Use of emanation thermal analysis to characterize thermal reactivity of brannerite mineral

Emanation thermal analysis (ETA) was used to characterize the thermal reactivity of amorphous brannerite mineral of general formula U_1–xTi_2+xO₆ (locality El Cabril, near Cordoba, Spain). It was demonstrated that on sample heating up to 880°C microstructure changes taking place in the sample were accompanied by the formation of new radon diffusion paths, followed by their closing up during the final transformation of amorphous to crystalline brannerite in the range 900–1020 °C. Relative changes in structure irregularities that served as radon diffusion paths during heating and subsequent cooling of the sample to temperatures of 300, 550, 750, 880, 1020 and 1130°C, respectively, were determined from the ETA results. Mass losses in temperature ranges of 230–315, 570–760 and 840–1040°C were observed by thermogravimetry. Mass spectrometry indicated the release of CO2 mainly due to the decomposition of minor carbon amount in the brannerite mineral sample.     

Rapid thermal analysis of processes of thermal decomposition of mineral salts

Kinetic curves of thermal decomposition and synthesis of mineral salts are obtained in the conditions of rapid heating approaching the heating conditions in a low-temperature plasma flow. The kinetic characteristics are used in calculations of transformations in the path of a chemical plasma reactor.

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Zusammenfassung Für thermische Zersetzung und Synthese von Mineralsalzen wurden die kinetischen Kurven unter den Bedingungen schnellen Aufheizens in Annäherung der Aufheizbedingungen in einem Niedertemperatur-Plasmastrom ermittelt. Die kinetischen Eigenschaften wurden zur Berechnung der Umwandlungen bei einem chemischen Plasmareaktor verwendet.

     

Application to polymer characterization by thermal analysis

The measured results of thermal analysis depend on experimental conditions. The international and national organizations have constituted a series of methods to characterize the physical and chemical properties for substances. The applications to physical transition, chemical reaction, and characteristic parameters of substances are given in the article as examples.     

On the thermal analysis of mineral components in clays

The paper deals with the problem of the interactions of the mineral components in clay and argillite samples during the thermal analysis. It is shown that depending on the experimental conditions, the interaction of pyrite and carbonates may cause atypical course of DTA and TG curves. Also the common occurring of sylvine and halite shifts the temperature of their melting to a lower value and this phenomenon occurs in pure salts as well as in the great dilution to some percent in clays.

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Zusammenfassung Es wird über Zwischenreaktionen der mineralischen Komponenten von Ton und Argillit während der thermischen Analyse berichtet. Von den Versuchsbedingungen abhängend produzieren die Zwischenreaktionen von Pyrit und Karbonat DTA und TG Kurven deren Verlauf nicht charakteristisch ist. Das gemeinsame Vorkommen von Sylvin und Halit verschiebt ihren Schmelzpunkt in Richtung der niedrigen Temperaturen in reinen Salzen ebenso wie bei großer Verdünnung von einigen Prozenten in Ton.

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Résumé Les interactions des constituants minéraux des échantillons d'argile et d'argilite pendant l'analyse thermique ont été examinées. Suivant les conditions expérimentales, l'interaction de la pyrite et des carbonates peut provoquer un tracé des courbes ATD et ATG qui s'écarte de l'allure type. La présence simultanée de sylvine et d'halite produit un abaissement de leur point de fusion et ce phénomène apparaít aussi bien avec les sels purs qu'avec ceux fortement dilués, à raison de quelques pour cent, dans les argiles.

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Application of thermal analysis to carbon black-elastomer systems

In this study a relationship between the surface and textural properties of carbon blacks and the gasification process induced thermally in air is noted. A temperature jump method was used to follow the gasification in air and to establish the relevant Arrhenius parameters. This can be associated with the activity of ‘basal’ plane carbon atoms as well as ‘edge’ carbon atoms at the surface. This is based on a model of carbon black structure consisting of the irregular packing of small graphite carbon structures. The carbon black surface was measured using a single measurement of adsorption based essentially on the BET volumetric method. The carbon black surface had a rate of oxidation per unit are which clearly indicated that the lower area carbon blacks had a predominately active area of ‘edge’ atoms at the surface while the surface of the higher area carbon blacks had a predominate amount of ‘basal’ plane graphite carbon atoms.     

