Carbon Nanoballs Research Articles

Nano Bowls of Carbon by Oxidative Chopping of Carbon Nano Sphere

Abstract Here, we report the preparation of novel carbon material having fairly uniform bowl shape in nanosize domain with varying oxygen content by a very simple oxidative chopping of carbon nanoballs, where we have effectively functionalized the inert CNS (carbon nano sphere) with carboxylate groups that can be utilized for the chemical immobilization of enzymes, bioactive compounds, and catalysts.

The synthesis of carbon nanoballs and its electrochemical performance

Carbon nanoballs were prepared in the presence of acetylene with coke powder as carbon source by arc discharge technique. The arc plasma was diagnosed in situ by optical emission spectroscopy (OES) in the formation process of carbon nanoballs. Field emission scanning electron microscopy (FE-SEM), field emission scanning and transmission electron microscope (STEM) equipped with energy dispersive X-ray (EDX), X-ray diffraction (XRD), and Raman spectroscopy are used to characterize carbon nanoballs. The electrochemical performance of carbon nanoballs as an electrode was measured on a multi-channel battery test system to analyze the electrochemical response. The FE-SEM and STEM results show that carbon nanoballs are the main products in acetylene medium. Many carbon nanoballs are sintered together with a few carbon nanotubes (CNTs) inserted into the sintered carbon nanoballs except for a few carbon nanoballs that exist as a single ball. The STEM results show that the diameter of carbon nanoball is mainly in the range of 50–100 nm. The XRD analysis shows that the graphitization of carbon nanoballs is relatively high. The charge–discharge curves of carbon nanoballs show that the cell electrode has a high reversible capacity and the capacity retention could reach 73.7%, which might contribute to the conductivity of CNTs inserted into the sintered carbon nanoballs.

Polymerization of a Confined π‐System: Chemical Synthesis of Tetrahedral Amorphous Carbon Nanoballs from Graphitic Carbon Nanocapsules

Polymerization of a Confined π‐System: Chemical Synthesis of Tetrahedral Amorphous Carbon Nanoballs from Graphitic Carbon Nanocapsules

Determination of phase transition from nematic to isotropic state in carbon nano-balls' doped nematic liquid crystals by electrical conductivity-dielectric measurements

The phase transition in carbon nano-balls' doped nematic liquid crystals has been investigated by electrical conductivity-dielectric measurements. The results of electrical conductivity and dielectric constant as a function temperature and frequency indicate that a phase transition, which is of the first order, takes place from nematic state and isotropic state. The phase transition for E7 and E7/C60 samples takes place at 326 and 321 K temperatures, respectively.

Investigation of refractive index dispersion and electrical properties in carbon nano-balls’ doped nematic liquid crystals

Electrical and refractive index dispersion properties of a carbon nano-balls’ (Fullerene C 60) doped Liquid crystal (LC) composite, are investigated by concerning the frequency-dependent dielectrical properties, laser-induced effects on current–voltage ( I – V ) characteristics and optical characteristics suggest that the samples exhibit voltage-controlled differential negative resistance behavior. Dielectric spectra reflect the presence of different relaxation modes at higher frequencies. The refractive index dispersion parameters (oscillator energy and strength, optical moments) were also determined by optical characterization. As a result, C 60 doping changes photoconductivity, dielectric and refractive index properties of LC in a favorable manner.

OPTICAL LIMITING STUDIES OF NEW CARBON NANOCOMPOSITES AND AMORPHOUS SixNy OR AMORPHOUS SiC COATED MULTI-WALLED CARBON NANOTUBES

By using fluence-dependent transmission measurement with nanosecond laser pulses, we have studied optical limiting (OL) properties of new carbon nanocomposites as well as amorphous Si x N y or amorphous SiC coated carbon nanotubes suspended in distilled water. The observed nonlinearity at 532 nm contributed to OL performance of the carbon nanocomposites or carbon nanoballs (CNBs) is suggested to have its origin in the optically induced heating or scattering effects. It is found that when the linear transmittance of the CNBs is less than or equal to 70%, the intensity-dependent transmission of the CNBs is comparable to that of C 60. While at 80% linear transmittance, CNBs possess better OL behavior than that of C 60. These findings strongly support a potential application of CNBs for all laser protection devices. We have also observed OL effects in the amorphous silicon nitride ( a - Si x N y) and amorphous silicon carbide ( a - SiC ) coated multi-walled carbon nanotubes (MWNTs) at wavelengths of 532 and 1064 nm, and found that their OL performances are slightly poorer than that of their parent MWNTs. The possible sources of thickness-dependent OL effects of a - Si x N y and a - SiC coated MWNTs are discussed.

