Influence of a buffer layer on the formation of a thin-film nickel catalyst for carbon nanotube synthesis

The formation of nanoparticles of a thin-film nickel catalyst applied on a buffer layer in the form of pure titanium, titanium oxide, or titanium nitride has been studied. It has been shown that if nanotubes are synthesized in three stages (oxidation, reduction, and growth of nanotubes), the situation may arise when the metallic catalyst becomes isolated from the surface, and hence, from the hydrocarbon flux, as a result of which the nanotube growth stops. Isolation takes place when the interface between titanium oxide and the gas phase in the reactor moves. In this case, titanium oxide goes round a nickel oxide nanoparticle and insulates it. The displacement rate of this interface and the coefficient of hydrogen diffusion in titanium dioxide have been determined.