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Abstract  

Supramolecular 2,3- and 2,5-pyridinedicarboxylate (PDC) intercalated ZnAl-layered double hydroxides (2,3- and 2,5-PDC–ZnAl–LDHs) have been prepared by ion exchange method. The structure and composition of the intercalated materials have been studied by X-ray diffraction (XRD) and inductively coupled plasma emission spectroscopy (ICP). The study indicates that the 2,3-PDC and 2,5-PDC anions are accommodated as interdigitated bilayer and monolayer arrangement respectively between the sheets of LDHs. Furthermore, their thermal decomposition processes were studied by the use of in situ high temperature X-ray diffraction (HT-XRD), and the combined technique of thermogravimetry-differential thermal analysis-mass spectrometry (TG-DTA-MS) under N2 atmosphere. Based on the comparison study on the temperatures of both decarboxylation and complete decomposition of interlayer PDC, it can be concluded that 2,5-PDC–ZnAl–LDHs has higher thermal stability than that of 2,3-PDC–ZnAl–LDHs.

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Journal of Thermal Analysis and Calorimetry
Authors: Mary Alves, Soraia Souza, Márcia Silva, Elaine Paris, S. Lima, R. Gomes, E. Longo, A. de Souza, and Iêda Garcia dos Santos

Abstract  

SrSnO3 was synthesized by the polymeric precursor method with elimination of carbon in oxygen atmosphere at 250 °C for 24 h. The powder precursors were characterized by TG/DTA and high temperature X-ray diffraction (HTXRD). After calcination at 500, 600 and 700 °C for 2 h, samples were evaluated by X-ray diffraction (XRD), infrared spectroscopy (IR) and Rietveld refinement of the XRD patterns for samples calcined at 900, 1,000 and 1,100 °C. During thermal treatment of the powder precursor ester combustion was followed by carbonate decomposition and perovskite crystallization. No phase transition was observed as usually presented in literature for SrSnO3 that had only a rearrangement of SnO6 polyhedra.

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Abstract  

Rare earth uranates Nd6UO12, Gd6UO12 and Eu6UO12 were prepared by combustion synthesis and characterized by XRD. Single-phase rhombohedral structure was observed for all the above compounds. Heat capacity measurements were carried out on Nd6UO12 and Gd6UO12 with differential scanning calorimetry in the temperature range 298–800 K. Enthalpy, entropy and Gibbs energy functions were computed. Heat capacity values of Nd6UO12 and Gd6UO12 at 298 K are 436 and 400 J K−1 mol−1, respectively. Thermal expansion characteristics were studied using high temperature X-ray diffraction (HTXRD) in the temperature range 298–873 K. The coefficients of thermal expansion measured for Eu6UO12 are 10.5 × 10−6 and 7.3 × 10−6 K−1 along a- and c-axis, respectively. Similarly, the coefficients of thermal expansion of Gd6UO12 along a-axis are 10.0 × 10−6 K−1 and along c-axis is 9.7 × 10−6 K−1.

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Abstract  

New cubic leucite-type compounds, CsMSi2O6 (M=B0.2Al0.8,Al0.2Fe0.8), Cs2MSi5O12 (M=Cd, Mg, Ni, Zn) have been synthesized by the two-stage heat treatment of the solid-state reaction. The thermal expansion properties of the synthesized leucite-type compounds have been studied with HTXRD and LTXRD in the temperature range of 123 to 1273 K. The thermal expansion rate of CsB0.2Al0.8Si2O6 was found to be considerably smaller than that of CsAlSi2O6, while the thermal expansion property of Cs2MSi5O12 (M=Mg, Zn, Cd) was found to have a linear relationship in the temperature range of 298 to 1273 K. By using Rietveld analysis it was found that the thermal expansion rate decreased with increasing the Si—O—M(Si) angle for cubic leucite-type compounds at 298 K, and that the phase transitions of CsAlSi2O6 and Cs0.9Al0.9Si2.1O6 were due to the relationship between the bond angle of Si—O—M(Si) of the three-dimensional framework structure and the space ratio in the unit cell at 298 K.

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weighing of the sample and (b) room temperature XRD (after cooling) [ 2 ], the high-temperature X-ray diffraction (HTXRD) presents the advantage of in situ analysis of the sample, at the desired temperature, eliminating errors that may appear due to factors

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Journal of Thermal Analysis and Calorimetry
Authors: A. Caneiro, L. Mogni, N. Grunbaum, and F. Prado

(TG) measurements along with the high temperature X-ray diffraction (HT-XRD) permitted us to obtain a more detailed phase diagram of SrFe 0.2 Co 0.8 O 3−δ compound. This compound undergoes a phase transition from a disordered cubic to an ordered

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applying monochromatic Cu K α radiation step by step at elevated temperatures using a high-temperature XRD cell (HT-XRD) applying heating rate of 10 °C/min. The mean crystallite size of the nickel particles was estimated by the Debye–Scherrer equation

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temperature-dependent X-ray diffraction (HT-XRD). The results presented in Fig. 6 show the temperature range in which La(OH) 3 (<420 °C), lanthanum hydroxide oxide (380–580 °C), and La 2 O 3 (>580 °C) were detected [ 10 ]. Further the specific surface area

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. Infrared spectra of nano metre granular Zirconia . J Phys Condens Matter . 11 : 2035 10.1088/0953-8984/11/32/303 . 18. Ali , A . 2002 . HT-XRD, IR, Raman characterization studies of

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shown because they were exactly the same as those for NO. In situ HT-XRD Thermal evolution of the hydrotalcite structure is presented in Fig. 5 . Basal reflections of the sample AN0 are sharp and intense below 300 °C

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