Triple-walled Carbon Nanotubes Research Articles

Diamond Needles Actuating Triple-Walled Carbon Nanotube to Rotate via Thermal Vibration-Induced Collision.

A rotary nanomotor is an essential component of a nanomachine. In the present study, a rotary nanomotor from wedged diamonds and triple-walled nanotubes was proposed with the consideration of boundary effect. The outer tubes and mid-tubes were used as nanobearing to constrain the inner tube. Several wedges of the diamond were placed near the inner tube for driving the inner tube to rotate. At a temperature lower than 300 K, the inner tube as the rotor had a stable rotational frequency (SRF). It is shown that both the rotational direction and the value of SRF of the rotor depended on the temperature and thickness of the diamond wedges. The dependence was investigated via theoretical analysis of the molecular dynamics simulation results. For example, when each diamond wedge had one pair of tip atoms (unsaturated), the rotational direction of the rotor at 100 K was opposite to that at 300 K. At 500 K, the rotating rotor may stop suddenly due to breakage of the diamond needles. Some conclusions are drawn for potential application of such a nanomotor in a nanomachine.

Instabilities of SWCNT conveying laminar, incompressible and viscous fluid flow

PurposeThis study aims to study the transverse vibration and instabilities of the fluid-conveying single-walled carbon nanotubes (CNTs). To this purpose, the Euler–Bernoulli beam model is used. Also, the surface effects, small-size effects of the both fluid and structure and two different elastic mediums viscoelastic and Pasternak elastic are investigated.Design/methodology/approachTo consider the nano-scale for the CNT, the strain-inertia gradient theory is used and to solve the governing equation of motion for the system, the Galerkin’s method is used. The effect of the flow velocity, aspect ratio, characteristic lengths of the mentioned theory, effects of Knudsen number and effects of the Winkler, the Pasternak elastic and the viscoelastic medium on the frequencies and stabilities of the system are studied. The effects of the above parameters on the vibrational behavior are investigated both separately and simultaneously.FindingsThe results show that the critical flow velocity value is increased as the aspect ratio, characteristic lengths, Winkler modulus, shear and damping factors increase. Also, the critical flow velocity is increased by considering the surface effects. In addition, the consequence of increase in the nano-flow-size effects (Knudsen number) is decreasing the critical flow velocity. Moreover, it can be observed that the effect of the shear factor on increasing the critical flow velocity is different from the rest of parameters.Originality/valueUse of Timoshenko and modified couple stress theories and taking into account Von-Karman expressions for investigating the nonlinear vibrations of triple-walled CNTs buried within Pasternak foundation.

Numerical investigation of nonlinear vibration analysis for triple-walled carbon nanotubes conveying viscous fluid

PurposeThe purpose of this paper is to investigate nonlinear vibrations of triple-walled carbon nanotubes buried within Pasternak foundation carrying viscous fluids.Design/methodology/approachConsidering the geometry of nanotubes, the governing equations were initially derived using Timoshenko and modified couple stress theories and by taking into account Von-Karman expressions. Then, by determining boundary conditions, type of fluid motion, Knudsen number and, ultimately, fluid viscosity, the principal equation was solved using differential quadrature method, and linear and nonlinear nanotube frequencies were calculated.FindingsThe results indicated that natural frequency is decreased as the fluid velocity and aspect ratio increase. Moreover, as the aspect ratio is increased, the results converge for simple and fixed support boundary conditions, and the ratio of nonlinear to linear frequencies approaches. Natural frequency of vibrations and critical velocity increase as Pasternak coefficient and characteristic length increase. As indicated by the results, by assuming a non-uniform velocity for the fluid and a slip boundary condition at Kn = 0.05, reductions of 10.714 and 28.714% were observed in the critical velocity, respectively. Moreover, the ratio of nonlinear to linear base frequencies decreases as the Winkler and Pasternak coefficients, maximum deflection of the first wall and characteristic length are increased in couple stress theory.Originality/valueThis paper is a numerical investigation of nonlinear vibration analysis for triple-walled carbon nanotubes conveying viscous fluid.

