Transport and Critical Behavior in Mesoporous Random Materials

CTS-0104323 Chimowitz，Eldred H/U of Rochester主要研究人员假设，在近临界区域，超临界流体-微孔膜系统的主要输运机制将是表面结合溶质物种的扩散，由于膜中临界减速的影响，表面结合溶质物种的贡献很小。在这种情况下，主要研究人员认为，HIS应该唯一地导致通过膜的高度浓缩的溶质通量，这对于所提议的研究对象将是一个重要的结果。项目第一年的具体目标将是使用计算机模拟来研究通过微孔膜系统的近临界传输现象，使用一种新的松弛-动力学模拟技术，特别适合于临界区的计算。弛豫-动力学模拟组合由两个室组成，这是一个现象学结构，用于模拟浓度驱动的扩散过程。每个腔室的结构都可以设置成类似于感兴趣的膜。两个腔室最初由不透水隔板隔开，两个轮廓在不连续的浓度界面相交。一旦分配被移除，两个腔室之间就会发生扩散，当系统在给定的热力学条件下向其整体平衡状态松弛时，分子通量/选择性可以直接计数。整个系综中的动力学将由动力学蒙特卡罗粒子交换算法产生。这些模拟的主要目的将是评估这种新的模拟方法，并使用它来研究上述近临界膜系统的性质。主要研究人员目前已经在均质流体系统中对这些计算程序进行了基准测试，并且现在拥有计算资源和理论，可以使用它们来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一问题的全面调查，从而产生新的结果，并打算将其公布。这些模拟结果将对指导这一领域的实验工作提供一个概念框架具有重要价值，他们希望在项目的后半段强调这一点。这里的目标将是建立和委托一个实验系统，用于可靠地获取作为超临界传输条件的中尺度无机膜的模型溶质渗透率的数据。主要调查人员认为，这样做的能力是探索本文所述概念的可行性的核心；已要求提供资金以促进这一努力。这将需要对他们目前实验室中的高压吸收设备进行改造，以适应他们打算从美国过滤器公司购买的陶瓷膜组件。在这段时间内，他们在这些系统中的动态模拟能力应该是完全起作用的，这将推进他们的目标，即在项目的模拟和实验方面进行有用的交互。

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.