Carbon nanostructures produced by pyrolysis under high pressure inside a nanosize silica matrix

• Published in: Journal of Raman spectroscopy 2012-08, Vol.43 (8), p.1029-1034
• Main Authors: Villanueva, Antonio E. L., Balzaretti, Naira M., da Jornada, Joao A. H.
• Format: Article
• Language: English
• Subjects: Carbon; Dispersions; Electron microscopy; Mathematical analysis; nanocarbon; nanocomposite; Nanostructure; Pyrolysis; Raman spectroscopy; Silicon dioxide
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.3150

In this work, the pyrolysis under high pressure of hydrocarbons dispersed inside a nanosized silica matrix (Aerosil) was investigated. The samples consisted of hydrophobic nanometric silica powder terminated by methyl groups with carbon contents ranging from 0.7 to 4 wt%. The pyrolysis was carried out in the temperature range from 1000 to 1600 °C under high pressure (1.25 up to 7.7 GPa) to keep the two‐dimensional distribution of carbon atoms originally at the silica grain boundaries. Evidences from Raman spectroscopy and transmission electron microscopy suggested that the resulting carbon nanostructures were actually graphene‐like nanoflakes. The size of the nanostructures calculated from the ID/IG ratio increased from 6 to 30 nm for processing temperatures increasing from 1000 to 1600 °C under pressure, respectively. The results revealed that the very good dispersion of the methyl groups inside the nanosize silica matrix, and the confinement under high pressure during the pyrolysis, played both a relevant role in the resulting carbon nanostructures. Copyright © 2012 John Wiley & Sons, Ltd. The pyrolysis of carbon precursors under high pressure is a promising new route to produce graphene‐like structures of very small dimensions (below 10 nm) in a controlled and confined way. Hydrophobic Aerosil samples are very suitable for creating these carbon structures, which can be probed by Raman and transmission electron microscopy analysis.