Effects of Al:Si and (Al + Na):Si ratios on the properties of the international simple glass, part II: Structure

Abstract

High-alumina containing high-level waste (HLW) will be vitrified at the Waste Treatment Plant at the Hanford Site. The resulting glasses, high in alumina, will have distinct composition-structure-property (C-S-P) relationships compared to previously studied HLW glasses. These C-S-P relationships determine the processability and product durability of glasses and therefore must be understood. The main purpose of this study is to understand the detailed structural changes caused by Al:Si and (Al + Na):Si substitutions in a simplified nuclear waste model glass (ISG, international simple glass) by combining experimental structural characterizations and molecular dynamics (MD) simulations. The structures of these two series of glasses were characterized by neutron total scattering and 27 Al, 23 Na, 29 Si, and 11 B solid-state nuclear magnetic resonance (NMR) spectroscopy. Additionally, MD K E Y W O R D S aluminosilicates, borosilicate glass, international simple glass, molecular dynamics, nuclear magnetic resonance, scattering F I G U R E 1 Neutron total scattering structure factor spectra obtained from (A-B) experimental data and (C-D) MD simulation for (A, C) ISG-An and (B, D) ISG-AnN glasses.

Effects of Al:Si and (Al+Na):Si ratios on the static corrosion of sodium‐boroaluminosilicate glasses

“…However, compositionalstructural property influence (direct or indirect) was identified by several authors for the fraction of [4] B and/or B linkage in the glass. 38,44,54,93 Important changes on the B coordination and linkage through the two series of glasses altered in this study could have a direct impact on their Stage II behavior as recently highlighted by Gin et al 54,66,67 As glasses transition from Stage I to Stage II, the elements build up in solution and alteration products, such as…”

“…Physical properties and structural changes caused by these substitutions were previously investigated via experimental characterization techniques and molecular dynamics. 67 These analyses showed ISG-AnN glasses were more depolymerized than ISG-An glasses.…”

“…Several structural properties of the ISG-An and ISG-AnN glasses were evaluated previously using MD modeling, including cation coordination numbers; polyhedral linkages; non-bridging oxygen (NBO), bridging oxygen (BO), tribridging oxygen (TBO) contributions; distribution of BOs around Al and Si (Al Q n and Si Q n ); fraction of [4] B (N 4 = [4] B/( [3] B+ [4] B)), network connectivity for each network former; and preferential distribution analysis of modifiers (i.e., Na, Ca) around each former. 67 The NL(α) and r 13m were compared to all these analyses and the glass compositions, and no direct relationship was discernable. However, compositionalstructural property influence (direct or indirect) was identified by several authors for the fraction of [4] B and/or B linkage in the glass.…”

“…The melting procedures of the glasses are fully described in Reiser et al 67 Precursor batches containing Al 2 O 3 , H 3 BO 3 , CaCO 3 , Na 2 CO 3 , SiO 2 , and ZrO 2 were melted using a 90% Pt-10% Rh crucible at temperatures between 1250 and 1550°C depending on glass composition. The glasses were quenched, ground, and remelted.…”

Predicting the dissolution rate of borosilicate glasses using QSPR analysis based on molecular dynamics simulations

“…Detailed structural analyses were performed and the overall structure is in agreement with high energy X‐ray diffraction and 11 B solid‐state NMR 39–41 . The effect of alumina and alumina + soda substitution of silica has also been investigated by combining MD and experimental methods 42,43 . The results show that MD generated structural models can now faithfully represent the structural features of these complex borosilicate glasses.…”