{sup 29}Si MAS-NMR study of the short-range order in potassium borosilicate glasses
- Iowa State Univ. of Science and Technology, Ames, IA (United States). Dept. of Materials Science and Engineering
- Coe College, Cedar Rapids, IA (United States). Physics Dept.
Potassium borosilicate glasses were prepared in families having the general formula of RK{sub 2}O{center_dot}B{sub 2}O{sub 3}{center_dot}NSiO{sub 2}, where R is the ratio of potassium oxide to boron oxide and N is the ratio of silicon dioxide to boron oxide. The glasses were prepared for values of R ranging from 0 to 7.0 in the families N = 0.5, 1.0, 2.0, and 4.0. {sup 29}Si MAS-NMR measurements were performed on these glasses to determine the short-range order around the silicon atom. A model of proportional sharing of the added potassium oxide between the silicate and the borate groups was suggested. This model was tested against other suggested models where proportional sharing begins after a minimum amount of potassium oxide, R{sub 0}, and was observed to provide a better fit to the {sup 29}Si chemical shifts obtained. As was observed in the {sup 29}Si MAS-NMR studies of the RLi{sub 2}O{center_dot}B{sub 2}O{sub 3}{center_dot}NSiO{sub 2} glasses, the proportional sharing model with R{sub 0} = 0 is in stark disagreement with that proposed by the {sup 11}B NMR studies of the alkali borosilicate glasses. This problem is as yet not understood. Since K{sub 2}CO{sub 3} was used as the starting material for K{sub 2}O, it was observed that at large R values, R > R{sub CO{sub 2}}, where R{sub CO{sub 2}} = 2.3 for N = 1, R{sub CO{sub 2}} = 4.0 for N = 2, and R{sub CO{sub 2}} = 5.0 for N = 4, CO{sub 2} was retained in the melt in the fashion similar to that observed for other high-alkali borate and silicate glasses. The N = 0.5 family did not exhibit retention at the compositions studied. {sup 29}Si MAS-NMR could be used to determine where CO{sub 2} retention began in composition and the proportion of K{sub 2}O/K{sub 2}CO{sub 3} in the melt (glass).
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 82587
- Journal Information:
- Journal of the American Ceramic Society, Vol. 78, Issue 4; Other Information: PBD: Apr 1995
- Country of Publication:
- United States
- Language:
- English
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