Thermal decomposition of a dickite-hydrazine intercalation complex

The intercalation complex of a low-defect dickite from Tarifa, Spain, with hydrazine was studied by high-temperature X-ray diffraction (HTXRD), differ ential thermal analysis (DTA), and thermogravimetry (TG). The X-ray diffrac tion (XRD) pattern obtained at room temperature indicated that the intercal ation of hydrazine and H2O into dickite caused an increase of the basal spa cing from 7.08 to 10.24 Angstrom, which is slightly lower than the 10.4-Ang strom spacing commonly observed after intercalation into kaolinite. Heating between 25-50 degreesC produced a structural rearrangement of the complex, which decreased the basal spacing from 10.24 to 9.4 Angstrom, and the resu lting 9.4-Angstrom complex was stable between 50-90 degreesC. Heating betwe en 90-300 degreesC caused a gradual reduction in spacing, which occurred th rough a set of intermediate phases. These phases were interpreted to be int erstratifications of intercalated and non-intercalated layers. These change s were also observed by DTA and TG. Two main endothermic reactions and two main stages of mass loss, respectively, were indicated in the DTA and the T G curves in the temperature range 25-200 degreesC. This behavior suggests t hat intercalated molecules. hydrazine and H2O, occupied well-defined sites in the interlayer of the dickite. The intercalated molecules were lost in a n ordered fashion as confirmed by the infrared analysis of the decompositio n products; H2O was lost in the first stage and ammonia was identified in t he second stage. Above 300 degreesC, complete removal of the intercalated m olecules restored the basal spacing of the dickite. However, the basal refl ections were broadened, the relative intensities were changed, and changes in the dehydroxylation temperature indicated that the intercalation-desorpt ion process induced some stacking disorder in the dickite structure.