In support of a depolymerization model for water in sodium aluminosilicate glasses: Information from NMR spectroscopy

A variety of ²⁹Si, ²⁷Al, ²³Na, ¹⁷O and ¹H NMR data are consistent with the formation of Q³ A1OH and SiOH groups upon dissolution of H₂O into aluminosilicate glasses. ²⁹Si single-pulse and ¹H-²⁹Si CP/MAS data present more direct evidence for the formation of Q³ Si species. A model that involves rupture of Si-O-Si, A1-O-Si, and A1-O-A1 linkages, and possibly cation exchange between H⁺ and Na⁺ is most consistent with the variety of data available. In this model the water dissolution process involves several reactions that are likely to proceed concurrently throughout the glass compositional space defined by A1/Si ratio and water content. Because the types of reactions do not change with A1/Si ratio, this model predicts smooth variations in hydroxyl and molecular water species abundances throughout compositional space within the system NaA1SiO₄-SiO₂-H₂O. Copyright (C) 2000 Elsevier Science Ltd.