Fabrication of carbon-coated cobalt nanoparticles by the catalytic method

A mass of carbon-coated cobalt nanoparticles were successfully synthesized by chemical vapor deposition of methane over Co/Al catalyst at 650 °C. The phases found in the as-prepared carbon-coated nanoparticles were fcc-Co. The diameter of these nanoparticles with 2–10 nm carbon coating shell was in the range of 5–80 nm. However, it is well-known that the Co nanoparticles are suitable for carbon nanotube synthesis, such as Co/Al2O3 and Co/SiO2 catalysts. Here, we speculated that the formation mechanism of carbon-coated cobalt nanoparticles might due to that the formation of carbon nanotubes was inhibited by the catalyst supporter of Al. Compared with Al2O3 and SiO2, Al possesses very low melting point (660 °C), very high diffusion coefficient and thermal conductivity, thus the isotropic precipitation of carbon species on the surface of cobalt particles took place, favoring the formation of carbon-coated Co nanoparticles.