Ropes Of Single-walled Carbon Nanotubes Research Articles

Giant nanomechanical energy storage capacity in twisted single-walled carbon nanotube ropes

AbstractA sustainable society requires high-energy storage devices characterized by lightness, compactness, a long life and superior safety, surpassing current battery and supercapacitor technologies. Single-walled carbon nanotubes (SWCNTs), which typically exhibit great toughness, have emerged as promising candidates for innovative energy storage solutions. Here we produced SWCNT ropes wrapped in thermoplastic polyurethane elastomers, and demonstrated experimentally that a twisted rope composed of these SWCNTs possesses the remarkable ability to reversibly store nanomechanical energy. Notably, the gravimetric energy density of these twisted ropes reaches up to 2.1 MJ kg−1, exceeding the energy storage capacity of mechanical steel springs by over four orders of magnitude and surpassing advanced lithium-ion batteries by a factor of three. In contrast to chemical and electrochemical energy carriers, the nanomechanical energy stored in a twisted SWCNT rope is safe even in hostile environments. This energy does not deplete over time and is accessible at temperatures ranging from −60 to +100 °C.

Processing of Single-Walled Carbon Nanotubes with Femtosecond Laser Pulses

There are continued efforts to process and join single wall carbon nanotubes (SWCNTs) in order to exploit their exceptional functional properties for real-world applications. In this work, we report experimental observations of femtosecond laser irradiation on SWCNTs, in order to process and join them through an efficient and cost-effective technique. The nanotubes were deagglomerated in ethanol by an ultrasonicator and thin slurries of SWCNTs were spread evenly on glass substrates. A laser micromachining workstation for laboratory FemtoLAB (workshop of photonics) has been employed to irradiate the different SWCNTs film samples. The effect of laser parameters, such as pulse wavelength, laser power, etc., were systematically tuned to see the possibility of joining the SWCNTs ropes. Several experiments have been performed to optimize the parameters on different samples of SWCNTs. In general, the nanotubes were mostly damaged by the infrared (1st harmonics femtosecond laser) irradiation on the focal plane. However, the less damaging effect was observed for second harmonics (green wavelength) irradiation. The results suggest some joining of nanotubes along the sides of the focus plane, as well as on the center at the brink of nanotubes. The joining is considered to be established within the region of the high field intensity of the exposed femtosecond laser beam.

Electrical conduction in aluminum nitride-single-walled carbon nanotube nanocomposites

Analysis of the temperature dependence of electrical conductivities of aluminum nitride (AlN)-single walled carbon nanotube (SWCNT) ceramic nanocomposite containing 1, 3 and 6 vol% SWCNT has been reported in this communication. A conductivity as high as 200 Sm−1 in the composite containing 6 vol% SWCNT has been explained with the low hopping parameter and high metallic conduction in three dimensions due to the presence of large quantity of metallic SWCNTs in the composite. Microstructure analyses of the composites reveal the presence of nets containing SWCNT ropes oriented in different directions and forming highly connected 3D networks in the grain boundaries.

Enhanced thermoelectric performance of Bi2Te3 through uniform dispersion of single wall carbon nanotubes

The advancement in nanostructured powder processing has attracted great interest as a cost effective and scalable strategy for high performance thermoelectric bulk materials. However, the level of technical breakthrough realized in quantum dot supperlattices/wires has not yet been demonstrated in these materials. Here, we report the first ever study on the uniform dispersion of single wall carbon nanotubes (SWCNTs) in nanostructured Bi2Te3 bulk, and their effect on thermoelectric parameters above room temperature. The Bi2Te3 based SWCNT composites were prepared through controlled powder processing, and their thermoelectric properties were finely tuned at the nanoscale by regulating various (0.5, 0.75, 1.0 and 1.5) vol% of SWCNTs in the matrix. The flexible ropes of SWCNT, making an interconnected network through the inter/trans granular positions of Bi2Te3, thus substantially change the transport properties of the composites. The perfect one-dimensional (1D) conducting structure of SWCNTs acts as a source of electrical transport through a percolating network, with significantly suppressed lattice thermal conductivity, via intensified boundary scattering. The remarkable increase in power factor is ascribed to energy filtering effects and excellent electrical transport of 1D SWCNTs in the composites. Consequently, with a considerable reduction in thermal conductivity, the figure of merit culminates in a several-fold improvement, at 0.5 vol% of SWCNTs, over pristine bulk Bi2Te3.

