The mass spectrometer is used to determine the composition of a sample and follow the evolution of changes in the gas phase composition during the SWNT synthesis. Gases from a reactor are pushed through the lines of the mass spectrometer to an ion source. From there, a mass analyzer determines the molecular weight of the compound. This information can be very important in determining a mechanism for a reaction.
The role of water in carbon feed on the surface-guided growth of horizontally aligned single-walled carbon
nanotubes (HA-SWCNTs) was investigated. It is shown that the amount of water can be optimized to favor HA-SWCNT growth, which is proposed to be due to selective etching of carbon deposits at carbon–metal interface. Without water, nanotube–nanotube interaction and carbon accumulation at the interface are disproportionately large compared to the rate of nanotube growth, leading to catalyst deactivation. With excess water, suppression of nanotube growth occurs, resulting in reduced carbon yield on the surface.
Intermediate carbon/water feed ratios achieve cleaner growth with high efficiency.