A two-step framework to analyze local microstructure variations of paper sheets based on 3D image data is presented. First, a multi-stage workflow efficiently acquires a large set of highly resolved tomographic image data, which enables—in combination with statistical image analysis—the quantification of local variations and pairwise correlations of morphological microstructure characteristics on length scales ranging from micrometers to centimeters. Secondly, the microstructure is analyzed in terms of the local behavior of porosity, thickness, and further descriptors related to transportation paths. The power of the presented framework is demonstrated, showing that it allows one (i) to quantitatively reveal the difference in terms of local structural variations between a model paper before and after unidirectional compression via hard-nip calendering and that (ii) the field of view which is required to reliably compute the probability distributions of the considered local microstru...

The paper presents the working principles of phase contrast x-ray microtomography and explains how 3D images of the paper structure may be obtained. Examples of visualisation of characteristic parameters for the 3D paper structure are shown. Principles for measurement methods of the paper structure are described and results for the porous structure according to "the equivalent pore" concept presented. The

The detailed 3D structure of paper was revealed applying both high and low resolution X-ray microtomography. The qualityof the two techniques with respect to resolution and volume size was compared by measuring various structural andtransport properties of the digital volumes.

Mercury intrusion porosimetry (MIP) is an inexpensive and common technique to characterize porous structures like paper. One major limitation of MIP is the lack of information about the arrangement of pores in the structure, information that is particularly relevant for multilayer structures such as thickness-structured paper. In this article, results from Synchrotron X-ray 3D microtomography are combined with MIP data to provide in-depth and improved information about the structures.

Paper is basically a spatial network consisting of fibres, fines and possibly fillers with partly connected voids in between. The three-dimensional paper structure controls most of the actual paper properties directly or indirectly. However, little is known of the paper structures three-dimensional ...

Synchrotron X-Ray microtomography has already been successfully applied to visualise the inner structure of various grades of papers at a micron scale. The image analysis tools, previously developed, can provide quantitative data characterising the microstructures of papers. We studied two widely different samples - a Eucalyptus pulp handsheet and a commercial blotting paper. Numerical calculations were carried out on the tomography data to evaluate two specific physical properties - effective thermal conductivity and permeability. The Representative Elementary Volume (REV) for each physical quantity considered, in terms of its 3 characteristic lengths in the three main directions, was defined by the respective correlation lengths (Lc). Despite the small imaged volume (1400 m x 1400 m x paper_thickness), for any given property, whether microstructural or physical -: - The REV characteristic lengths were similar for both samples, - The REV was smaller than the imaged volume, These re...

The effects of length and arrangement of carbon fibers on the pore structure formed by the accumulation of carbon fibers are discussed using two-dimensional network model and computer image processing technology. The results show that with the increase of carbon fiber length, the pore size distribution becomes wider and the average pore size and standard deviation increase. The porosity uniformity first deteriorates and then increases after the fiber length reaches a certain level. With the increase of carbon fiber in the plane X, Y, the difference in orientation arrangement increases. The pore size distribution and the standard deviation of the average pore diameter and the pore diameter are basically the same, but the porosity evenness is deteriorated. Therefore, in order to prepare carbon fiber paper meeting the requirements of mass transfer of proton exchange membrane fuel cells, the fiber length should be as long as possible under other parameters, and the arrangement should be...