Characterization of microporous, clay-sized particles in natural stone is essential for the understanding of their dynamics. These processes are importand in the fields of oil and gas, groundwater, building stone weathering and soil science. Methods such as X-ray micro-computed tomography is an excellent tool to study features larger than or just under 1 μm, but below the 400 nm limit, the technique falls short. Although destructive methods exists (e.g. FIB/SEM), non-destructive imaging at these very high resolutions has been impossible, until recent developments at synchrotron beam lines.
In this study, we use ptychographic tomography at the cSAXS beam line of the PSI in Switzerland, for imaging of clay microstructure at resolutions down to 45 nm, which is the first application of ptychographic tomography for geological samples to our knowledge. During these experiments, relative humidity of the sample’s environment was controlled, in order to asses the influence of R.H. on the analyzed clay minerals. Based on these images, quantitative data on mineral content, porosity, connectivity and behavior under changing environmental conditions of clay mineral clusters was acquired
