Bent Nanotubes Research Articles

Computer simulations of fast particle propagation through straight and bent nanotubes

We developed a new approach to the problem of channeling of charged particles in a nanotube rope with account taken of the incoherent scattering of particles on substance electrons and thermally vibrating atoms. We present the results of computer simulations of the spatial and angular distribution of ultra-relativistic particles channeled in straight and bent nanotubes and estimate possibilities of governing high-energy beams with nanotubes.

Fast ion passing through straight and bent nanotubes

The motion of fast positively charged particles in straight and bent nanotubes and ropes of nanotubes is considered. The possibility of the dynamical chaos phenomenon at scattering of such particles by nanotube is shown. The deflection of fast ions by a bent rope of nanotubes is demonstrated.

Channeling of high energy beams in nanotubes

We present simulations of particle beam channeling in carbon nanotubes and evaluate the possibilities for experimental observation of channeling effect in straight and bent nanotubes at IHEP and LNF. Different particle species are considered: protons of 1.3 and 70 GeV, and positrons of 0.5 GeV. Predictions are made for the experiments, with analysis of requirements on the quality of nanosamples and resolution of the experimental set-up. Based on Monte Carlo simulations, the capabilities of nanotube channeling technique for particle beam steering are discussed.

Nanotube diameter optimal for channeling of high-energy particle beam

Channeling of particle beam in straight and bent single-wall nanotubes has been studied in computer simulations. We have found that the nanotubes should be sufficiently narrow in order to steer efficiently the particle beams, with preferred diameter in the order of 0.5–2 nm. Wider nanotubes, e.g., 10–50 nm, appear rather useless for channeling purpose because of high sensitivity of channeling to nanotube curvature. We have compared bent nanotubes with bent crystals as elements of beam steering technique, and found that narrow nanotubes have an efficiency of beam bending similar to that of crystals.

Passage of fast charged particles through bent crystals and nanotubes

The present work deals with the analysis of the different deflection mechanisms of high-energy charged particles by bent atomic strings. Conditions for realization of deflection and splitting effects for a high-energy charged particle beam in a bent crystal due to donut scattering mechanism are considered. It is shown the possibility of charged particle beam deflection by a bent nanotube due to axial channeling mechanism. Conditions for realization of this effect are discussed. The influence of the particle charge sign, its magnitude and of the incoherent process by thermal oscillations of the strings atoms and by electrons of the target on the beam deflection efficiency are considered. Computer simulation results for relativistic charged particle beam passage through straight and bent crystals and bent nanotubes are presented.

Effect of a rippling mode on resonances of carbon nanotubes.

A recent study determined the Young's modulus of carbon nanotubes by measuring resonance frequency and using the modulus-frequency relation resulting from the linear vibration theory. It leads to the report that the Young's modulus decreases sharply, from about 1 to 0.1 TPa with the diameter D increasing from 8 to 40 nanometers, and the investigators attributed this decrease to the emergence of an unusual bending mode during the measurement that corresponds to rippling on the inner arc of the bent nanotubes. The nonlinear analysis presented in this paper that captures the rippling mode suggests that the effective Young's modulus can indeed decrease substantially with increasing diameter, and that the results from the classical linear theory may be invalid in such measurements.

Structures and electronic properties of small carbon nanotube tori

Fullerenes and nanotubes are promising candidates in the development of nanodevices. Recently, a form of carbon nanotube torus structures has been observed. In this regard, we have investigated the geometries, electronic structures, and energetics of small carbon nanotube tori, using both the tight-binding and semiempirical quantum chemical approaches. It is shown that ${D}_{5d}$ nanotube tori behave like semiconductors, while ${D}_{6h}$ nanotube tori exhibit metal (or metal-like) characteristics similar to bent nanotubes. We show that the ${D}_{5d}$ nanotube tori, which are as stable as the corresponding fullerenes, are energetically more favored than the corresponding nanotubes. In particular, the pentagons of the ${D}_{5d}$ nanotube tori are less deformed than those of bent nanotubes and ${D}_{6h}$ nanotube tori. This indicates that such small nanotube tori could be observed under optimal kinetic-driven conditions and eventually utilized as nanodevices.

Deformation of carbon nanotubes in nanotube–polymer composites

Composites of uniaxially oriented multiwalled carbon nanotubes embedded in polymer matrices were fabricated and investigated by transmission electron microscopy. In strained composite films, buckling was ubiquitously observed in bent nanotubes with large curvatures. By analyses of a large number of bent nanotubes, the onset buckling strain and fracture strain were estimated to be ≈5% and ⩾18%, respectively. The buckling wavelengths are proportional to the dimensions of the nanotubes. Examination of the fracture surface showed adherence of the polymer to the nanotubes.

Channeling of fast charged and neutral particles in nanotubes

We present a theory to describe the propagation of relativistic charged particles, X-rays and thermal neutrons through straight or slightly bent nanotubes and calculated the spectra of electromagnetic radiation accompanying the channeling of charged particles.

Investigations of diamond-graphite hybrids and fullerenes with seven-membered rings

The nature of diamond-graphite hybrids has been studied by molecular mechanics, by examining the structures of species such as C 84H x wherein the sp 3 to sp 2 carbon ratio is varied progressively. The dependence of the average coordination number on the atom fraction of hydrogen has been examined in the light of the random covalent network model. The HOMO-LUMO gap has been estimated in a graphite-like C 110H x and in a diamond-like C 120H x as a function of the sp 3 sp 2 carbon atom ratio. The gap increases exponentially with the fraction of sp 3 carbon. Shapes of fullerene-like structures with 7-membered rings, in addition to 6- and 5-membered rings, have been investigated along with structures of bent nanotubes having similar ring systems.

Structures and Images of Novel Derivatives of Carbon Nanotubes, Fullerenes and Related New Carbon Forms

In the light of the finding that carbon nanotubes get functionalized on reaction with acid and other oxidizing agents, the structures and shapes of nanotube derivatives resulting from possible reaction between functionalized nanotubes, are obtained by an energy minimization procedure and the structures, so obtained, are compared with the observed microscopic images. The shapes of fullerene -like and nanotupe - like structures containing seven - membered rings, in addition to six and five - membered rings, are depicted along with the structures of bent nanotubes containing similar ring systems. Diamond - graphite hybrid structures which constitute an important class of carbon materials are also investigated.