Coiled Nanotubes Research Articles

Prediction of Mechanical Properties of Coiled Carbon Nanotubes by Molecular Structural Mechanics Based Finite Element Modelling

Carbon nanotubes (NTC) have very spectacular mechanical properties related to their nanometric structure, their perfect arrangement and their one-dimensional geometry. As with all materials, structural defects are inevitable and affects NTC properties. Among these defects, we distinguish the topological defects, the dislocations and the penta-hepta defect. But the presence of these defects is not totally harmful, because the existence of some structure like the coiled nanotube is the result of these defects. For this, in the first part of this work, the coiled carbon nanotube structure is studied, a method for the designing of this structure is proposed, the geometric parameters are detailed and the structural coefficients are determined. Therefore, a procedure for moving from a graphene sheet to a coiled nanotube is developed. Then, the second part of this study represents an attempt to calculate the spring constants of the spiral carbon nanotube. Mechanical properties of this material are investigated by means of molecular structural mechanics (MSM) method in ANSYS finite element code. The model serves as a link between the computational chemistry and the solid mechanics by substituting discrete molecular structures, with an equivalent-structural model. A coiled carbon nanotube has been modeled on the nanoscale by one-dimensional elements (3D beam). The results show a considerable influence of structural parameters (diameter, chirality, pitch and defect position) on the coiled nanotube mechanical properties.

Coiled nanotube yarn generates electricity

A new material could help harvest the energy from ocean waves or even human movement. The material, a carbon nanotube yarn, generates electricity when stretched or twisted. An international team, led by Seon Jeong Kim of Hanyang University and Ray H. Baughman of the University of Texas, Dallas, made the materials by twisting multiwalled carbon nanotube yarns until they became tightly coiled. Stretching decreases the ability of the yarn to store electrical charge, which increases its voltage, leading to an electrical current (Science 2017, DOI: 10.1126/science.aam8771). The scientists also coated the yarns with a gel electrolyte and then interwove the fibers with fabric in a shirt, allowing the researchers to monitor a person’s breathing from the current generated as the person’s chest expanded and contracted. According to Baughman, the team’s “twistrons” generate more than 100 times as much power as similar electricity-generating materials that can be woven into fabric. The

Molecular structural mechanics applied to coiled carbon nanotubes

In this paper, mechanical properties of single-walled helically coiled carbon nanotubes are investigated by means of molecular structural mechanics method in ANSYS finite element code. To specify the geometry of coiled carbon nanotubes, a construction procedure is proposed which offers a full control over the morphology of the coiled nanotubes. In this construction approach, first a development map is drawn on a graphene sheet and then this graphene sheet is rolled to form a defected straight carbon nanotube; then, the sides of these defects are stuck together through a nonlinear analysis and finally, the straight carbon nanotube forms into coiled carbon nanotube. Using this construction procedure, several coiled nanotubes are built and their spring constants are calculated. It is shown that the spring constants found are in good agreement with those obtained from density function theory and tight-binding calculations reported in the literature. Moreover, in order to facilitate the simulation of those macroscopic systems which contain coiled carbon nanotubes, an equivalent continuum model is proposed and its mechanical properties are investigated. It is found that, as the tube diameter increases, both spring constant and shear modulus of the coiled carbon nanotube increase.

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

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.

Transfer helix and chirality to 1,4-phenylene silica nanostructures

1,4-Phenylene silica nanotubes were prepared using a chiral anionic gelator 12K with 3-aminopropyltriethoxysilane (TEAPS) as a co-structure-directing agent, and 1,4-bistriethoxybenzene (BTEB) as precursor. When sol–gel transcription process was carried out in pure water, left-handed coiled nanotubes, double helical nanotubes, and triple helical nanotubes were obtained. When sol–gel transcription process was carried out in mixtures of water and ethanol, hybrid silica nanotubes formed by left-handed coiled nanoribbons were obtained. With increasing the volume ratios of ethanol to water, mixtures of left-handed coiled tubular ribbons and tube-in-tube nanostructures were obtained. Circular dichroism (CD) spectrum indicates at least some of the aromatic rings within the walls pack in chiral.

