GOALI: Molecular Modeling of Confined Nano-Phases and Nano-Porous Materials

North Carolina State University, Raleigh NC

Investigators

Abstract

Keith E. Gubbins - North Carolina State University "GOALI: Molecular Modeling of Confined Nano-Phases and Nano-Porous Materials" The aim of this project is to use novel molecular simulation methodologies to obtain realistic molecular models of nanoporous materials, and to use these to derive new and more accurate characterization methods and to predict the behavior of adsorbed nano-phases. The emphasis will be on activated carbons and carbon nanotubes. Impact: Activated carbons are the most widely used industrial adsorbents, but are among the most difficult nano-structured materials to characterize experimentally. Carbon nanotubes have potential applications in many new technologies, including use as nano-reactors and for fabrication of nano-structured materials (nano-composites, nano-wires, one dimensional crystals, etc.). Broader aspects of the project include the training of two graduate students in modern, multi-scale molecular simulation methods, the inclusion of new methods and applications in an interdisciplinary graduate course taught at NC State University, and dissemination of the results via publication in scientific journals and the group web-site. The methods to be developed could benefit society by providing basic understanding for development of new nano-structured materials, nano-devices, sensors and nano-reactors. This is a GOALI project involving university-industry collaboration between researchers at North Carolina State University and at Westvaco's Charleston Technical Center. Westvaco will provide samples and characterization data for a series of industrial carbons prepared under different activation conditions and from different precursors, as well as advice on the direction of the research. Studies will be in three areas: 1. Molecular simulation protocols are developed for the construction of realistic molecular models of carbon nanotubes and of activated carbons prepared from a range of precursors and with a variety of activation methods. For activated carbons, methods based on a hybrid Monte Carlo method that matches the model to experimental structural data, subject to constraints imposed by the multi-body intermolecular potential, will be used. 2. Existing materials characterization methods for the pore size distribution, surface area, and micropore volume are tested using simulated nitrogen adsorption and heat of adsorption in these model materials. Improved characterization methods that incorporate network effects (connectivity) are developed. 3. Freezing and melting phenomena of host nano-phases in these materials are studied, with particular emphasis on the effect of confinement on freezing temperature, new surface- and confinement-driven phases, and the detailed structure of the phases. An understanding of such phenomena is central to the fabrication of many new nano-structured materials.