Abstract Arc discharge synthesis of single-walled carbon nanotubes (SWCNTs) remains largely uncontrollable, due to incomplete understanding of the synthetic process itself. We show that synthesis of SWCNTs by a carbon arc may not constitute a single continuous process, but may instead consist of two distinct modes. One of these, a “synthesis-on” mode, produces the majority of the nanomaterials. During the synthesis-on mode, proportionally more carbon nanotubes are collected than in another mode, a “synthesis-off” mode. Both synthesis-on and synthesis-off modes for a typical arc configuration, employing a hollow anode filled with a mixture of powdered metal catalyst and graphite, were characterized by using in situ electrical, imaging, and spectroscopic diagnostics, along with ex situ imaging and spectroscopy. The synthesis-on mode duration is rare compared to the total arc run-time, helping to explain the poor selectivity found in the final collected products, a known inadequacy of arc synthesis. The rarity of the synthesis on mode occurence may be due to the synthesis off mode being more favorable energetically.

中文翻译：

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碳纳米管合成过程中碳弧操作的“合成开启”和“合成关闭”模式

摘要 由于对合成过程本身的不完全了解，单壁碳纳米管 (SWCNT) 的电弧放电合成在很大程度上仍然无法控制。我们表明，通过碳弧合成 SWCNT 可能不会构成一个单一的连续过程，而是可能由两种不同的模式组成。其中之一是“合成”模式，可生产大部分纳米材料。在合成开启模式期间，与另一种模式（“合成关闭”模式）相比，按比例收集更多的碳纳米管。典型电弧配置的合成开启和合成关闭模式，采用填充有粉末金属催化剂和石墨混合物的空心阳极，其特征在于使用原位电学、成像和光谱诊断，以及非原位成像和光谱学。与总电弧运行时间相比，合成开启模式持续时间很少，这有助于解释在最终收集的产品中发现的选择性差，这是电弧合成的已知不足。合成模式出现的罕见性可能是由于合成关闭模式在能量上更有利。