Control of nano-carbon synthesized in liquid phase under high magnetic field

碳纳米管的合成通常采用各种化学气相沉积(CVD)方法、弧光放电和激光烧蚀技术。这些合成方法需要较高的合成温度，至少500℃。低温合成对于纳米管和纳米线在实际器件中的应用具有重要意义。自从我们报道了用电化学技术合成室温纳米碳以来，高达12特斯拉的强磁场被应用到电化学技术中来合成碳纳米管。用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和能谱仪(EDS)对沉积产物进行了表征。透射电子显微镜观察到，磁场使碳纳米线的长度增加。此外，将高达12特斯拉的强磁场应用于热化学气相沉积制备碳纳米管。透射电子显微镜观察到洋葱状纳米碳的增多，这是由于磁场的作用。除了这些合成方法外，我们还发现了另一种室温合成碳纳米管和碳纳米线的方法。这种新的室温合成方法是在金属催化剂和金属钠的作用下，通过超声辐照有机溶液的液相来实现的。沉积过程中的温升可以忽略不计，因为最多只有几度。这种低温合成方法对开发碳基新材料具有很大的优势。此外，本研究使用的仪器简单，价格也不贵。因此，这项技术将使开发其他纳米级新材料成为可能。

Carbon nanotubes have been commonly synthesized using a wide variety of chemical vapor deposition (CVD) methods, arc discharge and laser ablation techniques. These synthesis methods require a high synthesis temperature, at least 500℃. A low-temperature synthesis is important for an application of nanotubes and nanowires to practical devices. Since we have reported the room temperature nano-carbon synthesis by electrochemical techniques, high magnetic fields up to 12 Tesla are applied to electrochemical techniques for carbon nanotube synthesis. The deposits were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). An increase in the long carbon nanowires due to magnetic field was observed by TEM. In addition, high magnetic fields up to 12 Tesla are applied to thermal CVD for carbon nanotube synthesis. An increase in the onion-like nano-carbons and due to magnetic field was observed by TEM. Beside these synthesis methods, we have discovered another room temperature synthesis method of carbon nanotubes and carbon nanowires. The new room temperature synthesis has been achieved by a supersonic irradiation into a liquid phase of organic solution with a metal catalyst and metal Na. The temperature increase during the deposition is negligible, because of by a few degrees at most. This low temperature synthesis method has a great advantage to develop carbon-based new materials. In addition, the apparatus used in the present study is simple and is not expensive. Therefore, this technique will make it possible to develop other nanosized new materials.