Skip to Main content Skip to Navigation
Theses

Nucléation et croissance d'oignons de carbone synthétisés par implantation ionique de carbone dans l'argent à haute température

Abstract : This work deals with the challenge of synthesizing new nanostructured materials. Our aim is to understand the nucleation and growth mechanisms of the different carbon phases synthesized by carbon ion-implantation into silver substrates held at high temperature (> 400 °C). Carbon onions, nanocapsules and an amorphous carbon layer are produced during the implantation experiments. These different carbon structures were characterized by using two complementary techniques : transmission electron microscopy (TEM and HRTEM) and resonant nuclear reactions analysis (RNRA). The size and microstructure of the carbon onions, but also the amount of the two other components, strongly depend on the implantation parameters. It is shown that the formation of the amorphous carbon component results from the preferential sputtering of silver, that allows the formation of a surface layer, and from a carbon precipitation at silver grains boundaries. To explain the nanocapsules formation, it is proposed that the carbon atoms precipitate on nanometric silver grains boundaries, leading to the formation of graphene layers around these grains. Surprisingly, the encapsulated metal grains are thrown out the graphitic matrix to leave the core of the nanocapsules empty. It is suggested that carbon onions nucleation occurs in two steps. Firstly, carbon atoms precipitate into the volume and form stable germs above a local critical concentration. Then, the progressive transformation of these precipitates into onion-like structures is attributed to the catalytic effect of the silver matrix on graphitisation and to the atomic displacements induced by the irradiation. It is proposed that the carbon onions growth is essentially due to the precipitation of the new implanted carbon atoms on the already formed carbon onions.
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00005815
Contributor : Elsa Thune <>
Submitted on : Sunday, May 2, 2004 - 2:13:51 PM
Last modification on : Thursday, March 28, 2019 - 2:04:04 PM
Long-term archiving on: : Friday, April 2, 2010 - 8:18:10 PM

Identifiers

  • HAL Id : tel-00005815, version 1

Collections

Citation

Elsa Thune. Nucléation et croissance d'oignons de carbone synthétisés par implantation ionique de carbone dans l'argent à haute température. Mécanique [physics.med-ph]. Université de Poitiers, 2001. Français. ⟨tel-00005815⟩

Share

Metrics

Record views

334

Files downloads

132