Development of Mass-Production Technique of Carbon Nanohorn Based on Arc discharge Method

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Carbon nanohorn (CNH), which has a cone shape structure with rounding a graphene sheet, usually forms secondary particle (CNH particle) with approximately 50 nm diameter. CNH particle is greatly interested in the use of the electrode with dispersion of metal catalyst in direct methanol fuel cell (DMFC). Presently, mass-production technique has been developing by the laser evaporation method using an expensive high-power CO_2 laser. On the other hand, the investigators had found that the CNH particle could produce by inexpensive arc discharge method. In the present project, the purpose is that the technique of mass production of CNH particle with arc discharge method is established. The principal outcomes are as follows.1st year: The production condition of dahlia-like CNH particle with high-yield up to 80 %, was found in the present arc discharge apparatus. The amount was more than 1.5 g in 1 batch (less than 1 min.). Based on this result, a new apparatus that can operate for 1 hour wa … More s roughly designed.2nd year: A new apparatus for continuous production was designed in detail and partially made. In order to increase the yield, the relation between the product (arc soot) and operation condition (arc current, gas species, gas pressure) was investigated in old apparatus, and separation process using sieve, ultrasonic separator, nanomizer, and centrifugal separator, was examined. The arc soot was process in high-temperature and it was found that some of the arc soot transformed to carbon nanoballoon.Last year: In order improve the new apparatus for continuous production of CHN particle, the pressure control system, gas introduction system, and soot collection system was fitted up. The relation between the product (arc soot) and operation condition (arc current, gas species, gas pressure) was investigated in the new apparatus. As a result, the target production yield was achieved at higher pressure. However, it was found that the new apparatus was necessarily modified in electrode feed system. Moreover, it was found that non-dahlia-like CNH is suitable for DMFC electrode rather than the dahlia-like CNH. Less