Application of thermal analysis to the cement industry

Methods involving heat measurements have been applied in the cement industry for a long time. Differential thermal analysis (DTA) is used to explain the clinkering reactions, but it is a dynamic method which thus does not allow measurements and calculations of the thermal balance of the reactions to be made. In contrast, high temperature microcalorimetry may be used to measure the enthalpy of the clinkering reactions of industrial raw materials. Results obtained by using this technique allow us to determine the thermal profile of clinkering reactions in the kiln and to quantify the heat exchange in the solid material during its burning.Low temperature conduction microcalorimetry gives information on the hydration mechanism of the cement pastes. In this paper, we review the applications of thermal analysis in the cement industry paying special attention to new methods such as high temperature microcalorimetry.

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Zusammenfassung Seit langer Zeit werden in der Zementindustrie Verfahren mit Wärmemessung angewendet. Zur Erforschung der Verschlackungsreaktionen wird DTA verwendet, was jedoch ein dynamisches Verfahren ist und keine Messungen und Berechnungen bezüglich des thermischen Gleichgewichtes erlaubt. Im Gegensatz dazu kann Hochtemperatur-Mikrokalorimetrie zur Messung der Enthalpie von Verschlackungsreaktionen industrieller Rohstoffe dienen. Mit Hilfe der durch diese Methode erlangten Resultate kann das thermische Profil von Verschlackungsreaktionen im Kiln und der Wärmeaustausch im Festmaterial beim Brennen bestimmt werden.Niedertemperatur-Konduktions-Mikrokalorimetrie liefert Informationen über den Hydratationsmechanismus von Zementleim. Unter spezieller Beachtung neuer Methoden, wie z.B. der Hochtemperatur-Mikrokalorimetrie, wird in diesem Artikel ein Überblick über die Anwendungen der Thermoanalyse in der Zementindustrie gegeben.

     

Application of thermal analysis to study of the synthesis of K0.5Bi0.5Tio3 ferroelectric

Synthesis of potassium bismuth titanate ferroelectric by heating of mixtures prepared using oxide precursors, i.e. Bi₂O₃, TiO₂ and K₂CO₃ was investigated. DTA, TG, XRD and SEM methods were used to study the formation of intermediate compounds and the final product. Usage of associated homogenization and grinding of precursors mixture permits to decrease the temperature of formation of K_0.5Bi_0.5TiO₃. This revised version was published online in July 2006 with corrections to the Cover Date.     

Application of non-equilibrium thermodynamics to problems of thermal analysis

On the basis of non-equilibrium thermodynamics, the kinetic equations of thermal analysis are derived for several important chemical consecutive and concurrent reactions. These equations are solved analytically and numerically and the obtained solutions are discussed. Hereby hints are obtained for the further development of thermal methods. It is shown that, in most cases, the kinetics of coupled chemical reactions can only be determined with special selective methods.     

Application of thermal analysis to the investigation of catalysts

A short review of the possibilities of application of thermal analysis to the investigation of catalysts is given: analysis of catalysts, investigation of the processes during the preparation of catalysts, desactivation of catalysts, and interaction of reactants or catalytic poisons with the catalysts. Several examples are mentioned.

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Zusammenfassung Eine kurze Übersicht über die Möglichkeiten des Einsatzes der Thermoanalyse zur Prüfung von Katalysatoren wird gegeben: Analyse der Katalysatoren, Prüfung der Vorgänge während der Herstellung von Katalysatoren, Inaktivierung von Katalysatoren, Wechselwirkungen zwischen Reagenzien oder Katalysatorengiften und den Katalysatoren. Eine Anzahl von Beispielen wird erwähnt.

