Carbon Nanocoils Research Articles

Torsion fracture of carbon nanocoils

We fix a carbon nanocoil (CNC) on a substrate in a focused ion beam instrument and then fracture the CNC with a tensile load. Using the CNC spring index, we estimate the maximum to average stress ratio on the fractured surface to range from 1.3 to 1.7, indicating stress concentration on the coil wire inner edge. Scanning electron microscopy confirms a hollow region on the inner edge of all fractured surfaces.

The Interesting Influence of Nanosprings on the Viscoelasticity of Elastomeric Polymer Materials: Simulation and Experiment

AbstractAmong all carbon nanostructured materials, helical nanosprings or nanocoils have attracted particular interest as a result of their special mechanical behavior. Here, carbon nanosprings are used to adjust the viscoelasticity and reduce the resulting hysteresis loss (HL) of elastomeric polymer materials. Two types of nanospring‐filled elastomer composites are constructed as follows: system I is obtained by directly blending polymer chains with nanosprings; system II is composed of the self‐assembly of a tri‐block structure such as chain‐nanospring‐chain. Coarse‐grained molecular dynamics simulations show that the incorporation of nanosprings can improve the mechanical strength of the elastomer matrix through nanoreinforcement and considerably decrease the hysteresis loss. This finding is significant for reducing fuel consumption and improving fuel efficiency in the automobile tire industry. Furthermore, it is revealed that the spring constant of nanosprings and the interfacial chemical coupling between chains and nanosprings both play crucial roles in adjusting the viscoelasticity of elastomers. It is inferred that elastomer/carbon nanostructured materials with good flexibility and reversible mechanical response (carbon nanosprings, nanocoils, nanorings, and thin graphene sheets) have both excellent mechanical and low HL properties; this may open a new avenue for fabrication of high performance automobile tires and facilitate the large‐scale industrial application of these materials.

Bottom‐Up Tailoring of Plasmonic Nanopeapods Making Use of the Periodical Topography of Carbon Nanocoil Templates

AbstractAu nanoparticle chains embedded in helical Al2O3 nanotubes (“nanopeapods”) are synthesized by annealing carbon nanocoils coated with Au by sputtering and Al2O3 by atomic layer deposition. Regular spacing between nanoparticles with a sharp size distribution is achieved by fragmentation of the Au coating in agreement with the pitch of the nanocoils arising from three‐dimensional periodical topography of the carbon nanocoil templates. A strong plasmonic resonance behavior of the fabricated nanopeapods manifests itself in confocal laser scanning microscopy by a clear polarization contrast at red wavelengths, which is absent in the blue. Numerical simulations confirm an incisive resonance enhancement for longitudinal polarization and suggest the nanopeapods as promising candidates for highly efficient, ultrathin waveguides. The waveguiding properties of the nanopeapods are investigated by electron energy‐loss spectroscopy and energy‐filtered TEM imaging.

Electrically driven light emission from a single suspended carbon nanocoil

Electrically driven thermal radiation spectra from single suspended carbon nanocoils (CNCs) were investigated. The suspended CNC, whose structure is a hybrid between sp2 graphite-like nanocrystallites and sp3 amorphous carbon, shows thermally excited emission peaks superimposed on the blackbody radiation spectrum for wavelengths above 600nm. It is believed that at least four pairs of energy bands exist around the Fermi energy level and the observed emission peaks are attributed to thermally-excited interband electron transitions in the CNC. Photoluminescence measurements for the CNCs show similar emission peaks to the thermally excited emission, which further supports our speculation on the electronic structure of the CNC.

