Structural role of water in sodium silicate glasses: results from silicon-29 and proton NMR spectroscopy

Abstract

6405the function vRAB is small. The expansions of the two Bessel functions are KO(YRAB) = -In (vRAB)ym + In (2) ... K~(YRAB) = (vRAB)-' ...where ym is the Euler Mascharoni constant. Using these two expressions in eq 13, we obtain for the diffusion coefficientUsing the Arrhenius expression for the diffusion coefficient and for the diffusion-controlled rate coefficient and the definition of Y , given in eq 12, we arrive at kdc 217 Using the definition of T given in eq 2, we expand the rightmost expression in eq 22We now defineUsing these two definitions and taking the logarithm of both sides of eq 23, we arrive atFinally under the assumption that the prefactors Do and ko are similarly temperature dependent and differentiating eq 25 results in Registry No. Ru(bpy)32+, 15158-62-0; 02, 7782-44-7; silica, 7631-86-9. References and Notes(1) Photochemistry on Solid Surfaces; Anpo, M., Matsuura, T., Eds.; Elsevier, Amsterdam, 1989. Photochemistry in Constrained and Organized Media; Ramamurthy, V., Ed.; VCH: New York, 1991.(2) Rideal, E. K.

Influence of glass composition and alteration solution on leached silicate glass structure: A solid-state NMR investigation

“…Their physical and chemical properties can be better understood using structural characterizations, for example to determine whether the presence of water depolymerizes the glass network. Although this is still a subject of discussion (Zeng et al, 2000;Padro et al, 2003), these studies have extended our knowledge concerning proton sites using various NMR techniques (Kü mmerlen et al, 1992;Schaller and Sebald, 1995;Robert et al, 2001;Ai et al, 2004;Cody et al, 2005). Hydroxyl groups and molecular water are routinely observed in hydrated aluminosilicates such as albite (Kohn et al, 1989a) with 1 H chemical shifts approximately ranged from 0 to 20 ppm.…”

Dissolution mechanisms of water in depolymerized silicate melts: Constraints from 1H and 29Si NMR spectroscopy and ab initio calculations

“…Spectral interpretations are expected to be more straightforward for aluminum-free silicate compositions, which are thus ideal starting point for identifying and quantifying the variety of water species. Despite this advantage, there have been only limited spectroscopic studies, in particular NMR studies, on aluminum-free silicate compositions, and most of the NMR studies have been concentrated on silica and sodium silicate compositions (Farnan et al, 1987;Koller et al, 1990Koller et al, , 1995Kümmerlen et al, 1992;Schaller and Sebald, 1995;Zotov and Keppler, 1998;Robert et al, 2001).…”

“…This should not be confused with non-hydrogen-bonded SiOH groups that are also sometimes referred to as "free hydroxyls" in the glass literature (e.g., Scholze, 1959a,b;Wu, 1980). 29 Si magic angle spinning (MAS) and 1 H-29 Si cross-polarization (CP) MAS NMR results on silica and sodium silicate glasses and melts (Farnan et al, 1987;Koller et al, 1990Koller et al, , 1995Kümmerlen et al, 1992;Schaller and Sebald, 1995;Zotov and Keppler, 1998;Robert et al, 2001) have revealed that the glass and melt structures become more depolymerized with water dissolution, suggesting that the formation of SiOH through the rupture of Si-O-Si linkages is a major water dissolution mechanism. The reported 1 H MAS NMR spectra for hydrous silica, and sodium-, barium-, and strontiumsilicate glasses show peaks in the range between 2.7 and 17 ppm that have been attributed to molecular H 2 O and SiOH groups (Kohn et al, 1989a;Kümmerlen et al, 1992;Schaller and Sebald, 1995;Robert et al, 2001).…”

Solubility and solution mechanism of H2O in alkali silicate melts and glasses at high pressure and temperature

“…For example, experimental studies in binary metal oxide silicate melts may illuminate how alkali metals and alkaline earths interact with dissolved H 2 O and the extent to which H 2 O may react with bridging oxygen to form Si-OH groups in the melts and glasses (e.g., Mysen and Virgo, 1986;Kummerlen et al, 1992;Zotov et al, 1996;Zotov and Keppler, 1998). Existing data demonstrate that OH bonding involving alkalis and alkaline earths is possible, but there exist, to the knowledge of the authors, no systematic data on relationships between H 2 O solubility and solubility mechanisms, H 2 O content and the alkali/ silicon ratio of the melts (degree of melt polymerization).…”