The thermal oxidation of carbon nanotubes in air is investigated by in situ Raman spectroscopy. Etching rates are directly seen to be diameter, chirality, and type dependent. We directly track the evolution of bundled nanotube networks that undergo air etching from 300 to 600 °C. Some species are more robust than others. Changes to radial breathing mode (RBM) and G– peak structures suggest that metallic species etch away more rapidly, with smaller diameter semiconducting species etching more slowly and large diameter nanotubes, including semiconductors, etching last. The decay in integrated G and D band intensities is tracked and fit reasonably well with biexponential decay. The RBM evolution is better represented by a single exponential. All bands are fit to activation plots with RBMs showing significantly different rates.

The dynamical evolution of nanotube chemical vapor deposition growth was investigated by in situ spectroscopy of three main Raman bands: G, D, and RBM. The evolution in diameter distribution is inferred from RBM and G bands, and the evolution in crystallinity is determined from D and G bands. A consistent sequence of the growth evolution is observed, with four discernible phases: incubation, acceleration, linear growth, and termination. The temperature dependence of each of these stages of growth is experimentally determined, and characteristic energy scales apparently associated with each phase are extracted. The growth becomes slower as the temperature increases, with activated, parasitic reactions suggested as a cause. We explore to what extent one diameter grows in comparison to another and thus gain some insight into how the nanotube population changes with time.