High resolution transmission electron microscopy of catalytically grown carbon nanotubes (CNTs)

The paper reports the structural analysis of catalytically grown carbon nanotubes (CNTs), a nanostructured material using transmission electron microscopy. Here, carbon nanotubes were formed by catalytic decomposition of methane over different catalysts namely iron, cobalt and nickel. Of the many techniques which have been used to study the structures, high resolution tunneling electron microscopy (HRTEM), has undoubtedly been the most useful. While x-ray diffraction can provide more accurate crystallographic measurements, and scanning electron microscopy can give greater surface detail, only HRTEM can probe the internal structure of nanotubes, revealing details of the stacking arrangement of multiwalled tubes, the nature of defects, the structure of caps and so on. From TEM micrographs, the catalytically produced nanotubes are observed to be of the multiwalled type. Thermo gravimetric analyses (TGA) were also conducted in order to determine the degree of crystallinity of CNTs grown from different catalysts. Results of TGA revealed that the highest degree of crystalline perfection could be achieved by CNTs grown on iron followed by the ones grown on nickel and cobalt catalyst