Fluidized bed synthesis of carbon nanotubes - A review

Carbon nanotube is one of the most talked about materials in recent years due to its unique properties and potential applications in different fields. Out of different techniques, catalytic chemical vapour deposition in a fluidized bed is the most promising technique for bulk production of this exotic material. The objectives of this review are to bring out the science and technology behind this process, the present commercial scenario and to draw a future roadmap. We have critically examined the published literature on the nanoparticle fluidization, different forces involved in it and the hydrodynamics of a nano-agglomerate fluidized bed. The importance of use of discrete elemental method and computational fluid dynamics simulation in the fluidization of carbon nanotubes has also been highlighted. Different preparation routes of catalyst materials have been compiled. The reaction and growth mechanisms of nanotubes, including modeling have been discussed. The data on the effects of different process parameters on the quality and quantity of nanotubes have been critically analyzed. It has been indicated that the available data are scattered in nature and further understanding in the mechanism is required in order to find out the rate controlling step(s) and scale-up of the process. The present commercial scenario of carbon nanotube market has been depicted. At the end, based on the present knowledge gaps, future roadmaps have been suggested. (C) 2011 Elsevier B.V. All rights reserved.