Microstructure of metal-filled carbon nanotubes

Catalysts are usually required to produce carbon nanotubes (CNTs) and play important roles during the growth process. Any catalysts that remain after processing are expected to add extra properties and removal of the catalysts is usually required to achieve the original properties of CNTs. Recently, CNTs have been filled incidentally by catalysts, such as Pb, Sn, Ni and Bi. This has led to success in obtaining additional properties and a few models have been proposed to describe the encapsulating mechanisms. In the present study, CNTs were filled with palladium by a microwave plasma-assisted chemical vapor deposition method. Detailed structural and compositional investigations of these metal-filled CNTs were carried out by transmission electron microscopy to elucidate the growth mechanisms.