First direct visualization of oriented mesostructures in clay gels by synchrotron-based X-ray fluorescence microscopy

A direct in-situ visualization of montmorillonite gels at 50 gn has been ob tained for the first time, using silicon fluorescence yield imaging at the ESRF ID21 X-ray microscopy line. An unexpected superstructure formed by alt ernating clay-rich and clay-poor domains was evidenced with mesoscopic orie ntational order. The order and size of the oriented entities extends over d istances at least 2 orders of magnitude larger than the dimensions of indiv idual clay platelets. Such long-range organization must certainly be consid ered for assessing the formation mechanisms and properties of gels in syste ms of charged colloidal platelets.