Transport and Critical Behavior in Mesoporous Random Materials

chimowitz， Eldred H/ U of rochester的主要研究人员假设，在近临界状态下，超临界流体-微孔膜系统的主要输运机制将是表面结合的溶质物质的扩散，膜的空洞区域由于临界减速的影响，对其贡献很小。在这种情况下，主要研究人员认为，他应该独特地导致通过膜的高度富集的溶质通量，这将是拟议的研究目标的一个重要成果。该项目第一年的具体目标是使用计算机模拟来研究通过微孔膜系统的近临界输运现象，使用一种新的松弛动力学模拟技术，特别适合于临界区域的计算。松弛动力学模拟集合由两个腔室组成，这是一种现象学结构，用于模拟浓度驱动的扩散过程。每个单独的腔室的结构可以设置成类似感兴趣的膜。两个腔室最初由一个不透水的隔板隔开，两个剖面在一个不连续的浓度界面相遇。一旦隔板被移除，两个腔室之间发生扩散，当系统在给定的热力学条件下松弛到其总体平衡状态时，分子通量/选择性可以直接枚举。整个系综中的动力学将由动力学蒙特卡罗粒子交换算法生成。这些模拟的主要目的是评估这种新的模拟方法，并用它来研究上述近临界膜系统的性质。目前，主要研究人员已经在均质流体系统中对这些计算程序进行了基准测试，并且现在拥有了计算资源和理论，可以使用它们对受限结构中的近临界动力学进行系统研究。他们希望能够在明年内完成对这个问题的全面调查，得出新的结果，并打算发表。这些模拟结果将在为该领域的指导实验工作提供概念框架方面具有重要价值，他们的目标是在项目的后半段强调这一点。这里的目标将是建立和调试一个实验系统，以可靠地获取模型溶质在超临界运输条件下通过中孔无机膜的渗透数据。主要研究人员认为这样做的能力是探索本文所述概念可行性的核心；已要求提供资金以促进这项努力。这将需要修改高压吸收装置，目前在他们的实验室，以适应陶瓷膜模块，他们打算从美国过滤器公司购买。在此期间，他们在这些系统中的动态模拟能力应该完全发挥作用，这将推进他们的目标，即在项目的模拟和实验方面之间进行有用的交互。

ABSTRACT CTS-0104323Chimowitz, Eldred H/ U of RochesterThe principal investigators hypothesize that in the near-critical regime the dominant transport mechanism in supercritical fluid-microporous membrane systems will occur by diffusion of surface-bound solute species with little contribution from void regions of the membrane because of the effects of critical slowing-down therein. In this case the principal investigators have argued that his should uniquely lead to highly enriched solute fluxes through the membrane which would be a significant outcome for the proposed research objectives.The specific goal in the first year of the project will be to use computer simulation to study near-critical transport phenomena through microporous membrane systems using a novel relaxation-dynamics simulation technique, particularly suited for calculations in the critical region. The relaxation-dynamics simulation ensemble consists of two chambers, a phenomenological construction chosen to mimic concentration-driven diffusion processes. Each respective chamber's structure can be set up to resemble the membrane of interest. The two chambers are separated initially by an impermeable partition with the two profiles meeting at a discontinuous concentration interface. Once the partition is removed, diffusion between both chambers occurs, and molecular fluxes/selectivities can be directly enumerated as the system relaxes towards its overall equilibrium state at the given thermodynamic conditions. The dynamics in the entire ensemble will be generated by a kinetic Monte-Carlo, particle-exchange algorithm. The main objective of these simulations will be to evaluate this new simulation methodology and use it to study the properties of the near-critical membrane system described above. The principal investigators have currently benchmarked these computational procedures in homogeneous fluid systems and now have the computational resources and theory in had to use them to carry out a systematic study of near critical dynamics in confined structures. They hope to be able to complete a comprehensive investigation of this issue within next year, leading to new results that they intend to write up for publication.These simulation results will be of significant value in providing a conceptual framework for guiding experimental work in this area, which they aim to emphasize during the latter half of the project. The objective here will be to build and commission an experimental system for reliably acquiring data for model solute permeances through mesocale inorganic membranes as supercritical transport conditions. The principal investigators view the ability to do this as central to exploring the viability of the concepts described herein; funds have been requested to facilitate this endeavor. This will require the modification of a high-pressure absorption apparatus, currently in their laboratory, to accommodate a ceramic membrane module, which they intend to purchase from the US Filter Corporation. During this time their dynamic simulation capability in these systems should be fully functional, which will advance their goal of a useful interaction between both simulation and experimental aspects of the project.