Structural and chemical heterogeneity in ancient glass probed using gas overcondensation, X-ray tomography, and solid-state NMR

Sean P. Rigby, Lee Stevens, Thomas Meersmann, Galina E. Pavlovskaya, Gregory J. Rees, Julian Henderson, Saffron J. Bryant, Karen J. Edler, Robin S. Fletcher

Research output: Contribution to journalArticle

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 languageEnglish
Article number110467
JournalMaterials Characterization
Volume167
Early online date27 Jun 2020
DOIs
Publication statusE-pub ahead of print - 27 Jun 2020

Keywords

  • Ancient glass
  • Computerized X-ray tomography
  • FEG SEM
  • Gas sorption
  • Heterogeneity
  • Modeling
  • Overcondensation
  • Pore network
  • Solid-state NMR

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Rigby, S. P., Stevens, L., Meersmann, T., Pavlovskaya, G. E., Rees, G. J., Henderson, J., Bryant, S. J., Edler, K. J., & Fletcher, R. S. (2020). Structural and chemical heterogeneity in ancient glass probed using gas overcondensation, X-ray tomography, and solid-state NMR. Materials Characterization, 167, [110467]. https://doi.org/10.1016/j.matchar.2020.110467