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Fast diffusion path for water in silica glass

Minami Kuroda, Shogo Tachibana, Naoya Sakamoto and Hisayoshi Yurimoto
Fast diffusion path for water in silica glass
American Mineralogist (March 2019) 104 (3): 385-390


Diffusion experiments of 2H (sub 2) O at 900-750 degrees C and water vapor pressure of 50 bar found diffusion of water in SiO (sub 2) 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 2H observed in the fast diffusion in this study, suggesting that the free volume was not fully occupied by 2H (sub 2) O 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.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 104
Serial Issue: 3
Title: Fast diffusion path for water in silica glass
Affiliation: Hokkaido University, Departmant of Natural History Sciences, Sapporo, Japan
Pages: 385-390
Published: 201903
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 20
Accession Number: 2019-024147
Categories: General geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Secondary Affiliation: University of Tokyo, JPN, JapanJapan Aerospace Exploration Agency, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201914
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