Type

Journal Article

Authors

Denis P. Dowling
Michael T P McCann
Damian A. Mooney
J. M. Don MacElroy
Taslima Akter
Thomas C McDermott

Subjects

Chemistry

Topics
composite films diffusion molecular dynamics simulations pore structure silica films experimental structures

Diffusion within ultrathin, dense nanoporous silica films. (2011)

Abstract In this work the origin of permselectivity in dense silica films which possess a pore structure with pore sizes commensurate with the molecular size of the diffusing gas species is investigated. Much of the recently reported work in this field has involved the development of composite membrane films, and while it is generally assumed that the transport process of the gas species within the selective layer of these films is activated in nature, there are anomalies with this simplified picture. In this paper a new model is developed which, for the first time, explains the permselective behavior of the thin selective coatings ubiquitous to membrane separation processes. The model involves the existence of two primary transport domains within the solid film, one of which rapidly conducts the permeating gas (under non-Fickian conditions), while the second domain involves a slow diffusion mode characterized by normal Fickian transport. To validate the model, molecular dynamics simulations are conducted for diffusion of a number of simple gases (He, N(2), and CO(2)) within silica glasses over a range of solid densities. The silica media employed in these studies are based on a novel approach developed in this work for the construction of three-dimensionally periodic atomistic structures of silica of arbitrary density in which network bond connectivity is ensured. The results obtained from this work are in qualitative agreement with experimental observations and confirm the existence of dual mode transport which is central to the interpretation of the permselectivity in composite membranes systems.
Collections Ireland -> University College Dublin -> PubMed

Full list of authors on original publication

Denis P. Dowling, Michael T P McCann, Damian A. Mooney, J. M. Don MacElroy, Taslima Akter, Thomas C McDermott

Experts in our system

1
Denis P. Dowling
University College Dublin
Total Publications: 50
 
2
J. M. Don MacElroy
University College Dublin
Total Publications: 46