Production of Double-Walled Carbon Nanotubes

Besides small carbon clusters generated in the reaction zone anyway, the presence of hydrogen further gives rise to light hydrocarbons that contribute to the deposition of DWNT as well. Hence, in principle, this is a floating catalyst CVD performed in situ. It has indeed been applied in a multitude of experiments for the deliberate production of double-walled nanotubes. Normally, acetylene is employed as carbon source because apparently it suits best to surround an existing nanotube with a second layer of amorphous carbon (refer to Section 3.3.6). 

The CVD-synthesis of DWNT is conducted at conditions similar to those in the preparation of other nanotubes by deposition from the gas phase. The catalyst is 

DWNTs form a dense film ( Nature Publishing Croup 2005). 

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