Momentum angular mapping of enhanced Raman scattering of single-walled carbon nanotube

We perform momentum mapping of the Raman scattering of individual single-walled carbon nanotubes (SWNTs) or thin ropes of SWNTs enhanced by surface plasmons sustained by either a linear chain of nanoantennas or flower-shaped nanoparticles. The momentum spectroscopy of Raman scattering of the carbon nanotube (CNT) demonstrates the direct verification of momentum selection rules and identifies the characteristic bands of the molecules or the nanomaterials under scrutiny. The characteristic vibrational signatures of the D, G−, and G bands provide an isotropic response in k-space irrespective of the arrangement of the enhancing platform. However, other dispersive or double resonance bands, such as D−, D+, D′, M, and iTOLA bands appear as a dipolar emission oriented towards the long axis of the CNT regardless of the CNT orientation but strongly depend on the patterning of enhancement of the electromagnetic field.

Radiofrequency electric-field heating behaviors of highly enriched semiconducting and metallic single-walled carbon nanotubes

It is theorized that enhanced thermal heating may result from exposing single-walled carbon nanotubes (SWNTs) embedded in a conductive host to radiofrequency (RF) electric fields. We examine the RF-induced (13.56 MHz) heating behaviors of 95% metallic- and semiconducting-enriched SWNTs (m-/s-SWNTs) suspended in aqueous solutions with varying NaCl molarity (0.001 mM–1 M). The heating effects were only evident for host molarities below 1 mM (equivalent to 0.1 S/m) at which the s-SWNT heating rates dominated those of the m-SWNTs. The heating effects were localized to aligned and aggregated “SWNT ropes” ~1 cm in length that formed in suspension, parallel to the electric-field vector, during the RF exposure. For molarities above 1 mM, no enhancements were evident, owing to the large heating effects of the bulk ionic NaCl suspensions, which were observed in previous studies. Although larger enhancement effects proportional to the host conductivity have been theoretically predicted for m-/s-SWNT suspensions, this was not observed most likely because of the aggregation and screening effects, which diminished the scattered electric field near the m-/s-SWNTs. Our research may further the development of better nanoparticle heating agents for applications such as non-invasive RF-induced cancer hyperthermia.

Realizing one-dimensional quantum and high-frequency transport features in aligned single-walled carbon nanotube ropes

The superiority of the electronic transport properties of single-walled carbon nanotube (SWNT) ropes over SWNT mats is verified from low temperature and frequency-dependent transport. The overall change of resistance versus in nanotube mats shows that 3D variable range hopping is the dominant conduction mechanism within the 2–300 K range. The magneto-resistance (MR) is found to be predominantly negative with a parabolic nature, which can also be described by the hopping model. Although the positive upturn of the MR at low temperatures establishes the contribution from quantum interference, the inherent quantum transport in individual tubes is suppressed at elevated temperatures. Therefore, to minimize multi-channel effects from inter-tube interactions and other defects, two-terminal devices were fabricated from aligned SWNT (extracted from a mat) for low temperature transport as well as high-frequency measurements. In contrast to the mat, the aligned ropes exhibit step-like features in the differential conductance within the 80–300 K temperature range. The effects of plasmon propagation, unique to one dimension, were identified in electronic transport as a non-universal power-law dependence of the differential conductance on temperature and source-drain voltage. The complex impedance showed high power transmission capabilities up to 65 GHz as well as oscillations in the frequency range up to 30 GHz. The measurements suggest that aligned SWNT ropes have a realistic potential for high-speed device applications.

Rings and rackets from single-wall carbon nanotubes: manifestations of mesoscale mechanics.

We combine experiments and distinct element method simulations to understand the stability of rings and rackets formed by single-walled carbon nanotubes assembled into ropes. Bending remains a soft deformation mode in ropes because intra-rope sliding of the constituent nanotubes occurs with ease. Our simulations indicate that the formation of these aggregates can be attributed to the mesoscopic mechanics of entangled nanotubes and to the sliding at the contacts. Starting from the single-walled carbon nanotubes, the sizes of the rings and rackets' heads increase with the rope diameter, indicating that the stability of the experimental aggregates can be largely explained by the competition between bending and van der Waals adhesion energies. Our results and simulation method should be useful for understanding nanoscale fibers in general.

