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Fast diffusion path for water in silica glass

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Title: Fast diffusion path for water in silica glass
Authors: Kuroda, Minami Browse this author
Tachibana, Shogo Browse this author →KAKEN DB
Sakamoto, Naoya Browse this author
Yurimoto, Hisayoshi Browse this author →KAKEN DB
Keywords: Water
silica glass
diffusion pathway
free volume
Issue Date: Mar-2019
Publisher: Mineralogical Society of America
Journal Title: American mineralogist
Volume: 104
Issue: 3
Start Page: 385
End Page: 390
Publisher DOI: 10.2138/am-2019-6802
Abstract: Diffusion experiments of (H2O)-H-2 at 900-750 degrees C and water vapor pressure of 50 bar found diffusion of water in SiO2 glass more than one order of magnitude faster than that reported previously. The fast diffusion profile of water was observed as an extended tail of the normal water diffusion profile by a line scan analysis with SIMS, and it can be fitted with a diffusion model with a constant diffusivity. The obtained fast diffusion coefficient suggests that the diffusion species responsible for the fast diffusion is not molecular hydrogen but molecular water. The diffusivity and activation energy for the fast water diffusion can be explained by the correlation between diffusivities of noble gases in silica glass and their sizes. Because noble gases diffuse through free volume in the glass structure, we conclude that molecular water can also diffuse through the free volume. The abundance of free volume in the silica glass structure estimated previously is higher than that of H-2 observed in the fast diffusion in this study, suggesting that the free volume was not fully occupied by (H2O)-H-2 under the present experimental condition. This implies that the contribution of the fast water diffusion to the total water transport in volcanic glass becomes larger under higher water vapor pressure conditions.
Rights: ©2019 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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