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Abstract  

Three interesting new compounds formed as a result of phenols-iodine redox reactions were investigated by mass spectral fragmentation (MS) and thermal analyses (TA) as well as some other physicochemical methods as microanalysis and infra-red spectroscopy to elucidate their structures. The characterization of the compounds was satisfactorily achieved by using the above analytical tools and their proposed general formulae, were found to be C24H15O8I (PC-IO 3 ), C24H14O12 I2 (PG-IO 3 ) and C12H8O6I2 (PG-IO 4 ).The fragmentation pathways of PC-IO 3 , PG-IO 3 and PG-IO 4 have been examined using electron ionization (EI) mass spectrometry in comparison with thermal analyses (TG and DTA). Both decomposition modes were investigated, and the fragmentation pathways were suggested. The combined application of mass spectrometry and thermogravimetry (MS and TG) in the analysis of the products allowed the characterization of the fragmentation pathway in MS.The major pathway in both techniques of PC-IO 3 is due to the loss of CHO followed by CH3I+2H2O. It is due to the loss of 2H2O followed by the loss of 2CH3I for PG-IO 3 . While for PG-IO 3 it is related to the loss of 2H2O followed by loss of 2CH3I molecule stepwise. Different stabilities for initial products and some fragments are discussed.

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Abstract  

Copper forms of synthetic zeolite ZSM5 containing ethylenediamine (en) were characterised by methods of thermal analyses - TG, DTA and DTG in the temperature range 20-1000C, in air and in argon atmosphere. Mass spectroscopy was used for the study of the released gas products of thermal decomposition. The results of thermal analyses of three Cu(en)xZSM5 zeolitic products with different composition (x depends on the mode of preparation) checked their different thermal properties. The main part of the decomposition process occurs at considerably higher temperatures than the boiling point of ethylenediamine of all three products, it proves strong bond and irreversibility of en-zeolite interaction. According to the results of the mass spectroscopy method the decomposition process in inert atmosphere is characterised by the development of a large spectrum of products with atomic mass from 28 to 178 atomic mass units, and there is a correlation between the mode of sample preparation and the spectrum of the released products.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Olguin, M. Solache-Rios, D. Acosta, P. Bosch, and S. Bulbulian

Abstract  

The capacity of bentonite and purified bentonite to remove UO 2 2+ ions from aqueous solutions has been investigated. The UO 2 2+ uptake in these clays was determined for 0.2 and 0.002M uranyl nitrate solutions. It was found that under these conditions (0.2M) the maximum UO 2 2+ uptake was 1.010±0.070 meq UO 2 2+ /g of bentonite and 0.787±0.020 meq UO 2 2+ /g of purified bentonite. In purified bentonite UO 2 2+ sorption is irreversible up to 50 hours as no desorption was observed. Such is not the case in the natural bentonite. X-ray diffraction, thermal analyses, and transmission electron microscopy were used to characterize the solids. The uranium content was determined by neutron activation analysis.

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Abstract  

Two tris(oxouranium)-substituted Keggin and Dawson sandwich-type tungstophosphate heteropolyanions Na12[(UO)3(H2O)6(PW9O34)2]·21 H2O (1) and Na18[(UO)3(H2O)6(P2W15O56)2]·27 H2O (2) have been prepared by reaction of uranium sulphate with [PW9O34]9− and [P2W15O56]12−, respectively, in aqueous media at 4.7 pH. The products were characterized by elemental and thermal analyses, IR, UV-Vis spectroscopy and magnetical susceptibility. The results of these studies suggest that the compounds obtained from Keggin and Dawson trilacunary anions are 2∶3 sandwich-type complexes and both exhibit a square antiprismatic stereochemistry for uranium(IV) with retention of polyoxometallate parent structure.

