Shri Ramaswamy, Principal Investigator

Visualization and Characterization of Three-Dimensional Bulk Structure of Porous Materials

This research attempts to visualize and characterize the three-dimensional bulk structure of paper and board using non-intrusive techniques. Recent work has explored the use of x-ray microcomputed tomography (x-ray CT) to visualize the structure of porous materials. This technique is far superior to other techniques and the researchers are able to view the entire three-dimensional structure of thick (~300 mm) samples. These images are being binarized (black and white) using methodologies developed by this group. The researchers then use the supercomputers to analyze the binarized images for pore structure characterization. Structural parameters of interest include pore size distribution, average pore diameter, porosity distribution and average porosity, tortuosity, available transfer surface area, and fiber-fiber bonded area.

Initial estimates of the structure characteristics indicate an immense potential for this approach. Recent work using x-ray microtomography on paper samples of varying structures indicates that the technique is capable of visualizing the structure. The researchers’ methods to characterize the internal pore structures reveal interesting information on the anisotropic nature of the internal structure. Image analysis using high resolution xray CT images of different samples of paper indicate that the porosity, surface area, and tortuosity can be characterized reasonably well. Pore-size distribution of high resolution images are currently underway.

In addition, these researchers have developed a model to simulate the physics of simultaneous permeation and adsorption of liquid in porous media. The results indicate that, in addition to inherent absorption characteristics of cellulose fibers, the rate of permeation through the pore space has a strong influence on the overall absorption by porous media. The researchers are developing a nuclear magnetic resonance technique to visualize and characterize the transient three-dimensional structure of porous media during liquid penetration.