Carbon Nanotube Wires Research Articles

Self-assembly preparation of 3D nanorestricted domain catalysts based on carbon nanotube wires and in-depth analysis of tetracycline degradation performance, mechanism, and toxicology

In this study, the 3D intertwined tubular structure of carbon nanotube sponge (CNTS) was utilized to intersperse MIL-53(Fe) onto the nanofragments of CNTS. For the preparation of a novel composite catalyst, MIL-53(Fe)@CNTS, nanorestricted domain growth was combined with self-assembly regulation to realize the ordered growth of MIL-53(Fe) in the space of CNTS. The catalyst exhibited excellent activation performance for PMS within a wide pH range. The maximum removal of tetracycline (TC, 20 mg/L) was as high as 96.7 % within 90 min, and the maximum degradation rate constant (K) was as high as 0.1648 min−1. The performance of the catalyst was directly correlated with the number of domain-limited assemblies. Synchrotron radiation results and DFT theoretical calculations confirmed that the overall catalytic performance of MIL-53(Fe) was greatly improved after the nanorestricted domain assembly in CNTS. The TC degradation system involved radical–oxidative and nonradical pathways. The intermediates of the reaction system were identified by HPLC-MS, and several possible degradation pathways during the TC reaction were proposed. The toxicity degree of the intermediate monomers was analyzed in conjunction with the TEST program, and their effects on the biological environment were predicted. Combined with the toxicity prediction of the TC degradation pathways, the post-reaction degradation solution was used for practical biotoxicity assessment. The effects of the real solution before and after degradation on the ecotoxicity of different organisms were also determined. In conclusion, the composite catalyst MIL-53(Fe)@CNTS synthesized by precise assembly using the nanorestricted domain strategy has promising applications in pollutant degradation and environmental remediation.

Review of Carbon Nanotube Wire-to-Metal Connection Methods: Techniques, Challenges, and Prospects

This paper reviews the connection technologies between carbon nanotube (CNT) wires and metal materials, analyzes the technical principles, advantages, limitations and application prospects of different connection methods. It mainly focuses on the electrical contact issues of CNT wires in the field of microelectronics, and how to achieve a high-performance, reliable combination of metal and CNT wires through emerging material processing and connection technologies. The article also discusses the challenges these technologies face in overcoming interface resistance, improving mechanical connection performance, and maintaining the characteristics of CNT wires.

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.

A route towards metal-free electrical cables via carbon nanotube wires

Carbon nanotubes (CNTs) have unique properties with promise to outperform the electrical characteristics of bulk copper, giving rise to its primary driver for use in electronic devices. The challenge still hindering their full exploitation stems from an inability to manufacture them to long lengths, resulting in a requirement to align and entwine them into a yarn or wire. There have been several methods presented in achieving this, however, the common disadvantage has been that they are only applicable to specific types and morphologies of CNTs. In the work reported here, using electrospinning as a universally applicable route for any CNT type, we re-engineer and optimise the various formulation, fabrication and processing steps required to manufacture CNT wires. Through a series of investigations using a materials agnostic approach, we experimentally probe the choice of solvent, surfactant and thermal treatment temperature of the CNT inks, demonstrating the CNT-type optimum using a range of commercially available single- double- and multiwalled CNTs. Finally, this allowed us to develop and probe an electrical conditioning process to further enhance the electrical performance, achieving the highest reported un-doped electrical conductivity of 36,000 S⋅ m − 1 for electrospun CNT wires, or a specific conductivity of 0.2 × 10 6 S · m − 1 / g · c m − 3 .

