they are an engineering material with a wide range of uses. The creation and characterization of cement-based materials reinforced with CNTs have been studied by researchers. Comparisons between the effects of CNT and other fibers on concrete have also been made. This concrete reinforcement type's environmental impact and sustainability have also been discussed. According to studies, CNT can greatly enhance the performance of cement-based materials.

Flexible, stretchable, wearable electronic skins based on aligned carbon nanotube fiber arrays for motion detection and human–machine interaction

Flexible, stretchable, wearable electronic skins based on aligned carbon nanotube fiber arrays for motion detection and human–machine interaction

A Robust Bridge‐Type Airflow Sensor Based on Flexible Superhydrophobic Carbon Nanotube Fiber Thin Films

AbstractDespite a great deal of research about airflow sensors by far, it is still hard to maintain ultra‐low limit of detection, short response, and recovery time under humid and rainy environment, which compromises its practical applications. Herein, a robust bridge‐type airflow sensor base on flexible superhydrophobic carbon nanotube fiber thin films is developed, which can not only own remarkable sensitive properties with ultra‐low limit of detection, fast response, and rapid recovery, but also exclude the influence of moisture or water drops in real applications. Both response time and recovery time are reduced compared with that of the previously reported flexible carbon‐based airflow sensors. Particularly, recovery time is reduced by ≈2/3. Meanwhile, the superhydrophobic structure renders normal functioning of the sensor in severe environment of high humidity or even in the rain, so that the influence of moisture and raindrops can be excluded, a property deficient in the previously reported airflow sensors. Not only can the sensor detect ambient airflow sensitively, but it also exhibits outstanding performance in respiratory health monitoring. Hence, the novel sensor designed in this work realizes operation in the environment of high humidity and rain, which tremendously uplifts the applicability of flexible sensors.

Wet spinning of multi-walled carbon nanotube fibers

For the commercialization of macroscopic fibers of carbon nanotubes (CNTs), it is important to achieve solution processing using inexpensive commercial multi-walled carbon nanotubes (MWCNTs). However, so far, the solution processing of CNTs has been limited to single-walled CNTs (SWCNTs). Here, we report wet spinning of MWCNT fibers using a high-concentration MWCNT/surfactant dispersion in water for the first time. We established the phase diagram of MWCNT/surfactant dispersion by varying the mass ratio of surfactants and MWCNTs. The phase diagram successfully accounts for the phase behavior based on the balance between depletion-induced attraction from surfactant micelles and electrostatic repulsion from adsorbed surfactants on MWCNTs. Following the phase diagram, we obtained a homogeneous MWCNT dispersion with high concentration (1.4 wt%), which enabled us to fabricate MWCNT fibers by wet spinning.

Carbon nanotube fibers with excellent mechanical and electrical properties by structural realigning and densification

Carbon nanotube fibers with excellent mechanical and electrical properties by structural realigning and densification

Cobalt Ferrite Surface-Modified Carbon Nanotube Fibers as an Efficient and Flexible Electrode for Overall Electrochemical Water Splitting Reactions.

One of the most practical and environmentally friendly ways to deal with the energy crises and global warming is to produce hydrogen as clean fuel by splitting water. The central obstacle for electrochemical water splitting is the use of expensive metal-based catalysts. For electrocatalytic hydrogen production, it is essential to fabricate an efficient catalyst for the counterpart oxygen evolution reaction (OER), which is a four-electron-transfer sluggish process. Here in this study, we have successfully fabricated cobalt-based ferrite nanoparticles over the surface of carbon nanotube fiber (CNTF) that was utilized as flexible anode materials for the OER and overall electrochemical water splitting reactions. Scanning electron microscopy images with elemental mapping showed the growth of nanoparticles over CNTF, while electrochemical characterization exhibited excellent electrocatalytic performance. Linear sweep voltammetry revealed the reduced overpotential value (260 mV@η10mAcm-2) with a small Tafel slope of 149 mV dec-1. Boosted electrochemical double layer capacitance (0.87 mF cm-2) for the modified electrode also reflects the higher surface area as compared to pristine CNTF (Cdl = 0.022 mF cm-2). Charge transfer resistance for the surface-modified CNTF showed the lower diameter in the Nyquist plot and was consequently associated with the better Faradaic process at the electrode/electrolyte interface. Overall, the as-fabricated electrode could be a promising alternative for the efficient electrochemical water splitting reaction as compared to expensive metal-based electrocatalysts.

