TY - JOUR
T1 - The Charge-Balancing Role of Calcium and Alkali Ions in Per-Alkaline Aluminosilicate Glasses
AU - Thomsen, René Mossing
AU - Skibsted, J.
AU - Yue, Yuanzheng
PY - 2018
Y1 - 2018
N2 - 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 AlO
4 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 SiO
2 content. These observations strongly suggest that alkali ions preferentially charge-balance AlO
4
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 SiO
4 tetrahedra.
AB - 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 AlO
4 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 SiO
2 content. These observations strongly suggest that alkali ions preferentially charge-balance AlO
4
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 SiO
4 tetrahedra.
UR - http://www.scopus.com/inward/record.url?scp=85044718456&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcb.7b12437
DO - 10.1021/acs.jpcb.7b12437
M3 - Journal article
SN - 1520-6106
VL - 122
SP - 3184−3195
JO - Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
JF - Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
IS - 12
ER -