The intercalation complex of a low-defect (“well-crystallized”) kaolinite from Cornwall, England, with hydrazine was studied by high-temperature X-ray diffraction (HTXRD), differential thermal analysis (DTA), and thermogravimetry (TG). The X-ray pattern at room temperature indicated that intercalation of hydrazine into kaolinite causes an increase of the basal spacing from 7.14 to 10.4 Å, as previously reported. Heating between 25-200°C produces a structural rearrangement of the complex, which initially causes a contraction of the basal spacing from 10.4 to 9.6 Å. In a second stage, the basal spacing reduces to 8.5 Å. 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 endothermic reactions are observed at low temperature. This behavior suggests that intercalated molecules occupy several well-defined sites in the interlayer of the kaolinite complex. The intercalated molecules deintercalate in an ordered fashion, which explains the successive and discontinuous contraction of the basal spacing of the complex. Heating between 200-400°C caused a limited increase in stacking order of the kaolinite structure, whereas dehydroxylation of kaolinite and the disappearance of its X-ray reflections occurred between 450-640°C.

The intercalation complex of a low-defect dickite from Tarifa, Spain, with hydrazine was studied by high-temperature X-ray diffraction (HTXRD) differential thermal analysis (DTA), and ther-mogravimetry (TG). The X-ray diffraction (XRD) pattern obtained at room temperature indicated that the intercalation of hydrazine and H2O into dickite caused an increase of the basal spacing from 7.08 to 10.24 Å, which is slightly lower than the 10.4-Å spacing commonly observed after intercalation into kaolinite. Heating between 25–50°C produced a structural rearrangement of the complex, which decreased the basal spacing from 10.24 to 9.4 Å, and the resulting 9.4-Å complex was stable between 50–90°C. Heating between 90–300°C caused a gradual reduction in spacing, which occurred through a set of intermediate phases. These phases were interpreted to be interstratifications of intercalated and non-intercalated layers. These changes 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 TG curves in the temperature range 25–200°C. This behavior suggests that intercalated molecules, hydrazine and H2O, occupied well-defined sites in the interlayer of the dickite. The intercalated molecules were lost in an ordered fashion as confirmed by the infrared analysis of the decomposition products; H2O was lost in the first stage and ammonia was identified in the second stage. Above 300°C, complete removal of the intercalated molecules restored the basal spacing of the dickite. However, the basal reflections were broadened, the relative intensities were changed, and changes in the dehydroxylation temperature indicated that the intercalation-desorption process induced some stacking disorder in the dickite structure.

The intercalation complex of a kaolinite from Cornwall, UK, with dimethylsulfoxide (DMSO) was studied by high-temperature X-ray diffraction (HTXRD), differential thermal analysis (DTA) and thermogravimetry (TG). The X-ray pattern obtained at room temperature indicated that intercalation of DMSO into kaolinite caused an increase of the basal spacing of kaolinite from 7.14 to 11.19 Å. Heating between 25 and 300°C caused the removal of the DMSO, which occurred over several stages. In a first stage (25–125°C), an expansion (from 11.19 to 11.28 Å) followed by a contraction (from 11.28 to 11.19 Å) is observed, at the same time as the intensity of the basal reflection decreased and was replaced by a broad band extending from ~11 to ~7 Å. In a second stage (125–200°C), the loss of DMSO did not lead to changes in the HTXRD patterns; and finally, in a third stage, the loss of DMSO caused an important increase in intensity and sharpening of the basal reflections of the kaolinite. These stages were also shown by the DTA-TG curves for the complex. The TG curve indicated that the loss of ~15% of the intercalated DMSO occurs below 150°C, and caused the disruption of the structure. The remaining molecules, forming stronger bonds with the kaolinite surfaces, were lost between 150 and 300°C.

This paper describes a method to determine the equilibrium transformation temperatures in low C steels using the in situ high-temperature X-ray diffraction technique. The samples were heated and then cooled from 1000 to 720 °C in a stepwise manner decreasing to −10 °C. Austenite and ferrite fractions were determined by a quantitative method using the integrated intensities of austenite (111)γ and ferrite (110)α peaks from X-ray diffraction patterns. The effect of the temperature on interplanar d spacings of (111) and (110) crystallographic planes was determined using 2θ maximum positions of the austenite (111)γ and ferrite (110)α peaks. The equilibrium transformation temperatures were determined to be Ae1=720 °C and Ae3=950 °C. The results are in excellent agreement with those obtained by dilatometric analysis and Thermo-Calc phase diagram simulation software. In addition, the results were supported by microstructural observations: the formation of thin ferrite films (5–10 μm) was observed at temperatures near to experimental Ae3.

Rhombohedral-cubic transformation in Bi2Te3 doped-Pb1−xGexTe alloys is presented. Samples of Bi2Te3 doped Pb1−xGexTe were prepared by powder metallurgy approach. These powder samples were examined by high-temperature X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy. A bulk (pressed powder) cylindrical specimen was used for dilatometery characterizations. According to the XRD examinations it seems that upon increasing the temperatures a continuous transformation occurs from the rhombohedral to the cubic phase, accompanied by the formation of a small amount of the phase Ge0.74Pb3.26Te4.