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Atmospheric pressure microwave torch for synthesis of carbon nanotubes

机译：常压微波炬用于合成碳纳米管

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The microwave (mw) plasma torch at atmospheric pressure has been studied for carbon nanotube (CNT) synthesis. The depositions were carried out on silicon substrates with 5-15 nm thin iron catalytic overlayers from the mixture of argon, hydrogen and methane. The optical emission spectroscopy of the torch showed the presence of C-2 and CH radicals as well as carbon and hydrogen excited atoms. The vicinity of the substrate influenced the relative intensities and increased the emission of C2. For fixed mw power, the temperature of the substrate strongly depended on its position with respect to the nozzle electrode and on the gas mixture, particularly the amount of H-2. The speed of the substrate heating during an early deposition phase had a significant effect on the CNT synthesis. An abrupt increase of the temperature at the beginning increased the efficiency of the CNT synthesis. Areas of dense straight standing CNTs, 30 nm in average diameter, with approximately the same sized iron nanoparticles on their tops were found in accordance with the model of growth by plasma enhanced chemical vapour deposition. However, the deposit was not uniform and a place with only several nanometres thick CNTs grown on much larger iron particles was also found. Here, taking into account the gas temperature in the torch, 3100-3900K, we can see similarities with the 'dissolution-precipitation' model of the CNT growth by high temperature methods, arc or laser ablation.
机译：已经研究了大气压下的微波等离子体炬用于碳纳米管（CNT）的合成。使用氩气，氢气和甲烷的混合物，在具有5-15 nm薄铁催化覆盖层的硅基板上进行沉积。火炬的光发射光谱表明存在C-2和CH自由基以及碳和氢激发原子。基材附近影响了相对强度并增加了C2的排放。对于固定的MW功率，衬底的温度强烈地取决于其相对于喷嘴电极的位置以及气体混合物，特别是H-2的量。在早期沉积阶段，基板加热的速度对CNT的合成有重大影响。开始时温度的突然升高提高了CNT合成的效率。根据通过等离子体增强化学气相沉积的生长模型，发现了平均直径为30 nm的密集直立式CNT区域，其顶部几乎具有相同大小的铁纳米颗粒。但是，沉积物并不均匀，并且还发现了一个只有几纳米厚的CNT在更大的铁颗粒上生长的地方。在这里，考虑到割炬中的气体温度3100-3900K，我们可以看到与通过高温方法，电弧或激光烧蚀进行的CNT生长的“溶解-沉淀”模型相似。

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