Theoretical analysis of chirality and scale effects on critical bucklingload of zigzag triple walled carbon nanotubes under axial compression embedded in polymeric matrix

Using the non-local elasticity theory, Timoshenko beam model is developed to study the non- local buckling of Triple-walled carbon nanotubes (TWCNTs) embedded in an elastic medium under axial compression. The chirality and small scale effects are considered. The effects of the surrounding elastic medium based on a Winkler model and van der Waals\'(vdW) forces between the inner and middle, also between the middle and outer nanotubes are taken into account. Considering the small-scale effects, the governing equilibrium equations are derived and the critical buckling loads under axial compression are obtained. The results show that the critical buckling load can be overestimated by the local beam model if the small-scale effect is overlooked for long nanotubes. In addition, significant dependence of the critical buckling loads on the chirality of zigzag carbon nanotube is confirmed. Furthermore, in order to estimate the impact of elastic medium on the non-local critical buckling load of TWCNTs under axial compression, the use of these findings are important in mechanical design considerations, improve and reinforcement of devices that use carbon nanotubes.

English

The main objective of this research is to estimate the critical temperature for triple-walled carbon nanotubes (CNTs)/epoxy resin. Critical temperature in this study is the temperature that inter-laminar shear stress in interfaces of triple-walled CNTs and epoxy resin is the maximum value. At maximum inter-laminar shear stress, the stress concentration between triple-walled CNTs and epoxy resin is the maximum. This phenomenon may cause crack initiation, propagation and fracture in fibers/matrix interfaces. In the presented study, this temperature is derived by applying analytical method. The results of this research showed that maximum inter-laminar shear stress could occur at 85°C, which appears to be the critical temperature. The results of this research could be applied in any industry dealing with thermal stress and thermal cycles. Key words: Critical temperature, triple-walled carbon nanotube (CNT), nanocomposites, thermal analysis, inter-laminar shear stress, coefficient of thermal expansion.

From high pressure radial collapse to graphene ribbon formation in triple-wall carbon nanotubes

The radial stability and the irreversible transformation of triple-wall carbon nanotubes (TWCNTs) bundles are investigated at high pressure conditions both experimentally and theoretically (exp. up 72 GPa). The tubes having a mean internal diameter of 0.83nm and graphite-like intertube distance, show an onset of the radial collapse evidenced by the evolution of optical phonons. The nanotube collapse onset is observed at ∼22 GPa completes for the two external tubes at ∼29 GPa, however the innermost tube remains stable up to ∼37 GPa. Molecular dynamic calculations performed on smaller diameter TWCNTs bundles, as a model system, confirmed the multiple-stage pressure-induced collapse process. An analytical expression for the collapse pressure of carbon nanotubes having an arbitrary number of walls is proposed. Our experiments and modelling show that for pressures beyond ∼ 60 GPa an irreversible structural transformation of TWCNTs takes place. Ex situ transmission electron microscopy characterization on the recovered sample from 72 GPa revealed the mechanical failure of carbon nanotubes which evolve towards ribbon-like structures as corroborated by Raman spectroscopy. Modelling the tubes evolution at high pressure and high temperature showed the formation of new structures ranging from ribbon-like to graphite-like with either different degrees of amorphization or sp3 interlinking.

