Uniform diameter multi-walled carbon nanotubes with a controlled wall number obtained by a simple chemical vapor deposition method

► CNTs with uniform diameter and controlled wall number were prepared by CVD. ► The volume between vertically-aligned CNTs can be also tuned with this method. ► Layer by layer concentric graphene sheets were deposited on CNT arrays. ► The mechanism and kinetics were studied by SEM, HR-TEM, TGA, SAED, MS and Raman.