Search Results

You are looking at 41 - 50 of 257 items for :

  • "thermal analyses" x
  • Refine by Access: All Content x
Clear All

Abstract  

The mixed zirconium, titanium, hafnium and first-row transition metal oxides (containing phosphorous oxide) were prepared using ion exchange method followed by calcinations at 1020 K during 12 h. The resulted mixed oxides were identified by XRPD method and studied their thermal behaviour by TG-DTA analysis. As a result of thermal analysis there were found one exothermic (with a peak at about 950 K), and one endothermic (with a peak at about 1300 K) processes, both without mass loss. The observation was valid for all investigated samples. The analysis of XRPD patterns of the investigated samples showed well-defined crystal phases characteristic of each oxide. The XRPD analysis also verified the phase transition of tetravalent metal oxides from orthorhombic to tetragonal, observed by DTA analysis.

Restricted access

]. Fig. 4 XRD spectrographs of 7YSZ ( a ) and DySZ ( b ) Calorimetric and thermal analyses Calorimetric analyses of powder and sintered coating samples were

Restricted access

Quantitative study of hydration of C3S and C2S by thermal analysis

Evolution and composition of C–S–H gels formed

Journal of Thermal Analysis and Calorimetry
Authors: Sara Goñi, Francisca Puertas, María Soledad Hernández, Marta Palacios, Ana Guerrero, Jorge S. Dolado, Bruno Zanga, and Fulvio Baroni

furnace slag [ 32 ] and for quantitative determination of the chemical composition of the C–S–H gel and degree of hydration, which is the main aim of this study. In this article, a quantitative method, based on thermal analyses, has been used for

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Rusu, D. Rusu, C. Roşu, C. Crăciun, L. David, A.R. Tomşa, and Gh. Marcu

Abstract  

A new uranium tungstoborate heteropolyanion K12[U(BW11O39H)2]·23 H2O has been prepared and investigated by thermal analyses, IR, UV-Vis spectroscopy and magnetic susceptibility measurements. The compound obtained from Keggin monolacunary anions is 1:2 sandwich-type and exhibits a square antiprismatic stereochemistry for uranium (IV) ion.

Restricted access

Abstract  

An attempt to prepare directly the title uranate by precipitation from uranyl solutions was successful if the preparation temperature was close to 100°C. The product was chemically and thermally analyzed, its IR spectra and X-ray patterns were taken; these results are commented and a reason for explanation of the molecular water behaviour is proposed.

Restricted access

Abstract  

Iron: fullerides were prepared by chemical methodes in the solution using nitric acid as activation agent. Experimental results of thermal analyses, X-ray diffraction and Mössbauer spectroscopy of the products are presented. To interpret these results, standard quantum chemistry calculations were used to determine the geometry and charge distribution in Fe:C60 complexes, which might be formed in the reaction.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Katsumi Katoh, Shunsuke Ito, Shuhei Kawaguchi, Eiko Higashi, Katsuyuki Nakano, Yuji Ogata, and Yuji Wada

Abstract  

In the previous study, it was observed that the stability of nitrocellulose (NC) cannot be determined by thermal analyses such as differential scanning calorimetry (DSC) at heating rates of 1–10 K/min. This was because the thermal curves of NC samples with different stabilities could not be distinguished from one another. In this study, we explain why such thermal analyses cannot be used to evaluate the thermal stability of NC and identify the conditions under which thermal analyses can be used for this purpose. We investigated the effect of heating rate on the thermal behavior of pure NC and NC stabilized with diphenylamine (DPA) or akarditeII (AKII), which is a conventional stabilizer, by using the heat flux calorimeter (C80). At high heating rates (0.2–0.3 K/min), only single exothermic peak was observed in the thermal curves of both pure NC and NC/DPA and the thermal curve of pure NC was practically similar to that of NC/DPA. At low heating rate (0.02 K/min), two exothermic peaks were observed for both pure NC and NC/DPA. The heat amount of the first peak depended on the partial pressure of O2 in the atmosphere. The first peak in the thermal curve of NC/DPA was slightly suppressed as compared to that of pure NC. These results indicate that the stability of NC probably depends on the first exothermic peak that represents oxidation of NC by atmospheric O2. From this, on the thermal analyses at high heating rates, thermal curves of pure NC and NC/DPA could not be distinguished from one another. This is because the decomposition of NC itself occurs in the second exothermic peak before the oxidation of NC by atmospheric O2 in the first peak, which is attributed to the stability of NC. The results of the thermal analyses under isothermal conditions at 393 K in an O2 atmosphere revealed that the induction period of NC/DPA and NC/AKII was longer than that of pure NC. From these results, it is speculated that the stability of NC can be evaluated by thermal analyses carried out under O2-rich conditions at low heating rates.

Restricted access

Abstract  

Copper complexes of some 1-phenyl-3-methyl-4-acyl-5-pyrazolones have been prepared. The complexes were characterized by elemental analyses and thermal analyses. It was shown that the melting points decrease linearly in increasing the molecular weight of the complexes.

Restricted access

Abstract  

Thirteen tellurites of rare-earth elements from cerium group (Sc, La, Ce, Pr, Nd, Sm, Eu) have been synthesized and characterized by chemical, X-ray and thermal analyses. The space group, crystal systems and parameters of the elementary cells of most of the tellurites have been established. The temperatures, enthalpies and entropies of melting were measured. The change of melting temperatures vs. ion radius occurs gradually in a uniform mode with some exceptions.

Restricted access

In this study, combustion curves of twenty-five original and demineralized Turkish lignite samples were obtained through use of a differential thermal analyser. The lignite samples were demineralized by treatment with hydrochloric and hydrofluoric acids. Samples of 20 mg were heated up to 1074 K at a constant rate of 10 K min−1 in a 40 cm3 min−1 flow of dry air. The rates of heat release from the original and demineralized samples were compared and are discussed.

Restricted access