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Résumé On piésente une rapide vue d'ensemble sur les possibilités d'application de l'analyse thermique à l'étude des catalyseurs: l'analyse des catalyseurs, l'étude des processus ayant lieu lors de la préparation des catalyseurs, la désactivation des catalyseurs, l'interaction de réactifs ou de poisons sur les catalyseurs. Plusieurs exemples sont mentionnés.

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Application of thermal analysis to study smelting reduction kinetics

A thermal analysis study on the reduction of iron oxide rich slags under different conditions is presented in this paper. The effects of important process variables such as time, temperature, lime-silica ratio, FeO level in slag etc. are discussed. It is shown that the mechanism of reduction by externally added graphite is different from that by a carbon saturated bath although the activation energy values are similar.     

Application of constant rate thermal analysis (CRTA) to the synthesis of silicon nitride by carbothermal reduction of silica

The carbothermal reduction of silica under flowing nitrogen at a pressure of 1 atm has been followed by means of a CO IR detector attached to the gas output of a high temperature tubular furnace. The control of the reaction temperature is carried out by interfacing the analogical output of the IR detector to a controller that allows to monitor the sample temperature in such a way that the concentration of CO generated in the reaction is maintained constant at a value previously selected by the user. The reaction rate at a particular concentration of CO can be fixed by properly selecting the flow rate of the reactive gas. The influence of the reaction rate and the CO concentration on both the reaction temperature and the structure of the final product of the reaction are analysed.     

Application potential of emanation thermal analysis

The application potential of the emanation thermal analysis with respect to the actual needs of chemical technology and material science is given.

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Zusammenfassung Im Hinblick auf die praktischen Erfordernisse der chemischen Verfahrenstechnik und Materialkunde werden die Anwendungsmöglichkeiten der Emanationsthermoanalyse beschrieben.

     

Application of thermal analysis to the study of several Spanish peats

Thermogravimetry and differential thermal analysis have been applied to the study of peats from the main Spanish basements.The results obtained show that the degree of transformation of the organic matter increases as the depth of the peat increases.The intensity of the weight loss corresponding to the first exothermic effect (directly related to the carbohydrate content of the sample, and inversely related to the content of humic compounds) is, in the case of the peats with a high degree of transformation, strongly influenced by the nature of their humic acids.On the other hand, the displacement of this exothermic effect towards lower temperatures is directly related to the ash content of the samples.

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Zusammenfassung Die thermogravimetrische Analyse und die Differentialthermoanalyse wurden zum Studium von Torfen aus den wichtigsten spanischen Lagerstätten eingesetzt.Die erhaltenen Ergebnisse zeigen, daß der Umwandlungsgrad der organischen Substanz mit zunehmender Tiefe des Torfes zunimmt.Die Intensität des dem ersten exothermen Effekt entsprechenden Gewichtsverlustes (welcher dem Kohlenhydratgehalt der Probe direkt und seinem Huminverbindungsgehalt umgekehrt proportional ist) wird im Falle von Torfen von hohem Umwandlungsgrad durch die Beschaffenheit ihrer Huminsäuren stark beeinflußt.Andererseits ist die Verschiebung dieses exothermen Effekts in Richtung der niedrigeren Temperaturen dem Aschegehalt der Proben direkt proportional.

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Application of differential thermal analysis in mineralogy

In mineralogical research differential thermal analysis can be applied as either a single or a combined method for three purposes:

1. for the qualitative identification of minerals and the (semi-)quantitative determination of the components of rocks and soils,
2. for the characterization of crystal-physical and crystal-chemical properties, including the study of kinetics and the determination of thermodynamic data, phase and reaction equilibria,
3. for special petrogenetic investigations concerning the interrelation of mineralogical properties with the formation, decomposition or recrystallization of minerals.