STM imaging of carbon nanotube point defects

In this work the STM investigation of nanotube point defects created by ion irradiation (e.g. vacancies) is presented. The defects appeared as hillock-like features on the STM images. These defects were compared with similar features observed on the STM images of as-grown coiled carbon nanotubes. In this case the observed hillock-like features were attributed to the non-hexagonal carbon rings, which are responsible for the growth of bent and coiled nanotube structures. For irradiation, multi-walled carbon nanotubes produced by the arc-discharge method were dispersed on highly oriented pyrolitic graphite (HOPG) surface and irradiated with Ar + ions of 30 keV, using a low dose ofD = 5 x 10 11 ions/cm 2 .

High Yield Multiwall Carbon Nanotube Synthesis in Supercritical Fluids

Multiwall carbon nanotubes (MWNTs) with outer diameters of 10−50 nm and wall thicknesses of 5−20 nm were synthesized in supercritical toluene at temperatures ranging from 600 to 645 °C at 8.3 MPa. Nanotube formation was catalyzed by metallocenes such as cobaltocene, nickelocene, and ferrocene or cobalt or iron nanocrystals; toluene served as both the solvent and the carbon source for nanotube growth. Supplemental carbon sources, either hexane or ethanol (∼30 vol %), increased the yield of the carbon nanotubes relative to pure toluene, and catalytic amounts of water (0.75 vol %) minimized the formation of carbon filaments and amorphous carbon. Cobaltocene, with ethanol as a supplemental carbon source, gave the highest percentage of nanotubes in the product (∼70%) and the highest conversion of toluene to MWNTs (∼4%). The MWNTs tended to exhibit bamboo morphology and appear to grow by a folded-growth mechanism with graphitic sheets wrapped around the seed metal particles. Cobaltocene was also found to catalyze coiled nanotube formation, with the appearance of springs, hairpins, lassos, and coiled ropes.

Coiled carbon nanotubes: Synthesis and their potential applications in advanced composite structures

Since the discovery of carbon nanotubes, their applications benefit to a wide range of engineering, applied physics and biomaterials areas, because of their superior mechanical and electrical properties. In the advanced composite society, substantial works including the synthesis of different types of nanotubes, manufacturing process of nanotube-related composites, mechanical characterizations of these composites, have been conducted in the past few years. One of the major focuses, has not yet been solved, is on how to ensure a good bonding between straight nanotubes and their surrounding matrix, and also the integrity of the nanotubes' structures, in their atomic scale level after being bonded with the matrix. Physical nanotube pullout and push in tests can be used to determine the interfacial bonding properties of the nanotube/polymer composites. However, due to their size constraint, it is impossible to precisely conduct such tests, based on current testing technology. Although molecular dynamics (MD) simulations are another alternative to roughly estimate the bonding behaviour of the composites, the results are highly dependent on the basic assumptions applied to models. Recently, the development of coiled carbon nanotubes opens a new alternative to reinforce the traditional composites. The coiled configuration of the nanotubes can enhance the fracture toughness as well as mechanical strength of the composites even there is no direct chemical bonding between the nanotubes and matrix. Their coiled shape induces mechanical interlocking when the composites are subjected to loading. In this paper, a critical review on the synthesis of the coiled nanotubes and their applications in advanced composites is given.

Synthesis, Properties and Applications of Helical Carbon Nanotubes

Helical carbon nanotubes were produced on silica‐supported Co catalysts by chemical vapour decomposition of acetylene. Coiled nanotubes were examined. They have been found to be of various shapes, diameter, and pitch. Some of them are extremely long, up to 5 µm, with regular helices. The average outer diameter of coils are about 30–50 nm, the pitch is in the range 50–200 nm and the length about 1–1.4 µm. The helix‐shaped windings of the helical carbon nanotubes reveal characteristic mechanical resonances, which are determined by the elastic modulus, mass, shape, and dimensions.

Analytical Currents: Coiled nanotube resonators

ADVERTISEMENT RETURN TO ISSUEPREVNewsNEXTAnalytical Currents: Coiled nanotube resonatorsCite this: Anal. Chem. 2004, 76, 19, 346 APublication Date (Web):October 1, 2004Publication History Published online1 October 2004Published inissue 1 October 2004https://doi.org/10.1021/ac041644iRIGHTS & PERMISSIONSArticle Views109Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (69 KB) Get e-AlertsSUBJECTS:Nanotubes Get e-Alerts

