Modeling Nanoscale Confinement of Fluids: Applications to Fluids in Porous Materials and Liquids Wetting Nano-structured Surfaces

MONSON/0649552智能优点：该项目针对纳米尺度限制下流体性质的分子热力学建模。在该上下文中，限制一方面是指复杂多孔材料中的流体的情况，另一方面是指当液体与固体表面上的小规模图案接触时，其中通过表面图案的长度尺度来产生限制。对于多孔材料中的流体，对基本热力学行为的了解对从催化到吸附分离再到膜的应用，以及在利用吸附对多孔材料进行表征方面具有重要的影响。从防水纺织品的开发到气-液-固催化反应器的设计，液体对多孔、有结构或有图案的表面的界面润湿一直是许多技术领域的研究热点。近年来，液体与固体接触的纳米技术的应用也引起了人们的兴趣，如微纳流体、纳米光刻或芯片实验室技术。研究集中在两个领域：(I)复杂孔隙结构中流体的粗粒度模型的开发和应用。研究人员正在开发一种对复杂孔隙结构中的流体进行统一建模的方法，该方法可以在单一框架内处理润湿流体(气体吸附)和非润湿液体(汞测孔法)。该研究计划试图了解这些系统的平衡状态以及滞后和伴随的动力学。(Ii)了解液体如何弄湿具有拓扑和化学图案的表面。研究人员使用密度泛函理论和分子模拟来计算图案化表面上液滴的密度分布。我们的目标是了解三相固体-液体-蒸汽接触的细节，以及固体表面的结构是如何影响这种接触的。这些研究领域从根本上被流体限制和界面润湿现象这一共同主题联系在一起。统计力学在这些领域研究的一个中心问题是，需要处理这些系统中由几何复杂性造成的密度分布的三维。这些模型应该可以在纳米和介观长度范围之间架起一座桥梁。本研究采用了平均场密度泛函理论和蒙特卡罗模拟等多种计算方法。更广泛的影响：该项目代表了与重要工程应用密切相关的分子热力学基础研究的一个例子。这项研究的主要影响是应用于使用气体吸附和汞孔隙度测量的多孔材料表征。这项研究正在创建一个单一的分子建模框架，以理解这两种重要的表征技术。最近在纳米技术方面的研究表明，在小范围内理解界面的重要性。这里开发的用于研究受限流体的建模技术，其重点是三维界面结构，也可以在这一领域产生重大影响。该项目有重要的教育内容，首先是通过研究生、博士后学者和本科生的参与。研究小组活动旨在培养学生交流他们的研究成果的能力，我们的研究生参与本科课程的教学是他们学位课程的教育要求。在NSF的支持下开发的材料将用于为本科生开发吸附热力学讲座，并为化学工程研究生的统计热力学课程提供项目材料。该项目的特点是与工业研究人员(Quantachrome Corporation)合作，以及与莱比锡大学和柏林工业大学的研究小组进行国际合作。

Monson / 0649552Intellectual merit: This project is directed at the molecular thermodynamic modeling of fluid properties under nano-scale confinement. In this context, confinement refers on the one hand to the case of fluids in complex porous materials and on the other to when a liquid is in contact with a small scale patterning on a solid surface, where confinement is created by the length scale of the surface patterning. For fluids in porous materials, understanding of fundamental thermodynamic behavior has significant impact on applications ranging from catalysis to adsorption separations to membranes, as well as in the use of adsorption for porous materials characterization. The interfacial wetting of porous, structured or patterned surfaces by liquids has been of considerable interest in many technologies, ranging from the development water resistant textiles to the design of gas-liquid-solid catalytic reactors. Recently, interest is also emerging in applications in nanotechnology where liquids contact solids such as micro- and nano-fluidics,nano-lithography or "lab on a chip" technologies.The research focuses on two areas: (i) Development and application of coarse-grained models for fluids confined in complex pore structures. The investigators are developing a unified modeling approach to fluids in complex pore structures that can treat both wetting fluids (gas adsorption) and non-wetting liquids (mercury porosimetry) in single framework. The research program seeks to understand the equilibrium states of these systems as well as hysteresis and the accompanying dynamics. (ii) Understanding how liquids wet topologically and chemically patterned surfaces. The investigators use density functional theory and molecular simulations to calculate the density distributions for liquid droplets on patterned surfaces. The goal is to understand the fine details of the three-phase solid-liquid-vapor contacting and how this is influenced by the structure of the solid surface. These research areas are linked fundamentally by a common theme of fluid confinement and interfacial wetting phenomena. A central issue for statistical mechanics research in these areas is the need to deal with the three-dimensionality of the density distribution in these systems created by the complexity in the geometry. These models should allow one to bridge the nanoscopic and mesoscopic length scales. This research features several computational methods including mean field density functional theory and Monte Carlo simulation. Broader Impacts: The project represents an example of fundamental research in molecular thermodynamics that is closely linked with important engineering applications. The primary impact of the research is in application to porous material characterization using gas adsorption and mercury porosimetry. The research is creating a single molecular modeling framework for understanding both of these important characterization techniques. Recent research in nanotechnology has shown the importance of understanding interfaces at small length scales. The modeling techniques developed here for studying confined fluids, which focus on three-dimensional interfacial structure, can make a significant impact in this area also. The project has significant educational components, in the first instance through the involvement of graduate students, postdoctoral scholars and undergraduates. Research group activities are designed to develop the ability of students to communicate their research achievements, and our graduate students participate in teaching undergraduate courses as an educational requirement of their degree program. Material developed under NSF support will be used to develop lectures in adsorption thermodynamics for undergraduates and project materials for a course in statistical thermodynamics for chemical engineering graduate students. The project features collaboration with researchers in industry (Quantachrome Corporation) as well as international collaboration with research groups at the University of Leipzig and the Technical University of Berlin.