纳米球形炭的无催化化学气相沉积制备及其机理研究

Preparation of carbon nanospheres by non-catalytic chemical vapor deposition and their formation mechanism

摘要: 以天然气为碳源，氢气为载气，通过无催化化学气相沉积的方法，合成不同粒径的球形炭。研究了沉积温度、压力和气体比例对化学气相沉积球形炭的影响。用X射线衍射、扫描电子显微镜和透射电子显微镜对实验结果进行表征。研究结果表明制备纳米球形炭（50~100 nm）的优化工艺为沉积温度1 150℃、沉积压力5 kPa和天然气/氢气（气体流量比）1∶4。本研究对球形炭的气相沉积机理进行了详细的研究。沉积温度对球形炭的尺寸和微结构影响较小，沉积压力对炭核的碰撞几率影响较大。另外，氢在炭形核过程中起来很重要的作用，氢的存在有效的较少了炭核的碰撞几率。

Abstract: Carbon spheres with different sizes were prepared by non-catalytic chemical vapor deposition fromgas mixtures of CH₄ and H₂. The influence of the deposition temperature, pressure, and gas ratio on the formation and growth mechanism of the spheres was investigated. The carbon spheres obtained were characterized by XRD, SEM and TEM. Results indicated that carbon nanospheres (50-100 nm) could be obtained at 1 150℃ and 5 kPa from a gas mixture with a CH₄/H₂ volume ratio of 0.25. The deposition temperature had no obvious effect on the sphere size and structure. The sphere size increased with the deposition pressure and the gas ratio. A model was proposed to elucidate their formation and growth.