论文标题
纳米过冷限制中的过冷水的动态机械分析
Dynamic mechanical analysis of supercooled water in nanoporous confinement
论文作者
论文摘要
使用动力学机械分析（DMA）（F = 0.2-100 Hz）用于研究介孔凝胶中约有水的动态（2.6 nm和5 nm孔和5 nm孔）和Vycor（10 nm）和Vycor（10 nm）在T = 80 K到300 k的温度范围从300 k到300 k。毛孔的部分地区“没有人的土地”。在T1 = 145 K（P1）周围观察到两个不同的弛豫峰，而T2 = 205 K（P2）对于0.2 Hz时，凝胶2.6 nm和5 nm的Gelsil 5 nm。随着孔径D的增加，这两个峰都以系统的方式转移到较高的T，并以F的方式变化，这是相应松弛时间的Arrhenius行为的典型代表。对于P1，我们获得了EA = 0.47 eV的平均激活能，与文献值良好。建议P1对应于远离孔隙壁的超冷水的玻璃转变，而P2反映了孔表面附近的水分子的动力学。观察年轻的模量在165 K附近（0.2 Hz时凝胶2.6 nm）的明显软化与P1附近的玻璃至液体过渡一致。此外，我们发现计算出的玻璃过渡温度的清晰切割1 = d依赖性，该温度将其推断到Tg（1/d = 0）= 136 K，即水的传统值。
Dynamical mechanical analysis (DMA)(f=0.2 - 100 Hz) is used to study the dynamics of confined water in mesoporous Gelsil (2.6 nm and 5 nm pores) and Vycor (10 nm) in the temperature range from T=80 K to 300 K. Confining water into nanopores partly suppresses crystallization and allows us to perform measurements of supercooled water below 235 K, i.e. in water's so called "no man's land", in parts of the pores. Two distinct relaxation peaks are observed around T1 = 145 K (P1) and T2 = 205 K (P2) for Gelsil 2.6 nm and Gelsil 5 nm at 0.2 Hz. Both peaks shift to higher T with increasing pore size d and change with f in a systematic way, typical of an Arrhenius behaviour of the corresponding relaxation times. For P1 we obtain an average activation energy of Ea=0.47 eV, in good agreement with literature values. It is suggested that P1 corresponds to the glass transition of supercooled water far from pore walls, whereas P2 reflects the dynamics of water molecules near the surface of the pores. The observation of a pronounced softening of the Young's modulus around 165 K (for Gelsil 2.6 nm at 0.2 Hz) is in agreement with a glass-to-liquid transition in the vicinity of P1. In addition we find a clear-cut 1=d-dependence of the calculated glass transition temperatures which extrapolates to Tg(1/d=0)=136 K, i.e. the traditional value of water.
