Tailoring of surface melting of oxide based catalyst particles by doping to influence the growth of multi-walled carbon nano-structures

In catalytic chemical vapor deposition method, the growth of multi-walled carbon nano-tubes (MWCNT), nano-rods/fibers or nano-tapes takes place over cobalt oxide based catalyst particles at a growth temperature higher than the temperature for surface melting of the catalyst particles. Doping of cobalt oxide by copper oxide has been used to decrease the surface melting temperature of the oxide based catalyst particles in the size range of about 200–500 nm, which is important in determining the type of carbon nano structures growing over the catalyst. It has been observed that MWCNT forms at a small difference between the growth temperature and the surface melting temperature while nano-rods or nano-tapes form at relatively larger difference between these temperatures. The present study indicates the possibility of controlling surface melting temperature by the level of doping in order to get the desired nano-structure at a given growth temperature.