Mass specific performance of halogen and alkali metal based dopants in carbon nanotube wiring

High electrical conductivity, low mass density, and compatibility with spin fabrication processes have made carbon nanotube (CNT) based conductors a prime candidate for the replacement of copper in power transmission applications. Experimental research has successfully employed chemical doping to produce CNT wiring with very high electrical conductivity. However, due to the high molecular weight of the most successful dopants, these CNT based conductors show a mass specific conductivity very similar to that of copper and are therefore of limited interest in mass constrained applications, such as aircraft design. Ab initio analysis of the mass specific performance of nine widely studied dopants, including halogens, interhalogens, alkali metals, and alkali metal halides, suggests the principal reasons for their lack of success in producing high mass specific conductivity CNT based wiring. Their disparate doping effects on metallic CNTs, semiconducting CNTs, metallic nanotube junctions, and semiconducting nanotube junctions form a near orthogonal set, so that in the mix of metallic and semiconducting nanotubes typical of experimental investigations, much of the conductor mass is parasitic, no matter which of the dopants is applied.

Aspects of Coatings on Buckypaper as a Study into the Expected Effects of Coatings on Carbon Nanotube Wires

Buckypaper (BP) was used as an accumulation of nanotubes to simulate as carbon nanotube (CNT) wires to study the interaction between four different insulating coating materials and CNTs. The wettability and electrical conductivity performance of each CNT/coating pair was assessed. The BP was prepared by filtering a sonicated solution of single-walled carbon nanotubes and N,N-Dimethylformamide, through a polytetrafluoroethylene (PTFE) membrane of 0.45 µm pore size. It was observed with Scanning Electron Microscopy, its chemical composition determined by X-ray Photoelectron Spectroscopy, its imperfections and purity measured by Raman Spectroscopy and the porosity (%) and pore distribution obtained by Nitrogen Physisorption. The results showed similar porosity and surface structure to that of reported CNT wires. The surface free energy of the BP was obtained through the Owens-Wendt method, and surface tension of the coatings was calculated with pendant drop measurements to find the adhesion and wettability parameters. Epoxy resin showed the highest wettability and adhesion, which resulted in infiltration into the BP that decreased electrical conductivity by 65%. In contrast, the insulating varnish showed much lower level of wettability and adhesion which resulted in the lowest decrease in conductivity (9.3%).

Simulation and fabrication of carbon nanotube–nanoparticle interconnected structures

Abstract. With the rapid development of nanotechnology, the size of a device reaches sub-nanometer scale. The larger resistivity of interconnect leads to serious overheating of integrated circuits. Silicon-based electronic devices have also reached the physical limits of their development. The use of carbon nanotubes instead of traditional wires has become a new solution for connecting nano-structures. Nanocluster particles serving as brazing material play an important role in stabilizing the connection of carbon nanotubes, which places higher demands for nanoscale manipulation techniques. In this paper, the dynamic processes under different operating scenarios were simulated and analyzed, including probe propulsion nanoparticle operation, probe pickup nanoparticle operation and probe pickup nanocluster particle operation. Then, the SEM (Scanning Electron Microscope) was used for nanoparticle manipulation experiments. The smallest unit of carbon nanotube wire was obtained by three-dimensional (3D) construction of a carbon nanotube–silver nanocluster particle (CN-AgNP), which verified the feasibility of 3D manipulation of carbon nanotube wire construction. The experiments on the construction of carbon nanotube–nanocluster particle structures in three-dimensional operation were completed, and the smallest unit of carbon nanotube wire was constructed. This nano-fabrication technology will provide an efficient and mature technical means in the field of nano-interconnection.

Ultra-long carbon nanotube forest via in situ supplements of iron and aluminum vapor sources

A carbon nanotube forest with a length of 14 cm grew with an average growth rate of 1.5 μm s−1 and a growth lifetime of 26 h. Several key factors to realize this unprecedented long growth such as catalyst conditions, growth conditions in chemical vapor deposition, and reactor system were clarified. It was found that the combination of the catalyst system of iron/gadolinium/aluminum oxide (Fe/Gd/Al2Ox) and the in situ supplements of Fe and Al vapor sources at very low concentration was crucially important. A cold-gas system, where only the substrate is heated while keeping the gas at room temperature, was employed to suppress unnecessary reactions and depositions. The long carbon nanotube forest enabled macroscopic measurements of the tensile and electrical properties of the carbon nanotube wires, and it gave several important insights for industrial applications of the carbon nanotubes in the future.

