PECASE: Kinetics of Adsorption in Nanoporous Structures

这项由化学和生物分离计划颁发的职业奖支持南伊利诺伊大学卡本代尔分校的玛丽亚·梅赛德斯·卡尔比教授开发理论模型和方法的工作，这些模型和方法可以基本了解不同的原子或分子如何以及以多快的速度进入纳米孔结构并结合(吸附)到它们的表面。由于不同的原子在结构上的吸附方式不同(要么是因为它们被不同强度的表面吸引，要么是因为它们以不同的速度被吸附，或者两者兼而有之)，吸附过程被广泛用于从混合物中分离气体。这个项目的重点是一种特殊的纳米结构，即碳纳米管束，它是一组中空的非常长的管，它们自发地聚集在一起形成束或绳。管子的小直径和不同类型的吸附空间的存在使纳米管束成为研究这些吸附过程的独特的纳米结构。此外，碳纳米管最近已经成为分离和膜应用的很有前途的材料。气体分离设备广泛用于气体回收(包括氢气生产，这是氢气经济的一个重大挑战)、空气净化系统和环境修复，因此对社会产生了广泛的影响。在这个项目中，将实施计算机模拟和统计力学模型，以：1)探索导致纳米孔结构中吸附位置的实际可访问性的条件和参数，2)评估基于纳米管的系统用于分离和传输应用的能力，以及3)阐明由于被吸附的原子在有效的低维空间(表面和通道)中移动的限制而预期的独特的动力学行为。从更广泛的角度来看，这些结果将为理解更复杂的系统(其他多孔材料和/或更复杂的吸附材料)中的这些现象提供基础，并展望具有最佳性能的新型结构，用于分离和传输应用。该项目还包括一个重要的教育组成部分，通过以下活动：1)参与项目的学生在学习特定理论和计算技术的同时获得基本的研究技能；2)PI参与材料研究的跨学科计划，该计划将来自代表性不足的群体的学生带入SIUC从事研究项目；3)实施一门名为“纳米结构中的表面现象”的新课程，以填补当前课程中的教育空白，并加强最近批准的应用物理学博士课程。作为一项外展活动，旨在增加STEM(科学、技术、工程和数学)职业的女性入学率，PI领导了一个讲习班，对初中女生进行关键干预，以提高对以数学为基础的职业的认识，介绍通往这些职业的途径，最重要的是，提供成功的职业榜样。

This CAREER award by the Chemical and Biological Separations program supports work by Professor Maria Mercedes Calbi at Southern Illinois University at Carbondale to develop theoretical models and methods that can provide a basic understanding of how and how fast different atoms or molecules can gain access into nanoporous structures and become bound (adsorbed) to their surfaces. Since different atoms adsorb differently on a structure (either because they are attracted to its surfaces with different strength, or they are adsorbed at different speeds, or both), adsorption processes have been widely used for separating gases from a mixture. This project is focused on a particular nanostructure, a carbon nanotube bundle, which is a collection of hollow, very long tubes that gather spontaneously forming bundles or ropes. The small diameter of the tubes and the presence of different kinds of adsorbing spaces make a nanotube bundle a unique nanostructure in which to study these adsorption processes. Moreover, carbon nanotubes have recently emerged as promising materials for separation and membrane applications. Gas separation devices have an extensive impact on society due to their wide use for gas recovery (including H2 production, a significant challenge toward a hydrogen-based economy), air purification systems and environmental remediation. In this project, computer simulations and statistical mechanical models will be implemented in order to: 1) Explore the conditions and identify the parameters that lead to the actual accessibility of adsorption sites in nanoporous structures, 2) Assess the ability of nanotube-based systems for separation and transport applications, and 3) Elucidate the unique dynamical behavior that is expected as a consequence of the restriction on the adsorbed atoms to move in effectively lower dimensional spaces (surfaces and channels). From a wider perspective, these results will provide the basis to understand these phenomena in more complicated systems (other porous materials and/or more complex adsorbates) and to envision new kinds of structures with optimal performance for separation and transport applications. This project also comprises an important educational component through the following activities: 1) Students participating in the project acquire basic research skills while learning specific theoretical and computational techniques, 2) The PI participates in an interdisciplinary program in Materials Research that brings students from underrepresented groups to engage in research projects at SIUC, 3) A new course, entitled "Surface Phenomena in Nanostructures", is implemented to fill educational gaps in the current curriculum and strengthen the recently approved doctoral program in Applied Physics. As an outreach activity, aimed at increasing the female enrollment in STEM (Science, Technology, Engineering and Math) careers, the PI leads a workshop to make a critical intervention in junior high school girls to increase the awareness of math-based careers, to present information about the paths to those careers and, most importantly, to provide successful career role models.