Effect of ultrasonication on the cryogenic tensile properties of carbon nanocoil/poly-dicyclopentadiene composites

Cryogenic tensile properties of carbon nanocoil (CNC)/poly-dicyclopentadiene (poly-DCPD) composites have been investigated experimentally. Flat tensile specimens of CNC/poly-DCPD composites with 1.0 and 1.5vol.% CNCs were fabricated by an ultrasonic method and tested at room temperature (RT) and liquid nitrogen temperature (77K). The effect of ultrasonication time on the cryogenic tensile properties of CNC/poly-DCPD composites was discussed. A scanning electron microscope (SEM) was also used to observe the fracture surface morphology of CNC/poly-DCPD composites. Results indicated that the tensile strength of CNC/poly-DCPD composites at RT and 77K is affected by ultrasonication time and there is a trade-off between improving dispersion and damaging the CNC.

Rapid Dielectrophoresis Assembly of a Single Carbon Nanocoil on AFM Tip Apex

We assembled a single carbon nanocoil (CNC) on the tip apex of an atomic force microscope probe by utilizing dielectrophoresis in isopropyl alcohol (IPA). The total assembly process can be achieved within several seconds at room temperature by using a simple apparatus. Three-dimensional finite element simulations have been conducted to investigate the orientation and position of this assembly. Our experiment agrees well with the simulation. The results indicate that it is essential to filter the CNC/IPA suspension and manipulate the capillary meniscus for a single CNC to be vertically assembled on the tip apex. An inclined-edge electrode has, therefore, been suggested and found effectively confining the CNC/IPA suspension around the probe tip.

The effect of changes in synthesis temperature and acetylene supply on the morphology of carbon nanocoils

Carbon nanocoils (CNCs) with controlled shape, coil diameter and coil pitch have been synthesized in a chemical vapor deposition (CVD) system by changing the reaction temperature and acetylene flow rate. It is found that three-dimensional CNCs are produced at a lower temperature (700–770°C), while a higher temperature (810°C) leads to the growth of straight carbon nanofibers (CNFs). CNC–CNF hybrid structures are produced by increasing growth temperature from 750 to 810°C during a single synthesis run, while CNF–CNC hybrid structures are produced by decreasing the temperature from 810 to 750°C. Similarly, by changing growth temperature from 750 to 810°C and then back to 750°C during a single run, CNC–CNF–CNC complex hybrid structures can be obtained. During the CVD process, the pulsing of acetylene and the changing of acetylene flow rate are also found to be effective in controlling the structure of CNCs. CNCs with periodic helical structures can be produced by interrupting the acetylene flow or changing its flow rate periodically. It is found that the higher the flow rate of acetylene, the smaller the coil pitch and diameter of the grown CNCs.

Carbon Nanocoils as Unusual Electrode Materials for Supercapacitors

Carbon nanocoils (CNCs) are coiled carbon nanofibers of ca. 10 nm in fiber diameter, and 10–20 nm in internal coil diameter. They are prepared through several oxidation treatments, which lead to a graduate content in surface oxygen groups evolving as either CO or CO2 in temperature-programmed desorption. The CNCs show a moderate surface area (40–240 m2 g−1) and a relatively high electrical conductivity (0.1–0.2 S cm−1). Some CNCs are activated to develop surface area. The electrochemical behaviour of CNCs as supercapacitor electrode is studied in the electrolytes H2SO4 and Et4NBF4. From the parameters C1 (overall specific capacitance measured at 1 mA cm−2), SBET (BET specific surface area), and CO and CO2 content, the plots of C1/SBET vs. CO/SBET and vs. CO2/SBET are analyzed. In the acidic electrolyte, the oxygen groups evolving as CO2 contribute significantly to enhance C1 in addition to the groups evolving as CO. C1/SBET shows a linear dependence, with high slope, on CO2/SBET, and an exponential dependence on CO/SBET. In the organic electrolyte, the two kinds of oxygen groups contribute less to C1. The specific pseudocapacitance and double layer capacitance are determined and discussed in relation to the CO and CO2 content and the SBET value.

