Department of Chemical System Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
ACS Nano. 2013 Aug 27;7(8):6719-28. doi: 10.1021/nn401556t. Epub 2013 Jul 16.
We examined the use of low purity H2 (96 vol % H2 with 4 vol % CH4) in chemical vapor deposition (CVD) using a C2H2 feedstock, and obtained vertically aligned single-wall carbon nanotubes (VA-SWCNTs) with unexpectedly smaller diameters, larger height, and higher quality compared with those grown using pure H2. During the catalyst annealing, carbon deposited at a small amount from CH4 on the Fe particles, which kept them small and dense. During CVD, CH4 prevented the Fe particles from coarsening, resulting in an enhanced growth lifetime and suppressed diameter increase of growing SWCNTs. These effects were observed only for CH4, and not for C2H4 or C2H2. CH4-assisted CVD is an efficient and practical method that uses H2 containing CH4 that is available as a byproduct in chemical factories.
我们研究了使用低纯度 H2（96 体积% H2 和 4 体积% CH4）作为化学气相沉积（CVD）的原料，使用 C2H2 作为原料，得到了垂直排列的单壁碳纳米管（VA-SWCNTs），与使用纯 H2 生长的 SWCNTs 相比，其直径更小、高度更大、质量更高。在催化剂退火过程中，甲烷在 Fe 颗粒上沉积了少量的碳，使它们保持较小和密集。在 CVD 过程中，CH4 阻止了 Fe 颗粒的粗化，从而延长了生长寿命，并抑制了生长 SWCNTs 的直径增加。这些效果仅在 CH4 中观察到，而在 C2H4 或 C2H2 中未观察到。CH4 辅助 CVD 是一种有效且实用的方法，它使用含有 CH4 的 H2，而 CH4 可作为化工厂的副产品获得。