Efficient nitrate and oxygen electroreduction over pyrolysis-free mesoporous covalent Co-salophen coordination frameworks on carbon nanotubes

Co-salophen-enriched covalent organic frameworks (COFs) coating on carbon nanotube (CNT) wires were prepared with 1,3,5-triformylphloroglucinol and diaminobenzidine by one-step Schiff-base type condensation reaction. The prepared Co-salophen COF@CNTs exhibited the large-pore mesoporous (40–60 nm) nanostructures with cotton-like morphology, and high-density Co-salophen units were uniformly implanted on this easily accessible framework. This pyrolysis-free Co-salophen coordination polymers on CNTs demonstrated the outstanding oxygen reduction reaction (ORR) performance comparable to commercial Pt/C and the best Co-based catalysts, with a positive half-wave potential (E1/2) of 0.89 V (vs RHE) in 0.1 M KOH in half-cells and the maximum powder density of 156 mW cm−2 in rechargeable Zn–air battery. In particular, Co-salophen COF was firstly found to show the efficient electrocatalytic performance for reducing NO3−-N to harmless N2N (NO3−-RR). The NO3−-N conversion yield reached 87% within 12 h in neutral solution, with a N2N selectivity of 97%. This work paved a facile synthesis route for pyrolysis-free and efficient bifunctional electrocatalysts toward ORR and NO3−-RR.

In vitro Cytotoxicity Studies of Industrially Used Common Nanomaterials on L929 and 3T3 Fibroblast Cells

The unique structures and properties of nanomaterials have attracted many engineers and scientists to these resources for different applications, including biomedical, electronics, manufacturing, transportation, energy, and defense. The increasing applications of nanomaterials have also caused some concern among the scientific community about their safety and cytotoxicity. To successfully use nanomaterials in different fields, their interaction with mammalian cells in vitro must be addressed before in vivo experiments can be carried out successfully. In this study, the cytotoxicity values of commonly known nanomaterials, such as 100-ply Carbon Nanotube (CNT) wires, graphene, CNTs, nanoclay, and fullerene, were investigated through in vitro tests on human L929 and mice 3T3 fibroblast cells and compared with each other. The effects of cytotoxicity on both cell types were similar in many ways, but not closely identical due to structural and morphological differences. Compared to mice fibroblast cells, human fibroblast cells have a larger surface area; therefore, the viability values of L929 cells at different dilutions and time durations vary over a larger range. Pristine 100-ply CNT wires were found to be the least cytotoxic, with an average viability of 86.9%, whereas materials with high aspect ratio (e.g., CNTs and graphene) had higher cytotoxicity values due to their potential to pierce through cell membranes.

Enhanced saltwater stability of CNT wires under electrical bias

Wires formed of densified as-received and purified commercially available Carbon Nanotube (CNT) sheet material as well as a laid CNT wire were tested for long-term stability in a saltwater environment under an applied electrical bias. Tafel electrochemical measurements showed increased chemical stability for the CNT samples over copper, with the corrosion resistance of CNT samples showing further improvement after purification. Under constant DC voltage biases of 2.50 V, CNT materials show improvements in failure time by as much as 108 times over comparable diameter copper wires, with further improvement over copper at lower applied voltages due to material stability and an absence of gas evolution. Shear forces resulting from gas formation was found to significantly contribute to the failure of CNT wires at elevated voltages compared to chemical corrosion typical in copper wires.

