The synthesis and characterization of carbon nanotubes grown by chemical vapor deposition using a stainless steel catalyst

Multi wall carbon nanotubes (MWCNTs) were grown on a stainless steel (SS) sheet by chemical vapor deposition without the addition of external metal catalyst. We found that the key for highly efficient growth includes the nanoscale roughness of the SS surface, as shown by scanning tunneling microscopy, that acts as catalyst/template in the nanotube formation. Raman spectroscopy and electron microscopy were used to check the nature and quality of the synthesized nanotubes. We conclude that stainless steel favors a base-growth mechanism. Transmission electron energy loss spectroscopy performed on single metallic particles found inside the nanotubes clarified the atomic nature of the catalytic particles supplied by the steel. Only unoxidized iron was found and no traces of nickel and chromium were detected. In addition, the SS substrate has been used for a second growth process after carefully removing the synthesized CNTs, proving that a continuous production of CNTs from the same substrate is achievable.