Rapid Production of Carbon Nanotubes by High-Power Laser Ablation

Carbon nanotubes were synthesized in an atmospheric chamber by irradiating a metal-catalyst containing graphite target with a 2 kW continuous wave $CO2$ laser and capturing the soot in flowing distilled water to facilitate continuous, rapid production. The ablation products, swept away by an argon flow and collected in the distilled water, were further purified to result in a yield of 50%. The growth rate of purified aggregate ranged from 0.5 to $2g∕h$ depending on the laser power. Microscopic scanning electron microscopy, atomic force microscopy, transmission electron microscopy and spectroscopic (Raman) methods characterized the purified aggregate as a mixture of individual and bundle of single-wall nanotubes, nanoparticles, clusters, and impurities. Nanotubes accounted for approximately 10% of purified aggregate inferring a maximum production rate of $0.2g∕h$⁠. The average diameter and length of nanotubes were 1.3 nm and $1.5μm$⁠, respectively. The major benefits of this technique are absence of vacuum and high-temperature furnace that are associated with the traditional pulsed laser method, and scalability to meet the industrial production levels.