Investigation of surface vs. bulk diffusion in catalytic growth of carbon nanotubes


Catherine Michelle Cameron, cmcamero@bulldog.unca.edu1, Amar Nath, anath@unca.edu1, Airat Khasanov, akhasanov@unca.edu2, Stevens John G, stevens@unca.edu1, Gayatri Keskar3, and A. Rao4. (1) Department of Chemistry, University of North Carolina at Asheville, 20 Turnberry Drive, Arden, NC 28704, (2) Department of Chemistry, Mössbauer Research Group, UNC Asheville, One University Heights, Asheville, NC 28804, (3) Clemson University, (4) Department of Physics and Astronomy, Clemson University, Clemson, SC 29634
Understanding the mechanism of growth of carbon nanotubes is of great importance, for by achieving this knowledge, nanotubes could possibly be utilized in specific applications where their physical properties play an important role. When grown with a metal catalyst, the product is a combination of metallic and semi-conducting nanotubes. This research is attempting to address the question of whether carbon diffuses through the bulk of catalytic nanoparticles or predominately by surface diffusion. Nanotubes of varying diameters were grown and controlled by differing sizes of the iron catalysts. We expect to find a larger fraction of iron carbide in the nanoparticles of smaller diameter. 57Fe Mössbauer Spectroscopy examination of nanoparticles of iron after the growth of nanotubes gives us the fraction of carbide formed. Our results support the predominance of surface diffusion of carbon atoms on catalytic nanoparticles of iron as well as an indication of surface migration of iron atoms.