Single-walled carbon nanotube formation in a high-pressure non-equilibrium carbon monoxide plasma

Summary form only given, as follows. Single-walled carbon nanotubes (SWNTs) are synthesized in a thermally non-equilibrium flow reactor, in which extreme molecular vibrational mode dis-equilibrium of the primary feedstock, carbon monoxide (CO) gas, is maintained by using a powerful and efficient CO gas laser. The CO molecules absorb the laser radiation on the lowest 10 vibrational transitions and transfer energy to high vibrational states by vibration-vibration energy exchange collisions. This leads to a highly non-equilibrium energy distribution in the CO, which provides enough energy for the carbon-producing CO disproportionation reaction to occur. The vibrationally excited CO reacts in the presence of metal catalysts to form, primarily, carbon dioxide and structured carbon molecules, notably SWNTs, in this continuous (non-batch) process. Iron pentacarbonyl is employed as the catalyst precursor, which dissociates in the plasma and subsequently forms small iron clusters. The influence of iron pentacarbonyl concentration on the quality of the nanotube material is investigated. Ropes of single-walled carbon nanotubes with a high degree of alignment have been observed in deposits created in the CO plasma without any post-production processing. A nanotube content of better than 50% is observed in the deposited material for certain synthesis conditions. At low pressure, substantial quantities of about 20 mg/hour of nanotube containing material are produced. The non-equilibrium synthesis process has been successfully scaled to high plasma pressures up to an atmosphere. We will present results on the production rate and purity of the nanotube containing material under these conditions. IR, visible and UV spectroscopy in the flow reactor has been used to control process parameters.