강한 강도의 탄소나노튜브 섬유 제작을 위한 긴 탄소나노튜브 포레스트 합성

Abstract

In this study, the goal of research was synthesis of long Carbon Nanotube (CNT) forests to contribute to the fabrication of strong CNT fibers. To achieve the goal, unnecessary behavior of Fe catalyst particles interrupting the growth of long CNT forests was prevented by using the Fe implanted wafers and the effect of quartz tubes used in the synthesis of CNT forests was investigated to enhance the reproducibility of synthesis of long CNT forests. we studied the method for preventing the behaviors of Fe catalyst particles so called surface diffusion and subsurface diffusion respectively. The Fe deposited wafers were usually used before, but both behaviors of particle diffusion were prevented by using the Fe implanted wafers. To prevent the surface diffusion of Fe particles, annealed Fe implanted wafers were used. The Fe ions were gathered and formed the Fe particles in the implanted wafers initially. After annealing, the Fe particles diffused to the surfaces of wafers and anchored firmly that can prevent the surface diffusion. By preventing the surface diffusion, the distribution of diameters of Fe particles and CNTs can be narrower than before. To prevent the subsurface diffusion of Fe particles, Fe implanted wafers which were deposited with Fe layers were used. The implanted Fe ions can decrease the difference of Fe concentration between the surfaces and interiors of wafers by comparing with only Fe deposited wafers. It reduced the driving force of subsurface diffusion of Fe particles from the surfaces of wafers during the synthesis of CNT forests and the catalyst life time can be prolonged from 496 minutes to 660 minutes. Finally 21.5 mm length of CNT forests can be synthesized. Additionally, we studied the conditions of quartz tubes used in the CNT forest growth to enhance the reproducibility of synthesis of long CNT forests. After synthesis of CNT forests, the amorphous carbons were deposited on the inner wall of quartz tubes. These carbon deposits were regenerated in the ambient air and removed. Regenerated quartz tubes were assumed that they were same as fresh quartz tubes that had never been used. However, in the case of regenerated quartz tubes, some of the carbons were diffused into the interior of quartz tubes during the regeneration process. These carbonaceous impurities can make the difference of quartz tube conditions because carbon impurities were released prior to the growth of CNT forests and resulted in the high number density of Fe particles. The initial growth rate of CNT forests was increased following with high number density of Fe particles. As the growth rate of CNT forests gradually decreased from the initial rate, increased initial growth rate in regenerated quartz tubes is proper for the long CNT forest growth. As a result, the reproducibility of long forest growth in the regenerated quartz tubes can be demonstrated.