Interface Characterization of Epoxy Resin Nanocomposites: A Molecular Dynamics Approach

In polymer nanocomposites, the interface region between the matrix and the fillers has been identified as a key interaction region that strongly determines the properties of the final material. Determining its structure is crucial from several points of view, from modeling (i.e., properties prediction) to materials science (i.e., understanding properties/structure relationships). In the presented paper, a method for characterizing the interface region of polymer nanocomposites is described using molecular dynamics (MD) simulations. In particular, the structure of the polymer within the interface region together with its dimension in terms of thickness were analyzed through density profiles. Epoxy resin nanocomposites based on diglycidyl ether of bisphenol A (DGEBA) were studied using this approach, and the interface region with triple walled carbon nanotubes (TWCNT) and carbon fibers (CF) was characterized. The effect of carbon nanotube diameter, type of hardener, and effect of epoxy resin cross-linking degree on interface thickness were analyzed using MD models. From this analysis no general rule on the effect of these parameters on the interface thickness could be established, since in some cases overlapping effects between the analyzed parameters were observed, and each specific case needs to be analyzed independently in detail. Results show that the diameter has an impact on interface thickness, but this effect is affected by the cross-linking degree of the epoxy resin. The type of hardener also has a certain influence on the interface thickness.

Coaxial carbon nanotubes: from springs to ratchet wheels and nanobearings

Quantum mechanical calculations are performed for double-walled and triple-walled carbon nanotubes (DWCNTs, TWCNTs). We show how the DWCNTs may be modelled by mechanical analogues with interactions mediated by spring forces with weakening elastic constants in addition to a weak van der Waals -like interaction. This enables us to predict the natural frequency of longitudinal oscillations of the DWCNTs, their elastic spring constant and the corresponding interaction between the CNTs. Results of the interaction energy ΔE for the DWCNT system obtained from the mechanical model are in remarkable agreement with those obtained from our quantum mechanical calculations, and we obtain functional dependencies of ΔE on axial elongation and inter-wall separation of the DWCNTs. Our density functional theory calculations reveal that the armchair-armchair systems are significantly more stable than both the corresponding armchair-chiral configurations, as well as the corresponding stacked graphene sheets. The results obtained for translational and rotational motion (slide / roll) of the CNTs indicate a potential use of DWCNTs as springs, ratchet wheels, nanogears and bearings in miniaturized devices. Our work enables us to predict the behavior of DWCNTs of different dimensions and would be of practical importance in the actual construction of nanoscale mechanical parts.

Accumulation of Electrolytic Hydrogen by Carbon Nanotubes

The accumulation of electrolytic hydrogen synthesized in a 5 M KOH solution by double- and triple-walled carbon nanotubes (CNTs) deposited on a steel membrane and encapsulated by an electrolytic iron layer of the thickness of 10 nm was studied. CNTs were synthesized by catalytic pyrolysis of methane and are characterized by an inner diameter of 2–4 nm, a length of up to 10 μm and more, and a specific surface area of 600–800 m2 g–1. The studies were performed by electrochemical diffusion, cyclic voltamperometry, and electrochemical-impedance spectroscopy. It has been shown that the hydrogen-storage capacity in CNTs varies in the range of 4–25% depending on the content of nanotubes in the composite.

High-yield synthesis of bundles of double- and triple-walled carbon nanotubes on aluminum flakes

High-quality double- and triple-walled carbon nanotubes have been synthesized using Fe−Co catalysts supported on aluminum flake powder. The diameters and lengths of the obtained nanotubes are in the ranges of 3–8 nm and 150–300 μm, respectively, and the specific surface area were quoted as 600 m2/g. The yield of the nanotubes synthesis relative to the initial weight of the catalyst is in the order of 1200%, with 70% of the resulting material consisting of thin carbon nanotubes with less than 6 nm of outer diameter and carbon purity of greater than 90%. Our results indicate that the use of aluminum as catalyst support have a profound effect in the formation of the metal nanoparticles. In addition to boost the reduction the catalyst precursors, the high chemical reactivity of metallic aluminum drives the thermal formation of an oxide layer on the Al surface that suppresses the diffusion and aggregation of catalyst nanoparticles. As a result, a simple impregnation method can be adopted to produce catalyst nanoparticles with narrow size distribution that are suitable for the growth of few wall carbon nanotubes at high yield and large scale.

