Spatial distribution of pores in porous materials [Räumliche Verteilung von Poren in porösen Materialien]

Porous materials have been developed rapidly in recent years and have many particular properties due to their special geometries, such as lightweight, large specific surface area, good energy absorption and high heat-transfer capacity. A commonly used parameter to characterize porous structures is the number of pores per inch (PPI). In this work, PPI is computed in three-dimensional (3D) space rather than in two dimensions, for instance from a two-dimensional image. The studied structures are computer-generated or reconstructed from computed tomography (CT) scan images of real structures. The images segmented by the marker-based watershed algorithm (a part of the pore network model) are also used in this work. All the computations are conducted using the solver Parallel Algorithm for Crystal Evolution in 3D (Pace3D) for counting the number of pores accurately. The algorithm for counting the number of pores is proposed and modified according to the distribution of pores in different cases. This work is divided into three main stages: verifying the counting algorithm with an aligned structure, modifying it for complex structures, and applying it for real structures. ... mehrThe two modified algorithms are also validated by a periodic aligned structure, then two modified algorithms are used in complex structures to reduce the influence of periodic boundaries. The first modified algorithm is a subtraction of computed values and the second modified algorithm is an adjustment of the length of the measuring lines. The relationships between PPI and other important parameters, such as porosity, the total number of pores (Voronoi points) and strut radius, are observed. The effects of the stretching direction and degree of pores on PPI are also studied. The PPI of structures with different stretching factors in one or two directions is shown. In addition, the advantages and disadvantages of the two modified algorithms are also identified. By reconstructing the real structure and computing the PPI of the 3D models, the PPI of the real foams is found to be smaller than the value given by the manufacturer. This difference is particularly evident in the structure with a large PPI. By observing the PPI in different directions, it is possible to find the stretching of pores.