Few-walled Nanotubes Research Articles

Nanotubes and other allotropic carbon forms by chemical vapor deposition on an inconel surface

Allotropic carbon forms such as fullerenes, nanotubes and graphenes, have received a notable attention by the scientific community due to their unique configuration and interesting chemical and physical properties. In this respect, in this work, carbon nanotubes were synthesized through chemical vapour deposition. The reaction was carried out in tubular furnace by the catalytic reaction of ferrocene/ethanol solution onto an Inconel 600 surface and by the variation on the synthesis conditions for their production. The presence of double- and few-walled nanotubes grown in bundle arrays was observed. However, additionally, the presence of other carbon structures such as graphenes, graphitic onions and graphene nanoribbons were observed through electronic microscopy.

Boron-doped few-walled carbon nanotubes: novel synthesis and properties

Few-walled carbon nanotubes offer a unique marriage of graphitic quality and robustness to ink-processing; however, doping procedures that may alter the band structure of these few-walled nanotubes are still lacking. This report introduces a novel solution-injected chemical vapor deposition growth process to fabricate the first boron-doped few-walled carbon nanotubes (B-FWNTs) reported in literature, which may have extensive applications in battery devices. A comprehensive characterization of the as-grown B-FWNTs confirms successful boron substitution in the graphitic lattice, and reveals varying growth parameters impact the structural properties of B-FWNT yield. An investigation into the optimal growth purification parameters and ink-making procedures was also conducted. This study introduces the first process technique to successfully grow intrinsically p-doped FWNTs, and provides the first investigation into the impact factors of the growth parameters, purification steps, and ink-making processes on the structural properties of the B-FWNTs and the electrical properties of the resulting spray-coated thin-film electrodes.

Atomistic origin of radial corrugation in a few-walled carbon nanotubes: A molecular dynamics study

We perform molecular dynamics simulations of a few-walled (with 3–4 walls) carbon nanotubes using empirical interatomic potential. We demonstrate that the radial corrugation occurs in such thin nanotubes under hydrostatic pressure, which is apparently similar to the corrugation in thicker (e.g., several tens-walled) nanotubes that had been predicted using continuum mechanics approximation. The mechanism underlying the corrugation of a few-walled nanotubes, however, is found to be much distinct from thick nanotubes; i.e., the sp3 bonds between adjacent concentric walls and registry of atom arrangement take important roles in the formation and stabilization of corrugation modes in a few-walled nanotubes.

Effect of swift heavy ion irradiation on single- and multiwalled carbon nanotubes

The effect of irradiation with swift heavy ions on the structure and properties of carbon nanotubes was investigated by Raman spectroscopy. It was found that disordering of the system occurred mainly at the surface. No ordering phenomena have been observed over a whole range of both fluences and electronic stopping powers studied. The disorder parameter (i.e., the ratio of the D and G band intensities (ID/IG)) increases non-linearly with the irradiation dose, showing a tendency to saturate at high fluences. The increase in the disorder parameter upon irradiation was proportional to the square root of the ion fluence. The radiation stability of the few-walled nanotubes was ca. 1.6 higher than that of the single-walled ones. The irradiation with both the Xe and Kr ions leads to essentially the same increase in the ID/IG ratio with respect to the deposited electronic energy density. In the case of the Ar ion irradiation, the observed increase in the ID/IG ratio is much lower, suggesting that the electronic stopping power threshold for defects creation in carbon nanotubes is lower than that for graphite.

High temperature structural transformations of few layer graphene nanoribbons obtained by unzipping carbon nanotubes

Multilayer and few layer graphene nanoribbons produced by oxidative unzipping of carbon multiwalled carbon nanotubes (MWNT 10 > N > 5) and N ≤ 4 carbon few walled nanotubes (FWNT) were annealed at temperatures up to 1400 °C and the resulting carbon nanostructures were studied. Transmission electron microscopy imaging of the graphene nanoribbons annealed in bulk shows higher structural stability in larger width multilayer graphene nanoribbons than in narrow few layer nanoribbons. Fringes of dark and bright contrast along the edges of MLG indicate edge closure within the layers of the stacked graphene nanoribbons. On the other hand, narrow FLG nanoribbons fuse within each other or collapse when annealed leading to three different nanostructures: large area MLG plates several microns wide, graphitic onions of approximately 100 nm in diameter and nanocrystalline/amorphous composite particles.

Ultrastrong, Foldable, and Highly Conductive Carbon Nanotube Film

Preparation of strong, flexible, and multifunctional carbon-based films has attracted considerable interest not only in fundamental research areas but also for industrial applications. We report a binder-free, ultrastrong, and foldable carbon nanotube (CNT) film using aligned few-walled nanotube sheets drawn from spinnable nanotube arrays. The film exhibits tensile strengths up to ∼2 GPa and a Young's modulus up to ∼90 GPa, which is markedly superior to other types of carbon-based films reported, including commercial graphite foils, buckypapers, and graphene-related papers. The film can bear severe bending (even being folded) and shows good structure integrity and negligible change in electric conductivity. The unique structure of the CNT film (good nanotube alignment, high packing density) provides the film with direct and efficient transport paths for electricity. As a flexible charge collector, it favors a magnesium oxide coating to exhibit high charge/discharge rate stability and an excellent electrochemical capacitance close to its theoretical value.

