The growth of carbon nanotube (CNT) forests has been limited to the centimeter scale due to insufficient understanding of their growth kinetics. To investigate the growth kinetics of CNT forests, we characterized the mass transport phenomena arising during CNT forest. We formulated the hypothesis that such growth is mass transport limited and proposed a model describing this mass transport. According to our model, the effects of diffusion boundary layers on the growth rate are significant. The initial growth rate is expected to increase with the velocity of the bulk gas flow as the boundary layer thickness decreases. To test this prediction, CNT forests were grown at various total gas flow rates in the range 170–1700 sccm, which correspond to flow velocities in the range 0.79–to 7.9 cm/s. The initial growth rate was found to increase from 1.4 mm/h to 3.5 mm/h as the total flow rate increases from 170 sccm to 1700 sccm. Thus there is a clear inverse proportionality between the initial growth rate and the thickness of the diffusion boundary layer, which confirms that the growth of CNT forests is mass transport limited. These results provide new insight into the growth kinetics of CNT forests.
탄소나노튜브를 길게 합성하는 것이 매우 중요한데, 더 길게 합성하기 위해서는 속도 결정 단계를 이해하여야 한다. 본 논문에서는 기판 위에 수직정열된 탄소나노튜브를 합성할 때 기판 주위로 형성되는 경계층으로 인하여 유체의 물질이동 과정이 속도 결정 단계가 됨을 밝혔다. 최대 1.9 cm의 매우 긴 탄소나노튜브 포레스트가 합성되었으며, 더 긴 탄소나노튜브 합성을 위해서는 물질이동 속도를 높여야 함을 제시한다.