Conducting polymer/carbon nanocoil composite electrodes for efficient supercapacitors

Herein, we report for the first time, conducting polymer (polyaniline (PANI) and polypyrrole (PPY)) coated carbon nanocoils (CNCs) as efficient binder-free electrode materials for supercapacitors. CNCs act as a perfect backbone for the uniform distribution of the conducting polymers in the composites. In two electrode configuration, the samples exhibited high specific capacitance with the values reaching up to 360 and 202 F g−1 for PANI/CNCs and PPY/CNCs respectively. The values obtained for specific capacitance and maximum storage energy per unit mass of the composites were found to be comparable to one of the best reported values for polymer coated multi-walled carbon nanotubes. In addition, the fabricated PANI/CNC based supercapacitors exhibited a high value of 44.61 Wh kg−1 for maximum storage energy per unit mass. Although the devices exhibit an initial capacitance loss due to the instability of the polymer, the specific capacitance stabilizes at a fixed value after 500 charge–discharge cycles.

Structure changes of an individual carbon nanocoil and its field-emission enhancement by laser treatment

The electron field-emission properties of an individual carbon nanocoil (CNC) have been investigated. The electron diffraction patterns and Raman scattering spectra for the CNC before and after the field emission show that the sp2 grains in the amorphous sp3 network are increased both in size and amount and the graphitic sp2 grains turn to align to the same orientation in the CNC. Joule heating induced by the high field-emission current is considered to be the main reason for this result. Furthermore, morphology of a CNC is also modified by a laser irradiation. The modified CNC exhibits a lower turn-on voltage and a smaller slope of Fowler–Nordheim plot, indicating that the field-emission properties of the CNC are improved. It is found that the curvature radius of the modified CNC tip is smaller than that of the initial one, which is the main factor contributing to the enhancement of field-emission properties.

Necessity of base fixation for helical growth of carbon nanocoils

Abstract

Composites of Polyvinyl Alcohol and Carbon (Coils, Undoped and Nitrogen Doped Multiwalled Carbon Nanotubes) as Ethanol, Methanol and Toluene Vapor Sensors

We investigate the chemical sensing behavior of composites prepared with polyvinyl alcohol and carbon materials (undoped multiwalled carbon nanotubes, nitrogen-doped multiwalled carbon nanotubes and carbon nanocoils). We determine the sensitivity of thin films of these composites for ethanol, methanol and toluene vapor, comparing their conductance and capacitance responses. The composite that exhibits highest sensitivity depends on specific vapor, vapor concentration and measured electrical response, showing that the interactivity of the carbon structure with chemical species depend on structural specificities of the carbon structure and doping.

Thermal conductivity of a single carbon nanocoil measured by field-emission induced thermal radiation

The spectrum of thermal radiation induced by field emission from a single carbon nanocoil (CNC) is obtained, from which its thermal conductivity is investigated. It is found that the resistivity of the CNC shows an exponential decrease with increasing temperature. The spectrum calculated by the temperature distribution along the CNC coincides with that calculated by the single maximum temperature in the wavelength range below 1250 nm, but shows considerable differences in intensity and peak position for higher wavelengths. Based on this understanding, the thermal conductivity of the CNC is evaluated to be 38 W/m K by a one-dimensional thermal conduction model.

Controllable and large-scale synthesis of metal-free carbon nanofibers and carbon nanocoils over water-soluble Na xK y catalysts

Through the pyrolysis of acetylene at 450 °C, large quantities of carbon nanocoils or carbon nanofibers can be synthesized selectively by controlling the Na:K molar ratio of water-soluble Na x K y catalysts. We found that the temperature adopted for pyrolysis is an important factor for selectively obtaining the different kinds of products. Because the Na x K y catalysts are water-soluble, they can be easily removed, and the nanocarbon materials can be harvested undamaged in high purity. The process is simple, inexpensive, and environment-benign, giving a product yield matching those of the transition-metal catalysts. Based on the results, we conducted discussion on the role of catalyst, effect of pyrolysis temperature, and formation mechanism of the nanomaterials.

