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Formation and growth mechanism of natural nanotubes: Imogolites

Masion A., Levard C., Rose J., Doelsch E., Thill A., Borschneck D., Bottero J.Y.. 2009. Geochimica et Cosmochimica Acta, 73 (13) : A844. Annual V.M. Goldschmidt Conference. 19, 2009-06-21/2009-06-26, Davos (Suisse).

A distinctive feature of certain volcanic soils is the presence of short range ordered aluminosilicates imogolite and allophanes. Due to their high surface area and reactivity, these nanosized phases are an important factor affecting soil dynamics (carbon sequestration, pollutant mobility...). The structure of imogolite is well established: nanotubes with a diameter of ca. 2 nm and several hundreds of nm in length consisting of a curved gibbsite layer with isolated Si tetrahedra inside the tube. However, very little is known about the formation mechanisms of these nanotubes. In the present study, we synthesized these phases and examined the systems from the initial mixing of the reagents to the final products using a variety of analytical techniques (XRD, TEM, EXAFS, NMR and SAXS). Our results demonstrate that the precursors of the nanotubes are not a circular structure but roof tile shaped particules with sizes up 5 nm and varying curvatures. These precursors assemble to form short nanotubes or doughnuts. The final products are obtained by end-to-end assembly of these short nanotubes. (Résumé d'auteur)

Mots-clés : silicate; structure chimique; nanotube

Thématique : Chimie et physique du sol; Autres thèmes

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