C2 formation during high-temperature pyrolysis of fullerene C60 in shock waves

Sommer, T.; Kruse, Thomas; Roth, P.

doi:10.1021/j100036a030

Cited by 21 publications

(20 citation statements)

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“…It might be possible that the decline in fullerene mass is due in part to fragmentation of the fullerene molecules in addition to consumption by soot. However, previous studies have shown that C 60 is thermally stable in inert gas up to 1720 K [123,124]. As the temperature in these experiments did not exceed 1300 K, it is unlikely that any unimolecular fragmentation occurred.…”

Section: Discussionmentioning

confidence: 68%

Combustion synthesis of fullerenes and fullerenic nanostructures

Goel

Hebgen

Sande

et al. 2002

Carbon

117

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Fullerenes are molecules comprised entirely of sp 2 -bonded carbon atoms arranged in pentagonal and hexagonal rings to form a hollow, closed-cage structure. Buckyballs, a subset which contains C 60 and C 70 , are single-shell molecules while fullerenic nanostructures can contain many shells and over 300 carbon atoms. Both fullerenes and nanostructures have an array of applications in a wide variety of fields, including medical and consumer products. Fullerenes were discovered in 1985 and were first isolated from the products of a laminar low-pressure premixed benzene/oxygen/argon flame operating at fuel-rich conditions in 1991. Flame studies indicated that fullerene yields depend on operating parameters such as temperature, pressure, residence time, and equivalence ratio. High-resolution transmission electron microscopy (HRTEM) showed that the soot contains nanostructures, including onions and nanotubes.Although flame conditions for forming fullerenes have been identified, the process has not been optimized and many flame environments of potential interest are unstudied. Mechanistic characteristics of fullerene formation remain poorly understood and cost estimation of large-scale production has not been performed. Accordingly, this work focused on: 1) studying fullerene formation in diffusion and premixed flames under new conditions to identify optimal parameters; 2) investigating the reaction of fullerenes with soot; 3) positively identifying C 60 molecules in HRTEM by tethering them to carbon black; and 4) providing a cost estimation for industrial fullerenic soot production.Samples of condensable material from laminar low-pressure benzene/argon/oxygen diffusion flames were collected and analyzed by high-performance liquid chromatography (HPLC) and HRTEM. The highest concentration of fullerenes in a flame was always detected just above the height where the fuel is consumed. The percentage of fullerenes in condensable material increases with decreasing pressure and the fullerene content of flames with similar cold gas velocities shows a strong dependence on length. A shorter flame, resulting from higher dilution or lower pressure, favors the formation of fullerenes rather than soot, exhibited by the lower amount of soot and precursors in such flames. This indicates a stronger correlation of fullerene consumption to soot levels than of fullerene formation to precursor concentration. The maximum flame temperature seems to be of minor importance in formation. The overall highest amount of fullerenes was found for a surprisingly high dilution of fuel with argon. The HRTEM analysis showed an increase of the curvature of the carbon layers, and hence increased fullerenic character, with increasing distance from the burner up to the point of maximum fullerene concentration, after which it decreases, consistent with the HPLC analysis. The soot shows highly ordered regions that appear to have been cells of fullerenic nanostructure formation. The samples also included fullerenic nanostructures such as tubes and sp...

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Section: Discussionmentioning

confidence: 68%

Combustion synthesis of fullerenes and fullerenic nanostructures

Goel

Hebgen

Sande

et al. 2002

Carbon

117

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“…32,85,86 Moreover, the considerable scatter of published experimental and theoretical values for E a,60→58 indicates that this quantity, and consequently all other activation energies derived above, carry significant uncertainties. [1][2][3][4][5][6][7][8][9][10][11][12][13][15][16][17][18][19][20] Within the framework of our theoretical model, the major uncertainty in determining E a,60→58 lies in the nature of the transition state. 11 For the limiting case of a free-rotor transition state, the fitted critical energy would increase by roughly two electron-volts.…”

Section: Theoretical Breakdown Graphsmentioning

confidence: 99%

“…4 Neutral C, C 2 , C 3 , and C 4 fragments have been identified, mostly by optical techniques. 9,[52][53][54][55] The importance of C 4 ejection cannot be established from these data, because neither their relative abundances nor their time dependence can be assessed. The odd-sized neutral fragments, for example, are not accompanied by any significant trace of C 59 ϩ or C 57 ϩ .…”

Section: Introductionmentioning

confidence: 99%

Dissociation of singly and multiply charged fullerenes: Emission of C4, or sequential emission of C2?

Foltin

Echt

Scheier

et al. 1997

The Journal of Chemical Physics

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“…It should be noted that recent direct measurements have shown that the apparent activation energy for C 2 ejection from neutral C 60 following a pure thermal excitation is much lower ͑ϳ4.5 eV͒. [16][17][18][19] Although three independent molecular dynamics ͑MD͒ calculations were performed, 15,20,21 there is yet no direct experimental measurement ͑based on independent calibration͒ available for the vibrational excitation efficiency in any C 60 scattering experiment. The MD based theoretical estimations for the translational to vibration conversion efficiency for 60-250 eV collisions of C 60 ϩ ions with hydrogen terminated diamond ͑111͒ surface vary in the range of 15%-40%.…”

Section: Introductionmentioning

confidence: 99%

Impact induced vibrational excitation in surface scattering of hyperthermal neutral C60 molecule

Tsipinyuk

Budrevich

Grinberg

et al. 1997

The Journal of Chemical Physics

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Articles you may be interested inAn advanced molecule-surface scattering instrument for study of vibrational energy transfer in gas-solid collisions Rev. Sci. Instrum. 78, 104104 (2007); 10.1063/1.2796149Theoretical investigation of the stability of highly charged C 60 molecules produced with intense near-infrared laser pulses Negative ion formation in near grazing surface scattering of hyperthermal neutral C 60 : Image charge effects

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C2 formation during high-temperature pyrolysis of fullerene C60 in shock waves

Cited by 21 publications

References 1 publication

Combustion synthesis of fullerenes and fullerenic nanostructures

Combustion synthesis of fullerenes and fullerenic nanostructures

Dissociation of singly and multiply charged fullerenes: Emission of C4, or sequential emission of C2?

Impact induced vibrational excitation in surface scattering of hyperthermal neutral C60 molecule

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