Relating carbon nanotube growth parameters to the size and composition of nanocatalysts

A gas-phase approach to studying carbon nanotube (CNT) nucleation and growth from nanoparticle catalysts has been developed. Dimensionally- and compositionally-tuned metal particles with mean diameters between 2 and 5 nm and standard deviations less than 15% are initially synthesized from metallocene vapors in an atmospheric-pressure microplasma. The nanocatalysts are continuously fed with acetylene and hydrogen into a flow furnace reactor to grow CNTs. Kinetic studies are performed by in situ aerosol size classification of the nanotubes to relate the CNT length and thus, the growth rate in our thermal process to the catalyst size and composition. We find that reducing the catalyst size results in an increase in the growth rate while varying the catalyst composition affects the growth rate, activation energy, and the onset temperature for CNT growth.