The influence of water on the structure of hydrous sodium tetrasilicate glasses

Universitaet Bayreuth, Bayerisches Geoinstitut, Bayreuth, Federal Republic of Germany
Bulgarian Academy of Sciences, Bulgaria

The structure of sodium tetrasilicate (Na ₂ Si ₄ O ₉ ) glasses containing 0 to 10 wt% water was investigated by a combination of Raman, IR, and NMR methods. Both the ²⁹ Si magic angle spinning NMR data and Raman spectra in the Si-O stretching region clearly show that water depolymerizes the silicate network of the glasses. Q-species distributions calculated from Raman spectra, assuming equal scattering cross sections of all bands in the Si-O stretching region, closely agree with results obtained from NMR data. At low total water contents, the silicate network is depolymerized mainly by breaking of Q ⁴ -Q ⁴ bonds, whereas breaking of Q ³ -Q ³ bonds dominates at high water contents. Near IR spectra show the presence of both OH groups and molecular H ₂ O in the glasses. The number of nonbridging O atoms per silicon atom, calculated from the near IR data, closely agrees with the results obtained from Raman and NMR, and confirms the assignment of the 4500 cm (super -1) band in the near IR to a combination mode of Si-Oh groups. Moreover, the intensity of the fundamental Si-OH stretching band at 910 cm (super -1) in the Raman spectra varies proportionally to the intensity of the 4500 cm (super -1) near IR band. Both IR and Raman spectra show three main bands in the OH-stretching region, centered at 3580, 3000, and 2350 cm (super -1) , due to hydrous species with different hydrogen bond strengths. The relative intensities of these three bands are insensitive to total water content and OH/H ₂ O ratio, suggesting that both OH and H ₂ O contribute to each of these bands. This is consistent with the fine structure of the H ₂ O bending vibration in the IR spectra around 1640 cm (super -1) and with the polarization dependence of the OH-stretching bands in the Raman spectra. Near IR spectra of hydrous sodium tetrasilicate glasses and hydrous aluminosilicate glasses are very similar and show a similar dependence of band intensity on total water content, suggesting that there is no fundamental difference in the dissolution mechanism of water in these systems.

This record provided courtesy of AGI/GeoRef.

This article has been cited by other articles:

				C. D.M. Dufresne, P. L. King, M. D. Dyar, and K. N. Dalby Effect of SiO2, total FeO, Fe3+/Fe2+, and alkali elements in basaltic glasses on mid-infrared spectra American Mineralogist, November 1, 2009; 94(11-12): 1580 - 1590. [Abstract] [Full Text] [PDF]

				R. A. Lange, H. M. Frey, and J. Hector A thermodynamic model for the plagioclase-liquid hygrometer/thermometer American Mineralogist, April 1, 2009; 94(4): 494 - 506. [Abstract] [Full Text] [PDF]

				X. Xue and M. Kanzaki Depolymerization effect of water in aluminosilicate glasses: Direct evidence from 1H-27Al heteronuclear correlation NMR American Mineralogist, November 1, 2006; 91(11-12): 1922 - 1926. [Abstract] [Full Text] [PDF]

				S. Okumura and S. Nakashima Molar absorptivities of OH and H2O in rhyolitic glass at room temperature and at 400-600 {degrees}C American Mineralogist, February 1, 2005; 90(2-3): 441 - 447. [Abstract] [Full Text] [PDF]

				N. Tsomaia, N. Tsomaia, S. L. Brantley, J. P. Hamilton, C. G. Pantano, and K. T. Mueller NMR evidence for formation of octahedral and tetrahedral Al and repolymerization of the Si network during dissolution of aluminosilicate glass and crystal American Mineralogist, January 1, 2003; 88(1): 54 - 67. [Abstract] [Full Text] [PDF]

				J. V. Oglesby, S. Kroeker, and J. F. Stebbins Potassium hydrogen disilicate: A possible model compound for 17O NMR spectra of hydrous silicate glasses American Mineralogist, March 1, 2001; 86(3): 341 - 347. [Abstract] [Full Text] [PDF]

				R. H. Doremus Water speciation in silicate glasses and melts: Langmuir limited site model American Mineralogist, November 1, 2000; 85(11-12): 1674 - 1680. [Abstract] [Full Text] [PDF]

				S. C. Kohn The dissolution mechanisms of water in silicate melts; a synthesis of recent data Mineralogical Magazine, June 1, 2000; 64(3): 389 - 408. [Abstract] [Full Text] [PDF]