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Probing the chemistry, structure, and dynamics of the water-silica interface
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Lockwood, Glenn K.. Probing the chemistry, structure, and dynamics of the water-silica interface. Retrieved from https://doi.org/doi:10.7282/T3B856T3

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TitleProbing the chemistry, structure, and dynamics of the water-silica interface
NameLockwood, Glenn K. (author); Garofalini, Stephen H. (chair); Klein, Lisa C. (internal member); Danforth, Stephen C. (internal member); Cuitiño, Alberto M. (outside member); Rutgers University; Graduate School - New Brunswick
Date Created2013
Other Date2013-01 (degree)
SubjectMaterials Science and Engineering, Silica, Amorphous substances, Surface chemistry
Extentxxi, 197 p. : ill.
DescriptionDespite its natural abundance and wide-ranging technological relevance, much remains unknown or unclear about water-silica interfaces. Computer simulation stands to bridge the gaps of knowledge left by experiment, and a recently developed Dissociative Water Potential has enabled the simulation of large amorphous silica surfaces in contact with water without having to impose a model of surface chemistry a priori. Earlier work with this model has revealed the existence of several protonated surface sites such as SiOH2+ and Si-(OH+)-Si that have yet to be extensively characterized. However, both experiment and quantum mechanical simulation have provided an increasing body of evidence that suggests these sites exist, and these sites may play key roles in some of the unexplained phenomena observed in water-silica systems. To this end, this Dissociative Water Potential has been applied to develop a comprehensive picture of the chemistry, structure, and dynamics of the water-silica interface that is unbiased by any expectation of what sites should form. The bridging OH site, Si-(OH+)-Si, does form and is characterized as a highly acidic site that occurs predominantly on strained Si-O-Si bridges near the interface. Similarly, the transient formation of SiOH2+ is observed, and this site is found to be more acidic than Si-(OH+)-Si. In addition to H3O+ that forms near the interface, all of these sites readily deprotonate and are expected to play a role in the enhanced proton conductivity experimentally observed in hydrated mesoporous silica. The reactions between water and silica are particularly relevant to the engineering of nuclear waste forms, and the role of water-silica interactions are also explored within the context of the degradation of silica-based waste forms exposed to radiation. Despite the significant simulation effort employed in glassy waste form research, no molecular models of radiation damage in silica include the effects of moisture. This deficiency is addressed, and water is found to play a significant role in accelerating the degradation of amorphous silica under irradiation. Water inhibits healing of the network and promotes the formation of voids into which more water can penetrate, giving way to new damage accumulation mechanisms not seen in any past simulations.
NotePh.D.
NoteIncludes bibliographical references
NoteIncludes vita
Noteby Glenn K. Lockwood
Genretheses, ETD doctoral
Persistent URLhttps://doi.org/doi:10.7282/T3B856T3
Languageeng
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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