Electrical Performance Retention of Chemically Doped Carbon Nanotube Wires

Carbon nanotube (CNT) wires are light-weight and robust alternatives to conventional metal conductors. The weight savings, increased flexure tolerance, and corrosion resistance of CNT conductors make them a viable solution for a variety of space, defense, and power transmission applications. An individual CNT has orders of magnitude greater electrical conductivity than conventional metal conductors, but this has not been realized in bulk CNT networks. Recently, the use of chemical dopants has resulted in bulk CNT wire conductivities approaching 10 MS/m. As the electrical conductivity of CNT wires continues to approach that of conventional metals, deployment of these CNT conductors will require an understanding of how these CNT conductors and chemical dopants behave during practical operation.In the present work, commercially scaled CNT wires are physically densified through radial drawing dies and chemically doped with KAuBr4 resulting in an improvement in electrical conductivity to greater than 1 MS/m, a 6x improvement compared to the as-received CNT wire. The current density at failure of CNT wires increases with KAuBr4 doping and densification by 67% to 35 MA/m2. The electrical performance retention is determined by applying increasing current densities with intermittent rest steps and low current I-V sweeps. The low current I-V sweeps allow for changes in electrical conductivity due to permanent material degradation caused by previous high current density exposure to be determined. The instantaneous electrical conductivity averaged over the last 5 seconds of each current “on” step is used to determine the temperature dependent effects on electrical conductivity caused by Joule heat during high current application. The KAuBr4 doped and densified samples experience no permanent change in initial electrical conductivity at current densities up to ~32 MA/m2, 4x greater than the as-received CNT wires.The enhanced electrical conductivity retention of KAuBr4 doped and densified CNT wires at high current density was further probed though an analysis of the thermal stability of these doped CNT conductors. Thermogravimetric analysis indicated that minimal degradation of the KAuBr4 dopant occurs prior to thermal oxidation of the CNT materials at 400 °C. A variety of KAuBr4 doping and 400 °C thermal oxidation procedures were performed on CNT wires to understand how thermal degradation of the dopant relates to changes in the electrical conductivity and high current density stability. Energy dispersive X-ray (EDX) spectroscopy further related the changes in electrical conductivity to the elemental spatial analysis of gold and bromine in the KAuBr4-doped CNT samples before and after 400 °C thermal oxidation. This work concludes that the thermal stability of KAuBr4 results in improved electrical conductivity and stability at high current densities. Trace bromine and gold nanoparticles are maintained at temperatures below the onset of CNT degradation, thus providing residual doping until ultimate CNT wire failure.Recently chemical dopants such as I2 and IBr have also emerged as premiere dopants to improve the electrical conductivity of bulk CNT networks. These dopants will be used to further explore the effect doping procedures and the presence of excess dopant have on the electrical conductivity and high current stability of doped CNT wires. Developing a relationship between dopant thermal stability and electrical conductivity retention will allow for the development of a mechanism explaining dopant degradation at high current densities.

Enhanced copper–carbon nanotube hybrid conductors with titanium adhesion layer

Cu–carbon nanotube (CNT) hybrids combine the advantages of the high electrical conductivity of Cu with the low temperature coefficient of resistance for CNTs, but require enhanced interfacing to improve the electrical performance when exposed to elevated temperatures. Herein, Ti and Ni were investigated as adhesion metals by thermally evaporating 10 nm layers onto a CNT conductor. SEM analysis shows Ni deposits as discrete nanoscale crystallites which coalesce after annealing to 400 °C in H2/Ar. Ti deposits uniformly along the CNT surface and is stable over such temperatures. A 100 nm deposition of Cu is shown to delaminate from the CNTs after annealing, and the resistance per length (R/L) increases by 40%. The Cu–Ni–CNT exhibits a 125% increase, while the Cu–Ti–CNT achieves a 12% decrease in R/L, for similar annealing conditions. Thus, Ti emerges as an effective adhesion metal, warranting its use in metal–CNT wire technologies for elevated temperature operation.

Strong, lightweight, and highly conductive CNT/Au/Cu wires from sputtering and electroplating methods

In this study, we present a 2-step deposition method via sputtering and electroplating that uses carbon nanotube (CNT) wires synthesized from a wet-spinning technique to produce high-performance CNT/Au/Cu composite wires. After the Au sputtering pre-treatment, the deposition of Cu on the CNT wires was found to be much more homogeneous due to improved wettability and reactivity of the wire surface. At different electrodeposition time, the mechanical strength of the CNT/Au/Cu composite wires could be as high as 0.74 GPa (∼ 2 times stronger than metal wires) while their electrical conductivity could reach 4.65 × 105 S/cm (∼ 80% of that for copper). More importantly, the CNT/Au/Cu composite wires with high CNT volume fraction are expected to be lightweight (up to 42% lower than Cu mass density), suggesting that our high-performance composite wires are a promising candidate to substitute conventional heavy metal wires in the future applications.

