Formation and microstructural characterization of coaxial carbon cylinders consisting of aligned carbon nanotube stacks

The macroscopic coaxial carbon cylinders (dia. approximately 0.5 cm with varying lengths approximately 2-5 cm) consisting of aligned carbon nanotube (CNT) stacks have been prepared by spray pyrolysis of benzene-ferrocene solution in argon atmosphere at approximately 850 degrees C-900 degrees C temperature. The coaxial carbon cylinders of CNT stacks have been formed directly inside the quartz tube. We attempted to prepare superimposed multi carbon cylinder configurations, each consisting of ordered and aligned CNTs stacked over each other. For this, we have terminated the spray of precursor after run of about 25 minutes, for a short interval (approximately 5 min), and then the solution was sprayed again over the already deposited hot CNT stack. Gross structural characterization of CNTs was done through X-ray diffraction technique (XRD). Microstructural characterizations of as prepared coaxial carbon cylinders with CNT stacks were done by scanning electron microscopic (SEM) techniques. SEM studies show that the CNTs are well aligned along the periphery of the cross section of coaxial carbon cylinder, each consisting of CNTs of the type described in the above. Comparisons have been made between the present macroscopic coaxial carbon cylinders with CNT stacks studied earlier by several other workers. Plausible explanation for the synthesis of CNT stacks will be put forward.