Formation of noble-shaped carbon nanostructures

Noble-shaped carbon nanostructures which have a unique geometry, i.e., carbon nanofibers form along with the growth of the carbon tree branches were synthesized using C2H2/H2 as source gases under a thermal chemical vapor deposition system. Bunch-type Ni clusters (several hundred micrometers in size) were used as the catalyst for the growth of noble-shaped carbon nanostructures on the Al2O3 substrate. The characteristics of the carbon nanostructures were investigated under the condition of the different gas flow rate ratios of C2H2 and H2. In case of a high C2H2/H2 flow rate ratio, the predominant growth on the substrate was that of carbon tree branches. In case of a low C2H2/H2 flow rate ratio, on the other hand, we obtained noble-shaped carbon nanostructures. The growth mode and the cause for the formation of the noble-shaped carbon nanostructures was suggested and discussed.