Catalytic production, purification, characterization and application of single- and multiwall carbon nanotubes

摘要

From the beginning of the catalysis, coke formation on catalysts was an important part of the process, and hence, it is rather well documented. With the industrial recovery, this field became much more important since in most cases coke formation is undesirable. The prevention of carbon deposit accumulation is a high priority objective in many processes involving transformation of hydrocarbons. In the latter industrial reactions coke formation can cause not only the deactivation of the catalyst but since it represents a large amount of solid material, it can bring on the blockage of the reactors and deteriorating heat transfer properties. However, because of the numerous different and interesting carbon structures (fibers, cones, tubular structures, etc.) generated as byproduct during the catalytic reactions, the new family of these materials started to be investigated [1,2,3]. The story of the carbon family is grandiose: subtlety in simplicity. The mystery is only coming from the different hybridization that carbon atoms can assume. Carbon has four valence electrons. When they are shared equally (sp{sup}3), diamond is formed. When three electrons are shared in a plane and one is delocalized between the planes (sp{sup}2), the carbon forms graphite. All the catalytically generated carbon forms belong to the structure of sp{sup}2 bonded carbon. Since Iijima's discovery [4], the field of carbon nanotubes (Single- and Multiwall Carbon Nanotubes -SWNTs and MWNTs) has become a separate subject in material science. These materials attracted more and more attention from physicists and chemists. Their surprisingly new and unique physical and chemical properties generated tremendous interest. Let us note that carbon nanotubes are also considered as members of the recently discovered carbon allotropes, the fullerenes, for which the Nobel Prize was given in 1996 to Curl, Kroto and Smalley [5]. At the beginning, the quantity of carbon nanotubes available for experiments was very low, since the early arc-discharge method produced only tiny amounts. The increasing demand on having more and more nanotubes brought the fast development in the ways of production, including not only improvements of the arc-discharge technique but also new methods like the laser evaporation and the catalytic vapor decomposition (CVD) of gaseous hydrocarbons.