TEM investigation on the initial stage growth of carbon onions synthesized by CVD

We report an investigation on the initial stages of growth of carbon onions synthesized by CVD of methane. A special experimental procedure has been developed to stop the process after short duration (10 s–2 min). It has found that during the early stages (90 s), carbon atom cluster encapsulated nanoparticles were formed. With increasing synthesis time (2 min), the carbon clusters began to graphitize to form graphitic layers. High resolution transmission electron microscope observations showed that many catalytic particles were partially encapsulated with graphitic layers, which were responsible for the hollow carbon onion formation.