Growth of carbon nanocoils using Fe–Sn–O catalyst film prepared by a spin-coating method

Abstract

Fabrication of Carbon Nanocoil Field Emitters and Their Application to Display

Fabrication of Carbon Nanocoil Field Emitters and Their Application to Display

Electrochemical Energy Storage Devices Using Electrodes Incorporating Carbon Nanocoils and Metal Oxides Nanoparticles

Carbon nanocoil (CNC) based electrodes are shown to be promising candidates for electrochemical energy storage applications, provided the CNCs are properly functionalized. In the present study, nanocrystalline metal oxide (RuO2, MnO2, and SnO2) dispersed CNCs were investigated as electrodes for supercapacitor applications using different electrochemical methods. In the two electrode configuration, the samples exhibited high specific capacitance with values reaching up to 311, 212, and 134 F/g for RuO2/CNCs, MnO2/CNCs, and SnO2/CNCs, respectively. The values obtained for specific capacitance and maximum storage energy per unit mass of the composites were found to be superior to those reported for metal oxide dispersed multiwalled carbon nanotubes in two electrode configuration. In addition, the fabricated supercapacitors retained excellent cycle life with ∼88% of the initial specific capacitance retained after 2000 cycles.

Quantum conductance of armchair carbon nanocoils: roles of geometry effects

Armchair carbon nanocoils (CNCs) with different geometric parameters are constructed and optimized using a tight-binding (TB) total energy model. The quantum conductance of these nanocoils is simulated employing a π-orbital TB model incorporated with the non-equilibrium Green’s function theory. Compared with the perfect armchair carbon nanotubes (CNTs) and armchair CNTs with only Stone-Wales (SW) defects, the quantum conductance spectra of the armchair CNCs present distinct gaps around the Fermi level, which are mainly originated from the existence of sp3 carbon in the three-dimensional spiral structures. Moreover, the detailed conductance spectra of the armchair CNCs depend sensitively on their geometric parameters, such as tubular diameter and block-block distance.

Structural Analysis of Multi-Walled Carbon Nanocoils Synthesized with Fe–Sn Catalyst Supported on Zeolite

Thin carbon nanocoil (CNC) with a fiber diameter of less than 50 nm was synthesized by catalytic chemical vapor deposition using Fe-Sn catalyst supported on zeolite. The chemical vapor deposition parameters of reaction temperature, gas flow rate of N2 as dilute gas and C2H2 as source gas were 650-750 degrees C, 1000 ml/min and 50-300 ml/min respectively. Transmission electron microscopic observation revealed that thin CNCs had a hollow and multi-walled structure with cylindrical graphitic layers. More than 90% of the CNCs obtained were multi-walled CNCs (MWCNCs), and the remainder was columnar CNCs without a hollow structure. Three-dimensional images of an MWCNC with Au nanoparticles on its surface were reconstructed by electron tomography and confirmed that the MWCNC had a three-dimensional helical shape.

Radial growth of carbon nanocoils on stainless steel wires coated with tin particles using chemical vapor deposition from acetylene

Radial growth of carbon nanocoils (R-CNCs) on stainless steel (SS) wire has been achieved using thermal chemical vapor deposition from acetylene. A solution of tin acetate in ethanol with molarities of 0.01–0.2 M was coated on SS wire and oxidized as an active catalyst in air at 600–1000 °C. It was found that SS wire oxidized at 900 °C for 30 min with a tin solution of 0.1 M exhibited the highest catalytic activity. The optimum grain size of Fe–Sn was approximately 0.49 ± 0.15 μm for R-CNCs. The R-CNCs, which were hollow in the center, had an average fiber diameter of 360 nm, a coil diameter of 960 nm and a pitch of 1140 nm. The yield, which was the ratio of the number of R-CNCs to the total carbon products, was 80%. The resistance of as-grown CNC/SS wire coated with higher-molarity solutions was lower than that of the CNC/SS wire coated with lower-molarity solutions. Growing R-CNCs on metal wire provides excellent electrical contact, good alignment, and ease of handling and manipulation.