Abstract Submitted to the    NANOTUBE'04 Conference:

We report on roles of metal-support interaction in the growth of carbon nanotubes. The size-controlled iron oxide nanoparticles with two different diameters, 4 and 10 nm, supported on MgO powder were subjected to chemical vapor deposition (CVD). Both nanoparticles catalyzed the growth of double-wall carbon nanotubes (DWNTs) together with a small amount of single-wall carbon nanotubes (SWNTs). MWNTs with more than three layers were seldom observed. We found that the inner- and outer-diameters of the DWNTs were modified by the initial nanoparticle size; smaller nanoparticles catalyzed the growth of the DWNTs with smaller diameters. These results suggest that the MgO support strongly influence the catalytic activity of nanoparticles by reducing the catalytically-active size.