Abstract
Carbon nanofibers (CNFs) were efficiently produced by the Liquid Pulse Injection (LPI) technique, a method originally developed for the rapid production of vapor grown carbon fibers. The production of CNFs was achieved by simply suppressing the carbon source supply in this method. In this method, the catalyst source, typically a benzene solution of ferrocene, is injected into the reactor so as to hit the hot reactor wall as a liquid pulse. Extremely active ultrafine catalyst particles of iron are generated in a highly dense state through the instantaneous decomposition of ferrocene, and CNFs elongate through the catalysis of the generated catalyst particles using the carbon derived from benzene.This work was conducted to clarify the influences of synthesis conditions on the growth behavior of CNFs. It was found that controlling the timing of decomposition of the catalyst source ferrocene was effective to enhance the productivity of CNFs. Such controlling could be conducted by adjusting synthesis conditions such as the temperature of the reactor wall where the liquid pulse hits, the carrier gas flow rate, and the reaction zone temperature. Especially, it was found that increasing the temperature of the reactor wall where the liquid pulse hits, leads to a drastic increase in productivity. Through the adjusting of reaction conditions, we succeeded in producing CNFs at carbon yields over 60%. Moreover, it was found that CNFs with diameters close to carbon nanotubes could also be produced at fairly high carbon yields by adjusting the temperature distribution within the reactor.
