Developing a Theory of Relaxation Dynamics for Fluids Confined in Porous Materials

发展多孔材料中限制流体的弛豫动力学理论

• 批准号: 0853068
• 负责人: Peter Monson
• 金额: $ 30万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0853068&HistoricalAwards=false
• 关键词: Developing; Theory; Relaxation; Dynamics; Fluids

0853068Monson"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Intellectual Merit. This project supports for a research program on development and application of modeling techniques that can simultaneously describe both thermodynamic and dynamic transport phenomena for fluids confined in porous materials. The scientific motivation for this work is two fold. One motivation is the need to understand adsorption desorption hysteresis in mesoporous materials. The absence of true equilibrium in these systems makes it of particular interest to understand the dynamics. Another motivation is to develop a more sophisticated understanding of the transport resistances to equilibration in adsorption isotherms and how these depend on the structure of the porous materials. These are both problems with long histories and are even in some sense classical. However, the project proposes modeling research on developing a consistent description of both the thermodynamics and transport phenomena. This has the potential for a truly transformative contribution in this field. The approach we take here is to develop a theory of the time dependent molecular density distribution in the system. We then consider the dynamic evolution of this distribution in terms of the probabilities of transitions between states of the system. We use a lattice gas model to describe the interactions in the system and the PIs theory, dynamic mean field theory (DMFT), yields a mean field (classical density functional) description of the equilibrium and metastable states of the system. Ther proposed research has following components: i) Application of the DMFT to a variety of model pore geometries. They will choose geometries that illustrate the impact of pore structure on the relaxation dynamics. ii) Application to pore geometries in real systems. They will study systems of independent pores, including MCM 41 and porous silicon and ordered pore network systems such as KIT 6 and SBA 16, as well as disordered pore network systems exemplified by porous glasses. iii) Developing a theory of transport and self-diffusivities. The DMFT can also be analyzed from the point point of view of diffusion and provides a theory of transport diffusivity as well as self diffusivity. iv) Application to mercury porosimetry. We will use the DMFT to understanding the nature of mercury entrapment in mercury porosimetry, building on their recent work showing how gas adsorption and mercury porosimetry can be modeled in a single framework. v) Accuracy assessment and additional developments. They will make a detailed assessment of the impact of the approximations built into the approach using Kawasaki dynamics and molecular dynamics simulations. They also investigate including thermal fluctuations in the theory and plan to investigate an extension of the approach to off lattice molecular models.Broader Impacts. The research proposed here is fundamental in nature and addresses the nanoscale modeling of dynamic relaxation for fluids confined in porous materials. This is potentially transformative research since it will provide a bridge between two research communities in the area of confined fluid properties: one that focuses primarily on adsorption measurements and thermodynamics and the other that focuses on transport phenomena. The immediate impact is in the development of characterization methods for porous materials. However, given the very extensive world-wide effort in developing new porous materials for applications ranging from separationsto catalysis to microelectronics the ultimate impact could be very broad including energy-related applications. The project has a number of educational components including research experience for under- graduates, outreach to community colleges and development of course materials for undergraduate courses in thermodynamics, reaction engineering and transport phenomena based on the research.

0853068蒙森“这个奖项是根据2009年美国复苏和再投资法案（公法111-5）资助。“智力优势。该项目支持开发和应用建模技术的研究计划，该技术可以同时描述多孔材料中流体的热力学和动力学输运现象。这项工作的科学动机是双重的。一个动机是需要了解中孔材料中的吸附-脱附滞后。由于这些系统中没有真正的平衡，因此理解其动态特性特别有意义。另一个动机是发展一个更复杂的理解的运输阻力平衡吸附等温线，以及这些如何取决于多孔材料的结构。这两个问题都有很长的历史，甚至在某种意义上是经典的。然而，该项目提出了建立热力学和传输现象一致描述的建模研究。这有可能在这一领域作出真正的变革性贡献。我们在这里采取的方法是发展一个理论的时间依赖的分子密度分布的系统。然后，我们考虑这个分布的动态演化的概率系统的状态之间的转换。我们使用晶格气模型来描述系统中的相互作用和PI理论，动态平均场理论（DMFT），产生一个平均场（经典密度泛函）描述的平衡和亚稳态的系统。提出的研究具有以下组成部分：i）DMFT对各种模型孔几何形状的应用。他们将选择几何形状，说明孔结构对弛豫动力学的影响。ii）应用于真实的系统中的孔隙几何形状。他们将研究独立孔系统，包括MCM 41和多孔硅，有序孔网络系统，如KIT 6和SBA 16，以及以多孔玻璃为例的无序孔网络系统。（三）建立运输和自扩散理论。DMFT也可以从扩散的角度进行分析，并提供了传输扩散率和自扩散率的理论。iv）汞孔隙率测定法的应用。我们将使用DMFT来理解汞孔隙率法中汞截留的性质，建立在他们最近的工作基础上，这些工作展示了如何在一个框架中模拟气体吸附和汞孔隙率法。（五）准确性评估和进一步发展。他们将使用川崎动力学和分子动力学模拟对该方法中的近似值的影响进行详细评估。他们还研究包括热波动的理论和计划调查的方法扩展到离格分子模型。这里提出的研究是基本的性质，并解决了纳米级建模的动态松弛的流体限制在多孔材料。这是潜在的变革性研究，因为它将在受限流体性质领域的两个研究团体之间提供桥梁：一个主要关注吸附测量和热力学，另一个关注传输现象。直接影响是在多孔材料的表征方法的发展。然而，鉴于世界范围内在开发新的多孔材料方面的广泛努力，从分离到催化到微电子学，最终的影响可能非常广泛，包括与能源有关的应用。该项目有若干教育组成部分，包括为本科生提供研究经验，与社区学院联系，以及根据研究结果为本科生编制热力学、反应工程和运输现象方面的教材。