Surface modified carbon nanotubes fiber as flexible bifunctional electrocatalyst for overall electrochemical water splitting reactions

Electrocatalytic water splitting is regarded as a promising approach to produce hydrogen, which is a clean and renewable fuel. The process is mainly constrained due to the sluggish proton-coupled four-electrode transfer process at the anode for oxygen evolution reaction (OER) with high overpotential requirement. Herein this work, we used a one-step hydrothermal method for the in-situ synthesis of CoSe nanoparticles over the surface of carbon nanotube-based fiber (CNTs fiber) and utilized it as a bifunctional electrocatalyst for the electrochemical water splitting process. Surface-modified fiber showed excellent performance towards OER with a low overpotential (η10 = 414 mV) and Tafel slope (77 mVdec−1). We also exploited the same material as cathode, which exhibited an excellent hydrogen evolution reaction (HER) at the counterpart with improved catalytic performance as compared to bare CNTs materials. During the HER process in the cathodic potential region, the electrocatalyst displayed a current density of 10 mAcm−2 at an overpotential of 496 mV. Furthermore, the electrocatalyst exhibited excellent performance during the testing for the overall water splitting. The outcomes reveal that the fabricated electrode can be potentially applied as an efficient and flexible electrode to derive the hydrogen as fuels during the overall electrochemical water splitting reaction.

Strong Connection of Single-Wall Carbon Nanotube Fibers with a Copper Substrate Using an Intermediate Nickel Layer.

Lightweight carbon nanotube fibers (CNTFs) with high electrical conductivity and high tensile strength are considered to be an ideal wiring medium for a wide range of applications. However, connecting CNTFs with metals by soldering is extremely difficult due to the nonreactive nature and poor wettability of CNTs. Here we report a strong connection between single-wall CNTFs (SWCNTFs) and a Cu matrix by introducing an intermediate Ni layer, which enables the formation of mechanically strong and electrically conductive joints between SWCNTFs and a eutectic Sn-37Pb alloy. The electrical resistance change rate (ΔR/R0) of Ni-SWCNTF/solder-Cu interconnects only decreases ∼29.8% after 450 thermal shock cycles between temperatures of -196 and 150 °C, which is 8.2 times lower than that without the Ni layer. First-principles calculations indicate that the introduction of the Ni layer significantly improves the heterogeneous interfacial bond strength of the Ni-SWCNTF/solder-Cu connections.

Wire-shaped, all-solid-state, high-performance flexible asymmetric supercapacitors based on (Mn,Fe) oxides/reduced graphene oxide/oxidized carbon nanotube fiber hybrid electrodes

Wire-shaped flexible supercapacitors (FSCs) have attracted tremendous attention due to their tiny volume, lightweight, high flexibility, and wearability. In the present study, we report the MnO2- or Fe2O3-loaded three-dimensional (3D) nanostructure networks of reduced graphene oxide (rGO) composite on oxidized CNT (denoted as the OCNTF/3D-rGO/MnO2 and OCNTF/3D-rGO/Fe2O3) fibers as the cathode and anode, respectively, for the fabrication of a high-performance, wire-shaped, all-solid-state, flexible asymmetric supercapacitor (FASC). To this end, the 3D-rGO/OCNTF hierarchical structure was electrochemically fabricated, followed by further pulse electrodeposition of MnO2 and Fe2O3, respectively, into the 3D porous graphene networks and the insides of the OCNTF. As such, they were restricted to nano-sized particles and linked by the graphene and the OCNTF. The OCNTF/3D-rGO/MnO2 as the cathode was assembled with the OCNTF/3D-rGO/Fe2O3 as the anode with the carboxymethyl cellulose sodium (CMC)-Na2SO4 gel electrolyte, producing a wire-shaped, all-solid-state FASC that achieved a high specific capacitance of 59.2 F·cm−3 (171 mF·cm−2) and an exceptional energy density of 26.7 mWh·cm−3. The FASC device also showed good flexibility and cyclability, promising to advance power sources for wearable electronics.

