Nonwetting/Prewetting/Wetting Transition of Ammonia on Graphite
Simulations of ammonia adsorption on graphite were carried out over a range of temperatures to investigate the transition from nonwetting to wetting. The process is governed by a subtle interplay between the various interactions in the system and the temperature. At temperatures below the bulk tripl...
| Veröffentlicht in: | Langmuir : the ACS journal of surfaces and colloids. - 1992. - 35(2019), 3 vom: 22. Jan., Seite 641-652 |
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| 1. Verfasser: | |
| Weitere Verfasser: | , , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2019
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| Zugriff auf das übergeordnete Werk: | Langmuir : the ACS journal of surfaces and colloids |
| Schlagworte: | Journal Article |
| Zusammenfassung: | Simulations of ammonia adsorption on graphite were carried out over a range of temperatures to investigate the transition from nonwetting to wetting. The process is governed by a subtle interplay between the various interactions in the system and the temperature. At temperatures below the bulk triple point, the system is nonwetting; above the triple point, we observed continuous wetting, preceded by a prewetting region in which the so-called thin-to-thick film transition occurs. This system serves as an excellent example of wetting/nonwetting behavior in an associating fluid as a function of temperature because the heat of sublimation (or condensation) is greater than the isosteric heat of adsorption at zero loading. The nonwetting-to-wetting transition (NW/W) is also strongly affected by the adsorbate-adsorbate interaction, which becomes important when this contribution to the isosteric heat is of a similar magnitude to the heat of condensation. An appropriate indicator of a NW/W transition at a given loading is therefore the difference between the isosteric heat and the heat of sublimation (or condensation). Our simulation results show the "thin-to-thick" film transition in the temperature range between 195 and 240 K, which has not been previously explained. Above 240 K, continuous wetting occurs. This study provides a basis for a better understanding of adsorption in a range of systems because ammonia is an intermediate between simple molecules, such as argon, and strongly associating fluids, such as water |
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| Beschreibung: | Date Revised 20.11.2019 published: Print-Electronic Citation Status PubMed-not-MEDLINE |
| ISSN: | 1520-5827 |
| DOI: | 10.1021/acs.langmuir.8b03634 |