Mass fraction profiling based on x-ray tomography and its application to characterizing porous silica boules

Mass fraction profiling is a specialized tomographic technique designed to allow one to measure the concentration profiles of the component species of a synthetic composite material. While developed for the express purpose of determining the dopant, density, and porosity profiles of unsintered soot boules, the method hould also be useful in analyzing other types of ceramic such as dried gels. Mass fraction profiling amounts to a three-step process consisting of scanning the object of interest with well-collimated beams of x rays, reconstructing the attenuation coefficient profiles for several x-ray energies, and generating the density and concentration or mass fraction profiles. The method for determining these profiles is outlined, and some measurement results obtained for soot boules are presented.