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Abstract  

NiMoO4 obtained by calcination of precursors has been shown to be a very effective catalyst for oxidative dehydrogenation of propane into propene. Preparation conditions and thermal decomposition of two precursors have been studied by TG-DTA, HTXRD, FFT-IR, and thermo-desorption coupled to mass spectroscopy in order to determine their composition and to define the best treatment to favour the oxidative dehydrogenation process. The selectivity and activity for propane transformation into propene are very different depending on the nature of the precursor and of the active phases obtained after thermal activation. The more selective high-temperature β phase of NiMoO4 has been obtained at a lower temperature (500°C) than previously reported (700°C).

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Journal of Thermal Analysis and Calorimetry
Authors: Soraia de Souza, Mary Alves, A. de Oliveira, E. Longo, F. Ticiano Gomes Vieira, Rodinei Gomes, L. Soledade, A. de Souza, and Iêda Garcia dos Santos

Abstract  

In this work, the synthesis of Nd-doped SrSnO3 by the polymeric precursor method, with calcination between 250 and 700 °C is reported. The powder precursors were characterized by TG/DTA and high temperature X-ray diffraction (HTXRD). After heat treatment, the material was characterized by XRD and infrared spectroscopy. Ester and carbonate amounts were strictly related to Nd-doping. According to XRD patterns, the orthorhombic perovskite was obtained at 700 °C for SrSnO3 and SrSn0.99Nd0.01O3. For Sr0.99Nd0.01SnO3, the kinetics displayed an important hole in the crystallization process, as no peak was observed in HTXRD up to 700 °C, while a XRD patterns showed a crystalline material after calcination at 250 °C.

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Abstract  

Dysprosium hafnate is a candidate material for as control rods in nuclear reactor because dysprosium (Dy) and hafnium (Hf) have very high absorption cross-sections for neutrons. Dysprosium hafnate (Dy2O3·2HfO2-fluorite phase solid solution) was prepared by solid-state as well as wet chemical routes. The fluorite phase of the compound was characterized by using X-ray diffraction (XRD). Thermal expansion characteristics were studied using high temperature X-ray diffraction (HTXRD) in the temperature range 298–1973 K. Heat capacity measurements of dysprosium hafnate were carried out using differential scanning calorimetry (DSC) in the temperature range 298–800 K. The room temperature lattice parameter and the coefficient of thermal expansion are 0.5194 nm and 7.69 × 10−6 K−1, respectively. The heat capacity value at 298 K is 232 J mol−1 K−1.

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Abstract  

The thermal behaviour of the intercalation complex of a dickite from Tarifa, Spain, with dimethylsulfoxide was studied by high-temperature X-ray diffraction, differential thermal analysis and thermogravimetry, and attenuated total reflectance infrared spectroscopy. The ATR-FTIR study indicated that the heating between room temperature and 75C produced the elimination of adsorbed molecules. Above this temperature the elimination of intercalated molecules occurs through several stages. Loss of 6.5% of the intercalated DMSO first causes a slight contraction of the basal spacing at 90şC due to a rearrangement of the DMSO molecules in the interlayers positions. This contraction is followed by the formation of a single layer complex and the restoring of the dickite structure, at 300C, when the loss of intercalated species have been completed.

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Abstract  

Research into a new method for separating palladium from rhodium, based on radiochemical principles, necessitated a re-investigation of the Gmelins Handbuch data indicating that Rh has allotropes. Two independent and different methods were used, which both yielded the same results; i.e. that no allotropy can be found. Non-ambient temperature X-ray diffraction (HT-XRD) did not show any difference in the diffractograms due to phase transformation of Rh-metal at elevated temperatures. Differential thermal analysis (DTA) confirmed the HT-XRD result in the temperature range of 1000–1400 °C. In conclusion, the absence of allotropy of the metal rhodium was proven.

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Abstract  

The thermal behavior of montmorillonite and organically modified montmorillonite, both treated with heavy metal cations [Cu(II), Cd(II) and Hg(II)], was characterized via thermal analyses (TG, DTG and DTA) combined with evolved species gas mass spectrometry (MS-EGA), and X-ray diffraction at in situ controlled temperature (HTXRD). The reactions involving Cu(II)- and Cd(II)-montmorillonite samples are mostly related to H2O and OH loss, unlike Hg(II)-montmorillonite, where effects associated to Hg(II) loss are also present. Finally reactions related to dehydration, dehydroxylation and to organic matter decomposition can be observed in montmorillonite samples treated with cysteine.

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Abstract  

Processing thin films for advanced applications, for instance in electronics and optoelectronics, involves several steps starting from precursor synthesis and ending up with the devices. Especially when optimizing the first steps of this chain of processes, thermoanalytical techniques play an important role. The review will focus on the main chemical deposition methods (CVD, ALE, spray pyrolysis, sol-gel) giving selected examples of problem-solving by thermal analysis. The techniques discussed are TG, DTA/DSC, EGA and their combinations. High-temperature X-ray diffraction (HTXRD) is also a powerful tool for in situ studies of thin films. The examples are taken from solar cell, superconductor and flat panel electroluminescent display technologies.

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Abstract  

Copper chromite catalysts were prepared by using a new metal organic precursor, M(OR)n, which was dissolved in organic solvent, hydrolysed and condensed to form inorganic polymers containing M-O-M linkages. In the cases of Ba and Mn promotion, the corresponding metal oxide was admixed to the copper-chromium solution prior to gelification. After drying in helium atmosphere, the precursor was subjected to thermal treatment at different temperatures (373-873 K) and in different atmospheres (air, nitrogen or hydrogen). Both the catalysts and the industrial Engelhard catalyst were characterized by various techniques (TG-DTA, HTXRD, IR, BET, metallic copper surface area and porosimetry measurements) and evaluated for ester hydrogenation.

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Journal of Thermal Analysis and Calorimetry
Authors: Mei-Han Wang, Takayuki Konya, Masahiro Yahata, Yutaka Sawada, Akira Kishi, Takayuki Uchida, Hao Lei, Yoichi Hoshi, and Li-Xian Sun

Abstract  

A series of Alq3 thin films with the thicknesses of 50, 100, and 200 nm was deposited on Si substrates at room temperature using the thermal evaporation method. The thermal crystallization process of Alq3 thin films, especially 50 nm thick films, was successfully examined using high-temperature X-ray diffraction (HT-XRD) with the in-plane scan mode. Film thickness, density, and changes in surface roughness while heating were determined using X-ray reflectometry (XRR). The decreased density and increased surface roughness, which were accompanied by sublimation, indicate the instability of the Alq3 film. Thus, thermal instability is a major factor for device failure.

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Abstract  

The aim of the present study was to determine the kinetic equations for the thermal transformations of precipitated iron oxides and hydroxides, namely for the process of thermal dehydroxylation of goethite and consecutive of hematite crystal structure growth as well as for the oxidation of magnetite to maghemite and its thermal transformation into crystalline hematite. The investigations have been carried out using thermogravimetry (TG/DTG/DTA), X-ray powder diffractometry (XRD) and high temperature powder diffractometry (HT-XRD). This presentation contains the continuation of our earlier works.

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