The PoroDict module is, with the MatDict module, the module to characterize porous media, whereby PoroDict is used for the analysis of the pore space.

PoroDict is used to calculate pore-structure characteristics of 3D models obtained from CT-, µCT-, or FIB/SEM-image data or generated with GeoDict.

**The three most important properties to determine pore space characteristics are:**

**Geometric Pore Size Distribution**:

A pore radius is determined by fitting spheres into the pore volume. The method does not distinguish between through pores, closed pores, and blind pores, and it is purely geometrical.**Pore Size Distribution by Porosimetry**:

Equivalent to experimental porosimetry methods, such as MIP (Mercury Intrusion Porosimetry) or LEP (Liquid Extrusion Porosimetry), the volume of a non-wetting fluid which is pressed into the medium is calculated. This method works similar to the geometric pore size distribution, but the connectivity to the intrusion sided and closed pores are taken into account.**Percolation Path**:

The maximal diameter of a spherical particle that can move though the medium and the corresponding shortest path are calculated. Additionally the user can calculate e.g. the five largest pores (with corresponding shortest paths) or the eight shortest paths for a certain sphere diameter. The shortest paths of the spheres are visualized and animated.

PoroDict features

The PoroDict module can also determine:

**Surface Area**:

The surface area of a material is calculated with a statistical method [1], so that the rounded surface is approximated correctly. Additionally the surface of the voxels is calculated.**Open and Closed porosity**:

The number and volume of open and closed pores is calculated. Open pores lead from the material surface to the core, forming extensive networks of interconnected pores. Closed or isolated pores do not open to the surface in any direction.**Identify Pores through the Watershed algorithm**:

The Watershed algorithm is used to segment the pore volume of a media. The segmentation is then used to calculate the number and the distribution of the pores.**Three-Phase Contact Line**:

The length of the contact line between three phases of a system is calculated on the basis of the voxel edges in the Cartesian directions. The contact line length is strongly dependent on the structure's topology and affects the performance e.g. of catalytic materials.**Chord Length Distribution (CLD)**:

By CLD geometries of porous media can be precisely compared. CLD can be used for 2D cross-sections, for which pore size distribution cannot be determined by geometric PSD or PSD by porosimetry.**Euclidean Distance Transform (EDT)**:

The EDT gives the distance from any point (voxel) inside a pore to the nearest pore-solid boundary.**Bubble Point pressure**:

The bubble point is calculated on basis of the largest through pore and the Young-Laplace-equation.

Examples of PoroDict applications

Among many other applications, PoroDict can be used to:

- determine the geometrical structure characteristics of sandstone [2].
- analyze subsurface samples in respect to gas and oil extraction in reservoirs.
- characterize materials which are used in batteries.

Additional modules needed?

- The GeoDict Base package is needed for basic functionality.
- PoroDict works on 3D (micro-) structure models that can either be a segmented 3D image (microCT-scan, FIB-SEM) imported with ImportGeo-VOL, or a 3D structure model created with one of the GeoDict modules for
**Digital Material Design**, e.g. FiberGeo for nonwovens, GrainGeo for granular or sintered structure models or sphere-packings, or FoamGeo for foams.

References

[1]: J. Ohser and F. Mücklich, Statistical Analysis of Microstructures in Materials Science, Wiley and Sons, 2000, p. 115

[2]: S. Berg, H. Ott, S.A. Klapp, A. Schwing, R. Neiteler, N. Brussee, A. Makurat, L. Leu, F. Enzmann, J.-O. Schwarz, M. Kerstern, S. Irvine, and M. Stampanoni
Real-time 3D imaging of Haines jumps in porous media flow, Proceedings of the National Academy of Sciences US (PNAS),
Vol 110, No.10, pp.3755-3759, 2013.