UNSPECIFIED (2003) Boron and silicon speciation in waste simulant doped borosilicate glasses using multinuclear MAS-NMR. In: 4th International Conference on Borates Glasses, Crystals and Melts, 2002, CEDAR RAPIDS, IOWA.

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Abstract

The mixed modifier borosilicate glass used in high level radioactive waste immobilisation has been doped with between 2 and 12 mol% waste simulants including lanthanum oxide (La2O3), aluminium oxide (Al2O3) and bismuth oxide (Bi2O3) forming three series of glasses. These series have been examined using multinuclear, magic angle spinning, nuclear magnetic resonance (MAS-NMR) to characterise their structures. B-11 MAS-NMR experiments have yielded differences in the rate of conversion of [BO4](-) to [BO3] units between the series of glasses as the amount of waste simulant is increased. For example, N-4, the fraction of four coordinated borons, decreases at a greater rate for the Al2O3 series than for the Bi2O3 series. In the Al2O3 doped glasses a discontinuity in the N-4 data is observed at the 7 mol% point. From Si-29 MAS-NMR spectra, the chemical shift of the peak differs between each series as the amount of waste simulant is increased. A discontinuity is observed in the chemical shift of the Al2O3 doped series at the same point, 7 mol%, as in the B-11 MAS-NMR data. Deconvolution of the Si-29 peak gives evidence for three structural units, Q(4) (B), Q(3) and Q(4) (M), where M is either Al, La or Bi. At high La2O3 and Bi2O3 contents, Q(3) units are found to form links with boron and become Q(3)(B) units. Structural information on the Al2O3 containing glasses has been obtained using Al-27 MAS-NMR and Al3+ is shown to exist mainly as [AlO4](-).

Item Type:	Conference Item (UNSPECIFIED)
Subjects:	T Technology > TP Chemical technology
Journal or Publication Title:	GLASS TECHNOLOGY
Publisher:	SOC GLASS TECHNOLOGY
ISSN:	0017-1050
Date:	April 2003
Volume:	44
Number:	2
Number of Pages:	5
Page Range:	pp. 85-89
Publication Status:	Published
Title of Event:	4th International Conference on Borates Glasses, Crystals and Melts
Location of Event:	CEDAR RAPIDS, IOWA
Date(s) of Event:	2002
URI:	http://wrap.warwick.ac.uk/id/eprint/9534

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