The effect of oxide additions on medium-range order structures in borosilicate glasses

Abstract

Boron-11 nuclear magnetic resonance (MAS NMR) and Raman spectroscopies have been used to study four families of glasses: xCsO(100-x)ZMW (0<x<10), where ZMW represents the borosilicate glass MW to which oxides Z (AlO, LaO and MgO) are added such that, overall, 1.0≤R (= [modifier]/[BO])≤2.5; K (= [SiO]/[BO]) = 3.2. These glasses are related to the system used for the vitrification of high-level nuclear waste. The spectra reveal the presence of reedmergnerite and danburite medium-range order structural units in the glasses. The fraction of danburite units increases with the addition of caesium oxide when AlO or LaO are present, and decreases when MgO is present.

Quantitative measurement of Q3 species in silicate and borosilicate glasses using Raman spectroscopy

“…2(a)) were fitted in most cases with two Gaussian lines: one Q 3 peak and one Q 4 (B) peak, representing silicon atoms with predominantly two Si and two B next nearest neighbors [20]. Contributions from Q 2 units were negligible for all but typically the highest Cs 2 O contents and the high MgO content system.…”

Effect of minor additions on structure and volatilization loss in simulated nuclear borosilicate glasses

“…The danburite glass lost 12 ± 2% mass and the reedmergnerite lost 4 ± 2%. The occurrence of these two superstructural units in glasses is discussed in more depth in [37].…”

“…29 Si MAS NMR of borosilicate glasses has enabled the identification of the Q n fractions (n denoting the number of bridging oxygens). Most commonly these are observed as Q 4 , Q 3 and Q 4 (B) units, where (B) indicates 3Si + 1B or 2Si + 2B next nearest neighbors [37]. Q 2 sites are only possible when there is sufficient alkali oxide associated with the silicate network that the ratio of alkali oxide to silica exceeds 1:2.…”

Structure of borosilicate glasses and melts: A revision of the Yun, Bray and Dell model

“…Pyrex @ , or optical glasses and also for storage of nuclear waste. A considerable amount of results have been obtained about the structure of these glasses [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], mainly via NMR analyses of 11 B, 17 O, 23 Na and 29 Si, Raman spectroscopy and neutron diffraction [18]. A comprehensive model was proposed almost 30 years ago in the present journal by Yun and Bray, Yun et al [1,2] and by Dell et al [3], based on experimental 11 O 3 ] (where [Á] mol%) are the most important composition-related structural parameters.…”

“…Although this model is still a valuable starting reference for the structure evolution as alkali cations are added to the glass system, several authors have criticized it. In particular, some recent publications [4][5][6][7][8][15][16][17][18][19], have shown that in general alkali cations are more randomly mixed to the borate and silica networks than was assumed in [1][2][3]. At a quantum level, it is not always true that exactly one Na + is needed to compensate the charge of one BO À 4 unit [13], so it is not fully correct to assume the value R = 0.5 as a starting point for the formation of borosilicate units.…”