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.

International audienceNovel carbon nanotubes-metal-ceramic nanocomposite powders and dense materials have been prepared and their micro-structure and mechanical properties have been investigated. After a brief review on the structure, synthesis and physical properties of carbon nanotubes, we describe an original catalytic method that produces ceramic-matrix composite powders that contain in situ grown nanotubes. The synthesis parameters that favour the obtention of very high quantities of nanotubes are discussed. The quality of the nanotubes is also addressed. The microstructure and mechanical properties of the materials prepared by hot-pressing of these powders are presented. The in¯uence of carbon nanotubes in such composites is discussed in view of potential applications

International audiencePassing a H2-CH4 mixture over oxide spinels containing two transition elements as in Mg0.8MyM'zAl2O4 (M, M' = Fe, Co or Ni, y + z = 0.2) at 1070°C produces small alloy nanoparticles which enable the formation of carbon nanotubes. Surface area measurements are found to be useful for assessing the yield and quality of the nanotubes. Good-quality single-walled nanotubes (SWNTs) have been obtained in high yields with the FeCo alloy nanoparticles, as evidenced by transmission electron microscope images and surface area measurements. The diameter of the SWNTs is in the 0.8-5 nm range, and the multiwalled nanotubes, found occasionally, possess very few graphite layers