Eleven metals were laser-vaporized with carbon into Ar gas, and the growth of various nanocabon and composite
materials were investigated. Controlling the Ar gas pressure and the metal content for Fe, Co, Ni, Cu, and Ag enabled the
high yield (~70%) fabrication of single-wall carbon nanohorn particles including metal- or carbide-containing carbon
nanocapsules. With the use of B, multi-wall carbon nanotubes were grown with a high yield of ~50%. For Al, Si, La, Y,
and Gd, products such as carbide particles, polyhedra, and sea-urchin-type single-wall carbon nanotubes were formed.
We will discuss the growth of these structures based on metal-catalyzed graphitization together with thermal
Laser vaporization of graphite was carried out in the presence of high pressure Ar gas of 0.1-0.8 MPa. We compared the growth processes of three synthesized graphitic carbon particles: single-wall carbon nanohorn, multi-layer graphene, and polyhedral graphite particles. We believe graphitization processes occurred from supersaturated hot carbon vapor, dependent on resident carbon densities and their temperature gradients, lead to the growth of the three graphitic particles.
Catalytic activities of Fe, Pt, and Ni/Co metals were compared in the synthesis of single-wall carbon nanotubes (SWNTs) by using CO<SUB>2</SUB> laser vaporization. In room temperature laser vaporization in AR gas under pressures of 150-760 Torr, a small amount of SWNTs, forming thin bundles, were synthesized by Pt and Ni/Co catalysts. However, SWNTs were not synthesized by using an Fe catalyst. The central diameters of SWNTs were 1.51 and 1.33 nm for the Pt and Ni/Co catalysts, respectively. At 1200 degree(s)C, thick bundles of SWNTs with a central diameter of 1.39nm were synthesized for Ni/Co in high yield (>70%0. However, the increase in SWNT yield was not significant when using a Pt catalyst at 1200 degree(s)C. We discuss catalytic growth of SWNTs in terms of eutectic temperatures of Pt-C and Ni/Co-C phases.
Time-of-flight mass spectrometry has been used to probe neutral and positive ionic species produced by laser ablation of a graphite target at 266, 355, 532, and 1064 nm. The arrival time distributions of major carbon species (C<SUB>3</SUB>, C<SUP>+</SUP>, and C<SUB>3</SUB><SUP>+</SUP>) at a deposition substrate, 45 mm from a target, were fitted with a thermal Maxwell-Boltzmann (MB) distribution or a shifted MB distribution with a narrower width. The characteristics of laser ablation with shorter-wavelength laser light are the formation of atomic carbon species with high kinetic energies and the promotion of their ionization. We discuss the generation process of C<SUP>+</SUP> and the formation of a tetrahedral amorphous carbon film with a high fraction of sp<SUP>3</SUP> bonded carbon atoms.