Gas-dynamic consideration of the laser evaporation synthesis of single-wall carbon nanotubes

Rate-Limiting Processes in the Formation of Single-Wall Carbon Nanotubes: Pointing the Way to the Nanotube Formation Mechanism

“…This is necessary, as it is known that the SWCNT formation process can extend up to seconds. 4 The quenching, together with a nearly constant gas flow velocity in the hot zone of the furnace, i.e., constant timeof-flight of the SWCNT soot, enabled us to keep the time window allowed for SWCNT growth processes fairly constant. In addition, if the soot were allowed to slowly propagate through the temperature gradient from the hot zone to the end of the furnace tube (i.e., no quenching, with ongoing SWCNT formation during this propagation), a reliable determination of the role played by the hot zone temperature would not be possible.…”

Experimental and theoretical studies of particle generation after laser ablation of copper with a background gas at atmospheric pressure

“…laser fluence and wavelength, pulse duration, carrier gas type, pressure, and flow rate [15][16][17][18]. Experiments such as light scattering and photoluminescence have been used for real-time imaging of the particle production process to study the effects of different experimental parameters [5,19,20].…”

Formation of Various Nanocarbon and Composite Structures by Laser Ablation

“…B also has a C solubility (24.3 at.%) higher than those of Ni (2.7 at.%) and Co (4.2 at.%). Therefore, MWCNTs, which accompany the precipitation of large amounts of C are thought to be grown efficiently on large molten BC particles at temperatures higher than that (800-1300°C) for SWCNTs (Gorbunov et al, 1999). Although the actual temperature needed for C precipitation to form MWCNTs is not clear, temperatures up to ~2400°C may create favorable conditions for efficient MWCNT growth.…”

“…In addition, emission imaging and shadowgraphic studies implied that vaporized species had low expansion velocities of 10 2 -10 3 cm/s (Kokai et al, 1999) due to the high-pressure Ar gas restricting their expansion. Unlike a laser ablation method combined with an electric furnace for SW and MWCNT growth, where vaporized C and metal species kept at 800-1300°C are essential for an efficient CNT growth (Gorbunov et al, 1999), the heat sources available for the growth of various nanocarbon and composite structures in this study are laser-ablated C and metal species themselves confined by high-pressure Ar gas. The control of the resident densities and the maintenance of high-temperature of laser-ablated C and metal species, based on adjusting the metal content in graphite and the Ar gas pressure, results in various composite nanostructures with high yields in the deposits.…”