Rhenium and Molybdenum as Diffusion Inhibitors in Catalytic Metal Particles for growth of Ultra-Long Carbon Nanotubes (CNTs)

Bulk production by Chemical Vapor Deposition (CVD) of ultra-long Carbon Nanotubes (CNTs) with lengths greater than several centimeters is desirable for materials applications, but is not presently feasible. A principal reason for this limitation is cessation of CNT growth due to erosion of the nano-sized catalyst particles from which the CNTs nucleate and grow: at elevated CVD growth temperatures, atoms of catalytic metal detach and diffuse away from the particles, resulting in erosion and eventual deactivation of the particles. Recently, a novel idea was introduced to slow this diffusion and erosion by including heavy refractory metals with the catalyst metals in the nanoparticles. Here are presented recent and ongoing investigations into this method. The metal system investigated uses iron as catalyst and rhenium as diffusion inhibitor. Results show that inclusion of Re in the catalyst particles will substantially increase the catalysts particle lifetimes, and hence the growth time of the CNTs produced. These results are compared to previous results obtained using the iron/molybdenum system of catalyst/inhibitor.