Thermal behavior of the kaolinite-hydrazine intercalation complex

The intercalation complex of a low-defect ("well-crystallized") kaolinite f rom Cornwall, England, with hydrazine was studied by high-temperature X-ray diffraction (HTXRD), differential thermal analysis (DTA), and thermogravim etry (TG). The X-ray pattern at room temperature indicated that intercalati on of hydrazine into kaolinite causes an increase of the basal spacing from 7.14 to 10.4 Angstrom, as previously reported. Heating between 25-200 degr ees C produces a structural rearrangement of the complex, which initially c auses a contraction of the basal spacing from 10.4 to 9.6 Angstrom. In a se cond stage, the basal spacing reduces to 8.5 Angstrom. Finally, in a third stage, a reduction in spacing occurs through a set of intermediate phases, interpreted as interstratifications of intercalated and non-intercalated 1: 1 layers. Evidence for these changes was observed by DTA, where three endot hermic reactions are observed at low temperature. This behavior suggests th at intercalated molecules occupy several well-defined sites in the interlay er of the kaolinite complex. The intercalated molecules deintercalate in an ordered fashion, which explains the successive and discontinuous contracti on of the basal spacing of the complex. Heating between 200-400 degrees C c aused a limited increase in stacking order of the kaolinite structure, wher eas dehydroxylation of kaolinite and the disappearance of its X-ray reflect ions occurred between 450-640 degrees C.