The theoretical external specific surface area of single-and multi-walled carbon nanotubes and of carbon nanotube bundles is calculated as a function of their characteristics (diameter, number of walls, number of nanotubes in a bundle). The results are reported in diagrams and tables useful to correlate the microscopic characteristics and the specific surface area of samples. The calculated values are in good agreement with the microscopic characteristics and the specific surface area measurements which have been previously reported in the literature. The specific surface area is a macroscopic parameter which can be helpful to adjust the synthesis conditions of carbon nanotubes.

Carbon nanotube-metal-oxide composites (metal=Fe, Co or Fe/Co alloy; oxide=Al 2 O 3 , MgO or MgAl 2 O 4) have been prepared by hot-pressing the corresponding composite powders, in which the carbon nanotubes, mostly single or double-walled, are very homogeneously dispersed between the metal-oxide grains. For the sake of comparison, ceramic and metal-oxide nanocomposites have also been prepared. The microstructure of the specimens has been studied and discussed in relation to the nature of the matrix, the electrical conductivity, the fracture strength and the fracture toughness. The carbon nanotube-metal-oxide composites are electrical conductors owing to the percolation of the carbon nanotubes.

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