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 27Al, 23Na, 29Si, and 11B solid-state nuclear magnetic resonance (NMR) spectroscopy. Additionally, MD simulations were used to generate atomistic structural models of the borosilicate glasses and simulation results were validated by the experimental structural data. Short-range (eg, bond distance, coordination number, etc) and medium-range (eg, oxygen speciation, network connectivity, polyhedral linkages) structural features of the borosilicate glasses were systematically investigated as a function of the degree of substitution. The results show that bond distance and coordination number of the cation-oxygen pairs are relatively insensitive to Al:Si and (Al + Na):Si substitutions with the exception of the B-O pair. Additionally, the Al:Si substitution results in an increase in tri-bridging oxygen species, whereas (Al + Na):Si substitution creates nonbridging oxygen species. Charge compensator preferences were found for Si-[NBO] (Na+), [3]B-[NBO] (Na+), [4]B (mostly Ca2+), [4]Al (nearly equally split Na+ and Ca2+), and [6]Zr (mostly Ca2+). The network former-BO-network former linkages preferences were also tabulated; Si-O-Al and Al-O-Al were preferred at the expense of lower Si-O-[3]B and [3]B-O-[3]B linkages. These results provide insights on the structural origins of property changes such as glass-transition temperature caused by the substitutions, providing a basis for future improvements of theoretical and computer simulation models.
| Original language | English |
|---|---|
| Pages (from-to) | 183-207 |
| Number of pages | 25 |
| Journal | Journal of the American Ceramic Society |
| Volume | 104 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 2021 |
| Externally published | Yes |
Funding
The glass design, fabrication, MD modeling, NMR measurements, interpretation, and manuscript development were supported by the Center for Performance and Design of Nuclear Waste Forms and Containers, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences (BES) under Award # DE-SC0016584. Computational resources were provided by UNT's High Performance Computing Services, a division of the University Information Technology with additional support from UNT Office of Research and Economic Development. NMR were performed using facilities at the Environmental Molecular Science Laboratory (EMSL, grid.436923.9), a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research at Pacific Northwest National Laboratory (PNNL). Neutron Total Scattering analysis were performed using funding received from the DOE Office of Nuclear Energy's Nuclear Energy University Program under US-DOE contract DE-NE0008694. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The authors express gratitude to Oliver Dicks and Charmayne Lonergan for their assistance in this work and review of the draft manuscript. Pacific Northwest National Laboratory is a multi-program national laboratory operated for the US Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RL01830. The glass design, fabrication, MD modeling, NMR measurements, interpretation, and manuscript development were supported by the Center for Performance and Design of Nuclear Waste Forms and Containers, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences (BES) under Award # DE‐SC0016584. Computational resources were provided by UNT's High Performance Computing Services, a division of the University Information Technology with additional support from UNT Office of Research and Economic Development. NMR were performed using facilities at the Environmental Molecular Science Laboratory (EMSL, grid.436923.9), a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research at Pacific Northwest National Laboratory (PNNL). Neutron Total Scattering analysis were performed using funding received from the DOE Office of Nuclear Energy's Nuclear Energy University Program under US‐DOE contract DE‐NE0008694. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The authors express gratitude to Oliver Dicks and Charmayne Lonergan for their assistance in this work and review of the draft manuscript. Pacific Northwest National Laboratory is a multi‐program national laboratory operated for the US Department of Energy by Battelle Memorial Institute under Contract DE‐AC06‐76RL01830.
Keywords
- aluminosilicates
- borosilicate glass
- international simple glass
- molecular dynamics
- nuclear magnetic resonance
- scattering