Rapid synthesis of carbon nanotubes by solid-state metathesis reactions

Solid-state exchange reactions between carbon halides and lithium acetylide catalyzed by cobalt dichloride enable the rapid synthesis of carbon nanotubes as observed by TEM. Without the catalyst, only graphite and amorphous carbon form. These reactions are self-propagating and can be initiated with a heated filament. Regulating the reaction temperature provides a method for controlling these reactions. The theoretical temperature for a reaction between hexachloroethane and lithium acetylide is 2302 K assuming adiabatic conditions. Calculations indicate that increasing the length of the carbon chain can lower the reaction temperature by up to 61 K. Replacing chlorine with fluorine can further reduce the temperature by up to 384 K. Replacing chlorine with hydrogen can, in principle, lower the reaction temperature by up to 925 K. These calculations suggest that polymers such as poly(vinyl chloride), poly(vinylidene chloride), and poly(tetrafluoroethylene) can be used as precursors to carbon nanotubes. This is confirmed experimentally using a copolymer of poly(vinyl chloride) and poly(vinylidene chloride) with a 5 mol % (based on carbon) iron trichloride catalyst to produce multi-wailed carbon nanotubes.