X-ray micro-computed tomography and tortuosity calculations of percolating pore networks

Synchrotron source X-ray micro-computed tomography was used for non-destructive three-dimensional (3-D) imaging of porous alumina structures, in which the porosity was induced by a granular porogen, added in amounts of 10–60 vol.%. Microstructural characteristics related to transport properties, including connectivity and tortuosity, were measured from the resulting 3-D data sets. Connectivity of 94.5–99.6% was measured for samples produced with 35–60% porogen (30.8–49.6% porosity). Two methods of calculating tortuosity, path length ratio and gas phase flux were compared, and the effect of sample volume on calculated tortuosity value and computational time was examined. Average sample tortuosity calculated using the two methods generally agreed, although significant directional anisotropy was detected in some cases for the gas phase flux calculation method. Tortuosity values as low as 1.5 were measured for alumina components with 49.6% porosity.