(Invited) Macroscopically Aligned Carbon Nanotubes for Photonics, Electronics, and Thermoelectrics

The remarkable flexibility, stable chemical structure, and extraordinary thermal, electrical, and optical properties of carbon nanotubes (CNTs) are promising for a variety of applications in flexible and/or high-temperature electronics, optoelectronics, and thermoelectrics, including wearables, refractory photonics, and waste heat harvesting. However, the long-standing goal in the preparation of CNT ensembles is how to maintain the extraordinary properties of individual CNTs on a macroscopic scale. The polydispersity and randomness remain two main challenges. Here, we will discuss different methods for creating macroscopically aligned CNTs, including spontaneous formation of wafer-scale aligned CNT films via controlled vacuum filtration and production of ultrahigh-conductivity CNT fibers and films through solution spinning and coating. We will then describe the optical, dc and ac electrical, thermal, and thermoelectric properties of these materials. These results are promising for device applications in various fields such as flexible CNT broadband detectors, spectrally selective thermal emitters, and thermoelectric devices.

Flexible Hydrophilic Carbon Nanotube Fibers As Microelectrodes for Neuroscience

Implantable micro electrodes are generally employed to record and stimulate electrical activity of neurons in the nervous system. Most of the electrodes available today are made of metals and silicon that lack required flexibility resulting on a mechanical mismatch between soft tissues and rigid metals which induces faster biofouling and inconsistent performance for long-term applications. Biofouling triggered by inflammatory responses dramatically affect the performance of neural electrodes, resulting in decreased signal sensitivity and consistency over time. Thus, long-term clinical applications require electrically conducting flexible electrode materials with reduced dimensions and antibiofouling properties. These characteristics reduce the degree of inflammatory reactions and increase lifetime of neural electrodes. Carbon nanotubes (CNTs) are well known for their flexibility, electrical conductivity and chemical inertness. This talk will report the use of CNT fibers for neural stimulation and recording, and subsequent covalent functionalization of CNT fibers and films surfaces with hydrophilic, antibiofouling phosphorylcholine (PC) molecules. The electrochemical and spectroscopic characteristics, impedance properties, hydrophilicity, and in vitro antifouling nature of the functionalized CNT surfaces will be presented. The hydrophilicity of the functionalized CNT films was demonstrated by a decrease in the static contact angle from 134.4° ± 3.9° before to 15.7° ± 1.5° after one, and fully wetting after three functionalization cycles respectively. In addition, the extent of protein absorption on the functionalized CNT films were significantly lower than that on the non-functionalized CNT film. Surprisingly, the faradic charge-transfer properties and impedance of the CNT assemblies were preserved after functionalization with PC molecules. These functionalized CNT assemblies are promising for the development of low-impedance neural electrodes with higher hydrophilicity and protein-fouling resistance to inhibit inflammatory responses.

Expanded Carbon Nanotube Fiber at the Liquid-Air Interface for High-Performance Fiber-Based Supercapacitors and Electrochemical Sensors.

