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Effect of heat treatment on the surface chemical structure of glass: Oxygen speciation from in situ XPS analysis.
- Source :
-
Journal of the American Ceramic Society . Feb2018, Vol. 101 Issue 2, p644-656. 13p. 2 Diagrams, 1 Chart, 7 Graphs. - Publication Year :
- 2018
-
Abstract
- Compositional changes in unleached and acid-leached soda-lime silicate surfaces were tracked with in-vacuo heating and X-ray Photoelectron Spectroscopy. Surface oxygen speciation was determined using a stoichiometry-based algorithm via elemental composition, instead of the typical O 1s peak-fitting approach. Accurate surface hydroxyl quantification is shown to require dehydration at temperatures near 200°C. On the unleached surface, no change in surface hydroxyl density (~2.5 OH/nm²) is observed in the temperature range of 200°C-500°C after the initial dehydration. However, repolymerization in the network (non-bridging oxygen→bridging oxygen) is observed due to volatilization of sodium. The acid-leached surface undergoes sodium out-diffusion from the bulk at sub-Tg temperatures with laterally resolved inhomogeneity and shows a reduction in the concentration of hydroxyls from 4.5 OH/nm² (200°C) to 3.2 OH/nm² (500°C) accompanied by an increase in bridging oxygen. These results suggest that when [OH] > 2.5~3/nm², vicinal OH undergo dehydroxylation with evolution of water, whereas when [OH] < 2.5/nm², most OHs are non-interacting and isolated (at temperatures below Tg). Furthermore, at temperatures exceeding 300°C, sodium has enough thermal energy to desorb in vacuum and diffuse from the bulk (depending on the abundance & local structure). [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00027820
- Volume :
- 101
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Journal of the American Ceramic Society
- Publication Type :
- Academic Journal
- Accession number :
- 126622916
- Full Text :
- https://doi.org/10.1111/jace.15245