Stability of Carbon Nanoonion C20@C60@C240: Molecular Dynamics Simulations

The structural stability of carbon nanoonion C20@C60@C240 has been investigated by performing molecular dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that carbon nanoonion is not so resistive against heat treatment, nor is it as strong as isolated single carbon nanoballs. Although single nanoballs resist heat treatment up to 4300 K, nanoonion disintegrates after 2600 K.

The Fe(CO) 5 catalyzed pyrolysis of pentane: carbon nanotube and carbon nanoball formation

The Fe(CO) 5 catalyzed pyrolysis of pentane was investigated. The study, performed in a quartz tube, revealed that a range of carbonaceous materials could be formed with products determined by the temperature profile in the tube, the Fe(CO) 5 content in pentane, the carrier gas flow rate, the pyrolysis temperature and the pyrolysis time. The distribution of carbonaceous products also depends on the competition of the pyrolysis of Fe(CO) 5 and pentane in the different regions of the reactor. Carbonaceous materials produced included graphite film, carbon nanotubes and carbon nanoballs. The formation of carbon nanotubes takes place in a region in the quartz tube where both the pyrolysis of both Fe(CO) 5 and pentane occur, with carbon nanotubes formed by the pyrolysis of pentane. Alignment of carbon nanotubes was found when a high Fe(CO) 5 concentration was used.

STRUCTURAL AND ELECTRONIC PROPERTIES OF CARBON NANOBALLS: C20, C60, AND C20@C60

The structural stability of carbon nanoballs (fullerenes) C 20, C 60, and onion type C 20@ C 60 has been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that C 20 is relatively resistive to heat treatment, however, the onion type structure is relatively less strong against heat treatment. The electronic structure of the systems considered has been also studied by performing density functional theory type calculations.

Catalytic growth of carbon nanoballs with and without cobalt encapsulation

Carbon nanoballs encapsulated with cobalt were prepared by decomposition of methane. After acid treatment, the encapsulated cobalt can be removed to produce hollow carbon nanoballs. The content of hollow carbon nanoballs as high as 90 vol% in acid-treated carbon product can be obtained by increasing the content of cobalt from 50 to 75 mol% in the catalysts. However, under the same catalytic conditions, the main carbon products are multi walled carbon tubes (MWNTs) over Co/Al 2O 3, Co/La 2O 3, Co/CeO 2 and Ni/MgO catalysts by decomposition of CH 4, or by decomposition of CO over Co/MgO catalysts. These carbon nanoballs encapsulated with cobalt are novel magnetic materials.

Photoinduced transformation of C60 aggregates to Carbon Nanoballs

C60 aggregates, which were formed in benzene solution below their freezing points, have been transformed to ball-like nanoscale particles by irradiation of laser light. This transformation has been confirmed by the high-resolution transmission electron microscopy (HRTEM). The size distribution of the photoproducts, carbon nanoball, was directly obtained from the HRTEM images. The characteristics of the transformation from C60 molecules to aggregate is well characterized by the photoluminescence spectroscopy.

Microstructural characteristics of alumina-based composite prepared by in situ reaction of alumina-silicon carbide-nickel system

In situ reaction of nickel and silicon carbide has been attempted to prepare alumina-based composites containing some kinds of dispersed phases. The composites were fabricated by reducing and sintering of Al2O3/NiO/SiC mixtures. Reaction products (Ni3Si and C) and metallic Ni were found to disperse at the matrix grain boundaries, while Ni was partly trapped into A12O3 grains. In addition, carbon nanoballs encapsulating Ni3Si were produced and dispersed in the composites. The carbon cages were approximately 80–100 nm in diameter with polyhedral shape, and had lattice spacing of 0.35 nm that was typical for the graphite. Encapsulated Ni3Si had facet planes which were parallel to the carbon layers surrounding. Production of metal encapsulated carbon nanoball within ceramic materials is the first successive result that might promote researches on such novel ceramic composites.

In-situ fabrication of tungsten nanocrystal encapsulated carbon ball in TEM

Carbon nanoballs and tungsten nanocrystal encapsulated carbon nanoballs were in-situ synthesized by heating starting materials in a transmission electron microscope. The carbon nanoballs of a few nm in diameter were structured by 1 to 5 layers of carbon shells. For the tungsten nanocrystal encapsulated carbon nanoball, the motion (moving, vibration and/or rotation) was in-situ confirmed at elevated temperatures, which might suggest a new possibility of the organic-inorganic composite materials.