The effect of catalyst evolution at various temperatures on carbon nanostructures formed by chemical vapor deposition

Solid carbon nanofibers (CNFs), hollow CNFs, metal-filled carbon nanotubes (CNTs), and carbon onions were synthesized by chemical vapor deposition (CVD) using a novel Ni/Y catalyst supported on Cu at different reaction temperatures. XRD, TEM, and EDS analyses reveal that the structure of the catalyst changes with increasing reaction temperature. The evolution of Y doped in Ni directly influences the morphologies of the products. At relatively low temperature, Y is doped in Ni and causes CNF formation, and when the temperature is increased to above 650 °C, Y separates from Ni as yttria nanoparticles and carbon onions are synthesized. The catalyst evolution and carbon nanostructure growth mechanism are discussed in detail.