在200K以下的MIL-101 ((Cr)) 框架的球形纳米孔内存在无形固体水:PALS,XRD和BDS研究
Vivek Sudhir1, Debarati Das2,3, Pranav Utpalla4
1Cochin University of Science and Technology, Cochin - 682022, Kerala, India.
Physical chemistry chemical physics : PCCP
|August 22, 2025
概括
超冷水局限于MIL-101 ((Cr) 纳米孔过渡到无形固体水 (ASW) 玻璃相,大约在190-200 K. 这项研究使用X射线衍射,正子灭绝寿命光谱和宽带介电光谱来揭示这种低温相变.
科学领域:
- 物理化学
- 材料科学
- 纳米技术
背景情况:
- 纳米封闭超冷水的玻璃过渡是有争议的,之前的研究显示没有明确的过渡在2nm以下.
- 之前的研究表明,在封闭水中 (1-1.8 nm) 观察到的转变是由于融化前或非合作性放松.
研究的目的:
- 在MIL-101 ((Cr) 金属有机框架 (MOF) 纳米孔中研究水的低温相变.
- 通过使用多种先进的光谱和衍射技术阐明受限水的行为.
主要方法:
- 低温正子消灭生命周期光谱 (PALS).
- 基于同步射线的X射线衍射 (XRD).
- 宽带介电光谱 (BDS).
主要成果:
- PALS在280K (结构重新排列),230K (部分结晶) 和200K (过渡到无形固体水) 周围的正正寿命中显示出明显的变化.
- 在230K以下的XRD证实了部分结晶,但在200K没有变化,表明非晶体过渡.
- 在190K左右,BDS表明从脆弱的液体 (Vogel-Fulcher-Tammann) 转变为强的玻璃状行为 (Arrhenius).
结论:
- 结合XRD,PALS和BDS证实,在MIL-101 (Cr) 纳米孔 (0.7-1.8nm) 中超冷水在190-200K之间转化为无形固体水 (ASW) 玻璃相.
- 这种转变与结晶不同,代表了纳米限制下水的结构动态的变化.
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