The Charge-Balancing Role of Calcium and Alkali Ions in Per-Alkaline Aluminosilicate Glasses

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

DOI

  • René M. Thomsen, Department of Chemistry and Bioscience, Aalborg University
  • ,
  • Jørgen Skibsted
  • Yuanzheng Yue, Department of Chemistry and Biosciences, Aalborg University, Aalborg, Denmark.

The structural arrangement of alkali-modified calcium aluminosilicate glasses has implications for important properties of these glasses in a wide range of industrial applications. The roles of sodium and potassium and their competition with calcium as network modifiers in peralkaline aluminosilicate glasses have been investigated by 27Al and 29Si MAS NMR spectroscopy. The 29Si MAS NMR spectra are simulated using two models for distributing Al in the silicate glass network. One model assumes a hierarchical, quasi-heterogeneous aluminosilicate network, whereas the other is based on differences in relative lattice energies between Si-O-Si, Al-O-Al, and Si-O-Al linkages. A systematic divergence between these simulations and the experimental 29Si NMR spectra is observed as a function of the sodium content exceeding that required for stoichiometric charge-balancing of the negatively charged AlO4 tetrahedra. Similar correlations between simulations and experimental 29Si NMR spectra cannot be made for the excess calcium content. Moreover, systematic variations in the 27Al isotropic chemical shifts and the second-order quadrupole effect parameters, derived from the 27Al MAS NMR spectra, are reported as a function of the SiO2 content. These observations strongly suggest that alkali ions preferentially charge-balance AlO4 3- as compared to alkaline earth (calcium) ions. In contrast, calcium dominates over the alkali ions in the formation of nonbridging oxygens associated with the SiO4 tetrahedra.

Original languageEnglish
JournalJournal of Physical Chemistry B
Volume122
Issue12
Pages (from-to)3184-3195
Number of pages12
ISSN1520-6106
DOIs
Publication statusPublished - 29 Mar 2018

    Research areas

  • ALUMINUM, ENVIRONMENT, MQ-MAS NMR, PHYSICAL PERFORMANCES, SI-29, SILICATE, SPECIATION, SUPPLEMENTARY CEMENTITIOUS MATERIAL, TECTOSILICATE, WASTE GLASS

See relations at Aarhus University Citationformats

ID: 126104510