Three-dimensional pore structure visualization and characterization of paper using X-ray computed tomography

Porous biomaterials such as paper and board have a complex structure that influences their mechanical, optical, and transport properties and thereby their performance during manufacturing and end uses. Reconstruction of the three-dimensional (3D) pore spaces in paper was obtained by X-ray computed tomography and used to study the structure and its impact on properties. A set of laboratory-made paper samples of varying freeness was prepared, and the 3D structures of the samples were visualized and characterized. Tomographic reconstruction images were processed using techniques such as anisotropic diffusion, minimum error thresholding, and isolated voxel removal to enhance image quality. The pore structures were analyzed to determine porosity, fiber-pore interfacial surface area, geometric tortuosity, and pore size distributions (using a sphere growing algorithm). These properties were compared with experimental data and were found to be in good agreement. The results from 3D visualization and characterization were then compared with experimental data of various samples using conventional pore structure characterization techniques, such as mercury intrusion porosimetry.