On the buckling properties of concentric carbon/boron-nitride multi-walled nanotubes: A finite element investigation

ABSTRACTFinite element modeling approach is used here to investigate the behavior of concentric multi-walled boron-nitride and carbon nanotubes under the compressive loadings. Double-walled and triple-walled concentric boron-nitride and carbon nanotubes with different arrangements and geometries are considered. It is shown that multi-walled boron-nitride nanotubes lose their stabilities at larger compressive forces than other arrangements in which at least one carbon wall exists. Comparing the armchair and zig-zag multi-walled nanotubes, the latter one has larger buckling force than the former one. It is also shown that the nanotubes with smaller radii have larger critical compressive forces than those with larger radii.

Effect of Carbon Nanotubes on Direct Electron Transfer and Electrocatalytic Activity of Immobilized Glucose Oxidase.

Carbon nanotubes (CNTs) are excellent supports for electrocatalysts because of their large surface area, excellent electronic conductivity, and high chemical and structural stability. In the present study, the activity of CNTs on direct electron transfer (DET) and on immobilized glucose oxidase (GOX) is studied as a function of number of walls of CNTs. The results indicate that the GOX immobilized by the CNTs maintains its electrocatalytic activity toward glucose; however, the DET and electrocatalytic activity of GOX depend strongly on the number of inner tubes of CNTs. The GOX immobilized on triple-walled CNTs (TWNTs) has the highest electron-transfer rate constant, 1.22 s–1, for DET, the highest sensitivity toward glucose detection, 66.11 ± 5.06 μA mM–1 cm–2, and the lowest apparent Michaelis–Menten constant, 6.53 ± 0.58 mM, as compared to GOX immobilized on single-walled and multiwalled CNTs. The promotion effect of CNTs on the GOX electrocatalytic activity and DET is most likely due to the electron-tunneling effect between the outer wall and inner tubes of TWNTs. The results of this study have general implications for the fundamental understanding of the role of CNT supports in DET processes and can be used for the better design of more effective electrocatalysts for biological processes including biofuel cells and biosensors.

The formation mechanism of chiral carbon nanotubes

The nuclei and the formation mechanism of chiral carbon nanotubes, namely, single-, double-, and triple-walled carbon nanotubes are simulated by the first principle density functional theory. The formation mechanism from nuclei to corresponding infinitely long carbon nanotubes occurs spirally and via absorbing carbon atoms layer by layer. Carbon atoms at the open end are metastable state compared with ones in the tube wall or the closed end, which indicate the growth point of chiral carbon nanotubes is located at the open end. Growth of outer layer tubular clusters takes precedence over the inner layer in the process of forming multi-walled nuclear structures. Because of the ratio of carbon atoms at the open end to all carbon atoms decreases, the stability of the tubular clusters increases with their length. The infinitely long carbon nanotubes are obtained by executing periodic boundary conditions depend on corresponding nuclear structures.

Pressure-induced radial collapse in few-wall carbon nanotubes: A combined theoretical and experimental study

We study the pressure induced collapse of single-, double- and triple-wall carbon nanotubes. Theoretical simulations were performed using density-functional tight-binding theory. For tube walls separated by the graphitic distance, we show that the radial collapse pressure, Pc, is mainly determined by the diameter of the innermost tube, din and that its value significantly deviates from the usual Pc∝din−3 Lévy-Carrier law. A modified expression, Pcdin−3=α(1−β2∕din2) with α and β numerical parameters, which reduces the collapse pressure for low diameters is proposed. For din ≳ 1.5 nm an enhanced stability is found which may be assigned as due to the bundle intertube geometry-induced interactions. If the inner and outer tubes are separated by larger distances, the collapse process is found to be more complex. High-pressure resonant Raman experiments were performed in double-wall carbon nanotubes having inner and outer diameters averaging 1.5 nm and 2.0 nm, respectively. A modification in the response of the G-band and the disappearance of the radial breathing modes between 2 GPa and 5 GPa indicate the beginning and the end of the radial collapse process. Experimental results are in good agreement with our theoretical predictions, but do not allow to discriminate from those corresponding to a continuum mechanics model.

