Growth and microstructure of Co-filled carbon nanotubes

Cobalt-filled carbon nanotubes were prepared in situ in the decomposition of benzene over Co/silica-gel catalysts. Unlike the previous reports, in our experiments, the catalysts need not pre-reduced. Transmission electron microscopy (TEM) investigation showed that the as-made products contained abundance of carbon nanotubes (CNTs) and almost 100% of them were filled with metallic nanoparticles or nanorods. High-resolution TEM (HRTEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Co inside the nanotubes. The encapsulated Co was further identified as alpha-Co with face-centered cubic (fcc) structure, which frequently consists of twinned boundaries. Based on the experimental results, a possible growth mechanism of the Co-filled nanotubes was proposed.