According to the variable correlation, surface area and roughness for the NaOH samples first increase with the milling time and then decrease again, whereas a decrease can generally be observed for the SPC/NaOH series. If one now includes the DVS data, the SAXS data would support the postulated adsorption mechanism. An increase in water adsorption of the SPC/NaOH-60min sample is more likely to be caused by a chemical modification at the surface, creating hydrophilic centers, than by a physical modification in the sense of a larger and or rougher surface. This is also supported by TEM images, where no significant changes in particle size or shape can be noticed (Fig. ).