The University of Shiga Prefecture · Faculty of Engineering · 教授

Research keywordschemically strengthened glass・borosilicate glass・silicate melts・Soret effect・glass fracture mechanics・indentation deformation・Raman spectroscopy・molecular dynamics simulation

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• Ultra-high temperature Soret effect in a silicate melt: SiO2 migration to cold side2023 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌） DOI： 10.1063/5.0167239
• Composition-dependent sign inversion of the Soret coefficient of SiO2in binary borosilicate melts2022 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Journal of Chemical Physics Using a laser-induced local-heating experiment combined with temperature analysis, we observed the composition-dependent sign inversion of the Soret coefficient of SiO2 in binary silicate melts, which was successfully explained by a modified Kempers model used for describing the Soret effect in oxide melts. In particular, the diffusion of SiO2 to the cold side under a temperature gradient, which is an anomaly in silicate melts, was observed in the SiO2-poor compositions. The theoretical model indicates that the thermodynamic mixing properties of oxides, partial molar enthalpy of mixing, and partial molar volume are the dominant factors for determining the migration direction of the SiO2 component under a temperature gradient. DOI： 10.1063/5.0090939 Scopus その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85131561520&origin=inward
• Determination of thermodynamic and microscopic origins of the Soret effect in sodium silicate melts: Prediction of sign change of the Soret coefficient2021 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： AIP Publishing LLC. 参加形態： 共同（副担当） The Soret effect in silicate melts has attracted attention in earth and material sciences, particularly in glass science and engineering, because a compositional change caused by the Soret effect modifies the material properties of silicate melts. We investigated the Soret effect in an Na2O–SiO2 system, which is the most common representative of silicate melts. Our theoretical approach based on the modified Kempers model and non-equilibrium molecular dynamics simulation was validated for 30Na2O–70SiO2(mol. %). The sign and order of the absolute values of the calculated Soret coefficients were consistent with the experimental values. The positive Soret coefficient of SiO2 in the SiO2-poor composition range was accurately predicted. Previous experimental studies have focused on SiO2-rich compositions, and only the negative sign, indicating SiO2 migration to the hot side, has been observed. In the SiO2-poor composition range, the Q0 structure was dominant and had four Si–O–Na bonds around an SiO4 unit. The Si–O–Na bond had high enthalpic stability and contributed to the large negative enthalpy of SiO2 mixing. According to our model, components with a large negative partial molar enthalpy of mixing will concentrate in the cold region. The microscopic and thermodynamic origins of the sign change in the Soret effect were determined. DOI： 10.1063/5.0040513
• Soret coefficient of a sodium germanate glass melt: Experiment, theory, and molecular dynamics simulation2020 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Journal of the American Ceramic Society The Soret effect is a diffusion phenomenon driven by a temperature gradient in a multicomponent system. This effect in condensed systems is not fully understood. Previously, we reported a theoretical model called “adjusted Kempers model” to predict the Soret coefficient in glass melts, and compared the experimental value to the theoretical value for 11Na O-89B O (mol%) melts. Here, molecular dynamics calculations, as well as theoretical and experimental values, are quantitatively compared in 10Na O-90GeO melts. We used a vertical tubular furnace to cause a temperature gradient and heated the sample from top side to reduce the natural convection. We measured the composition of 10Na O-90GeO glass samples after 45, 90, and 180 hours of heat treatment under a temperature gradient, and estimated the steady-state Soret coefficient near 1373 K to be 1.09 × 10 K . In addition, we calculated Soret coefficients to be 3.65 × 10 K and 1.85 × 10 K in theory and molecular dynamics calculation, respectively. The ratios between the experimental and theoretical Soret coefficients were 1.2 and 3.3 for 11Na O-89B O melts and 10Na O-90GeO melts, respectively. The difference in ratios may be attributed to the mass and size of diffusion species in the glass melts. 2 2 3 2 2 2 2 2 2 3 2 2 −3 −1 −3 −1 −3 −1 DOI： 10.1111/jace.17375 Scopus その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85089012684&origin=inward

• ガラス科学 （熱物性，破壊特性，光物性）1985 · 1985年4月 - 現在
• Thermal properties (heat capacity, thermal conductivity, glass transition behavior, isotope effect) of glasses in relation to their composition and structure
• Melt properties (viscosity, optical absorption, densicy, heat capacity, redox etc.) of glass in relation to their composition, temperature and structure
• Fracture behavior of glasses in relation to ther composition and structure

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