Limitation in growth temperature for water-assisted single wall carbon nanotube forest synthesis
Limitation in growth temperature for water-assisted single wall carbon nanotube forest synthesis
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DOI：
10.1557/adv.2018.92
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发表时间：
2018-01
期刊：
影响因子：
0.8
通讯作者：
Shunsuke Sakurai;Maho Yamada;K. Hata;D. Futaba
中科院分区：
文献类型：
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作者：
Shunsuke Sakurai;Maho Yamada;K. Hata;D. Futaba
在这项研究中，我们研究了生长温度的限制，单壁碳纳米管（SWNT）森林合成使用水（H_2O）的生长促进剂，突出了在高温下的生长效率急剧下降。使用一氧化碳（CO）生长促进剂的比较合成表现出更宽的温度窗口SWNT森林合成。结果表明，在850 °C以上，用H_2O不能合成出100 μm以上的单壁碳纳米管森林，而用CO可以在900 °C以上合成出800 μm以上的森林。H_2O浓度的依赖性表明，H_2O本身是导致在较高温度下观察到的生长效率降低的原因。相比之下，增加的CO浓度在整个温度范围内没有导致碳纳米管（CNT）产率的任何下降。虽然当使用CO时观察到高于950 °C的CNT产率的严重下降，但发现起源源于通过表面上的扩散而增强的催化剂颗粒聚集，而不是CO本身。因此，当使用更稳定的碳原料如甲烷时，在较高生长温度下合成的能力是有利的。
In this study, we examined the limitations in growth temperatures for single-walled carbon nanotube (SWNT) forest synthesis using a water (H_2O) growth enhancer as highlighted by a dramatic decrease in growth efficiency at high temperatures. Comparative synthesis using a carbon monoxide (CO) growth enhancer demonstrated a wider temperature window for SWNT forest synthesis. We found that SWNT forests taller than 100 μm could not been synthesized above 850 °C by using H_2O, but by using CO, tall (>800 μm) forests could be synthesized at growth temperatures exceeding 900 °C. The dependency of H_2O concentration showed that H_2O, itself, was the cause for the reduced growth efficiency observed at higher temperatures. In contrast, increased CO concentrations did not result in any drop in the carbon nanotube (CNT) yield across the entire temperature range. While a severe drop of CNT yield above 950 °C was observed when CO was used, the origin was found to stem from catalyst particle aggregation enhanced by diffusion on the surface rather than CO itself. Therefore, the ability to synthesize at higher growth temperatures is advantageous when using more stable carbon feedstocks, such as methane.