| Titre : |
Multilayer adsorption of gases on graphite studied by ellipsometry |
| Type de document : |
texte imprimé |
| Auteurs : |
Mahrez Drir, Auteur ; George B. Hess, Directeur de thèse |
| Editeur : |
University of Virginia |
| Année de publication : |
1986 |
| Importance : |
156 f. |
| Présentation : |
ill. |
| Format : |
27 cm. |
| Note générale : |
Thèse de Doctorat : Physique : Virginia, University of Virginia : 1986
Bibliogr. f. 157 - 165 |
| Langues : |
Anglais (eng) |
| Mots-clés : |
Adsorption -- gases
Single cleaved surface
Highly oriented pyrolitic graphite
Ellipsometric technique |
| Index. décimale : |
D002486 |
| Résumé : |
In this work we report adsorption measurements on a single cleaved surface of highly oriented pyrolitic graphite (HOPG).
This eliminates the possibility of capillary condensation, while providing a surface with larger facet size and better energy uniformity than exfoliated graphite.
We have measured adsorbate coverage by a phase-modulation ellipsometric technique, using laser light reflected from a 0.1 x 0.2 mm spot on the graphite surface.
We have studied various gases (Kr, O₂, C₂H₄ and CF₄) in the vicinity of their respective bulk triple point Tt (except for the case of Kr where all the data were recorded below Tt).
We have observed layer-by-layer adsorption where as many as nine steps could be seen.
The overall features were characteristic of wetting at the triple point: below Tt, bulk crystallite formation preempts film growth after a limited number of layers.
Above Tt, the film grows to a thickness equivalent to about 40-50 layers.
However, indications of bulk droplets appear above about 10-12 layers.
Our results suggest not quite complete wetting by the liquid phase of the various gases studied. |
Multilayer adsorption of gases on graphite studied by ellipsometry [texte imprimé] / Mahrez Drir, Auteur ; George B. Hess, Directeur de thèse . - University of Virginia, 1986 . - 156 f. : ill. ; 27 cm. Thèse de Doctorat : Physique : Virginia, University of Virginia : 1986
Bibliogr. f. 157 - 165 Langues : Anglais ( eng)
| Mots-clés : |
Adsorption -- gases
Single cleaved surface
Highly oriented pyrolitic graphite
Ellipsometric technique |
| Index. décimale : |
D002486 |
| Résumé : |
In this work we report adsorption measurements on a single cleaved surface of highly oriented pyrolitic graphite (HOPG).
This eliminates the possibility of capillary condensation, while providing a surface with larger facet size and better energy uniformity than exfoliated graphite.
We have measured adsorbate coverage by a phase-modulation ellipsometric technique, using laser light reflected from a 0.1 x 0.2 mm spot on the graphite surface.
We have studied various gases (Kr, O₂, C₂H₄ and CF₄) in the vicinity of their respective bulk triple point Tt (except for the case of Kr where all the data were recorded below Tt).
We have observed layer-by-layer adsorption where as many as nine steps could be seen.
The overall features were characteristic of wetting at the triple point: below Tt, bulk crystallite formation preempts film growth after a limited number of layers.
Above Tt, the film grows to a thickness equivalent to about 40-50 layers.
However, indications of bulk droplets appear above about 10-12 layers.
Our results suggest not quite complete wetting by the liquid phase of the various gases studied. |
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