Encapsulation of manganese carbides within carbon nanotubes and nanoparticles Original Research Article

The structures and morphologies of manganese-filled carbon nanotubes and nanoparticles, produced by an arc-discharge method by using a composite anode, were examined with high-resolution transmission electron microscopy, selected-area electron diffraction, and electron nanodiffraction techniques. The HRTEM images and corresponding diffraction patterns show that various manganese carbides (Mn3C, Mn5C2, Mn7C3, and Mn23C6) were formed within nanotubes and nanoparticles. Most encapsulated Mncarbides appeared as perfect single nanocrystals. Some, however, were found to be twins or crystals with ordered or modulated structures. Compared with other metal encapsulation, manganese encapsulation shows several unique features, such as encapsulation-induced tube distortion, formation of all types of carbides, and the preferential carbon graphitization on manganese carbide surfaces. No evidence has been found for the existence of intermediate phase between carbon sheets and encapsulated nanocrystals.