SNF – Sorption Induced Deformations

Sorption induced deformations of microporous materials

Applicant: Carmeliet, Jan

Other applicants: Derome, Dominique

Starting date: 01.10.2012

Duration in months: 36 Months

Adsorption originates at the molecular scale from the interactions between the atoms of the solid skeleton and the molecules of the fluid. When the size of the pores is in the order of the range of the molecular interactions (micro or nanoporous materials), a mechanical pressure arises orthogonal to the porous interface leading to sorption induced deformations (swelling). Microporous media showing sorption induced deformations are important for a huge variety of engineering application: for instance for sequestration of carbon dioxide in coal, for storage of hydrogen in metal-organic frameworks, for the purification of water etc. They may also be used as moisture activated shape memory materials in e.g. biomedical applications. Sorption in microporous materials may also induce undesired internal effects such as a decrease in permeability or cracking due to a restraining of the deformations. These processes may lead to operational or durability problems.

To study sorption induced deformations in microporous materials, we will use in this proposal a new poromechanical approach taking into account explicitly solid-fluid interactions arising in complex random microporous materials. To determine the mechanical effects of adsorption, the amount of adsorbed fluid in the medium has to be known in function of both the chemical potential of the fluid and the volumetric strain of the porous medium. This information can be gained by experiments or by molecular simulation. In this project we propose a multiscale modeling approach exploring the possibilities of a dependent domain approach to link different scales in hierarchical materials in order to determine the macroscopic material properties including coupling coefficients. In the dependent domain theory, the global material behavior results from the interaction of basic elements situated at different scales and characterized by statistical distributions.

In a first step, we develope a general framework for the determination of sorption induced deformations using dependent domain theory and computational upscaling, which allows to determine nonlinear coupling coefficient and the hysteretic coupled behavior. Then we will apply this general framework to different microstructures containing microporous materials. Systems of interest are consolidated granular media, cellular materials and composite materials. Subsequently hierarchical materials like wood will be studied and we will focus especially on understanding shape memory effects upon moistening.