Growth Mechanisms of Carbon Onions

1 Growth Mechanisms of Carbon Onions Obtained by Electron Irradiation 

Therefore, due to their small mass, the electrons used must convey a minimum energy of 100 keV to transfer in an elastic collision the momentum required for the displacement. 

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Ozawa et al. proposed another growth mechanisms of carbon onions based on TEM observations of carbon black irradiated by an electron beam [13]. Spiroids are first formed and then carbon onions (Figure 3.3). Qin and lijima also studied the formation of spheroid graphitic particles by irradiating diamond crystals inside a TEM [14]. Since the mechanism of carbon onion formation was not known, several studies were carried out to follow the transformation of diamond nanoparticles into carbon onions directly inside a transmission electron... 

Figure 3.3 Growth mechanism of carbon onion from spiroid proposed by Ozawa et al. Reproduced by permission of American Chemical Society from Ozawa et al. [13], Figure 3, (2002) American Chemical Society...

Thus far, four mechanisms for the formation of concentric shell carbon particles as zero-dimensional carbon allotropes have been proposed. The first mechanism is the formation of a corannulene carbon framework followed by a spiral-shell growth [48], The second mechanism is that the regular concentric arrangements of carbon layers in the onion-like caibon sphere occur tlirough the solidification process of a carbon droplet under ultrafast condensation (49J. The third mechanism is due to a solid—>quasi-liquid—>solid process tliat is, reorganization of soot-containing tubular and polyhedral graphitic particles by... 

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