Freezing Water with Sonoluminescing Bubbles

用声致发光气泡冷冻水

• 批准号: 1805202
• 负责人: R Holt
• 金额: $ 32.89万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1805202&HistoricalAwards=false
• 关键词: Freezing; Water; Sonoluminescing; Bubbles

It is an everyday occurrence for water to freeze into solid ice when the temperature drops to 0 degrees Centigrade. But water can exhibit a variety of frozen forms, sometimes crystalline solids, sometimes disordered gels, depending on how (and how fast) it is frozen. These unique forms possess sometimes fantastic properties, being very dense or very viscous. Creating these unusual forms of water to study their remarkable properties usually requires confinement in high-pressure chambers at extremely cold temperatures, and contact with the chamber wall affects how the water freezes. This project seeks to create a novel form of ice without requiring the use of pressure chambers. Focused lasers will create individual nano-sized bubbles, and acoustic waves will grow these bubbles to millimeter sizes. Then, the bubbles will be allowed to collapse in pressurized water, a process often termed "acoustic cavitation". When the bubbles collapse, the water moving with the bubble rapidly pressurizes because it is contracting down to a tiny volume. By controlling the acoustics, water pressures just outside the collapsing bubble can reach 10,000 atmospheres in only a few nanoseconds, causing the water to freeze into a single ball of "ice" with no contact with any container surface. By employing diagnostics such as imaging ultrasound and laser scattering, researchers will probe both the mechanical properties and molecular structure of these remarkable ice balls. By learning about how water freezes at ultra-high pressures and nanosecond time scales, researchers can use the knowledge in a variety of ways. First, since the ice balls have such different properties from regular water, it may be possible to create a hybrid "ice-water" having novel optical and acoustic properties that change back to water properties in a few milliseconds. Second, there are many biomedical and industrial processes that currently employ acoustic cavitation, ranging from ultrasonic cleaners to contrast ultrasonic imaging to emulsification and extraction of food products. By systematically studying these violent bubble collapse events this research will shed light on similar but less energetic processes commonly occurring in industry and medicine.There is ample data and theory in agreement that the outcome for quasi-static near equilibrium compressions to GPa pressures at cryogenic or more modest temperatures is a crystalline ice (Ice VII, for example). There have been fewer studies of rapid compression, and while some of these studies show an amorphous high density and/or high viscosity phase, a very recent study of ns shock wave compression [Gleason et al., Compression freezing kinetics of water to Ice VII. Phys. Rev. Lett. 119, 025701 (2017)] seems to definitively show the formation of the crystalline Ice VII. In contrast, recent experiments from the principal investigator's lab [Sukovich et al., Outcomes of the Collapses of Large Single Bubbles in Water at High Ambient Pressures. Phys. Rev. E. 95 (2017) 43101] indicate the water surrounding a collapsing, sonoluminescing bubble "freezes" on the ns time scale. The result is an apparent phase transition to a spherical ice ball which displays properties of either hyper-elasticity or hyper-viscosity. However, the data are incomplete, as the Sukovich et al. experiment had only high-speed imaging as a diagnostic, and a parametric investigation was not carried out. This project will fill the gap in knowledge by investigating the formation, duration, and material properties of these ice balls resulting from high-pressure bubble collapse. Material properties will be investigated by employing both high-frequency time-reversal-aided acoustic scattering (probing the elastic modulus) and simultaneous femtosecond laser scattering (probing the molecular bonding). These experimental results will be complemented by molecular dynamics simulations at precisely the nanosecond time scales and high strain rates exhibited by the experiments and which are intrinsic to molecular dynamics simulations. These simulations will help determine the nature of the phase transition observed. A graduate student and several undergraduate students will be trained in research methods as a part of this work.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.

当温度降到摄氏零度时，水结成固体冰是每天都会发生的事。 但是水可以表现出各种各样的冻结形式，有时是结晶固体，有时是无序的凝胶，这取决于它冻结的方式（以及速度）。 这些独特的形式有时具有奇妙的特性，非常密集或非常粘稠。 创造这些不寻常的水形式来研究它们的显着特性通常需要在极冷的温度下限制在高压室中，并且与室壁的接触会影响水的冻结方式。 该项目旨在创造一种不需要使用压力室的新型冰。 聚焦激光将产生单个纳米大小的气泡，声波将这些气泡生长到毫米大小。然后，气泡将被允许在加压水中破裂，这一过程通常被称为“声空化”。 当气泡破裂时，随着气泡移动的水迅速加压，因为它收缩到很小的体积。 通过控制声学，破裂气泡外部的水压可以在几纳秒内达到10，000个大气压，导致水冻结成一个“冰”球，而不与任何容器表面接触。 通过采用超声成像和激光散射等诊断方法，研究人员将探测这些非凡冰球的机械特性和分子结构。 通过了解水如何在超高压和纳秒时间尺度下冻结，研究人员可以以各种方式使用这些知识。 首先，由于冰球具有与常规水如此不同的性质，因此可以产生具有在几毫秒内变回水性质的新颖光学和声学性质的混合“冰水”。 其次，目前有许多生物医学和工业过程采用声空化，从超声波清洁器到对比超声成像，再到食品的乳化和提取。 通过系统地研究这些剧烈的气泡崩溃事件，这项研究将揭示类似的，但较少的能量过程中通常发生在工业和medicine.There是大量的数据和理论一致的准静态近平衡压缩GPa压力在低温或更温和的温度下的结果是一个结晶冰（冰VII，例如）。 对快速压缩的研究较少，并且虽然这些研究中的一些显示出无定形高密度和/或高粘度相，但是最近对ns冲击波压缩的研究[Gleason等人，水到冰的压缩冻结动力学VII. 物理修订信函119，025701（2017）]似乎明确显示了结晶冰VII的形成。 相比之下，主要研究者实验室最近的实验[Sukovich等人，在高环境压力下水中大的单个气泡崩溃的结果。物理学修订版E。95（2017）43101]指示围绕塌陷的声致发光气泡的水在ns时间尺度上“冻结”。 其结果是一个明显的相变到一个球形冰球，显示出超弹性或超粘性的属性。然而，数据是不完整的，因为Sukovich等人的实验只有高速成像作为诊断，并且没有进行参数研究。这个项目将填补知识的差距通过调查的形成，持续时间，以及这些冰球的材料特性，高压气泡崩溃。材料特性将通过采用高频时间反转辅助声散射（探测弹性模量）和同时飞秒激光散射（探测分子键合）进行研究。 这些实验结果将得到补充，分子动力学模拟在精确的纳秒时间尺度和高应变率所表现出的实验，这是固有的分子动力学模拟。 这些模拟将有助于确定观察到的相变的性质。 作为这项工作的一部分，一名研究生和几名本科生将接受研究方法培训。该奖项反映了NSF的法定使命，并且通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。