Bulk Synthesis of Helical Coiled Carbon Nanostructures

ABSTRACTThree dimensional helical coiled carbon nanostructures including coiled nanowires and nanotubes were synthesized at ambient pressure using a thermal chemical vaporization deposition (CVD) process in which xylene and acetylene were used as the primary carbon source. A bi-metal catalyst formed from a mixture of ferrocene and indium isopropoxide served as the seed to initiate the growth of these helical coiled nanostructures. The as-synthesized coiled nanowires and nanotubes are pure without the presence of amorphous carbon nanoparticles. By precisely controlling the atomic ratio of In / (Fe+In), coiled nanowires or nanotubes can be synthesized exclusively. The diameters of the as-grown coiled nanowires vary from several tens to several hundreds nanometers, whereas the diameters of the coiled nanotubes are around 20 nm. The structure of coiled nanowires and nanotubes were determined using scanning electron microscopy and transmission electron microscopy. The key novel aspects of this research are: (i) to synthesize helical coiled nanotubes or nanowires exclusively by controlling the bi-catalyst concentration of Fe and In, and (ii) no preformed substrates are required which implies that our process is amenable for scaled-up synthesis of these nanostructures.

Persistent currents in carbon nanotube based rings

Persistent currents in rings constructed from carbon nanotubes are investigated theoretically. After studying the contribution of finite temperature or quenched disorder on covalent rings, the complexity due to the bundle packing is addressed. The case of interacting nanotori and self-interacting coiled nanotubes are analyzed in detail in relation to experiments.

Coiled carbon nanotube structures with supraunitary nonhexagonal to hexagonal ring ratio

By assembling azulene units (fused pentagon-heptagon pairs) and hexagons, and applying specific wrapping rules to these structures resembling some recently-proposed Haeckelite structures [Terrones et al., Phys. Rev. Lett. 84, 1716 (2000)], a large variety of toroidal, coiled, screwlike, and double-helix structures can be generated. In particular, the coiling appears naturally by rolling up stripes made of heptagons, hexagons and pentagons. In the structures examined here, the ratio of nonhexagonal rings to hexagonal units varies from 4:1 to 4:3. In the coiled nanotubes produced actually by catalytic chemical vapor deposition, it is not impossible that such a high concentration of nonhexagonal units in the nanotube structure be the result of a fast kinetic leading to metastable states that cannot anneal out due to the low growth temperatures used.

Carbon nanotubes, nanofilaments and nanobeads by thermal chemical vapor deposition process

From commercial kerosene, straight and coiled nanotubes, nanofilaments and nanobeads are grown by suitably adjusting pyrolysis temperature and catalysts by the thermal chemical vapor deposition (CVD) technique. Nickel and iron facilitate the growth of straight and coiled nanotubes, respectively, at a temperature of 1000 °C. With an increase of pyrolysis temperature to 1100 °C, carbon nanobeads resulted in the presence of both the catalysts. Although, coiled nanotubes are formed at 900 °C in the presence of iron catalysts but nickel gives nanofilaments of diameter in the range 80–100 nm at the same temperature. The crystallinity and thermal properties are studied.

Synthesis and characterization of carbon nanotubes

Catalytic synthesis and physicochemical characterization of multi- and single-wall carbon nanotubes are presented. Supported transition metal(s) catalysts were prepared by different methods and were tested in the production of nanotubes by decomposition of hydrocarbons at 700 and at 1000 °C, using a fixed bed flow reactor. The carbon deposits were measured and the quality of the nanotubes was characterized by transmission electron microscopy. The inner and outer diameters of the nanotubes were also measured and the diameters distribution histograms were established: Thick multi-wall straight and coiled nanotubes with inner diameters (minimum-[average]-maximum) of 4-[6]-10 nm, outer diameters of 8-[25]-50 nm and with lengths up to 50 mm. Thin multi-wall straight and coiled nanotubes with inner diameters of 3-[4]-7 nm, outer diameters of 5-[15]-25 nm and with lengths up to 50 mm. Very thin multi-wall straight and coiled nanotubes with inner diameters of 2-[4]-7 nm, outer diameters of 3-[10]-15 nm and with lengths up to 50 mm. Single-wall nanotubes isolated or as bundles with diameters of 1-[2]-4 nm and with lengths up to 1 mm. The influence of various parameters such as the way of catalyst preparation, the nature and the pore size of the support, the nature of the metal(s), the quantity of catalyst active particles and the reaction conditions on the nanotubes formation were studied.