Sustaining Enhanced Electrical Conductivity in KAuBr4-Doped Carbon Nanotube Wires at High Current Densities

Densification and chemical doping with KAuBr4 are shown to improve the electrical conductivity of commercially scaled CNT wires by a factor of 6 to values greater than 1 MS/m, while increasing the ...

A double-walled carbon nanotubes conducting wire prepared by dip-coating

Carbon nanotube (CNT) wires and cables with low electrical resistivity were synthesized through a wet chemical method (dip-coating) which is inspired from the commercial metal cable production. The double-walled carbon nanotube (DWCNT) wire is composed of a Polytetrafluoroethylene (PTFE) core, a DWCNT layer coated on PTFE surface and an exterior polyimide (PI) insulating layer. The results showed that the optimal concentration of DWCNT paste for dip-coating is between 1.8 wt% and 2.0 wt%. The direction of the DWCNTs in the conducting layer is substantially oriented along with the drawing direction. The coating layer is even and the thickness of DWCNT layer is around 90 μm. And the corresponding resistivity of obtained CNTs wire is about 8.2 × 10−6 Ω·m. After treatment with iodine, its resistivity could be reduced by about 50%, reaches to 4.5·10−6 Ω·m. More importantly, the coating of PI insulation layer results in DWCNT layer densification without reducing its electrical conductivity.

High temperature performance of coaxial h-BN/CNT wires above 1,000 °C: Thermionic electron emission and thermally activated conductivity

The development of wires and cables that can tolerate extremely high temperatures will be very important for probing extreme environments, such as in solar exploration, fire disasters, high-temperature materials processing, aeronautics and astronautics. In this paper, a lightweight I high-temperature coaxial h-boron nitride (BN)/carbon nanotube (CNT) wire is synthesized by the chemical vapor deposition (CVD) epitaxial growth of h-BN on CNT yarn. The epitaxially grown h-BN acts as both an insulating material and a jacket that protects against oxidation. It has been shown that the thermionic electron emission (1,200 K) and thermally activated conductivity (1,000 K) are two principal mechanisms I for insulation failure of h-BN at high temperatures. The thermionic emission of h-BN can provide the work function of h-BN, which ranges from 4.22 to 4.61 eV in the temperature range of 1,306-1,787 K. The change in the resistivity of h-BN with temperature follows the ohmic conduction model of an insulator, and it can provide the "electron activation energy" (the energy from the Fermi level to the conduction band of h-BN), which ranges from 2.79 to 3.08 eV, corresponding to a band gap for h-BN ranging from 5.6 to 6.2 eV. However, since the leakage current is very I small, both phenomena have no obvious influence on the signal transmission at the working temperature. This lightweight coaxial h-BN/CNT wire can tolerate 1,200 °C in air and can transmit electrical signals as normal. It is hoped that this lightweight high-temperature wire will open up new possibilities for a wide range of applications in extreme high-temperature conditions.

Carbon Nanotubes and Carbon Nanotube Structures Used for Temperature Measurement.

Accurate measurement of temperatures with low power consumption with the highest sensitivity and smallest possible elements is still a challenge. The thermal, electrical, and mechanical properties of carbon nanotubes (CNTs) have suggested that their use as a very sensitive sensing element will allow the creation of different sensors, far superior to other devices of similar size. In this paper, we present a short review of different constructive designs of CNTs based resistive sensors used for temperature measurement, available in literature, assembled using different processes, such as self-assembly, drop-casting from a solution, thin films obtained by gluing, printing, spraying, or filtration over a special membrane. As particular cases, temperature sensors obtained from CNT-polymer nanocomposite structures, CNTs filled with uniformly dispersed Fe3O4 nanoparticles or with gallium, and carbon nanotube wires (CNWs) hybrids are presented. Using these preparation procedures, mixtures of CNTs with different dimensions and chirality, as well as with a variable level of impurities and structural defects, can be produced. The sensors’ performance charts are presented, highlighting a number of aspects regarding the applicability of CNT structures for temperature measurement ranging from cryogenic temperatures to high temperatures, the limitations they have, their characteristics and advantages, as well as the special situations that may arise given the particular structure of these new types of materials, together with basic relationships and parameters for CNTs characterization. Further research will be required to develop the techniques of manipulating and depositing individual CNTs on supports and electrodes for the development of temperature sensors.

