Synthesis of Nanodiamonds in Argon Arc from Carbon Vapor

The paper presents results on the synthesis of carbon nanostructures in argon arc from carbon vapor. Two types of nanostructures were synthesized: carbon nanotubes and nanodiamonds. Carbon nanotubes are open-type, multilayered, with diameters of the order of 18–22 nm. Carbon nanotubes are well calibrated in diameter. Some nanotubes have grown a second layer, chemically unconnected to the first layer as a tube within a tube. Both visible nanotubes are cylindrical in shape. Inside the lower nanotube, several other nanotubes may be contained, also not chemically bonded to each other. Carbon nanotubes can reach a length of about 40 µm. They grow on the cathode and are assembled into cylindrical bundles with a diameter of about 50 µm. The space between the nanotube bundles is filled with nanodiamonds and single nanotubes. The content of nanotubes in the carbon precipitate can approach 50% in some areas, and the remaining nanostructures are nanodiamonds. Interestingly, the growth of nanodiamonds in this particular situation is favored by the surface of the nanotubes. The size of nanodiamonds is of the order of 60–80 nm.