|Budget Amount *help
¥2,500,000 (Direct Cost : ¥2,500,000)
Fiscal Year 1997 : ¥1,500,000 (Direct Cost : ¥1,500,000)
Fiscal Year 1996 : ¥1,000,000 (Direct Cost : ¥1,000,000)
0.3 mum pore sized membrane filter made by poly-ether sulfone was selected for a filter separating the single wall carbon nanotubes (SWNTs) from the arc or laser vaporized carbon soot containing SWNTs. In prior to the microfiltration, the soot was dispersed in an aqueous solution of 0.1% cationic surfactant (benzalkonium chloride) using a conventional ultrasonic vibration bath.If a starting soot contains numerous number of amorphous carbon nanospheres and other nanoparticles, it was necessary to carry out a pre-treatment to increase the SWNT content in the soot using a centrifugal separation. Because, the nanospheres easily stick on the surface /or in the pore of the membrane filter. The sample solution for the centrifugal separation is the same as that for the microfiltration. The spinning speeds of centrifuge with a 8 cm of rotor radius were selected at 5000 rpm and 12000-15000 rpm, respectively, for multiwall carbon nanotubes (MWNTs) and SWNTs to separate the tubules and the carbon
nanospheres. By this centrifugal process, the contents of MWNTs and SWNTs could be increased, respectively, to in excess of 85 % and 40 % from a few tens (MWNTs) to a few (SWNTs) % of tubule content in the arc derived as-prepared soot (from an Fe/Ni or Co/Ni bimetallic catalyst). After increasing the tubule content, we applied the mictofiltration separation and succeed to increase the tubule content up to 70-80 %.
Futher purification for SWNTs was carried out by using a combustion at 420-450ﾟC in dry air for 20-40 min. followed by a soaking in concentrated HCl solution to remove amorphous carbons and metal residua. Here, it is important to carry out the combustion in dry air, since the moisture in air easily attack the carbon network of the tubule at much lower temperature. Purity of the final SWNT product was in excess of 90 %. About 10 to 30 mg of purified SWNTs are now available to prepare per one purification procedure stated above.
The electron spin resonance, Raman scattering and alkaline metal doping studies are now progressing. A researching plan for the study of hydrogen adsorption into the SWNT bundles will be scheduled. Less