Use of X­ray microtomography for understanding structure­property relationships

The paper reviews some recent applications of X­ray tomography (XMT), carried out at Leeds University, to establish links, through numerical simulations, between microstructures and various macroscopic properties. Two cases are highlighted. The first is the development of virtual permeametry where XMT is used to capture microstructural details as input to Lattice Boltzmann Method (LBM) – a numerical technique for simulating flow through porous media – to predict bulk permeability of the material the scanned sample represents. Applications of this include performance assessment of filters and filter cakes, assessment of soil quality and its relationship to plant growth. In the second case, XMT scanned granule is used as input to a simulation model of dissolution. The model uses convective­diffusion equation for the dispersion of the dissolved in the host liquid, Noyes­Whitney equation for the mass transfer at the solid/liquid interface, and LBM to provide the convective flow field. Use of GPGPU (general purpose graphics processing units) is shown to speed up the simulations by at least 10 times over the CPU version. The model can be used to study how microstructure of tablets or granules affects drug release rate, or how heap structure influences mineral release in a leaching process. Some other, and more speculative, uses of XMT and numerical modelling that we are currently pursuing will also be mentioned.