Carbon nanotube fibers (CNTFs) are widely utilized in flexible and wearable electronics due to their outstanding electrical and mechanical properties. However, the spinning process of CNTFs has limited the CNTs from exposure, leading to an ultralow usage efficiency of individual CNTs. Here, we propose an electrochemical expansion strategy of a single CNTF at the liquid-air interface, forming a macroscopic spindle-shaped CNTF (SS-CNTF) with an enlarged volume of up to 5000-fold upon the spindle. The obtained spindle-shaped structure endows CNTF with a high specific surface area together with excellent conductivity and good mechanical properties. Therefore, the SS-CNTF-based devices exhibit outstanding performances both in energy storage (electrical double-layer supercapacitor, energy density: 11.22 Wh kg-1, power density: 203.9 kW kg-1) and electrochemical sensing (ascorbic acid: 1.26 μA μM-1 cm-2; dopamine: 103.91 μA μM-1 cm-2; uric acid: 11.53 μA μM-1 cm-2). The novel architecture of SS-CNTF prepared by one-step electrochemical expansion at the liquid-air interface enabled its high performance in multiple applications, providing new insight into the development of CNTF-based devices.

Comparative analysis between Graphene and Carbon Nanotube reinforced epoxy composite

Composite structures are very high in demand because of their high strength-to-weight ratio and directional strength. The arrangement of fibers in the matrix is the major design criterion for the composites. Past studies prove that the fiber reinforcement of carbon nano allotropes such as Carbon Nanotubes (CNTs) and Graphene fibers develop reliable and durable structures for different applications. In this work, three different composite laminate sheets are designed and modeled using finite element analysis (FEA) software. Carbon nano allotropes, CNTs, Graphene, and CNT-Graphene fibers are used as reinforcements in the resin epoxy matrix. The modeled laminate sheets are analyzed for deformation and stress distribution using Hashin’s Failure criteria. The FEA results indicate that the CNTs fiber-reinforced laminate shows minimum deformation (0.000064 mm) and experiences minimum stress (3.81 MPa) compared to Graphene and CNT-Graphene reinforced laminates. The results of FEA can be used as a research basis for further study of composites in the future.

Preparation and investigation of porous chitosan/carbon nanotube biocomposite coating by space holder method

For implants that can be used instead of bone, a porous chitosan/carbon nanotube biocomposite coating on the titanium surface was produced by the spacer holder method. Different chemical contents and varying amounts of space-holding material were studied. Carbon nanotube fibers and pore distributions are homogeneously dispersed in the biopolymer chitosan matrix. NaCl was used as a space holder, and the rate of space holder was increased by 90 % to obtain a trabecular bone-like structure successfully. By increasing the amount of spacer in the coating content from 0.45 g to 0.90 g, the pore size has reached from approximately 1–3 μm to 12 μm. XRD, FTIR, and Raman analysis interpreted the characterization of the coatings. With the addition of carbon nanotubes to the chitosan matrix coating, the stiffness and elastic modulus increased by 55 % and 80 %, respectively. The elastic modulus (12 GPa) of the chitosan/carbon nanotube composite coating is compatible with that of cortical bone. The surface roughness of the chitosan/carbon nanotube coating reached from 1 to 6 μm to 6–16 μm, forming a porous structure. The surface properties of the porous biocomposite coating are promising for orthopedic implant applications.

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.

Self-Assembly of Uniaxial Fullerene Supramolecules Aligned within Carbon Nanotube Fibers.

The conductivity and strength of carbon nanotube (CNT) wires currently rival those of existing engineering materials; fullerene-based materials have not progressed similarly, despite their exciting transport properties such as superconductivity. This communication reveals a new mechanically robust wire of mutually aligned fullerene supramolecules self-assembled between CNT bundles, where the fullerene supramolecular internal crystal structure and outer surface are aligned and dispersed with the CNT bundles. The crystallinity, crystal dimensions, and other structural features of the fullerene supramolecular network are impacted by a number of important production processes such as fullerene concentration and postprocess annealing. The crystal spacing of the CNTs and fullerenes is not altered, suggesting that they are not exerting significant internal pressure on each other. In low concentrations, the addition of networked fullerenes makes the CNT wire mechanically stronger. More importantly, novel mutually aligned and networked fullerene supramolecules are now in a bulk self-supporting architecture.