Thermoelectric Power of a Single-Walled Carbon Nanotubes Rope

In this work, a rope of single-walled carbon nanotubes is prepared by using a diamond wire drawing die. At atmospheric condition, the electrical conductance and the thermoelectric voltage of single-walled carbon nanotubes rope have been investigated with the hot-side temperature ranging from 292 to 380 K, and cold-side temperature at 292 K. For different temperatures in the range of 292 to 380 K at hot-side, the current-voltage curves are almost parallel to each other, indicating that the electrical conductance does not change. The dynamic characteristics of voltage at positive, zero and negative current bias demonstrate that a thermoelectric voltage is induced with a direction from hot- to cold-side. The induced thermoelectric voltage shows linear dependence on the temperature difference between hot- and cold-side. The thermoelectric power of single-walled carbon nanotubes rope is found to be positive and has a value about 17.8 +/- 1.0 microV/K. This result suggests the hole-like carriers in single-walled carbon nanotubes rope. This study will pave the way for single-walled carbon nanotubes based thermoelectric devices.

On the Thermal Conductivity of Single-Walled Carbon Nanotube Ropes

Recently measured thermal conductivity in single-walled carbon nanotube ropes in the temperature range 8 - 350 K has been explained using an anisotropic dynamical model which not only takes into account the quasi two-dimensional nature of the folded graphene sheets that forms the nanotubes, but also the intertube coupling, in addition to the phonon frequency and dimensionality dependent relaxation time of phonon-phonon scattering and interaction.

Suspended SWNT electrode with nanosize gaps

Abstract We report a robust method to fabricate a single walled carbon nanotube (SWNT) electrode array with nanosize gaps. As a first step, several SWNTs are suspended between a pair of preformed gold electrodes utilizing dielectrophoresis (DEP) and turned into a rope configuration by capillary densification during drying process. Electrical breakdown is followed to make a gap in the SWNT rope and the dimension of the gap can be controlled by the bias sweep rate. When an electric voltage is applied to the SWNT rope, electrical joule heating increases the temperature, oxidizes the SWNT, and the rope eventually breaks at the midpoint. The SWNT electrodes are successfully fabricated with gaps in the range of 1–60 nm by controlling the bias sweep rate. As a demonstration in nanoscale electronics, the electrical resistance of fullerene (dimension of ∼1 nm) is measured by capturing it between the SWNT electrodes with one nanometer gap.

Aligned carbon nanotube, graphene and graphite oxide thin films via substrate-directed rapid interfacial deposition

A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated.

Self-Supporting Electrode Based-on SWNT Paper for Supercapacitors

Self-supporting film of single-walled carbon nanotubes (SWNTs), also known as SWNT paper, is held together by Van der Waals force without any chemical binders. Prepared by vacuum filtration method, SWNT paper was then decorated wirh polypyrrole (PPy) through pulsed potentio amperometric polymerization. The results indicated that the SWNT paper had a typical network structure, after polymerizing PPy, cauliflower-like structure was observed on the surface of SWNT ropes. The composite thin film has good cyclic voltammetry (CV) property and the specific capacitance wass ca.420Fg-1, which was much larger than that of pure SWNT paper.

Direct transition of potential of water droplets to electric energy using aligned single-walled carbon nanotubes

In this paper, we report that an electromotive force (EMF) can be induced in a rope of aligned single-walled carbon nanotubes (SWNTs) when water droplets fall on this rope. The magnitude of this EMF depends sensitively on the slant angle of the SWNTs. Most interestingly, both the magnitude and the direction of the induced EFM can be modulated by applying a current to the SWNTs. The concepts of electrical slip and no-slip are proposed and can be quantitatively described by “electrical slip resistance". This kind of generator does not need any magnet, rotor, etc and shows quite a different operating mechanism and design compared with a conventional large scale hydroelectric power generator.

