Determination of phase-volume fractions from tomographic measurements in two-phase systems

A method is proposed to determine the phase-volume fractions in tomographic representations of two-phase systems. The method is applicable in cases where no independent mean values for the phase-characteristic property (alpha) are available, such as in standard X-ray computed tomography (CT) using a polychromatic source. The proposed procedure is based on fitting a sum of three parametric expressions to the histogram of alpha-values. The terms include two normal probability-density functions to account for noisy pure-phase values, and an analytical expression to account for intermediate Values due to interface-containing voxels and blurring. To test the method, it was applied to several X-ray CT data sets of two-phase systems with known Volume fractions and varying alpha-ranges, including a system with only about one standard deviation difference between the mean phase alpha-values, i.e., with substantial overlap between the noisy pure-phase distributions. The accuracy for the considered cases was found to be approximately 2 vol% or better. As an example, the proposed fitting procedure was used to determine the representative elementary volume needed for porosity estimation of a porous medium consisting of 0.5-mm glass beads. (C) 1999 Elsevier Science Limited. All rights reserved.