The structural change of vermiculite during dehydration processes: A real-time in-situ XRD method

The structural change of clay minerals caused by hydration and dehydration is strongly dependent on the minor changes of the ambient environment conditions which could significantly affect the properties of clay minerals. In this study, a real-time in-situ X-ray diffraction method was used to investigate the structural evolution of vermiculite as a function of time and temperature. The results showed that this method could delicately record the structural transition under minor changes in temperature and time progresses. The mix-layer structures with heterogeneous hydration states occurred in both dehydration and rehydration processes of vermiculite. Structural heterogeneity was developed via the transition from bi- to mono-hydrated states or from mono-hydrated to dehydrated states. The presence of non-uniform stacking layer structure and different interlayer cations of the vermiculite might result in the heterogeneous structural evolution during dehydration and rehydration.