CARBON NANOTUBES-Fe-ALUMINA NANOCOMPOSITES. PT.1. INFLUENCE OF THE Fe CONTENT ON THE SYNTHESIS OF POWDERS

Oxides based on alpha-alumina and containing various amounts of Fe (2, 5, 10, 15 and 20 cat%) were prepared by decomposition and calcination of the corresponding mixed-oxalates. Selective reduction of the oxides in a H2-CH4 atmosphere produces nanometric Fe particles which are active for the in-situ nucleation and growth of carbon nanotubes. These form bundles smaller than 100 nm in diameter and several tens of micron long. However, the carbon nanotubes-Fe-Al2O3 nanocomposite powders may also contain Fe carbide nanoparticles as well as undesirable thick, short carbon tubes and thick graphene layers covering the Fe/Fe carbide nanoparticles. The influence of the Fe content and the reduction temperature on the composition and micro/nanostructure of the nanocomposite powders was investigated with the aim of improving both the quantity of nanotubes and the quality of carbon, i.e. a smaller average tube diameter and/or more carbon in tubular form. 51 refs.