The nacrite-LiCl hybrid composite material was prepared at room temperature by indirect intercalation of lithium chloride between the planar layers of nacrite, a clay mineral, using acetone as a solvent. The structural identification of the hybrid clay material was determined by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA) and infrared spectroscopy (IR). The qualitative XRD analysis showed that the basal spacing value increased from 0.72 nm to 1.14 nm and revealed that the alkali halide intercalated successfully in the interlayer space of the nacrite framework. The quantitative XRD analysis allowed us to determine the optimum structural parameters related to the position and number of keyed ions and water molecules per half unit cell calculated along the c* axis and the goodness of fit parameter (Rp). The thermal properties of the elaborated hybrid were in great accordance with the XRD study and confirm the intercalation of the hydrated salt in the interlamellar space of nacrite. Moreover, IR spectroscopy enabled the study of the interactions between the silicate ''networks'' and the alkali halide.

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The intercalation complex of nacrite with an alkali halide (Caesium chloride: CsCl) has been successfully prepared by mixing a CsCl saturated solution with a 8.4Å-hydrated nacrite. The homogeneous nacrite/CsCl complex has been studied by X-ray diffraction (XRD). Using an oriented clay aggregate, 10 basal reflections were obtained. The XRD pattern showed basal spacing of 10.5Å with integral series of 00l reflections indicating an ordered stacking of parallel 1:1 layers. A direct method involving a monodimensional electron density projection, along the normal to the layers, is used to determine the number and the position of intercalated compounds. The best agreement between observed and simulated p(Z) (R = 5%) is obtained by placing one Cl- ion at Z=6.7Å; one Cs+ ion at Z=8.3Å and two H O molecules at 6.3 and 7.4Å.

This work deals with understanding the structural evolution of the dehydration of the 10 A Ê unstable hydrate of kaolinite. The method used to characterize this hydrate is based on a comparison between the experimental and the calculated X-ray diffraction pro®les. The study was achieved in two steps: (i) the quantitative interpretation of 00l re¯ections enabled the determination of the number of intercalated water molecules, their positions and the stacking mode of the clay layers along the normal to the (a,b) plane; and (ii) the study of the hkl re¯ections with h and/or k T 0 enabled the characterization of the structural evolution in the (a,b) plane of the hydrated kaolinite during dehydration. The hydrate is made up of two demixed phases. The ®rst phase is homogenous and corresponds to a 10 A Ê hydrated kaolinite, characterized by two H 2 O molecules per Si 2 Al 2 O 5 (OH) 4 situated at Z = 7.1 A Ê from the surface oxygen. Two adjacent layers are translated with respect to each other, with T 1 = À0.155a + 0.13b + 10n. The abundance of this phase decreases during dehydration. The second phase is made up of 10 A Ê hydrated layers, 8.4 A Ê hydrated layers and 7.2 A Ê dehydrated kaolinite layers, randomly interstrati®ed. The abundance of this second phase increases during dehydration. The corresponding interlayer shifts are respectively T 21 = À0.155a + 0.13b + 10n for the 10 A Ê hydrated layer, T 22 = À0.355a + 0.35b + 8.4n for the 8.4 A Ê hydrate and T 23 = À0.36a À 0.024b + 7.2n for the natural kaolinite. In addition to these interlayer shifts, some translation defects are introduced, such as Àb/3, which exists in the initial kaolinite. The interpretation of the small-angle X-ray scattering (SAXS) patterns showed that the particle thickness remained the same before and after the hydration treatments, whereas X-ray diffraction (XRD) results indicated that the hydration of kaolinite caused a decrease of the mean number of layers " m per crystallite from 40 to 20 layers. This decrease is related to the presence of H 2 O molecules situated within the micropores in the kaolinite particles that leave their interlayer space after heating at 573 K. The resulting dehydrated compound is characterized by the same basal distance and mean number of layers " m per crystallite as for the natural kaolinite, while the proportion of the defects, such as the Àb/3 translation, increases in the completely dehydrated compound (45%) compared with the natural kaolinite (10%).