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Updated: Dec 10, 2025
In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging
Published on: September 2, 2016
Evaluation methodology of diffusion coefficient of guest substances associated with angstrom-scale open spaces in
Kiminori Sato1, Nagayasu Oshima2
1Department of Environmental Sciences, Tokyo Gakugei University, 4-1-1 Koganei, Tokyo 184-8501, Japan.
Abstract:
The knowledge of elemental migration associated with angstrom-scale open spaces is a prerequisite for sophisticated material design with respect to nanodispersion as well as a better understanding of molecular migration in a geological environment. Here, we show the methodology for evaluating the diffusion coefficient of guest substances focusing on angstrom-scale open spaces, where the depth-variation of open spaces caused by elemental diffusion in the micrometer-scale surface region is examined by the variable-energy slow positron beam. The present methodology determines a low diffusion coefficient of ∼10-14 cm2 s-1 for potassium at 533 K in SiO2 glass within the framework of Fick's principle providing the evidence that ∼2.5 Å open spaces intrinsically present in the glass matrix govern the diffusion process.
