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Title: Nonlinear dynamics of aqueous dissolution of silicate glasses and its implications to glass waste form durability.

Abstract

Abstract not provided.

Authors:
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1367313
Report Number(s):
SAND2017-5392C
653486
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Proposed for presentation at the 12th Pacific Rim Conference on Ceramic and Glass Technology (PACRIM 12), including Glass & Optical Materials Division Meeting (GOMD 2017) held May 21-26, 2017 in Waikoloa, Hawaii.
Country of Publication:
United States
Language:
English

Citation Formats

Wang, Yifeng. Nonlinear dynamics of aqueous dissolution of silicate glasses and its implications to glass waste form durability.. United States: N. p., 2017. Web.
Wang, Yifeng. Nonlinear dynamics of aqueous dissolution of silicate glasses and its implications to glass waste form durability.. United States.
Wang, Yifeng. Mon . "Nonlinear dynamics of aqueous dissolution of silicate glasses and its implications to glass waste form durability.". United States. doi:. https://www.osti.gov/servlets/purl/1367313.
@article{osti_1367313,
title = {Nonlinear dynamics of aqueous dissolution of silicate glasses and its implications to glass waste form durability.},
author = {Wang, Yifeng},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}

Conference:
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  • Aqueous dissolution of silicate glasses and minerals plays a critical role in global biogeochemical cycles and climate evolution. The reactivity of these materials is also important to numerous engineering applications including nuclear waste disposal. The dissolution process has long been considered to be controlled by a leached surface layer in which cations in the silicate framework are gradually leached out and replaced by protons from the solution. This view has recently been challenged by observations of extremely sharp corrosion fronts and oscillatory zonings in altered rims of the materials, suggesting that corrosion of these materials may proceed directly through congruentmore » dissolution followed by secondary mineral precipitation. Here we show that complex silicate material dissolution behaviors can emerge from a simple positive feedback between dissolution-induced cation release and cation-enhanced dissolution kinetics. This self-accelerating mechanism enables a systematic prediction of the occurrence of sharp dissolution fronts (vs. leached surface layers), oscillatory dissolution behaviors and multiple stages of glass dissolution (in particular the alteration resumption at a late stage of a corrosion process). In conclusion, our work provides a new perspective for predicting long-term silicate weathering rates in actual geochemical systems and developing durable silicate materials for various engineering applications.« less
  • There is no abstract currently available for this item
  • Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy has been used to characterize the structural and chemical environments of B, Al, and Si in model Hanford low-activity waste glasses. The average {sup 29}Si NMR peak position was found to systematically change with changing glass composition and structure. From an understanding of the structural roles of Al and B obtained from MAS-NMR experiments, the authors first developed a model that reliably predicts the distribution of structural units and the average {sup 29}Si chemical shift value, {delta}, based purely on glass composition. A product consistency test (PCT) was used to determine themore » normalized elemental release (NL) from the prepared glasses. Comparison of the NMR and PCT data obtained from sodium boro-aluminosilicate glasses indicates that a rudimentary exponential relationship exists between the {sup 29}Si chemical shift value, and the boron NL value.« less
  • The Raman spectra of nuclear waste glasses are composed of large variations in half-width and intensity for the commonly observed bridging (Q0) and nonbridging (Q1 to Q4) bands in silicate structures. With increase in waste concentration in a boroaluminosilicate melt, the bands of quenched glasses are distinctly localized with half-width and intensity indicative of increase in atomic order. Since the nuclear waste glasses contain disparate components, and since the bands depart from the typical random network, a systematic study for the origin of these bands as a function of composition and crystallization was undertaken. From a comparative study of Ramanmore » spectra of boroaluminosilicate glasses containing Na2O-ZrO2, Na2O-MgO, MgO-Na2O-ZrO2, Na2O-CaO-ZrO2, Na2O-CaO, and Na2O-MgO-CaF2 component sets and orthosilicate crystals of zircon and forsterite, intermediate order is inferred. An edge-sharing polyhedral structural unit is proposed to account for narrow bandwidth and high intensity for Q2 antisymmetric modes, and decreased leaching of sodium with ZrO2 concentration in glass. The intense Q4 band in nuclear waste glass is similar to the intertetrahedral antisymmetric modes in forsterite. The Raman spectra of zircon contains intratetrahedral quartz-like peaks and intertetrahedral non-bridging silicate peaks. The quartz-like peaks nearly vanish in the background of forsterite spectrum. This difference between the Raman spectra of the two orthosilicate crystals presumably results from their biaxial and uniaxial effects on polarizability ellipsoids. The results also reveal formation of 604, 956 and 961 cm-1 defect bands with composition and crystallization.« less
  • A Gd-rich crystalline phase precipitated in a sodium gadolinium alumino-borosilicate glass during synthesis. The glass has a chemical composition of 45.39-31.13 wt% Gd2O3, 28.80-34.04 wt% SiO2, 10.75-14.02 wt% Na2O, 4.30-5.89 wt% Al2O3, and 10.75-14.91 wt% B2O3. Backscattered electron images revealed that the crystals are hexagonal, elongated, acicular, prismatic, skeletal or dendritic, tens of mm in size, some reaching 200 mm in length. Electron microprobe analysis confirmed that the crystals are chemically homogeneous and have a formula of NaGd9(SiO4)6O2 with minor B substitution for Si. The X-ray diffraction pattern of this phase is similar to that of lithium gadolinium silicate apatite.more » Thus, this hexagonal phase is a rare earth silicate with the apatite structure. We suggest that this Gd-silicate apatite in a Gd-borosilicate glass is a potential glass-ceramic nuclear waste form for actinide disposition. Am, Cm and other actinides can easily occupy the Gd-sites. The potential advantages of this glass-ceramic waste form include: (1) both the glass and apatite can be used to immobilize actinides, (2) silicate apatite is thermodynamically more stable than the glass, (3) borosilicate glass-bonded Gd-silicate apatite is easily fabricated, and (4) the Gd is an effective neutron absorber.« less