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Simple model of the interrelation between single- and multiwall carbon nanotube growth rates for the CVD process

机译:CVD过程中单壁和多壁碳纳米管生长速率之间相互关系的简单模型

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摘要

Recent time-resolved measurements of carbon nanotube (CNT) growth on Fe and Fe/Mo catalysts have identified a maximum growth rate and temperature corresponding to the onset of small-diameter, single-wall CNT (SWNT) formation. A simple model described here emphasizes the essential role of the SWNTs in the growth process of CNTs. Remarkably, it shows that the growth rate (i.e., the time derivative of the length) of a multiwalled CNT is the same as that of a SWNT at the carbon flux and diffusion coefficient corresponding to a given temperature. Moreover, below ~700℃, the temperature above which SWNT growth is observed for a 6 sccm (cubic centimeter per minute at STP) C_2H_2 flow rate, the number of walls as a function of temperature is uniquely determined by the interplay of the incident flux of atomic C and diffusion rates consistent with bulk diffusion. Even partial melting of the catalytic particle is unnecessary to explain the experimental results on growth rate and number of walls. Above 700℃, where severe catalyst poisoning ordinarily begins, the growth rate without poisoning is consistent with recent results of Hata and co-workers [Science 306, 1362 (2004); Phys. Rev. Lett. 95, 056104 (2005)] for "supergrowth."
机译:最近在Fe和Fe / Mo催化剂上进行的碳纳米管(CNT)生长的时间分辨测量已经确定了最大生长速率和最高温度,对应于小直径,单壁CNT(SWNT)形成的开始。这里描述的简单模型强调了SWNT在CNTs生长过程中的重要作用。显着地表明,在对应于给定温度的碳通量和扩散系数下,多壁CNT的生长速率(即长度的时间导数)与SWNT的生长速率相同。此外,在〜700℃以下,在6 sccm(STP下为立方厘米/分钟)的C_2H_2流量下观察到SWNT生长的温度,壁数随温度的变化唯一地取决于入射通量的相互作用原子C的分布和扩散速率与体扩散一致。甚至不需要催化颗粒的部分熔融来解释关于生长速率和壁数的实验结果。 700℃以上通常开始严重的催化剂中毒,但没有中毒的增长率与Hata及其同事的最新结果一致[Science 306,1362(2004);物理牧师95,056104(2005)]中的“超增长”。

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