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

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 1150°C 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.