Mechanisms for Chemical Vapor Deposition Carbon Nanotube Growth by Surface Modification of 316L Stainless Steel

We attempt to model the mechanisms responsible for carbon nanotube growth via chemical vapor deposition on a stainless steel substrate. The 316L steel substrates require no deposited iron catalyst to initiate CNT growth. Instead, iron-rich nanoparticles were created from the substrate itself using several gas treatments. First, an iron-rich oxide layer is grown on the surface of the steel in air at 800 °C. The steel is then exposed to ethylene gas at the same temperature, which reduced the oxide to form catalyst nanoparticles. These iron particles are the primary sites for CNT growth on the steel surface, and particles of iron were also pulled into the tips of the nanotubes. The CNTs had a multi-walled structure and an average diameter of 39 nm at the start of growth. Nanotube diameters grew over the course of growth, suggesting carbon infiltration. Samples were analyzed using both Scanning and Transmission Electron Microscopy to characterize the CNTs and the steel substrate. X-Ray spectroscopy is performed on cross-section of the nanotubes and substrate to characterize the oxide layer and metallic nanoparticles over the course of CNT growth. From our results, we conclude that by oxidizing and reducing the surface, we can create ideal nanoparticles for CNT production.