AFM detection of the mechanical resonances of coiled carbon nanotubes

We introduce a method for atomic force microscopy (AFM)-based detection of mechanical resonances in helix-shaped multi-walled carbon nanotubes. After deposition on an oxidized silicon substrate, the three-dimensional structure of suspended nanotubes, which bridges an artificially created step on the surface, can be visualized using AFM operating in the non-contact mode. The suspended coiled nanotubes are resonantly excited, in situ, at the fundamental frequency by an ultrasonic transducer connected to the substrate. When the AFM tip is positioned above the coiled nanotube, the cantilever is unable to follow the fast nanotube oscillations. Nevertheless, an oscillation amplitude-dependent signal is generated due to the non-linear force-to-distance dependence. Measurement of the mechanical resonances of the helix-shaped carbon nanotubes can be used to quantitatively determine their elastic properties. Assuming that a coiled nanotube can be modeled as a suspended helix-shaped uniformly thin elastic beam, the obtained resonance frequency is consistent with a Young’s modulus of 0.17±0.05 TPa.

Production of differently shaped multi-wall carbon nanotubes using various cobalt supported catalysts

Catalytic synthesis and transmission electron microscopy (TEM) of multi-wall carbon nanotubes are presented. Silica, zeolite and alumina supported cobalt catalysts were prepared by different methods (impregnation and ion-adsorption precipitation) and were used to produce nanotubes. The synthesis was carried out in a fixed bed flow reactor and the process was optimized in order to produce carbon nanotubes on a gram scale. The influence of various parameters such as the method of catalyst preparation, the nature of the support, cobalt concentration and reaction conditions on the formation of nanotubes was investigated. The carbon deposits were measured and the quality of nanotubes was determined by low and high resolution TEM. Multi-wall straight and coiled nanotubes were found to be fairly regular with an average inner (outer) diameter of 4–7 nm (8–23 nm) and with lengths up to 0.1 mm.

Synthesis of single- and multi-wall carbon nanotubes over supported catalysts

The quantities of deposited carbon were measured and the quality of the nanotubes was characterized by means of transmission electron microscopy and scanning tunneling microscopy. The inner and outer diameters of the nanotubes were also measured and the diameter distribution histograms were established. The multi-wall straight and coiled nanotubes were found to be quite regular with an average inner (outer) diameter of 4–7 nm (15–25 nm) and with lengths up to 50 μm. The walls contain concentric cylindrical graphene sheets separated by the graphitic interlayer distance. The single-wall nanotubes were found as bundles of hundreds of aligned straight 1-nm-diameter nanotubes with lengths up to 1-μm. The influence of various parameters such as the method of catalyst preparation, the nature and the pore size of the support, the nature of the metal, the quantity of catalyst active particles, and the reaction conditions on the nanotubes formation were studied. The numbers and dimensions of the catalyst active particles dispersed on the support were found to be of importance in regulating the shape of the produced nanotubes. Following these results, a model of growth mechanism was suggested for the nanotubes obtained by this method.

Scanning tunnelling microscopy (STM) imaging of carbon nanotubes

Carbon nanotubes prepared by thermal decomposition of hydrocarbons on supported Co catalysts were investigated by STM in air. An interpretation of the STM images is proposed which accounts for specific distortions taking place while scanning three-dimensional objects whose dimensions are of the order of the curvature radius of the tip. These distortions have both geometric and electronic origins, and cannot be neglected. The distortion mechanism was found to be different for nanotube diameters in the ranges of 1 nm and 10 nm. The 1 nm tubes are more strongly affected by their apparent broadening, reflecting the finite size of the tip apex. Here the distortion can reach up to 300% of the geometric diameter, whereas for 10 nm tubes the distortions are in the range of 50% of the geometric diameter. An apparent flattening of the nanotubes in the vertical direction was also found, which is attributed to differences in electronic densities of states between the substrate and the nanotube, and to an additional tunnelling barrier between the nanotube and the substrate. STM images with atomic resolution and line cut topographic profiles show similar structures as for the case of HOPG. However, the atomic corrugation was found to be five times smaller on the 1 nm diameter tubules than for the 10 nm family, the latter being close to the value obtained with HOPG. Coiled nanotubes have been imaged by STM for the first time. Here both the electrical resistance of the coiled nanotube and its elastic deformation play a significant role in the image formation process, these effects being more important than for straight nanotubes.