Vapor-Liquid-Ice: Exploring Water's Phase Transitions Far from Equilibrium

化学系的化学结构、动力学和机理-A(CSDM-A)和环境化学科学(ECS)项目获得该奖项，资助俄亥俄州立大学(OSU)的Barbara Wyslouzil教授探索水在蒸气、液体和固体之间的运动方式。正在研究的两种现象是过冷水和过饱和水蒸气。液态水通常会在32华氏度(0摄氏度)以下转变为冰固体水，但有时它会在远低于冰点的温度下以液体的形式存在(由此得名“过冷”)。同样，有时水可以以蒸汽的形式存在，远远高于它应该形成液体(凝结)的浓度；这一点被称为“过饱和”。Wyslouzil教授和她的研究团队正在使用超音速喷嘴、红外光谱和x射线散射工具来确定水蒸气过饱和和液态水过冷的极限，以及最终冻结和凝结发生的速度。这些问题在大气中很重要，水的状态既影响云将阳光反射回太空的能力，也影响云内发生的化学反应。在工业中，了解水何时凝结对于开发高效的能源提取方案非常重要。Wyslouzil教授参与了俄亥俄州立大学的科学早餐冠军计划，并与OSU的蒸汽工厂合作，蒸汽工厂是俄亥俄州立大学的一项倡议，旨在促进科学、技术、工程、艺术和数学之间的跨学科合作。为了研究过冷和过饱和水的相变，Wyslouzil团队开发了一种可移动的超音速喷嘴设备，该设备可以很容易地与各种分析工具集成。在她的实验室里，标准方法包括静态压力测量来表征流动，以及红外光谱来量化可凝聚分数在蒸气、液体和固体中的分布。为了充分确定气溶胶液滴的大小及其晶体结构，需要进行空间分辨小角和广角X射线散射实验，这些实验是在国家用户设施中进行的。测量到的高转化率也接近于可以直接使用分子模拟进行研究的转化率。探索远离平衡的水的行为和/或变化的实验，对于促进我们对水的相图的理解、高级水模型的有效性、这种迷人化合物的反常行为以及开发自然和工业过程的准确模型至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

With this award, the Chemical Structure, Dynamics and Mechanisms-A (CSDM-A) and Environmental Chemical Sciences (ECS) Programs of the Division of Chemistry are funding Professor Barbara Wyslouzil at Ohio State University (OSU) to exploring how water moves between the vapor, liquid and solid states. Two phenomena that are being studied are supercooled water and supersaturated water vapor. Liquid water generally changes into ice solid water) below 32 degrees Fahrenheit (0 degrees Celsius), but sometimes it remains in liquid form well below the freezing temperature (hence the name "supercooled"). Similarly, sometimes, water can remain in vapor form well above the concentration at which it should form a liquid (condense); this point is called "supersaturated." Professor Wyslouzil and her research team are using a supersonic nozzle, infrared spectroscopy, and x-ray scattering tools to determine the limits to which water vapor can be supersaturated and liquid water supercooled, and how fast the eventual freezing and condensation occur. These questions are important in the atmosphere where the state of water affects both the ability of clouds to bounce sunlight back into space and the chemical reactions taking place within the clouds. In industry, understanding when water condenses is important to developing efficient energy extraction schemes. Professor Wyslouzil participates in OSU's Breakfast of Science Champions program and collaborates with the Steam Factory, an OSU initiative to promote interdisciplinary collaboration across Science, Technology, Engineering, Arts, and Math.To investigate phase transitions involving supercooled and supersaturated water, the Wyslouzil group has developed a transportable supersonic nozzle apparatus that is easily integrated with a broad range of analytical tools. In her lab, standard methods include static pressure measurements to characterize the flow and infrared spectroscopy to quantify the distribution of the condensable fraction among the vapor, liquid and solid states. To fully characterize the size of the aerosol droplets and their crystal structure requires spatially resolved small- and wide- angle X-ray scattering (SAXS/WAXS) experiments and these are made at national user facilities. The high transformation rates that are measured also approach those that can be directly investigated using molecular simulations. Experiments, exploring how water far from equilibrium behaves and/or transforms, are critical to advancing our understanding of the phase diagram of water, the validity of advanced water models, the anomalous behavior of this fascinating compound, and for developingaccurate models of natural and industrial processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.