Electron Microscopy Investigation of Coated Multiwall Carbon Nanotubes Prepared by Reactive Ball Milling.

Homogeneous and stable inorganic coating of SiO₂, Al₂O₃ and TiO₂ was obtained on the surface of multiwall carbon nanotubes (MWNTs) by mechanically mixing them with precursor compounds in a planetary ball mill and by subsequent hydrolysis. Detailed studies by means of transmission and scanning electron microscopy revealed that the milling time as well as the number of balls significantly affects the homogeneity of the layer formed. Our results demonstrate that planetary ball milling can be an effective and low-cost process for the production of homogenous coating of oxides on MWNTs in a large-scale.