(Invited) Synthesis and Properties of All SWCNT Metallic Nanotube Wire

Copper and aluminum wire conductors are the principal means of conducting electricity. However, they add weight, possess poor fatigue and corrosion resistance and suffer from electromigration under severe conditions. Carbon nanotube (CNT) conductors have long been thought able to replace metals but still fall short of copper in electrical conductivity. CNT wires have so far displaced metal conductors in only a few high value-added applications. In this presentation, we outline an approach to create CNT conductors that address copper shortcomings. These carbon-based wires are made by a new high rate process to grow all metallic (armchair) CNT single wall tubes which are spun into wire in situ within the reactor all in one step, thereby keeping air away from the contacting surfaces of the tubes. We discuss a model of growth in terms of entropy of formation and radiation induced sympathetic vibration. In all other CNT yarn formation methods known to us, multistep processes are required which add cost or omit spinning. This latter process is necessary to add strength and improve conductivity. The innovations described in this talk include (1) methods for synthesis of nearly all metallic single chirality carbon nanotubes, and (2) the in situ spinning of these nanotubes within the reactor to a finished wire. We describe their properties determined by Raman, TGA, and structure by SEM and TEM. The conductivity of CNT wires depends on CNT alignment, surface contamination, control over the interfaces (Schottky barriers), and density. Yarns made from nanotubes of exactly the same diameters are also expected to pack well in the wire and provide better properties than the more typical random and larger diameters sometimes made. The combination of Boronite’s approach to create all CNT wire from uniform nanotubes with metallic chirality with the increasing commercial pressure to reduce weight, increase strength, and operational temperature, opens up commercial opportunities for very lightweight wiring in applications from aircraft to rotating machinery used at high temperatures. Weight saving in a variety of products is especially important for aircraft, cars, and even for large electric systems required to deliver very high current pulses. Boronite has also developed a unique method for infiltrating CNT spun yarn with copper, silver or aluminum to create electromigration resistant materials that can carry extreme currents.

Interwoven Carbon Nanotube Wires for High-Performing, Mechanically Robust, Washable, and Wearable Supercapacitors.

An energy storage system with large storage capacity, rapid power release, and simultaneous tolerance to harsh mechanical stresses is a major bottleneck for realizing self-sustaining, wearable electronics. Addressing this, we demonstrate carbon nanotube wire (CNT-wire) interwoven solid-state supercapacitive energy storage devices (sewcaps) exhibiting superior storage capacity (30 Wh/kg, compared to electrochemical capacitors at ∼10 Wh/kg) and 14-fold higher power density (3511 W/kg) compared to Li-ion batteries (∼250 W/kg). While the high specific surface area and electrical conductivity of CNT-wires and high ionic conductivity of the electrolyte enable high energy density, the device design enables the combination of planar and radial diffusive pathways for ultralow interface resistance (∼0.2 mΩ/sewcap) and rapid charging-discharging ability (τ = 1.16 ms). Thus, this versatile approach of interweaving to form functional devices provides tunable power delivery across six orders of magnitude (2 μW to 2 W) through reconfiguration of the interweaving pattern and density. Importantly, such textile-integrated sewcaps exhibit unaltered performance (>95% retention across 4000 charge-discharge cycles) under extreme mechanical punishments such as repeated laundering, flexing (∼68°), rolling (360°), and crushing (∼21.8 kPa), implying direct interfacing with wearable platforms.