The presented results were obtained under strongly standardized and reproducible conditions of analysis and by means of some methods recently developed by the author. They include the construction of key diagrams ofΔT versus peak temperatures to identify unknown minerals; the dependence of dehydration and decomposition peak temperatures on the partial pressure of gaseous reaction products (= PA curves); the determination of chemical and crystal-chemical parameters of minerals by using the dependence of dehydroxylation peak temperatures on solid solution (chlorites, smectites) or by using the interrelation between the peak temperatures of structural transformations and crystal-chemical substitutions (sulfides, carbonates, phosphates, silicates); the determination of the degree of disorder of minerals formed in sedimentary environments by using the dehydration or inversion peak temperature and peak shape dependence on the defect character of these crystal structures (clay minerals, quartz, cristobalite, hydroxides); the subdivision of mineral groups by using the interrelation of crystal chemistry and dehydration behaviour (zeolites, mixed-layer clay minerals); the characterization of ferromagnetic minerals by studying the Curie temperatures as a function of the chemical composition; the development of a DTA method to measure the degree of weathering of granitic rocks, etc. Data of 150 minerals are given.     

Use of thermal analysis in the synthesis of vinylidenediphosphonic acid

Simultaneous TG-DTA was applied to establish the optimum conditions for the synthesis of vinylidenediphosphonates via the intramolecular dehydration of 1-hydroxyethylidenediphosphonate salts (Li, Na, K, Rb, NH₄, Ca and Ba). The tested salts underwent water elimination at different temperatures. Consequently, they are of different values for the synthesis of vinylidenedi phosphonates. The dibarium salt proved to be the best for this purpose, whereas the tetrammonium salt can not be used because of its uncontrolled thermal decomposition. The kinetic parameters do not reveal any influence of the metal cation on the intramolecular dehydration process.

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Zusammenfassung Simultane TG-DTA wurde eingesetzt, um die optimalen Bedingungen für die Synthese der Vinidylidendiphosphonate durch intramolekulare Wasserabspaltung aus den 1-Hydroxiethylidendiphosphaten des Li, Na, K, Rb, NH₄, Ca und Ba zu ermitteln. Aus den untersuchten Salzen wurde das Wasser bei verschiedenen Temperaturen abgespalten, sie sind daher unterschiedlich brauchbar zur Synthese der Vinylidenphosphonate. Das Bariumsalz erwies sich am geeignetsten, während das Tetra-ammoniumsalz wegen seiner unkontrollierten thermischen Zersetzung ungeeignet ist. Die kinetischen Parameter der intramolekularen Wasserabspaltung zeigen keinen Einfluss des vorhandenen Metallkations.

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Application of new instrumentation and measurement techniques to thermal analysis of materials

Principles and operation of the infrared gold image furnace are discussed and its advantages over conventional resistance furnaces for studies of advanced materials listed. Using the gold image furnace in combination with a standard microscope allows continuous monitoring of materials to very high temperatures. New approaches to measurement of heat capacity and thermal diffusivity/conductivity are also described.     

Application of thermal analysis to the study of the kinetics of two-stage reactions

A method is suggested for studying the kinetic parameters of two-stage reactions from thermoanalytical experimental data. The method allows determination of the kinetic characteristics of the process on the basis of integral thermoanalytical data, without separation of the individual stages. Parallel, independent and successive reactions taking place under isothermal and non-isothermal conditions are considered.

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Zusammenfassung Eine Methode zur Untersuchung der kinetischen Parameter von Zweistufenreaktionen unter Verwendung experimenteller thermoanalytischer Daten wird vorgeschlagen. Die Methode ermöglicht, die kinetischen Kennwerte des Prozesses basierend auf integralen thermoanalytischen Werten ohne Trennung der individuellen Schritte zu bestimmen. Unter isothermen und nichtisothermen Bedingungen parallel, unabhängig voneinander und nacheinander verlaufende Reaktionen werden diskutiert.

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