Nature of the Catalyst Particles in CCVD Synthesis of Multiwalled Carbon Nanotubes Revealed by the Cooling Step Study

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• 作者：Vasile Heresanu ; Celia Castro ; Julien Cambedouzou ; Mathieu Pinault ; Odile Stephan ; Cecile Reynaud ; Martine Mayne-L'Hermite ; Pascale Launois
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：May 15, 2008
• 年：2008
• 卷：112
• 期：19
• 页码：7371 - 7378
• 全文大小：547K
• 年卷期：v.112,no.19(May 15, 2008)
• ISSN：1932-7455

文摘

The true chemical nature and physical state of the catalyst particles in Catalytic Chemical Vapor Deposition(CCVD) synthesis of carbon nanotubes are the subject of intense discussions, as it is one of the keys tounderstand their growth mechanisms. The CCVD method considered in this article involves pyrolysis ofmixed liquid aerosols and leads to the synthesis of large carpets of multiwalled nanotubes (MWNTs) partiallyfilled with iron-based materials. The experimental approach consists in studying the influence of the coolingprocedure applied at the end of the synthesis. Both slow standard cooling or quenching were performed, andthe structure and chemical state of the iron-based particles were compared through complementary local andglobal investigations involving X-ray diffraction, electron microscopy, electron diffraction, as well as electronenergy loss spectroscopy. We clearly demonstrate that iron-based catalyst particles are carbon-rich and oxygen-free in quenched samples, and that they oxidize during the slow cooling step. It is inferred that they are veryprobably molten supersaturated carbon-metal particles during the NT growth.