Nondestructive purification of single-walled carbon nanotube rope through a battery-induced ignition and chemical solution approach

A two-step method for the purification of single-walled carbon nanotube (SWCNT) rope containing substantial catalyst particles embedded in carbonaceous shells was developed. The first step was the triggering of rope ignition using a 9-V battery, which resulted in pre-oxidization of the carbon shells on the Fe3C catalyst and oxidation of the exposed Fe3C to form Fe2O3. In addition, SWCNTs with open-end structures due to ignition-induced cutting remained. In the second step, both oxalic acid (H2C2O4) and hydrochloric acid (HCl) were used as the reactants to remove the Fe2O3 particles. No damage on the SWCNT walls after H2C2O4 or HCl purification was found. In addition, adsorption of H2C2O4 was also found on the H2C2O4 purified SWCNT rope and it can be effectively removed by heating the rope at 200°C in vacuum for 40min. Samples were characterized by SEM, TEM, Raman spectroscopy, TGA, FTIR, XPS, and UV–Vis–NIR.

Oscillation induced worm-like locomotion of carbon nanotubes

Harmonic oscillation of a doubly clamped single-walled carbon nanotube rope is significantly damped by the resistive force of friction at intertube contacts and the energy transmission rate has been estimated to be lower than that on a metal wire excited at similar frequency and vibrating length by one order of magnitude.

Exploiting the effect of twisting on the electrical resistance of a single-walled carbon nanotube rope to trigger ignition using a 9-V battery

The effect of twisting on the electrical resistance of a raw single-walled carbon nanotube (SWCNT) rope was investigated and found to increase with increasing number of twists, varying from 28.7 Ω initially to 35.2 Ω after 12 twists. There are two reasons for this. One is that the twisting generated more contact points between the SWCNTs and catalytic nanoparticles, resulting in a high density of high local resistance points. The other is that the protrusion of SWCNTs in a rope twisted a large number of times (12–15 twists) partially interrupted the conducting path. By using a 9-V battery, ignition of the rope could be produced at a threshold resistance between 17.5 and 21.1 Ω, and this could be used to ignite ferrocene with the process lasting for several minutes.

Meissner effect in films of ropes of boron-doped single-walled carbon nanotubes; Correlation with applied pressure and boron-doped multi-walled nanotubes

Superconductivity in carbon nanotubes (CNTs) is attracting considerable attention. Recently, we have reported successful boron doping into single-walled CNTs (SWNTs) and also revealed its correlation with superconductivity. In the present study, we report results of pressure-applied magnetization measurements in films consisting of ropes of boron-doped SWNTs. It reveals that Tc and magnitude for Meissner effect is mostly independent of applied pressure, while magnitude of graphite diamagnetism drastically increases as pressure increases. We also report result of resistance measurements in the samples and also correlation of boron doped SWNTs with multi-walled CNTs, in which we reported superconductivity previously.

Pressure dependence of Meissner effect in films of ropes of boron-doped carbon nanotubes

Superconductivity in carbon nanotubes (CNTs) is attracting considerable attention. Recently, we have reported successful boron doping into single-walled CNTs (SWNTs) and also revealed its correlation with superconductivity. In the present study, we report results of high-pressure magnetization measurements in films consisting of ropes of boron-doped SWNTs. It reveals that T c and magnitude for Meissner effect are mostly independent of applied pressure, while the magnitude of graphite diamagnetism drastically increases as pressure increases. We also report the observation of resistance drop and correlation of boron doping with multi-walled CNTs, in which we reported superconductivity previously.

Ab initiostudy of the dielectric response of crystalline ropes of metallic single-walled carbon nanotubes: Tube-diameter and helicity effects

The dielectric-response functions of crystalline ropes of metallic single-walled carbon nanotubes were determined from time-dependent density-functional theory in the random-phase approximation. Interband transitions and plasmonic excitations were studied as a function of momentum transfer. The impact of the tube diameter was shown for the $(n,n)$ armchair-type series ($n$ ranging from 3 to 8) covering a diameter range from 4 to $11\text{ }\text{\AA{}}$. Helicity effects were examined for the thinnest tubes, the armchair (3,3) versus the zigzag (5,0) configurations. Our results give detailed insight into the various kinds of excitations that can be observed in ropes of nanotubes. Recent experimental findings and trends by electron energy loss and Raman spectroscopies are reproduced and explained.