Helically Coiled Carbon Nanotubes (original) (raw)

Synthesis, Model and Stability of Helically Coiled Carbon Nanotubes

ECS Solid State Letters, 2012

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Structure and stability of coiled carbon nanotubes

physica status solidi (b), 2012

Helically coiled carbon nanotubes are modeled using topological coordinate method which is based on the toroidal triply connected graphs, containing pentagons, hexagons, and heptagons. Their regular incorporation into the hexagonal carbon net induces transition from the straight to the helical geometry. Relaxation of the structural model is performed in two steps: Firstly, molecular dynamics based on the Brenner potential is applied and then the coil parameters are, once again, optimized within symmetry preserving density functional tight binding (DFTB) method. Model of smooth regularly helically coiled single-walled nanotube structure is obtained. Correlations between the helical angle, tubular and helical diameter are found. Cohesive energy of the coiled structure is calculated by DFTB method within symmetry based POLSym code. Its dependence on the diameter of the coil is shown. The calculated energies range from 7.5 to 8.0 eV/atom.

Current Distribution Dependence on Electric Field in Helically Coiled Carbon Nanotubes

Contemporary materials, 2017

Experimentally is confirmed that helically coiled carbon nanotube (HCCNT) could be used as a small solenoid for generating spatially localized magnetic field. Current distribution during diffusive electronic transport likewise the inductivity of this quantum conductor depends on electric field. Despite slightly lower electron mobility in HCCNTs than that of the straight single wall carbon nanotubes, the coiled nanotubes are attractive for application as nonlinear nano-solenoids. Nonequilibrium electron distribution functions obtained by solving Boltzmann transport equation are used to predict average helical radius of current flow as a function of electric field intensity. Change of spatial distribution of electronic flow with applied electric field is considered and nonlinear inductivity of HCCNT is predicted.

Thermal Conductance of Helically Coiled Carbon Nanotubes

Contemporary Materials, 2014

Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This quantity has been extensively explored experimentally and theoretically using different approaches like: molecular dynamics simulation, Boltzmann-Peierls phonon transport equation, modified wave-vector model etc. Results of these investigations are of great interest and show that carbon- based materials, graphene and nanotubes in particular, show high values of thermal conductivity. Thus, carbon nanotubes are a good candidate for the future applications as thermal interface materials. In this paper we present the results of thermal conductance s of a model of helically coiled carbon nanotubes (HCCNTs), obtained from phonon dispersion relations. Calculation of s of HCCNTs is based on the Landauer theory where phonon relaxation rate is obtained by simple Klemens-like model.

Transport in Helically Coiled Carbon Nanotubes: Semiclassical Approach

Contemporary Materials, 2015

Semiconducting single wall carbon nanotubes (SWCNTs) exhibit high electron mobility in low electric field. Tube diameter and temperature have been found to strongly affect transport properties of SWCNTs. We have investigated electron mobility of helically coiled carbon nanotubes (HCCNTs). Electron and phonon band structures of HCCNTs are used in calculation of electron-phonon matrix elements. Scattering rates are calculated using the first order perturbation theory while taking care of energy and momentum conservation law. In order to obtain electron drift velocities, steady state simulation of charge transport is performed using Monte Carlo method.

Synthesis and characterisation of coiled carbon nanotubes

Catalysis Today

Recent results from our group and from literature data are summarized. Emphasis is put on the various supported catalysts that can lead to the formation of helical (or coiled) carbon nanotubes. Detailed analysis of transmission electron microscopy images reveals that not all types of nanotubes -having any type of coil pitch and coil diameter -are equally probable: stability islands can be found in the 3D representation of the number of nanotubes as a function of both coil pitch and coil diameter. In most of the cases the coils are formed by introducing pairs of five-membered and seven-membered rings into the nanotubes containing the basic six-membered rings. Possible applications of the helical carbon nanotubes are discussed.

Structural origin of coiling in coiled carbon nanotubes

Carbon, 2005

The statistical distribution of a large number of helically coiled carbon nanotubes was analyzed in a cross-correlated way in their geometrical configuration space defined by diameter and pitch. Stability islands were identified, in which the number of coils exceeds about 15-10 times the value corresponding to a uniform distribution. When comparing our data with data from literature, a good agreement is found. The statistical findings are interpreted as indirect evidence that the geometric configuration of coiled carbon nanotubes is rather decided by the atomic structure of carbon layers building up the coils than by the external parameters which on the other hand may induce the particular conditions under which coiling occurs. The possible effect of impurities like N and S on the incorporation of non-hexagonal rings and tubular growth is pointed out.

Crossover from ballistic to diffusive thermal conductance in helically coiled carbon nanotubes

Physica Status Solidi B-basic Solid State Physics, 2014

Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This quantity has been extensively explored experimentally and theoretically using different approaches like: molecular dynamics simulation, Boltzmann-Peierls phonon transport equation, modified wave-vector model etc. Results of these investigations are of great interest and show that carbon-based materials, graphene and nanotubes in particular, show high values of thermal conductivity. Thus, carbon nanotubes are a good candidate for the future applications as thermal interface materials. In this paper we present the results of thermal conductance  of a model of helically coiled carbon nanotubes (HCCNTs), obtained from phonon dispersion relations. Calculation of  of HCCNTs is based on the Landauer theory where phonon relaxation rate is obtained by simple Klemens-like model.

Review A Review of the Properties and CVD Synthesis of Coiled Carbon Nanotubes

2010

The CVD route for carbon nanotube production has become a popular method to make large amounts of multiwall carbon nanotubes. The structure, morphology and size of carbon materials depend critically on the catalyst preparation and deposition conditions. According to current knowledge, CVD method is the only process which can produce carbon nanocoils. These nanocoils are perfect candidates for nanotechnology applications. One might indeed hope that these coils would have the extraordinary stiffness displayed by straight nanotubes. Based on theoretical studies, regular coiled nanotubes exhibit exceptional mechanical, electrical, and magnetic properties due to the combination of their peculiar helical morphology and the fascinating properties of nanotubes. In spite of its technological interest, relatively low attention has been paid to this special field. In this paper we attempt to summarize results obtained until now.

A Review of the Properties and CVD Synthesis of Coiled Carbon Nanotubes

Materials, 2010

The CVD route for carbon nanotube production has become a popular method to make large amounts of multiwall carbon nanotubes. The structure, morphology and size of carbon materials depend critically on the catalyst preparation and deposition conditions. According to current knowledge, CVD method is the only process which can produce carbon nanocoils. These nanocoils are perfect candidates for nanotechnology applications. One might indeed hope that these coils would have the extraordinary stiffness displayed by straight nanotubes. Based on theoretical studies, regular coiled nanotubes exhibit exceptional mechanical, electrical, and magnetic properties due to the combination of their peculiar helical morphology and the fascinating properties of nanotubes. In spite of its technological interest, relatively low attention has been paid to this special field. In this paper we attempt to summarize results obtained until now.