Growth of unusual carbon nanofilaments in methane pyrolysis

Two types of carbon nanofilaments (nanotubes) differing markedly in morphology and growth rate grow on substrate plates containing a supported catalyst in a methane atmosphere at ～1050°C. According to provisional estimates, nanofilaments of one of these types grow at a rate of 5–10 μm/s, which is 50–100 times as high as the growth rate observed for ordinary catalytic filaments (tubes). These filaments are as long as several millimeters, being 50 to 100 nm in diameter. A preliminary examination of their structure has demonstrated that there is no catalyst particle at the filament end and that the filament is likely a carbon-rich polymer. A possible mechanism of the growth of these carbon filaments is discussed.