2023 Fiscal Year Research-status Report
| Project/Area Number |
22KF0218
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| Allocation Type | Multi-year Fund |
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| Research Institution | Kyoto University |
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Principal Investigator |
堀毛 悟史 京都大学, 理学研究科, 教授 (70552652)
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| Co-Investigator(Kenkyū-buntansha) |
KOSASANG SORACHA 京都大学, 理学研究科, 外国人特別研究員
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| Project Period (FY) |
2023-03-08 – 2025-03-31
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| Keywords | Metal-organic frameworks / Coordination polymers / Glass / Conductivity |
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| Outline of Annual Research Achievements |
The properties of traditional inorganic glass ceramics,electronic conductivity and thermal stability, are variable and often dependent on crystallinity content or size. The high processing temperatures of these conventional glass ceramics pose significant challenges. In our research, we introduce a class of glass ceramics called "metal-organic glass ceramics" (MOGCs), which are prepared using metal-organic frameworks (MOFs). These MOGCs exhibit relatively low phase transition temperatures, typically below 150°C, including melting, glass transition (Tg), and crystallization temperatures. This property allows easier control of their crystallinity content and size within the glass-ceramic matrix. During this period, we have synthesized crystalline MOFs using the M(H2PO4)2(1,2,4-triazole)2 system, where M represents Cd2+ and Mn2+. The glass phase of these MOFs was prepared by mechanical milling. By heating the MOF glasses above their Tg, we were able to control the amount and size of crystallinity by adjusting the heating time. We also prepared solid solutions of the MOGCs by mixing the two glass phases of Cd2+ and Mn2+ in different ratios and subjecting them to specific heating times above their Tg. All of these materials, in their various states, have been thoroughly characterized and analyzed using various techniques, confirming the formation of MOGCs with different crystallized contents and sizes. These materials will serve as a basis for further investigation of the correlation between crystallinity content and size within MOGCs and their proton conductivity behavior.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Crystalline M(H2PO4)2(1,2,4-triazole)2, where M represents Cd2+ and Mn2+ ions, has been prepared and used to study the proton conductivity behavior based on crystallinity with its glass matrix. By mechanical milling of the crystalline state, complete amorphization of the sample was obtained, as evidenced by the absence of Bragg diffraction in the X-ray diffraction (XRD) pattern. The short- to medium-range order in the local structure of the amorphous sample remained, which is similar to its crystalline state, while the long-range order correlations are absent using synchrotron X-ray total scattering. We confirmed the glass properties of the amorphous samples using differential scanning calorimetry (DSC) to clarify the glass transition (Tg) and recrystallization temperatures. Subsequent heating of the glass above its Tg in an Ar atmosphere induces recrystallization with the same diffraction pattern as the original state. We illustrate a progressive increase in XRD peak intensity and narrowing of peaks with increasing heating time at heating temperatures above Tg, suggesting that crystallite size and unit cells of metal-organic glass-ceramics are controllable. The percentage of crystallinity calculated from DSC is also adjustable when heating to a specific temperature for a specific time. Solid solution formation between two glasses upon heating above Tg was confirmed by XRD and atomic pair distribution function (PDF) analysis.
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| Strategy for Future Research Activity |
The properties of glass ceramics, such as mechanical strength, electrical conductivity and thermal stability, are largely dependent on the degree of crystallinity and crystal size. We aim to show how our metal-organic glass ceramics (MOGCs), with their low phase transition temperatures, influence the proton conductivity and its proton transfer direction. We will demonstrate that the value of proton conductivity can be tuned by (I) varying the crystallinity within the glass matrix and (II) manipulating the metal ion composition within the MOGCs. This proton conductivity will be measured by variable temperature AC impedance spectroscopy without humidification. We will show that our system allows control of the proton transfer direction to achieve unidirectional conductivity. To demonstrate unidirectional proton conductivity, we will design the experimental setup, fabrication process, and measurement methods. Finally, we aim to demonstrate the generalizability and applicability of our concept of MOGCs to various systems.
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| Causes of Carryover |
電気化学測定にあたり、測定を実施する試料数が予定より少なくなったため、消耗品費として次年度使用額が生じた。次年度に計画どおり実施する予定である。
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