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Water diffusion in silica glass through pathways formed by hydroxyls

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Title: Water diffusion in silica glass through pathways formed by hydroxyls
Authors: Kuroda, Minami Browse this author
Tachibana, Shogo Browse this author
Sakamoto, Naoya Browse this author
Okumura, Satoshi Browse this author
Nakamura, Michihiko Browse this author
Yurimoto, Hisayoshi Browse this author →KAKEN DB
Keywords: Water
silica glass
diffusion pathway
Issue Date: Mar-2018
Publisher: Mineralogical Society of America
Journal Title: American mineralogist
Volume: 103
Issue: 3
Start Page: 412
End Page: 417
Publisher DOI: 10.2138/am-2018-6208
Abstract: Water diffusion in silicate melts is a fundamental process controlling physical and chemical consequences for magmatism, but mechanisms of diffusion in silicate glasses and melts are not fully understood. In this study, water diffusion experiments in silica glass were performed at temperatures of 650-850 degrees C and water vapor pressure of 50 bar, with the aim of improving our understanding of the mechanism of water diffusion in a simple SiO2-H2O system, and to construct a general water diffusion model for multi-component silicate glasses. Hydrogen diffusion profiles in silica glass were measured by secondary ion mass spectrometry (SIMS) down to a water concentration of similar to 10 ppm. Water diffusion profiles indicate that water diffusion becomes slower with decreasing water concentration in silica glass, with the water concentration dependence being greater than in multi-component silicate glasses, particularly at low concentrations (e.g., Doremus 1969, 2000; Zhang and Behrens 2000). A new water diffusion model is proposed for silica glass, where the greater concentration dependence is attributed to the limited number of diffusion pathways in silica glass, formed by breaking Si-O-Si bonds through hydroxyl formation. The model was applied to multi-component silicate glasses, taking into account the effects of metal cations that act as network modifiers by providing additional diffusion pathways for water molecules. The lower water concentration dependence in multi-component silicate glasses and melts is explained by little dependence of the number of diffusion pathways on water concentration because it is controlled extrinsically by network modifier cations. It is concluded that the number of diffusion pathways is an essential controlling factor for water diffusion in silica and silicate glasses.
Rights: ©2018 Mineralogical Society of America
Type: article (author version)
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 圦本 尚義

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