The structures of higher fullerenes are described based on 13C NMR measurements of isolated and purified samples. The most interesting aspect deduced from the present structural work on the higher fullerenes up to C90 is that among 19 kinds of fullerenes with different sizes and isomers, 18 fullerenes commonly have at least one C2 symmetry axis in their molecular frame. Only one exception is C90 fullerene with a C1 symmetry. The spectral feature of UV/Visible absorption obtained for the HPLC-isolated C120 fullerene gives, on the other hand, a strong indication that the numbers of co-existing isomer of very large fullerenes are extremely limited, probably one or two. Considering the huge numbers of IPR-(isolated pentagon rule) satisfying isomer of C120 (10,774), these experimental evidences may suggest the presence of very strong selectivity for the formation of stable higher fullerenes, which, in turn, is closely associated with the unknown growth process of a fullerene cage network.

The high intensity of solar radiation, obtained with the Odeillo (France) solar furnace facilities, is used to vaporize graphite in inert gas atmosphere. The soot obtained contains C60, C70 and other heavier fullerenes. We discuss the possibility of increasing the evaporation rate of graphite and the yield of soot with this technique. From our last experiments, we obtain a first estimate of the soluble fullerene yield Y ( greater than 12%) and we have shown that 13C enriched fullerenes can be easily produced by this process.

The formation of fullerenes by combustion was investigated for nine benzene/oxygen/argon flames, one acetylene/oxygen/argon- and one toluene/oxygen/argon flame burning at 75 mbar. The flame-generated soot was Soxhlet extracted with toluene and the extract analyzed by HPLC. It was shown that the C60/C70 ratio depends on the percentage of argon in the fresh gas mixture, which is directly related to the flame temperature. The use of acetylene and toluene as combustible led also to the formation of fullerenes, the yield in the toluene flame being 3.71% of the generated soot, so that toluene represents a serious alternative to benzene for fullerene fabrication in flames.

The reaction chamber in the arc production of fullerenes was redesigned with a nozzle surrounding the decomposition zone to allow for clean collection of soot in a filtering cartridge. Quantitative analysis in the region of 300–430 nm in UV-visible spectra permits determination of the abundance of C60 and C70 in the soot. Calibrated curves of absorptivity for both pure fullerenes were employed. In equivalent conditions of current and pressure, electrographites of different origins have different decomposition rates and yields. A mechanism to interpret the cathodic deposit formation is proposed. Decomposition inside a closed cathodic cylinder yields 100% deposit.

Details of the carbon-coated nanoparticle growth mechanism are revealed by a comparison of product morphology and reactor parameters. Carbon-coated metal or metal carbide clusters nucleate in the gas phase, grow to characteristic sizes, and deposit on surfaces within the reactor. The surface temperature determines the crystallinity of the nanoparticles and the surrounding carbon. Tungsten carbide nanoparticles show that the carbon coating arises due to phase segregation when the nanoparticle has a lower melting point than that of graphite.

The effect of increasing metal fraction on carbon arc nanoparticle production is examined for 10–50 weight percent cobalt starting materials. With 500 Torr of helium buffer gas, the carbon arc process yields carbon-coated FCC Co nanoparticles of similar sizes throughout this range. The saturation magnetization is believed to scale linearly with the relative abundance of Co. The variation in the coercivity with abundance is small compared to the dramatic changes which can arise from changes in the size of fine particles. The approach to magnetic saturation is more rapid in high abundance samples. This is attributed to interparticle interactions which align the easy axes when the nanoparticles crystallize within interconnected carbon shells. The switching field distribution as a function of Co abundance arises from both rotational barriers and from barriers due to the particle size distribution.

Using X-ray powder diffraction and transmission electron microscopy we examine the morphology and crystallographic structure of carbon-coated nanoparticles produced in a modified Huffman-Kratschmer carbon arc process. Graphite rods containing Ho were consumed in the arc and soots sampled from both the reactor walls and the inner core of the cathode deposit are compared. The inner core soot displays increased crystallinity and less amorphous carbon than wall-deposited soot, and nanoparticles in the inner core have more graphitic layers in the encapsulating shells, more gaps between the carbon coating and the core, and exhibit a greater degree of facetting than particles harvested from the reactor walls. These differences are interpreted as manifestations of the high temperature post-formation environment of the inner core of the cathode deposit.

Using a boron-containing composite anode in an arc discharge, we found in the soot on the reactor walls graphitic multiwalled carbon clusters that contained boron carbide crystals, as identified by high resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and electron diffraction. The encapsulants are compounds of the lightest element that has yet been encapsulated, and the first of the non-metallic. The multiwalled graphitic cages partially encapsulating the boron compounds have rarely been observed in the soot of arc-discharge material produced from anodes not containing boron. We explain this exception by the known tendency of boron to catalyze graphitization.

Ultrafine boron nitride powders were synthesized by laser driven reactions in BC13-NH3 mixtures. The structure and morphology of the graphitic nanoparticles generated in this process were investigated by high-resolution electron microscopy. Polyhedral concentric shells (ranging in size from 30 nm to more than 100 nm) are a major constituent of the as-pyrolyzed powder. This onion-like configuration is very similar to that observed in carbon materials. After heat treatment at 1650°C under nitrogen atmosphere, plate-like particles with a few perfectly flat graphitic sheets (10 to 50 layer thick, 50 nm in diameter) are formed.

Efforts to control the growth of individual carbon nanotubes from nanotube seed crystals have led to a characterization of their field-induced electron emission behavior. The application of a bias voltage in our growth apparatus was motivated by the prolific formation of nanotubes in the carbon arc growth method, in which the electric field appears to play a central role. We report here the ability to achieve various tube tip configurations by the controlled application of voltage, heat and chemicals to an individual nanotube, and that these states are well characterized by the emission currents they induce.

