Purification of Carbon Nanotubes by Physical Method

1991年以后，我们明确了用直流电弧蒸发石墨棒作为阴极存款的方法可以制备多壁碳纳米管。当我们使用纯氢气作为气氛气体时，可以获得具有较少共存碳纳米颗粒的高质量多壁碳纳米管（1997）。因此，如果共存的碳纳米颗粒最初较少，则容易去除共存的碳纳米颗粒并进行纯化。实际上，在空气（1998）中，用红外辐射加热器在500 ℃下照射样品30 min，可以得到纯化的多壁碳纳米管;在纯氢气中蒸发石墨电极，可以得到内径为1.0nm的多壁碳纳米管。内管被等间距的石墨烯片包围，0.34nm，并且具有高结晶度。我们可以得到纯化的多壁碳纳米管的X射线衍射图、拉曼散射或电导率（1998）。特别是在低频区（180- 500 cm ~ 2），我们发现了类似于单壁碳纳米管呼吸模式的新峰<-1>，在1850 cm ~ 2附近发现了较强的新峰<-1>，这些纯化的多壁碳纳米管有望作为场发射的良好电子源。

After 1991, we made clear that multiwalled carbon nanotubes could be prepared by DC arc evaporation of graphite rods in atmospheric gas as cathode deposit. When we used pure hydrogen gas as atmospheric gas, high quality multiwalled carbon nanotubes with less co-existing carbon nanoparticles could be obtained (1997). Thus, if co-existing carbon nanoparticles were less originally, it is easy to remove co-existing carbon nanoparticles and to purify. In fact, we could get purified maltiwalled carbon nanotubes irradiating the specimen in air (1998) by infrared radiation heater at 500ﾟC for 30min.When we evaporated the graphite electrode in pure hydrogen gas, we could get maltiwalled carbon nanotubes having extremely narrow inner tube of the diameter 1.Onm in the order. The inner tube was surrounded by graphene sheets of equal distance, 0.34nm, and with high crystalline. We can get X-ray diffraction patterns, Raman scattering, or electric conductivity of purified multiwalled carbon nanotubes (1998). Especially, we could fmd new peaks similar to breathing mode for siglewalled carbon nanotubes at low frequency region (180-500cm_<-1>), and strong new peaks near 1850 cm^<-1>, These purified multiwalled carbon nanotubes are expected to use as good electron source for field emission.