Measurement and control of cooling/synthesis processes of carbon clusters in an arc reactor

1)被动米氏散射实验在正常重力条件下，将障碍板放置在反应堆中，由CCD摄像机记录散射光。研究发现，在弧光等离子体周围产生了约0.5微米大小的碳团簇，它们通过自然对流向上流动(v~0.5m/S)。该流动情况与流体模拟结果吻合较好。碳团簇的产生地点在等离子体周围，气体温度从8000K降到1200K以下。2)主动Mie散射实验激光通过弧形等离子体的中心从底侧向上方照射。利用脉冲调制技术和锁相放大技术对90度散射激光进行了探测和处理。结果表明，根据放电电流和氦气压力可以得到较大的信号。3)单壁碳纳米管的制备工艺：在弧光等离子体旁放置一个8通道的团簇收集器，在每个位置收集即将到来的碳粒子。通过这种测量，可以测量纳米管的空间分布。4)气体流动和热CVD法制备多壁碳纳米管在垂直放置的玻璃管中，放置一个小钢球，在其上涂覆镍触媒粉末。通过流动的Ar气体和乙醇气体，以及800℃的加热，我们可以制备出碳纳米管。随着碳氢气体流动方向的不同，纳米管密度也会发生变化。

1) Passive Mie scattering experimentUnder normal gravity condition, an obstacle plate is set in a reactor, and dispersed light is recorded by a CCD camera. It is found that about 0.5 micrometer size of carbon clusters generate around the arc plasma, and they flow upwards by natural heat convection (v~0.5 m/s). This flow is in good consistent with the result of fluid simulation. The generation place of carbon clusters is around the plasma, where the gas temperature decreases from 8000 K to less than 1200 K.2) Active Mie scattering experimentLaser light is irradiated from bottom side to upper side through center of the arc plasma. 90 degree-scattered laser-light is detected and processed by the pulse-modulation technique and the Lock'in amplification technique. As a result, larger signal is obtained according to the discharge current and the He-gas pressure. Vertical distribution of the scattered intensity changes a little above the arc plasma.3) Production process of single-walled carbon nanotubesA 8-ch cluster-collector is set aside of the arc plasma, and coming carbon particles are collected at the each position. From this measurement, spatial distribution of nanotubes is measured. As a result, nanotubes are almost produced around the periphery of the arc plasma, where the gas temperature sharply decreases.4) Gas flow and production of multi-walled carbon nanotubes by a thermal CVD methodIn a vertically set glass tube, a small steel-ball is set, on which Ni-catalyst-powder is coated. By flowing Ar gas and ethanol gas, and by 800 C of thermal heating, we could make carbon nanotubes. Depending on the flow direction of hydrocarbon gas,nanotube-density is changed.