Outer and inner diameters of multi-walled carbon nanotubes grown by laser vaporization

Abstract

Multi-walled carbon nanotubes (MWCNTs) were grown by continuous-wave laser vaporization of graphite containing B4C in Ar, Ne, and He gases. The use of Ne and He gases resulted in the growth of shorter (up to 12 and 6μm long for Ne and He, respectively) and thinner (3.3–41.7nm thick) MWCNTs, compared to long and thick (up to 30μm long and 6.6–53.2nm thick) MWCNTs grown in Ar, along with their reduced fractions in the deposits (approximately 30 and 1% for Ne and He, respectively). Measurements of the outer and innermost diameters and wall numbers of the more than 150 MWCNTs grown in each gas indicated that the outermost diameters of the grown MWCNTs correlated with wall numbers rather than with innermost diameters. The sizes of the molten boron carbide particles, acting as seeds in a vapor-liquid-solid growth process, and their dynamic deformation in the nucleation stage of cone-shaped caps, which lead to the growth of MWCNTs, are thought to be crucial in determining MWCNT outer and inner diameters.