Molecular Dynamics Simulation of Water Confinement in Disordered Aluminosilicate Subnanopores

Ohkubo, Takahiro; Gin, Stéṕhane; Collin, Marie; Iwadate, Yasuhiko

doi:10.1038/s41598-018-22015-3

Cited by 19 publications

(16 citation statements)

References 60 publications

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“…1,[20][21][22][23][24][25] In particular, the formation of several individual layers with largely different porosity inside a single SAL (exp. QBG-90/150) is difficult to explain by a leaching model that considers (i) the SAL as a residual and restructured glass and (ii) its porosity as a reflection of the free space created by the selective removal of certain network formers and modifiers from the glass, 26 and (iii) a transitional zone presented as hydrated glass 2 ahead of the SAL. On the other hand, the structural, textural, and isotopic features are fully consistent with the ICDP model that considers the SAL as being an amorphous silica precipitate.…”

Section: Discussionmentioning

confidence: 99%

“…In this model, it is assumed that the porosity in the gel layer directly reflects the free space created in the glass by the removal of cations from the glass structure. 26 Although this interdiffusion-based ion exchange or leaching model became widely accepted, particularly in the glass community, there has been a long dispute about the passivating effect of the SALs that is reflected by an experimentally observed drop in the corrosion rate with time. 27 It has been suggested that the SAL may be protective against further glass corrosion by pore closure or by restructuring of the hydrated glass, forming a passivating reactive interphase (PRI).…”

Section: Introductionmentioning

confidence: 99%

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Towards a unifying mechanistic model for silicate glass corrosion

et al. 2018

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Borosilicate glasses are currently used for the immobilization of highly radioactive waste and are materials of choice for many biomedical and research industries. They are metastable materials that corrode in aqueous solutions, reflected by the formation of silica-rich surface alteration layers (SAL). Until now, there is no consensus in the scientific community about the reaction and transport mechanism(s) and the rate-limiting steps involved in the formation of SALs. Here we report the results of multi-isotope tracer (2 H, 18 O, 10 B, 30 Si, 44 Ca) corrosion experiments that were performed with precorroded and pristine glass monoliths prepared from the six-component international simple glass and a quaternary aluminum borosilicate glass. Results of transmission electron microscopy and nanoscale analyses by secondary ion mass spectrometry reveal a nanometer-sharp interface between the SAL and the glass, where decoupling of isotope tracer occurs, while proton diffusion and ion exchange can be observed within the glass. We propose a unifying mechanistic model that accounts for all critical observations so far made on naturally and experimentally corroded glasses. It is based on an interface-coupled glass dissolution-silica precipitation reaction as the main SAL forming process. However, a diffusion-controlled ion exchange front may evolve in the glass ahead of the dissolution front if SAL formation at the reaction interface significantly slows down due to transport limitations.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Towards a unifying mechanistic model for silicate glass corrosion

et al. 2018

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“…Water transport, dynamics, and structure in nano-porous materials have been shown to be different from those in the bulk. 9,20,21,32,59 It was shown for alteration layers formed on ISG corroded in aqueous solutions that there is an evolution of pore size in the layers with corrosion time and it is accompanied by a structural rearrangement of the alteration layer. 9,40 In consequence, the transport and behavior of water and mobile elements would change with the evolution of alteration layer and they need to be considered in theoretical modeling and computational simulation of glass corrosion.…”

Section: Xps Depth Profilementioning

confidence: 99%

Hydrogen bonding interactions of H2O and SiOH on a boroaluminosilicate glass corroded in aqueous solution

et al. 2020

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Hydrogen bonding interactions play an important role in many chemical and physical processes occurring in bulk liquids and at interfaces. In this study, hydrous species (H 2 O and Si-OH) on nano-porous alteration layers (gels) formed on a boroaluminosilicate glass called International Simple Glass corroded in aqueous solutions at pH 7 and pH 9, and initially saturated with soluble siliconcontaining species were analyzed using linear and non-linear vibrational spectroscopy in combination with molecular dynamics simulations. The simulation results revealed various possible types of hydrogen bonds among these hydrous species in nanoconfinement environments with their populations depending on pore-size distribution. The nano-porous gels formed on corroded glass surfaces enhance hydrogen bond strength between hydrous species as revealed by attenuated total reflectance infrared spectroscopy. Sum frequency generation spectroscopy showed some significant differences in hydrogen bonding interactions on alteration layers formed at pH 7 and pH 9. The glass dissolution under the leaching conditions used in this study has been known to be ten times faster at pH 7 in comparison to that at pH 9 due to unknown reasons. The simulation and experimental results obtained in this study indicate that the water mobility in the gel formed at pH 9 could be slower than that in the gel formed at pH 7, and as a result, the leaching rate at pH 9 is slower than that at pH 7.npj Materials Degradation (2020) 4:1 ; https://doi.

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“…In Molecular Dynamics (MD) simulations, the modeling of dissociation of water and reaction with silicates is a critical component simulating glass‐water interactions . While the transport of glass components into solution can be modeled with nonreactive force fields . use of a reactive potential is critical for analyzing all the reactions and material transport inside the glass and solution.…”

Section: Introductionmentioning

confidence: 99%

“…27,30 While the transport of glass components into solution can be modeled with nonreactive force fields. 31,32 use of a reactive potential is critical for analyzing all the reactions and material transport inside the glass and solution. Recent improvements of reactive MD force fields have allowed for several advances in the modeling of silica-water interactions.…”

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confidence: 99%

Hydration and reaction mechanisms on sodium silicate glass surfaces from molecular dynamics simulations with reactive force fields

Mahadevan

2020

J Am Ceram Soc

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Recent development of reactive force fields have enabled molecular dynamics simulations of interactions between silicate glasses and water at the atomistic scale. While multicomponent silicate glasses encompass a wide variety of compositions and properties, one common structural feature in these glasses is the combination of the network structure that is made up of silica tetrahedra linked through corner sharing interspersed with network modifiers like alkali and alkaline‐earth ions that break up the Si–O–Si linkages by forming nonbridging oxygen. In reactions with water, ion exchange between alkali ions in the glass and proton or hydronium in the solution, as well as hydrolysis reaction of the Si–O–Si linkages and subsequent silanol formation, is observed and well documented. We have used a set of recently developed reactive force field to investigate the reactions between water and the surfaces of silica and sodium silicate glasses of different compositions for reactions up to 8 nanoseconds. Our results indicate sodium leaching into water and diffusion of water molecules up to 25 Å into the glass surface. We examined the structural and compositional changes inside the glass and around the diffused ions and use these to explain the rates of silanol formation at the surface. We also observed proton transport in the glass which has an indirect influence on the silanol formation rates. While the surface of the glass was rough to start with, it undergoes further modification into a hydrated gel‐like structure in the glass for up to 5 Å in the higher alkali containing glasses. It was found that the leached sodium ions remain close to the interface and that fragments of silicate network from the surface is capable of dislodging from the bulk glass and enter the aqueous solution. These simulations thus provide insights into the formation and structure of an alteration layers commonly observed in multicomponent silicate glasses corroded in aqueous solutions.

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Molecular Dynamics Simulation of Water Confinement in Disordered Aluminosilicate Subnanopores

Cited by 19 publications

References 60 publications

Towards a unifying mechanistic model for silicate glass corrosion

Towards a unifying mechanistic model for silicate glass corrosion

Hydrogen bonding interactions of H2O and SiOH on a boroaluminosilicate glass corroded in aqueous solution

Hydration and reaction mechanisms on sodium silicate glass surfaces from molecular dynamics simulations with reactive force fields

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