Linear vibrations of triple-walled carbon nanotubes

In this paper, the linear vibrations of triple-walled carbon nanotubes (TWNTs) are investigated. A multiple elastic thin shell model is applied. The TWNT dynamics is studied in the framework of the Sanders–Koiter shell theory. The van der Waals interaction between any two layers of the TWNT is modelled by a radius-dependent function. The shell deformation is described in terms of longitudinal, tangential and radial displacements. Simply supported, clamped and free boundary conditions are applied. The three displacement fields are expanded by means of a double mixed series based on Chebyshev polynomials for the longitudinal variable and harmonic functions for the tangential variable. The Rayleigh–Ritz method is applied to obtain approximate natural frequencies and mode shapes. The present model is validated in the linear field by means of comparisons with data from the literature. This study is focused on determining the effect of geometry and boundary conditions on the natural frequencies of TWNTs.

Interactions of moving charged particles with triple-walled carbon nanotubes

We study plasmon excitations and channeling trajectories of charged particles in triple-walled carbon nanotubes (TWNTs) based on a semi-classical kinetic model combined with the Molecular Dynamics method. Numerical results show that the outer and inner tubes of a TWNT exert strong influence on the peak structures of the self-energy (or the image potential) and the stopping power curves for the channeling ion, resulting in one or two narrow peaks in the low speed region. In addition, the radial dependencies of the total potential, which includes the image potential due to dynamic polarization of the electron gas in nanotubes and a reactive empirical bond order potential for atomic interactions, are compared for single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs) and TWNTs. By comparing the ion channeling trajectories in those types of nanotubes, we conclude that the variation of the total energy of ions with their channeling distance along the nanotube axis is related to the types of channeling trajectories, exhibiting smooth helical shapes in TWNTs and a succession of sharp reflections off the wall in SWNTs and DWNTs.

Zeptogram Mass Detection Using Triple Walled Carbon Nanotubes

Background: The aim of this paper is to use triple walled carbon nanotubes (TWCNT) as a sensor and explore the effect of change in the length of outer and middle tubes keeping smaller tubes length constant. Keywords: Vibration, finite element method, triple walled carbon nanotubes, resonators, supporting, degradation.

Finite element investigation of the vibrational behavior of concentric multi-walled boron nitride and carbon nanotubes

This paper concerns the vibrational behavior of concentric double-walled and triple-walled carbon and boron nitride nanotubes using the finite element method. Armchair and zigzag nanotubes with different lengths and diameters are considered. Moreover, different boundary conditions are applied on the nanotubes. It is observed that in double-walled nanotubes, when the inner and outer layers are respectively from boron nitride and carbon, the frequencies are larger than those in the reverse arrangement. Investigating the effect of diameter on the first 10 natural frequencies of double-walled and triple-walled nanotubes showed that nanotubes with larger diameters possess smaller frequencies. The effect of diameter is more significant for higher modes. Finally, comparisons are made between the vibrational behavior of concentric carbon and boron nitride double-walled and triple-walled nanotubes. Considering the effect of vacancy defect on the vibrational characteristics of the nanotubes revealed that when all of the walls of the nanotubes are defective, the largest diminish occurs for the fundamental natural frequencies.

Helical double and triple walled carbon nanotubes from combustion catalyst by chemical vapour deposition techniques

Helical double and triple walled carbon nanotubes from combustion catalyst by chemical vapour deposition techniques

Helical double and triple walled carbon nanotubes from combustion catalyst by chemical vapour deposition techniques

Helical double and triple walled carbon nanotubes from combustion catalyst by chemical vapour deposition techniques