Enhancement of the hardness and impact strength of epoxy-based metal oxide nanocomposites through hybridization

In this study, hybrid polymer nanocomposites were produced by combining epoxy (EP) with varying amounts of zirconia (ZrO[Formula: see text] and yttria (Y2O[Formula: see text] nanoparticles (NPs), reinforced with multi-walled carbon nanotube (MWCNT) and glass fiber (GF). The objective of this study is to develop and examine the performance of EP nanocomposites through hybridization; for this purpose, hardness and impact tests were conducted in accordance with American Society for Testing and Materials (ASTM) standards. Different sets were produced to investigate the effect of used fillers, including EP/ZrO2, EP/Y2O3, EP/MWCNT, EP/GF, EP/ZrO2/Y2O3, EP/MWCNT/ZrO2/Y2O3, and EP/MWCNT/GF/ZrO2/Y2O3. All findings were compared with the net EP sample. The results showed that the EP nanocomposite samples with low NPs content exhibit much higher mechanical performance than net EP. Furthermore, the additions of MWCNT and GF separately at 0.1 and 0.06[Formula: see text]wt.% have increased the impact strength, respectively, to 165.2% and 338.8%, compared with pure EP. As a result, the presence of MWCNTs and GF in the EP-based nanocomposite matrix could make the product both stronger and tougher.

The effect of novel advanced method on the properties of novolac hybrid nanocomposites reinforced with carbon nanotube and glass fiber

AbstractIn this study, the effects of ball milling (BM) technique and carbon nanotube (CNT) content on the thermal and mechanical properties of hybrid reinforced composites were investigated. The composites were prepared using glass fiber (GF), novolac resin (No), and CNTs with different wt% (1, 2, and, 4). Various milling times were used to optimize the entanglement/agglomeration of CNTs in the polymer matrix and subsequently enhance the final thermal and mechanical properties. Through precise investigations, it was found that the nanocomposite with 2 wt% CNT reinforcement, subjected to 2 h of BM, exhibited remarkable enhancements in key properties. The tensile strength was significantly improved to 45.6 MPa, while the elastic modulus reached 3.419 GPa. Hardness was measured at 96 HRM, and thermal conductivity was enhanced to 0.463 W/mK. Moreover, this sample demonstrated a weight loss that was 43.65% lower compared to the sample reinforced with 1 wt% CNT and subjected to 1 h of BM. Overall, this study highlights the importance of optimizing the milling time and CNT content in the preparation of polymer nanocomposites, and it provides valuable insights for the development of advanced materials with superior performance in various applications.

Pretension-Free and Self-Recoverable Coiled Artificial Muscle Fibers with Powerful Cyclic Work Capability.

Similar to natural muscle fibers, coiled artificial muscle fibers provide a straightforward contraction. However, unlike natural muscle fibers, their recovery from the contracted state to the initial state requires high stress, resulting in almost zero work during a full actuation cycle. Herein, a self-recoverable coiled artificial muscle fiber was prepared by conformally coating an elastic carbon nanotube (CNT) fiber with a very thin liquid crystal elastomer (LCE) sheath. The as-obtained muscle fiber demonstrated excellent actuation properties comprising 56.9% contractile stroke, 1522%/s contraction rate, 7.03 kW kg-1 power density, and 32,000 stable cycles. The LCE chains were helically aligned in a nematic phase, and the phase change of the LCE caused by Joule heating drove the actuation process. Moreover, the LCE/CNT fiber had a well-separated, torsionally stable, and elastic coiled structure, which permitted large contractile strokes and acted as an elastic template for external-stress-free recovery. Thus, the use of self-recoverable muscle fibers to mimic the natural muscles for object dragging, multidirectional bending, and quick striking was demonstrated.

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.