Abstract
Rare ancient glasses have complex, multi-scale structures requiring more sophisticated and non-destructive pore characterisation techniques than usual. Homotattic patch models for nitrogen adsorption gave better fits to the isotherm data, more accurate void space descriptors, and also greater understanding of the underlying physical factors affecting adsorption, than standard BET. These homotattic patch models revealed the critical role of iron impurities in determining adsorption behaviour. Non-destructive sodium-23 NMR relaxometry validated the homotattic patch model for some natron glasses, and, in turn, was validated using multiple quantum magic-angle spinning (MQMAS) 23Na NMR. X-ray tomography images of the glasses showed the presence of large macroporous bubbles, while FEG-SEM revealed nanopores within the glass matrix. A newly-developed, gas overcondensation technique, suitable for small amounts of low porosity material, assessed the inter-relationship between the disparate levels in this hierarchical porosity. This technique demonstrated that the nanoporosity did not form a ‘corona’ around the bubbles, due to leaching from the glass, as initially supposed from tomography data, but was completely disconnected, and, thus, is probably associated with glass alkalinity. Gas overcondensation is demonstrated as a non-destructive alternative to mercury porosimetry for probing multi-scale porosity in rare artefacts.
Original language | English |
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Article number | 110467 |
Journal | Materials Characterization |
Volume | 167 |
Early online date | 27 Jun 2020 |
DOIs | |
Publication status | Published - 30 Sept 2020 |
Keywords
- Ancient glass
- Computerized X-ray tomography
- FEG SEM
- Gas sorption
- Heterogeneity
- Modeling
- Overcondensation
- Pore network
- Solid-state NMR
ASJC Scopus subject areas
- General Materials Science
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
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