Abstract Gas-phase reactions among carbon precursors could have a significant effect on the catalytic synthesis of vertically aligned (VA-) carbon nanotubes (CNTs). State-of-the-art adjustment of the gas-phase reaction conditions is done ad hoc with low reproducibility, ascribed partly to an incomplete understanding of the mechanism how the gas-phase reaction influences the growth kinetics of VA-CNTs. Here, we investigate this mechanism and propose that in the presence of prominent gas-phase reaction, the growth kinetics characterization shifts from a single rate-limiting reaction to a multi-route reaction with each pathway having its own rate-limiting step. The rate of the gas-phase reaction could be tailored by the partial pressure and thermal history of a carbon feedstock (e.g., acetylene). According to in-situ mass spectrometry and numerical simulation, a rich set of thermally rearranged secondary species (e.g., C4H4 and C6H6) are found above the catalyst surface. It appears that these secondary species, along with a chief precursor (C2H2), can give variation to a yield of CNTs through various reaction pathways with altering the overall growth rate of VA-CNTs. Our findings would further the current understanding of the VA-CNT growth from thermally rearranged precursors, instrumental to applications such as diameter-controlled growth and CMOS-compatible low-temperature growth.

中文翻译：

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气相反应对温度梯度化学气相沉积垂直排列的碳纳米管生长的影响

摘要 碳前驱体之间的气相反应可能对垂直排列 (VA-) 碳纳米管 (CNT) 的催化合成产生显着影响。最先进的气相反应条件调整是临时进行的，重现性低，部分原因是对气相反应如何影响 VA-CNT 生长动力学的机制没有完全理解。在这里，我们研究了这种机制，并提出在存在显着的气相反应的情况下，生长动力学表征从单一的限速反应转变为多途径反应，每个途径都有自己的限速步骤。气相反应的速率可以通过碳原料（例如乙炔）的分压和热历程来调整。根据原位质谱和数值模拟，在催化剂表面上方发现了一组丰富的热重排次级物质（例如，C4H4 和 C6H6）。似乎这些次要物质以及主要前体 (C2H2) 可以通过各种反应途径改变 CNT 的产量，从而改变 VA-CNT 的整体生长速率。我们的发现将进一步加深目前对热重排前驱体的 VA-CNT 生长的理解，有助于直径控制生长和 CMOS 兼容低温生长等应用。通过改变 VA-CNTs 的整体生长速率，可以通过各种反应途径改变 CNTs 的产量。我们的发现将进一步加深目前对热重排前驱体的 VA-CNT 生长的理解，有助于直径控制生长和 CMOS 兼容低温生长等应用。通过改变 VA-CNTs 的整体生长速率，可以通过各种反应途径改变 CNTs 的产量。我们的发现将进一步加深目前对热重排前驱体的 VA-CNT 生长的理解，有助于直径控制生长和 CMOS 兼容低温生长等应用。