The discovery of a catalytic route to the growth of single-layer carbon nanotubes suggests that it may be possible to produce these materials with better selectivity and in higher yield. Increasing the production efficiency is essential for characterization and application of these materials. We have discovered several catalyst promoters, in particular S, Bi, and Pb, that greatly enhance the single-layer carbon nanotube yield, and extend the distribution of nanotube diameters to much larger sizes (> 3 nm). Co crystallites encapsulated in graphitic polyhedra also form abundantly when S, Bi, or W is present. Understanding these catalytic process is of substantial scientific and technological importance.

Several oxidants were examined for their abilities in opening carbon nanotube end caps. Up to 91% of carbon nanotubes were found to have at least one open end when treated by 0.2 M KMnO4/ 10% H2SO4 or 0.2 M KMnO4/ 0.2 M CrO3 aqueous solution at 100° C, 90 min. That is, σ82% of carbon nanotubes was converted to “nanostraws”. The morphologies of the processed carbon nanotubes reflect the relative strength of these oxidants. The mechanism of carbon nanotube end cap opening processes will be discussed.

Fine molecular straw, carbon nanotube (NT) is aligned to form a bundle. The purified NTs are mixed with a plastic polymer (polypropylene: PP) and extruded from a small die with a diameter of 2 mm kept at 200°C. The threads of NT/PP blend are characterized by small angle X-ray diffractometry and transmission electron microscope to confirm the existence of nanobundle of NTs, which orient along the spinning direction.

Very hot carbon vapor was deposited on highly-oriented pyrolytic graphite (HOPG) and on sapphire substrates. Using atomic force microscopy, the obtained carbon structures are analyzed. It is found that carbon nanotubes and cones had formed on the graphite substrate but not on sapphire. Instead, spherical-type nanoparticles are analyzed on sapphire. A particle with double-conical shape is found on the graphite substrate. The two observed cone angles 19° and 60° are explained by perfect network closure of sectors of curled graphene sheets.

We discuss experiments and theory directed towards the development of a buckytube cold field emitter array electron cathode.

We present the finding of experiments of considerable field emission from the films consisting of nanotube carbon structureson various substrates (Si, quartz, glass): density of emission current was up to 1-3 A/cm2 while electric field was about 100 V/μ. The “reconstruction” and “inversion” of field emission have also been observed after current breakdown.

Measurements of diamond bulk density change of carbon powder in the annealing of UDD to OLC (293-2400 K) was performed by irradiating the samples with a narrow beam of gamma quanta (137Cs gamma-ray source). The intermediates of UDD to OLC transformation were registered by high resolution TEM. The annealing products were also characterized by true density and specific area adsorption measurements. The structural rearrangement of UDD begins from the surface towards a crystal bulk. UDD annealing proceeds via particles composed of semi-spherical shells enclosed one-to-one with the rest of diamond core and quasispiral carbon shells. The influence of particle size on the temperature of UDD to OLC transformation was found.

The gas-phase reaction between MoO3-x and H2S in a reducing atmosphere and at elevated temperatures (800° to 950°C) has been used to synthesize large quantities of an almost pure nested inorganic fullerenes (IFs) phase of MoS2. A uniform IF phase with a relatively narrow size distribution was obtained. The x-ray spectra of the different samples show that as the average size of the IF decreases the van der Waals gap along the c axis increases, largely because of the strain involved in folding of the lamella. Large amount of quite uniform nanotubes were obtained under modified preparation conditions.

In the second part of this work MoS2 nested fullerenes were grown on Ti and Nb and Mo oxide substrates. In one set of conditions hollow nested fullerenes of MoS2 were collected on a titanium oxide matrix, and analyzed by local area energy dispersive analysis. Under different flow conditions of the reacting gasses nested fullerenes with endohedral metal oxides were obtained and analyzed by electron diffraction.

Since the initial discovery of fullerenes nearly a decade ago [1], material scientists have focused attention on the possibility of encapsulating one or more metal atoms inside these spheroidal carbon frames. The experimental realization of macroscopic quantities of endohedral metallofullerenes (Am@C2n, n=30-55) in the early 1990's has heightened interest in developing this new class of tunable materials with possible electronic and/or optical applications [2,3]. They have been characterized by a number of spectroscopic techniques, for example, scanning tunneling microscope [4,5], EXAFS [6,7] and x-ray diffraction and electron microscopy [8]. However, low production yields and purification difficulties have hampered the development of this new class of materials. The soluble product distribution usually consists of high levels of the empty-caged fullerenes C60, C70, C84 and decreasing levels of the higher fullerenes, while the endohedral metallofullerene fraction usually constitutes less than 1% of the total soluble yield. Furthermore, the endohedral metallofullerene fraction consists of molecules with different numbers of metal atoms encapsulated (m=1-3), cage sizes (C2n) and isomers of the same mass (e.g., Er2@C82). The purification process is further complicated by the chemical reactivity of several endohedral metallofullerenes [9] in aerobic environments. For several years, we have been involved in a collaborative effort to develop methodology for detection, isolation, and characterization of endohedral metallofullerenes. The focus of the present study is on fullerenes encapsulating metals from Group II1b, (Sc@C2n, Y@C2n, and La@C2n) and the lanthanide series metal (Er@C2n).

Two abundant ESR-active lantanofullerene species have been isolated with an efficient HPLC method. Each of isolated species was well identified as a stable metallofullerene molecule. Both mass and ET 9 spectra confirmed that they were La@C82 with 1.159-G and 0.836-G 139La hyperfine splittings. Visible and near-IR absorption spectra, cyclic and differential pulse voltammograms, and 13 C hyperfine splitting structures in ESR spectra for the samples showed features quite different from each other. Their differences were discussed on the basis of their structures.