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Abstract

In the present study, thermal decomposition of mono- and di-azocalix[4]arene derivatives (A1A8 and B1B8) was investigated by means of thermogravimetry (TG), differential thermal analysis (DTA) and derivative thermogravimetry (DTG). The exclusion of methanol, hydrolysis of benzoyl ester and methyl ketone groups in lower rim, and decomposition of azo groups in upper rim have occurred during thermal analysis, consecutively. The thermal decomposition degrees amount of volatile pyrolysis products were determined in air atmosphere using TG, DTA and DTG curves. In conclusion, the thermal analyses of azocalix[4]arenes demonstrated that its stability depends on the substituted groups and their positions in the calix[4]arene structure.

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Abstract  

In this paper, novel results on the blue thermally stimulated luminescence (TSL) emission of ulexite (NaCaB5O6(OH)65H2O) have been studied. The four maxima appearing at 60, 110, 200 and 240C on the TSL glow curves of this borate could be respectively associated to: (i) the first dehydration (NaCaB5O6(OH)65H2O→NaCaB5O6(OH)63H2O), (ii) the creation-annihilation of the three-hydrated phase, (iii) the Na-coordinated chains dehydroxylation and the starting point of the alkali self-diffusion through the lattice and (iv) the amorphisation of the lattice. These results are fairly well correlated with the differential thermal analyses (DTA), in situ thermal observations under environmental scanning electron microscope (TESEM) and thermal X-ray diffraction (TXRD) techniques.

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Abstract  

Heat-treatable aluminium alloys are widely used for structural applications. Their strength is obtained through age hardening phenomena, that are sensitive to microalloying. In the present paper the results of thermal analyses on the ageing behaviour of an Al-Cu-Mg-Si alloy with silver and zirconium additions are presented. Specimens were water quenched after solution heat treatment, then aged at 453 K and a hardness-versus-time plot was drawn. Samples representative of different ageing conditions were subjected to DSC scans. Peaks were identified taking into account θ and Q phases precipitation sequences. Solution treated samples showed GP/θ″/θ′/Q sequence, while in peak aged condition GP and θ″ precipitation peaks disappeared and a reduction of θ′ peak area was observed, witnessing the concurrent presence of θ″ and θ′ phases at peak hardness condition. Experimental data were compared with results from analogous investigations performed on a conventional commercial Al-Cu-Mg-Si alloy.

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Abstract  

The aim of this paper is to define the characteristics of crystalline phase ETS-10 obtained from gel with dodecyltrimethylammonium bromide, as an organic template. ETS-10 zeolites has been synthesised under hydrothermal conditions from gels of composition 5Na2O–3KF–TiO2–6.4HCl– xC12TMAB –7.45SiO2–197.5H2O (where x=0.0, 0.25, 0.55, 1.0 and 1.5) with dodecyltrimethylammonium bromide. The crystalline phases synthesised with organic salt have an exothermal peak at ca. 360°C, due to the degradation of organic entrapped in the porous structure. Physical-chemical properties of C12TMAB -ETS-10 are studied by XRD, SEM and thermal analyses.

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DSC of as-deposited thin films dip-coated on the substrate

Thermal change of indium(III) 2-ethylhexanoate to form In2O3 thin films

Journal of Thermal Analysis and Calorimetry
Authors: Y. Sawada, K. Omika, Y. Ito, F. Muta, and M. Momota

Abstract  

The formation process of a ceramic (indium oxide) thin film (thickness: approximately 20 nm to several microns) was investigated by thermal analyses. Thermal changes of an organic precursor, indium(III) 2-ethylhexanoate, dip-coated on a glass substrate was successfully detected by DSC in air. Exothermic phenomena were observed at marked lower temperatures for the thin films than for the bulk material; thinner films had slightly lower peak temperatures. The reaction mechanism is discussed with reference to mass spectra of the evolved gases.

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Abstract  

In this study, combustion curves of twenty-five Turkish lignites were obtained through use of a differential thermal analyser. 20 mg lignite samples were heated at a constant rate of 10 deg·min−1 in a 40 cc/min flow of air up to 1073 K and held for 10 minutes at this constant temperature. The combustion curves of the samples are compared and discussed.

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