Nobuharu Okazaki

In Situ Study of Iron Catalysts for Carbon Nanotube Growth Using X-Ray Diffraction Analysis

We have investigated how an iron catalyst changes during the growth of vertically aligned carbon nanotubes by in situ measurement of X-ray diffraction. It is found that heating the catalyst film to a growth temperature of 700°C in He atmosphere induces its oxidation beyond 100°C due to adsorbed moisture and changes the film to particles at approximately 600°C. At 700°C, the catalyst particles consist mainly of iron oxide with a cubic system. By feeding C2H2, the catalyst starts to be deoxidized and then absorbs carbon atoms to form Fe-C and Fe3C. The growth mechanism of nanotubes is discussed in terms of the crystalline phase and orientation of the catalyst.

Synthesis of Multiwalled Carbon Nanocoils Using Codeposited Thin Film of Fe–Sn as Catalyst

Multiwalled carbon nanocoils (CNCs) have been synthesized by a method of thermal chemical vapor deposition (CVD) using a codeposited thin film consisting of Fe and Sn as catalysts. It has been found that the multiwalled CNCs are thinner and have a higher crystallinity than conventional CNCs. The catalyst particles are observed at the roots of CNCs, with diameters much larger than the line diameters of the coils. These large particles are formed by the aggregation of Sn and Fe reduced by the C2H2 gas in CVD. These results indicate that Sn plays a crucial role in the growth of the multiwalled CNCs, and a base growth mechanism that differs from conventional growth mechanisms has been experimentally observed and analyzed.