Home Bonding preferences of non-bridging O atoms: Evidence from 17O MAS and 3QMAS NMR on calcium aluminate and low-silica Ca-aluminosilicate glasses
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Bonding preferences of non-bridging O atoms: Evidence from 17O MAS and 3QMAS NMR on calcium aluminate and low-silica Ca-aluminosilicate glasses

  • Jeffrey R. Allwardt EMAIL logo , Sung Keun Lee and Jonathan F. Stebbins
Published/Copyright: March 31, 2015
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Abstract

The fraction of O atoms as non-bridging O atoms (NBO) can be well approximated based on composition alone in many silicate glasses, but the NBO preference for specific network forming cations is much less well known. Using oxygen-17 (17O) NMR on low-silica calcium aluminosilicate (CAS) glasses, this study shows that Al-NBO (155 ppm) can be readily distinguished from Si-NBO (110-120 ppm), and that there is a strong preference for the latter. This study also presents a consistent equilibrium constant formulation that indicates that for thermodynamic modeling of most CAS melts with Si > Al, Al-NBO are of minor importance, although they could be significant in some models of diffusion and viscosity. Al-27 one pulse NMR and analyses of spinning side bands show that AlO5 and AlO6 species are below detection limits (<0.5%) in the low-silica (SiO2 ≤ 20 mol%) glasses of this study (NBO/T = 0.6 to 0.8). In addition, 17O MAS NMR does not detect any obvious (<2%?) Al3O triclusters; hence calculations of NBO assignments can be assigned unambiguously.

Received: 2002-7-10
Accepted: 2002-12-19
Published Online: 2015-3-31
Published in Print: 2003-7-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Bonding preferences of non-bridging O atoms: Evidence from 17O MAS and 3QMAS NMR on calcium aluminate and low-silica Ca-aluminosilicate glasses
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  9. Chemistry of grain boundaries in mantle rocks
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  17. The crystal chemistry of julgoldite-Fe3+ from Bombay, India, studied using synchrotron X-ray powder diffraction and 57Fe Mössbauer spectroscopy
  18. Partitioning of Sr, Ba, Rb, Y, and LREE between plagioclase and peraluminous silicic magma
  19. Infrared and TEM characterization of amphiboles synthesized near the tremolite-pargasite join in the ternary system tremolite-pargasite-cummingtonite
  20. Coupling between non-convergent ordering and transition temperature in the C2/c ↔ P21/c phase transition in pigeonite
  21. 57Fe Mössbauer-effect studies of Ca-rich, Fe-bearing clinopyroxenes: Part I. Paramagnetic spectra of magnesian hedenbergite
  22. 57Fe Mössbauer-effect studies of Ca-rich, Fe-bearing clinopyroxenes: Part II. Magnetic spectra of magnesian hedenbergite
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