Thermal stability of fullerenes: a shock tube study on the pyrolysis of and

Abstract

The thermal stability of fullerenes and dispersed in Ar was studied behind shock waves by following the time-dependent absorption and emission of the proposed decomposition product . The gas - particle mixtures filled into the shock tube were heated to temperatures at pressures of . Because of the relatively high vapour pressure of the fullerenes, they evaporate in a few microseconds so that both and are in the gas phase during most of the observation time. concentration profiles were measured by a ring dye laser spectrometer at . Simultaneously, the time behaviour of spectrally resolved light emitted from the shock-heated aerosol was recorded by an intensified CCD camera. A simplified reaction mechanism with both formation and consumption reactions was proposed and the experimental results were discussed in terms of kinetic parameters. Rate coefficients and of the initial pyrolysis reactions (R1) and (R2) were determined. Two different models for the further decomposition of fullerene fragments were discussed and compared with computer simulations.

Atomistic Mechanism of Carbon Nanostructure Self-Assembly as Predicted by Nonequilibrium QM/MD Simulations

“…Elimination of C 2 molecules from buckminsterfullerene is associated with genuinely high energy barriers since its cage possesses such a strong, rigid framework (the original motivation for Buckminster Fuller to create lightweight yet very stable large dome structures). The high temperatures required for pyrolytic decomposition of I h -C 60 (2,650 K) and D 5h -C 70 (2,440 K) [131] demonstrate that these cages, once formed, are extremely hard to destroy. The Stone-Wales transformation for I h -C 60 with barriers of 6-8 eV (depending on the choice of the DFT method) requires a temperature exceeding 1,100 K [132], and it can be assumed that, once a perfect I h -C 60 cage was obtained by the combination of C 2 elimination and Stone-Wales transformations, no more structural transformations should occur below this temperature.…”

Deposition of amorphous carbon films from C60 fullerene sublimated in electron beam excited plasma

“…Even higher maximum boundaries of thermal stability for fullerenes have been indicated. For example, the decomposition of C 60 and C 70 molecules in the gas phase has been pointed out to begin at 2650 and 2440 K, respectively [25]. In addition, one carbon atom in the C 60 fullerene connects with the other carbon atom with sp 2 hybridization bonds to form the delocalizationconjugated π bonds that can be broken down by argon ion bombardment [26].…”

Towards the understanding of structure formation and dynamics in bio-nano systems

“…While it is known that fragmentation of the cage can be induced by pyrolysis [26] laser-irradiation [27] or collisions with charged/neutral particles [28][29][30], the mechanism of formation has remained unclear [31,32]. The processes of thermal fragmentation and reassembly of fullerene molecules in the gas phase has been recently reconsidered [25].…”