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Simultaneous TG, DTG, DTA measurements along with the continuous and selective monitoring of carbon monoxide, carbon dioxide and water evolved were carried out on K3[M(C2O4)3].3H2O-type transition metal complexes (whereM=Cr, Fe and Co). Based on the comparison of the recorded curves a detailed description of the decomposition mechanism was possible. In the case of the cobalt complex an exothermic process corresponding to modification of electron configuration is superimposed on the endothermic dehydration reaction.

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Abstract  

Two lactates and four new mixed ligand complexes with formulae Co(lact)22H2O, Ni(lact)23H2O, Co(4-bpy)(lact)2, Co(2,4'-bpy)2(lact)2, Ni(4-bpy)(lact)22H2O and Ni(2,4'-bpy)2(lact)2 (where 4-bpy=4,4'-bipyridine, 2,4'-bpy=2,4'-bipyridine, lact=CH3CH(OH)COO-) were isolated and investigated. The thermal behaviour of compounds was studied by thermal analysis (TG, DTG, DTA). In the case of hydrated complexes thermal decomposition starts with the release of water molecules. The compounds decompose at high temperature to metal(II) oxides in air. A coupled TG-MS system was used to analyse the principal volatile products of thermolysis and fragmentation processes of obtained complexes.

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The so-called pozzolanic activity of waste catalysts from fluidised cracking was investigated. For this purpose a series of cement mixtures with this waste material were prepared and subsequently the pastes and mortars were produced. Waste aluminosilicate catalyst was used both in raw form and after grinding in a ball mill for 60 min. The hydrating mixtures were subjected to the calorimetric measurements in a non-isothermal/non-adiabatic calorimeter. After an appointed time of curing the hydrating materials were studied by thermal analysis methods (TG, DTG, DTA). The pozzolanic activity factors were determined, basing on the compressive strength data. The increased activity of cement — ground pozzolana systems has been thus proved. An accelerated Ca(OH)2 consumption as well as higher strength were found for materials containing ground waste catalyst, as compared to those, mixed with the raw one. Thus grinding was also proved to result in mechanical activation in the case of the waste catalyst from fluidised cracking.

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Abstract  

The thermal decomposition of lithium hexa(carboxylato)ferrate(III) precursors, (Li3[Fe(L)6xH2O, L = formate, acetate, propionate, butyrate), has been carried out in flowing air atmosphere from ambient temperature upto 500 °C. Various physico-chemical techniques, i.e., TG, DTG, DTA, XRD, SEM, IR, Mössbauer spectroscopy, etc., have been employed to characterize the intermediates and end products. After dehydration, the anhydrous complexes undergo decomposition to yield various intermediates, i.e., lithium oxalate/acetate/propionate/butyrate, ferrous oxalate/acetate and α-Fe2O3 in the temperature range of 185–240 °C. A subsequent decomposition of these intermediates leads to the formation of nanosized lithium ferrite (LiFeO2). Ferrites have been obtained at much lower temperature (255–310 °C) as compared to conventional ceramic method. The same nano-ferrite has also been prepared by the combustion method at a comparatively lower temperature (400 °C) and in less time than that of conventional ceramic method.

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This paper presents qualitative and quantitative comparative results on the simultaneous TG-DTG DTA of five commercial and low-grade bauxites. The methodology of qualitative determination of the basic mineral forms contained in bauxites is currently being established. The weight losses relating to the steps in the TG curve allow determination of the contents of the basic minerals in bauxite. These are recalculated as percentages of Al2O3, SiO2, CaO moisture and total volatiles. The final results are in accordance with the results of classical chemical analyses, and this jusitifies the use of this technique as a quick method for qualitative and quantitative determinations of both commercial and low-grade bauxites.

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Abstract  

Non-isothermal dehydration of copper chloride dihydrate and nickel chloride hexahydrate were studied by using TG, DTG, DTA and DSC measurements. The copper chloride salt loses its two water molecules in one step while nickel chloride salt dehydrates in three consecutive steps. The first two steps involve the loss of 4 water molecules in two overlapped steps while the third step involves the dehydration of the dihydrate salt to give the anhydrous NiCl2. Activation energies (ΔE) and the frequency factor (A) were calculated from DTG and DTA results. We have also calculated the different thermodynamic parameters, e.g. enthalpy change (ΔH), heat capacity (C p) and the entropy change (ΔS) from DSC measurements for both reactants. The isothermal rehydration of the completely dehydrated salts was studied in air and under saturated vapour pressure of water. Anhydrous nickel chloride was found to rehydrate in three consecutive steps while the copper salt rehydrated in one step.

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Thermoanalytical studies of pitch pyrolysis

Comparison with polycyclic aromatic hydrocarbons

Journal of Thermal Analysis and Calorimetry
Authors: A. Martínez-Alonso, J. Bermejo, and J. M. D. Tascón

Characterization of pitches by thermal analysis techniques is highly relevant to the practical use of these materials, as they undergo heat treatments in all of their utilization processes. The aim of this work was to improve the interpretation of the complex DTA curves of pitches by comparison with model compounds. For this, TG/DTG/DTA was used to study under identical conditions the pyrolysis of a petroleum pitch and a coal tar pitch as well as a number of polycyclic aromatic hydrocarbons. Results were interpreted as a function of the molecular structure, pyrolysis reactivity and graphitizability of cokes from the hydrocarbons. It is concluded that condensation and polymerization, which are the most likely exothermal reactions predominant in petroleum pitches, indicate the presence therein of reactive molecules. Alternatively, endothermal phenomena such as distillation, depolymerization and cracking, predominant in coal tar pitches, suggest the presence of light, little reactive aromatic molecules.

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The thermal decompositions of Te(OH)6, CO(NH2)2 and the adduct Te(OH)6. 2 CO(NH2)2 in air and in an inert atmosphere were studied using TG, DTG, DTA and GC methods in the interval between laboratory temperature and 750°. The first gaseous product of the decomposition of urea is water vapour; the decomposition yields first cyanamide, and then biuret in four steps. The adduct is primarily decomposed to diammonium metatellurate and urea, with liberation of H2O and CO2. Diammonium metatellurate is decomposed toα-TeO3 as intermediate-product.

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A systematic TG/DTG/DTA analysis is reported of anhydrous and heptahydrate forms of tris-phenanthroline and tris-pyridyl complexes of nickel(II), whose kinetic parameters were calculated by five different methods. The dehydration and de-ligation steps are descrete in Ni(phen)3Cl2 · 7 H2O, while those in Ni(bipy)3Cl2 · 7 H2O are mixed. Partial loss of the ligand is common for both hydrated and anhydrous compounds. In most cases the activation energyE a calculated from the mechanism-non-invoking equation of Horowitz and Metzger is in good agreement with that found from the mechanism-based relation of Mampel. There is an appreciable variation in magnitude in the results obtained from the different relations for the evaluation ofE a. It is inferred that such kinetic data are of significance in comparisons of the decomposition processes in related systems but not as absolute quantities.

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The thermal properties of some complexes of copper(II) with pyridine-2-aldoxime (HPAO), where the ligand appears either as the ion (PAO) or as a neutral molecule, were determined in vacuo and in dynamic nitrogen and oxygen gas atmospheres. The study was carried out by thermoanalytical (TG, DTG. DTA), spectroscopic and spectrometric (UV-visible, IR, diffuse reflectance, mass) techniques.

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