Calculation of the sizes of individual few-walled carbon nanotubes and their bundles

The temperature dependences of the number of nucleating single-walled and few-walled nanotubes and their diameter have been determined over a wide range of model parameters in the framework of the problem regarding the nucleation of carbon nanotubes from catalytic particles supersaturated with carbon. It has been demonstrated that, initially, individual nanotubes nucleate and grow and, then, they can be joined together into bundles. The mechanism of the formation of bundles in the proposed model follows from the quantum-chemical analysis of the steady-state growth of nanotubes at the level of release of individual carbon atoms. During the growth, the axis of the nanotube rotates about the normal to the surface of the catalytic particle. This leads to the cross-linking of nanotubes into bundles. The characteristic diagram of the regions of the existence of individual single-walled, few-walled, and multiwalled nanotubes and their bundles has been constructed as a function of the temperature and the size of catalytic particles.

Investigation of Optimal Parameters for Oxide-Assisted Growth of Vertically Aligned Single-Walled Carbon Nanotubes

An investigation into the optimal growth of single-walled carbon nanotubes (SWNTs) in vertical arrays, or carpets, is presented utilizing atomic hydrogen catalyst activation with hot filament chemical vapor deposition. Using acetylene decomposition over Fe catalyst, we study the effect of oxidant-assisted growth using O2, CO2, and H2O. Whereas trace amounts of O2 result in the lack of any catalytic activity, CO2 and H2O are found to dramatically enhance the catalyst lifetime. On the basis of the saturation effect of oxidant concentration for both CO2 and H2O, we present this as being due to catalyst stabilization from surface hydroxyl groups, with H2O having the most dominant effect upon carpet growth. Utilizing water-assisted growth, this process is further optimized to yield high-quality single-walled carbon nanotubes. High temperature growth (∼775 °C) yields the highest-quality SWNTs, whereas controllable growth of double- and few-walled nanotubes can also be achieved at lower temperatures (550−600 °C)...

Effect of ion bombardment on the synthesis of vertically aligned single-walled carbonnanotubes by plasma-enhanced chemical vapor deposition

The synthesis of vertically aligned single-walled carbon nanotubes (VA-SWNTs)by plasma-enhanced chemical vapor deposition (PECVD) was achieved at500–600 °C, using ethylene as the carbon source and 1 nm Fe film as the catalyst. For growth ofhigh-quality VA-SWNTs in a plasma sheath, it is crucial to alleviate the undesirable ionbombardment etching effects by the optimization of plasma input power and gas pressure.The resistibility of synthesized VA-SWNTs against ion bombardment etching was foundto be closely related to the growth temperature. At relatively low temperature(500 °C), the VA-SWNTs were very susceptible to ion bombardments, which could inducestructural defects, and even resulted in a structural transition to few-walled nanotubes. Forcapacitively coupled radio frequency (rf) PECVD operating at moderate gas pressure(0.3–10 Torr), the ion bombardment etching effect is mainly dependent on the ion flux,which is related to the plasma input power and gas pressure.

Impact of the etching gas on vertically oriented single wall and few walled carbon nanotubes by plasma enhanced chemical vapor deposition

Vertically oriented single wall nanotubes (SWNTs) and few walled nanotubes (FWNTs) have been grown by electronic cyclotron resonance plasma enhanced chemical vapor deposition (PECVD) on silica flat substrates. The impact of the plasma parameters on SWNT and FWNT growth has been investigated using two different etching gas mixtures, namely, C2H2∕NH3 and C2H2∕H2 with various ratios and applied bias voltages. Kinetic studies are also proposed in order to describe the FWNT growth mechanism by plasma techniques. A key role played by the reactive gas (NH3 and H2) is observed in the PECVD process, contrary to multiwalled nanotube growth. It is demonstrated that the balance between FWNT growth versus FWNT etching can be widely modulated by varying the gas mixture and bias voltage. It is shown that the use of hydrogen for hydrocarbon gas dilution restricts the destruction of SWNT and FWNT by the plasma species (ions and radicals).

Physical Modeling of Temperature Coefficient of Resistance for Single- and Multi-Wall Carbon Nanotube Interconnects

Equivalent circuit models are presented for the resistance of single- and multi-wall carbon nanotubes (MWCNs) that capture various electron-phonon scattering mechanisms as well as changes in the number of conduction channels as a function of temperature. For single- and few-wall nanotubes, the temperature coefficient of resistance (TCR) is always positive and increases with length. It reaches 1/(T-200 K) for lengths much larger than the electron mean free path, where T is the temperature in kelvin. For MWCNs with large diameters (>20 nm), TCR varies from -1/T to +0.66/(T-200 K) as the length varies from zero to very large values

Growth kinetics of low temperature single-wall and few walled carbon nanotubes grown by plasma enhanced chemical vapor deposition

Single-wall, double walled or few walled nanotubes (FWNT) are grown by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) at temperature as low as 600 °C. Most of these structures are isolated and self-oriented perpendicular to the substrate. The growth mechanism observed for single-wall and few walled (less than seven walls) nanotubes is the “base-growth” mode. Their grow kinetics is investigated regarding two parameters namely the growth time and the synthesis temperature. It is shown that nucleation and growth rate is correlated with the number of walls into FWNT. It also provides an evidence of a critical temperature for FWNT synthesis.