Thermally-induced Rayleigh-taylor like instabilities for nanoscale synthesis

用于纳米级合成的热致瑞利泰勒样不稳定性

• 批准号: 1402962
• 负责人: Ramki Kalyanaraman
• 金额: $ 28.23万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-15 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1402962&HistoricalAwards=false
• 关键词: Thermally; induced; Rayleigh; taylor; like

CBET-1402962KalyanaramanOne way the United States can continue to be the global leader in technology innovation with a sound economic plan for the future is if it can employ large fractions of the population in high-tech manufacturing jobs. One potentially untapped, but high growth, area, is the manufacturing of sophisticated nanomaterials for use in solar cells, computer data storage devices, and sensors for disease detection. It is widely acknowledged that nature has found many ways to make useful and complex materials in economical fashion. One of the principles often found in nature is that of self-organization or self-assembly, in which competing forces lead to the emergence of a useful structure. For example, the Rayleigh-Taylor (RT) effect is at the heart of the formation of a uniform collection of water droplets on the underside of a ceiling. In this case, it is the result of gravity disturbing the water film-air interface that leads to droplet formation. Besides being evident in liquids, the RT effect can also be found in the behavior of astronomical structures such as black holes and supernova, and in geophysical phenomenon. If the RT effect can be applied to the nanoscale, a cost-effective way to make nanomaterials could result. However, since gravity rarely influences the nanoscale, other ways need to be found to create the RT effect. The research proposed here will explore the hypothesis that rapid heating of a material in liquid ambient can produce RT effects in the nanoscale. The experimental component will involve creating such a scenario by using laser pulses to heat the material of interest. A variety of microscopy and computer modeling techniques will be employed to study the resulting nanomaterials. During the course of this research, training of minority and underrepresented students from K-12, undergraduate, and graduate programs will be achieved. They will be trained in basic and applied principles of science and engineering, with the goal of making them future leaders of the society in STEM disciplines and/or in technologically relevant industries. The research proposed here is an understanding of the Rayleigh-Taylor (RT) instability in the nanoscale. Recent experimental findings show that the RT instability can be observed in thin films melted by laser pulses in a fluid ambient. The preliminary hypothesis underlying the discovery is that the large thermal gradient that develop at the film/vapor interface due to the rapid heating under nanosecond laser pulses lead to large pressure gradients, which are ultimately responsible for the observed behavior. Early results of thermal modeling support this hypothesis. However, the role of fluid properties, laser parameters and other thin film hydrodynamic instabilities is presently lacking in order to unequivocally establish an understanding of this phenomenon. Motivated by this, several model systems based on a combination of fluid (glycerol, water, toluene), film (Au, Ag, Si, TiO2), and substrate (Glass, Si, Sapphire) properties have been identified. The following tasks will be performed. (1) Theoretical modeling of thermal transport to understand ns pulsed laser heating of various fluid/film/substrate systems. (2) Laser melting experiments of various combinations of fluid, film and substrate. (3) Characterization of pattern morphology, nanoparticle structure, and chemical composition by various nanoscale tools. This includes scanning and transmission electron microscopy, atomic force microscopy, Raman spectroscopy, electron energy loss spectroscopy, and optical spectroscopy. (4) Modeling of the experimental results in the context of fluid dynamics theories to explain the observations.

CBET-1402962KalyanAramanone如何继续成为技术创新的全球领导者，并为未来制定合理的经济计划，即它是否可以在高科技制造业工作中雇用大量人口。一种潜在的未开发但高生长区域是生产精致的纳米材料，用于太阳能电池，计算机数据存储设备和疾病检测传感器。人们普遍承认，自然已经找到了许多方法来以经济方式制作有用且复杂的材料。自然界中经常发现的原则之一是自组织或自组装，其中竞争力导致有用的结构的出现。例如，雷利 - 泰勒（RT）效应是在天花板下面的水滴集合形成的核心。在这种情况下，这是重力干扰水膜空气界面的结果，导致水滴形成。除了在液体中很明显外，RT效应还可以在天文结构（例如黑洞和超新星以及地球物理现象）的行为中找到。如果可以将RT效应应用于纳米级，则可能导致一种成本效益的制作纳米材料的方法。但是，由于重力很少会影响纳米级，因此还需要找到其他方法来产生RT效应。这里提出的研究将探讨以下假设：液体环境中材料的快速加热可以在纳米级中产生RT效应。实验组件将涉及通过使用激光脉冲来加热感兴趣的材料来创建这种情况。将采用多种显微镜和计算机建模技术来研究所得的纳米材料。在这项研究过程中，将实现对K-12，本科和研究生课程的少数民族和代表性不足的学生的培训。他们将接受有关科学和工程学基本和应用原则的培训，目的是使他们在STEM学科和/或技术相关行业中的社会未来领导者。这里提出的研究是对纳米级雷利 - 泰勒（RT）不稳定性的理解。最近的实验发现表明，在流体环境中激光脉冲融化的薄膜中可以观察到RT不稳定性。该发现的基础上的初步假设是，由于纳秒激光脉冲下的快速加热导致在膜/蒸气界面上发展的大型热梯度导致了较大的压力梯度，最终导致了观察到的行为。热建模的早期结果支持这一假设。然而，目前缺乏流体特性，激光参数和其他薄膜流体动力学不稳定性的作用，以明确地建立对这种现象的理解。由此激励的是，已经确定了基于流体（甘油，水，甲苯），膜（Au，Ag，Si，Tio2）和底物（玻璃，SI，SI，Sapphire）特性组合的几种模型系统。将执行以下任务。 （1）热传输的理论建模，以了解各种流体/膜/底物系统的NS脉冲激光加热。 （2）流体，膜和底物的各种组合的激光熔化实验。 （3）各种纳米级工具的模式形态，纳米颗粒结构和化学组成的表征。这包括扫描和透射电子显微镜，原子力显微镜，拉曼光谱，电子能量损失光谱和光谱法。 （4）在流体动力学理论的背景下对实验结果进行建模，以解释观察结果。