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Catalytic synthesis and some characterization of multi-and single-wall carbon nanotubes are presented. Supported transition-metal catalysts were prepared by different methods and were tested in the production of nanotubes by decomposition of hydrocarbons at 700 • C, using a fixed-bed flow reactor.The quantities of deposited carbon were measured and the quality of the nanotubes was characterized by means of transmission electron microscopy and scanning tunneling microscopy. The inner and outer diameters of the nanotubes were also measured and the diameter distribution histograms were established. The multi-wall straight and coiled nanotubes were found to be quite regular with an average inner (outer) diameter of 4-7 nm (15-25 nm) and with lengths up to 50 µm. The walls contain concentric cylindrical graphene sheets separated by the graphitic interlayer distance. The single-wall nanotubes were found as bundles of hundreds of aligned straight 1-nm-diameter nanotubes with lengths up to 1-µm.The influence of various parameters such as the method of catalyst preparation, the nature and the pore size of the support, the nature of the metal, the quantity of catalyst active particles, and the reaction conditions on the nanotubes formation were studied. The numbers and dimensions of the catalyst active particles dispersed on the support were found to be of importance in regulating the shape of the produced nanotubes. Following these results, a model of growth mechanism was suggested for the nanotubes obtained by this method.The recent discovery of fullerenes [1], fullerenic onions [2], and hollow turbostratic carbon tubes of nanometer diameter [3] opened a new chapter in carbon chemistry. Because of their calculated chemical and physical properties [4][5][6][7], speculations about the possible applications of carbon nanotubes have been reported [8][9][10]. For the synthesis of carbon nanotubes several methods have been reported. The arc-discharge method developed for C 60 synthesis supplied a very surprising result, namely the growth of fullerene tubes on the carbon cathode [3,[11][12][13][14]. Other nanotube synthesis methods were also used such as plasma decomposition of hydrocarbons [15,16] and co-evaporating a catalyst during a carbon arc-discharge [17][18][19][20][21]. Single-wall nanotubes could be produced by the catalytic method evaporating cobalt or iron in the system. Recently, another catalytic process involving decomposition of hydrocarbons over supported catalysts and working under relatively mild conditions has been reported for carbon nanotube production [22,23]. Compared with other synthesis methods, the selectivity of this process to carbon nanotubes is significantly higher [24]. The advantages of the latter method increase if applying zeolites as catalyst supports [25]. Single-and multi-shell nanotubes of regular dimensions are produced by catalytic decomposition of hydrocarbons over Co/Y-zeolite catalysts. ExperimentalDifferent silica-and zeolite-supported transition-metal (Co, Cu, and Fe) catalysts have...

Large scale quantities of quasi-aligned carbon nanotube bundles have been synthesized by catalytic decomposition of acetylene over well dispersed metal particles (cobalt and vanadium) embedded in commercially available zeolite at 700°C. Scanning electron microscopy analysis revealed the homogenous nature of the sample while transmission electron microscopy studies revealed the perfect graphitization as well as the inner and outer diameters of the tubes.

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