Carbon nanotube formation directly on the surface of stainless steel materials by plasma-assisted chemical vapor deposition

We have developed a method for forming carbon nanotubes (CNTs) directly on the surfaces of stainless steel materials that are important industrially. Using plasma-assisted chemical vapor deposition (PCVD), CNTs are formed at comparatively low temperatures, thus avoiding excessive annealing and degradation of the stainless steel. Because the catalytic metals needed for CNT formation are contained in the stainless steel materials themselves, coating processes of catalytic metals can be omitted. In the experiment, we prepared sample substrates made from stainless steel 304, which is representative of austenitic stainless steels. The PCVD was performed at 550~600°C by introducing methane gas to the substrates at a pressure of 260 Pa. The deposited samples were observed with SEM, TEM, and TEM-EDX. The results reveal that aligned multi-walled CNTs were formed directly on the sample substrates. The CNTs were typically ten layers and 15 nm in total diameter. To improve the uniformity of CNT growth across the substrate, we have tried a new pretreatment method in which the substrates are heated in the atmosphere before initiating PCVD.