水のガラスの移行は,ハイパークエンシング実験に基づいています
V Velikov1, S Borick, C A Angell
1Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
Science (New York, N.Y.)
|December 18, 2001
まとめ
水のガラス化温度 (Tg) が165Kに修正され,以前の研究における不一致が解決された. この発見は,水質を明確にします.
科学分野:
- 物理化学 物理化学
- 材料科学 材料科学とは
- 熱力学は熱力学である.
背景:
- 水のガラス化温度 (Tg) は議論の対象であり,実験値が矛盾しています.
- 水を含む過熱したガラスは,再加熱すると,重要なエンタルピーリラクゼーションエクソサームを示します.
- グラスでのエンタルピーリラクゼーションの標準的な分析は,典型的には,Tg.によるエクソサーム温度をスケーリングすることを含む.
研究 の 目的:
- 超静止水のガラス化温度 (Tg) に関する不確実性を解消する.
- 水のカロメトリック行動を調査し,他のガラス形成システムと比較する.
- 水のグラスでのエンタルピーリラックスを理解するための一貫した枠組みを確立する.
主な方法:
- ディフェンショナル・スキャニング・カロメトリー (DSC) は,エンタルピー・リラクゼーション・エクソサームを測定する.
- 熱計データの分析は,エクソサーム温度をグラス移行温度 (Tg) でスケールすることで行う.
- ハイパークエンシェットされた水の振る舞いを,他の既知のガラス形成物質とバイナリ溶液との比較.
主要な成果:
- 一般的に受け入れられている136 KのTgを使用すると,超静止水は他のガラスと比較して異常な行動を示します.
- Tgを165 ± 5Kに再計算すると,正常なガラスの動作が回復し,水を他の超静止システムと整列させます.
- この改訂されたTgは,H2O,ZnCl2,およびBeF2のようなネットワーク型以前のシステムと一致しています.
結論:
- 水の136 KのTgは以前から認められていたが,おそらく誤りであり,ガラスの移行行動の誤った解釈につながっている.
- 165 ± 5 Kの改訂されたTgは,他のガラス形成材料と比較して,水のエンタルピーリラクゼーションの一貫した理解を提供します.
- この改訂された値は,水と生物分子の相互作用を正確にモデリングし,生物学的システムを理解するために不可欠です.
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