Behaviors of metals in production of nanonetwork materials investigated by radiochemical technique

The iron atoms in the SWNTs soot produced from a carbon rod with Fe-Ni metal by the arc-discharge method were studied for their chemical species by Mössbauer spectroscopy. They were found present as a mixture of some Fe-Ni alloys and the α-Fe metal particles of sizes more than 10 nm that were dispersed. No change was observed in the Mossbauer spectra by the treatment of the soot with 1 M HCl but a drastic temperature dependence of the spectra observed for the samples burned in air indicated that more than 50% of the iron was oxidized to Fe₂O₃ in small particles of less than 10 nm. Effects of acid leaching and baking commonly used for separation of SWNTs were quantitatively studied by use of a radiotracer. Effectiveness of various kinds of metal atoms for forming nanonetwork materials were also investigated by taking advantage of the use of multi-radiotracers. A clear dependence of the yield of metal-containing fullerene species on the boiling point of the metal was indicated, and the yields were found sensitively affected by the amount of the current at the time of dc arc-discharge for the metal elements that were known to take +2 oxidation state in M@C₈₂.