Dynamics of supercooled water in confined geometry
Dynamics of supercooled water in confined geometry
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DOI：
10.1038/35002027
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发表时间：
2000-01-20
期刊：
影响因子：
64.8
通讯作者：
Swenson, J
中科院分区：
文献类型：
--
作者：
Bergman, R;Swenson, J
与大多数液体一样，过冷(1-4)水是可能的；这通常包括将液体冷却到其熔化温度I以下(避免结晶)，直到它最终形成玻璃。玻璃形成液体的粘度和相关的松弛时间(Tau)通常表现出非Arrhenius温度(T)相关性：在过冷区具有高度非Arrhenius行为的液体被称为“易碎”，相反，其行为接近Arrhenius定律(ln tau与1/T成正比)的液体被称为“强”(参考文献[1])。5)。对于过冷水，已经提出了一个独特的在228K左右的“脆弱-强烈”转变(6)；然而，在这个温度范围内，巨型过冷水的实验研究通常会因为结晶的发生而受到阻碍。在这里，我们使用宽带介电谱来研究过冷水在很宽的温度范围内的弛豫动力学，包括通常无法到达的温度区域。这是可能的，因为过冷水被保存在层状的蛭石粘土中--几何限制和夹层钠离子的存在阻止了大部分水的结晶。我们发现了一个具有Arrhenius温度依赖性的弛豫过程，这与所提出的深过冷体体水的强性质是一致的。因为过冷度较低的水已经被确定为高度脆弱的，我们的结果支持脆弱-强烈转变的存在。
As with most liquids, it is possible to supercool(1-4) water; this generally involves cooling the liquid below its melting temperature I(avoiding crystallization) until it eventually forms a glass. The viscosity and related relaxation times (tau) of glass-forming liquids typically show non-Arrhenius temperature (T) dependencies: Liquids with highly non-Arrhenius behaviour in the supercooled region are termed 'fragile', In contrast, liquids whose behaviour is close to the Arrhenius law (ln tau proportional to 1/T) are termed 'strong' (ref. 5). A unique 'fragile-strong' transition around 228 K has been proposed(6) for supercooled water; however, experimental studies of hulk supercooled water in this temperature range are generally hampered because crystallization occurs. Here we use broad-band dielectric spectroscopy to study the relaxation dynamics of supercooled water in a wide temperature range, including the usually inaccessible temperature region. This is possible because the supercooled water is held within a layered vermiculite clay-the geometrical confinement and presence of intercalated sodium ions prevent(7) most of the water from crystallizing. We find a relaxational process with an Arrhenius temperature dependence, consistent with the proposed strong nature of deeply supercooled bulk water. Because water that is less supercooled has been established(6) as highly fragile, our results support the existence of a fragile-strong transition.