A thermoanalytical study of the oxidation of chalcocite

A sample of chalcocite of particle size 45–75 μm, has been oxidised in a TG-DTA apparatus at a heating rate of 10 deg·min⁻¹ and the products at various temperatures characterised by XRD, SEM, FTIR and EPMA. This has enabled the events in the TG-DTA record to be assigned to specific chemical reactions, as well as the development of a full reaction scheme for the oxidation of chalcocite. Only minor reactions occurred up to 430°C, but above this temperature there was significant oxidation which resulted in an exotherm and mass gain. These events were due primarily to the oxidation of sulfide to copper(I) oxide, and the formation of copper(II) sulfate. The reaction then slowed, but melting commenced at 490°C which permitted further oxidation to take place with the appearance of a second exotherm and mass gain. By 570°C, sulfide oxidation was complete, but solid-solid reactions took place between Cu₂O and CuSO₄ to produce CuO·CuSO₄. Some conversion of Cu₂O had occurred. By 775°C, CuO and CuO·CuSO₄ were the only phases detected. Above this temperature the latter phase was unstable and decomposed to the end product CuO. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

A spectroscopic and thermoanalytical study of the mineral hoganite

A comprehensive spectroscopic analysis consisting of Raman, infrared (IR) and near infrared (NIR) spectroscopy was undertaken on the newly discovered mineral hoganite (copper(II) acetate monohydrate (Cu(CH(3)COO)(2) x H(2)O)). Assignments of vibrational bands due to the acetate anion have been made in all three forms of spectroscopy. Thermal analysis of the mineral was undertaken to follow its decomposition under a nitrogen atmosphere. Two major mass loss steps at 90 and approximately 220 degrees C were revealed. These mass losses correspond very well to firstly, the loss of a single water molecule, and then the loss of the acetate anion which quickly decomposes to form carbon dioxide and water.     

A thermoanalytical study of the cure of xylok 225 resin

The cure of Xylok 225 resin with a range of concentrations of hexamethylene tetramine has been studied by DTA, DTA-TG and DSC. The process has also been followed by IR spectroscopy. Two reaction peaks were observed during the cure, an exotherm occurring near to 150°C and an endotherm near to 250°C. The exotherm appeared to be affected by the concentration of hexamethylene tetramine, at a low concentration (4.8%) its onset was delayed until near 190°C, whilst at a higher concentration (13.0%) the heat of reaction was diminished. Both the exothermic and endothermic phases of cure were accompanied by evolution of volatiles.     

A thermoanalytical study of the formation and activation of novel copper-carbon catalysts

Simultaneous DSC-TG and DTA-TG were used to investigate the calatytic effect of the metal on the thermal decomposition of a cellulose matrix containing small copper particles. The techniques were also used to demonstrate the effect of the metal particles on the subsequent activation of the carbon matrix, a process which develops the pore structure necessary to expose the metal particles to the gas phase. Temperature programmed desorption was used to study the initial mass loss found on activation. To quantify the catalytic effect of the copper particles on the activation process an estimate was made of the activation energy of the catalysed and uncatalysed reactions. The work gives valuable information on the processes involved in the preparation of a new range of metal-carbon catalysts. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

A thermoanalytical assessment of an organoclay

High resolution thermogravimetric analysis (TG) has attracted much attention in the synthesis of organoclays and its applications. In this study, organoclays were synthesised through ion exchange of a single cationic surfactant for sodium ions, and characterised by methods including X-ray diffraction (XRD) and TG. The changes of surface properties in montmorillonite (MMT) and organoclays intercalated with surfactant were determined using XRD through the changes in the basal spacing. The TG was applied in this study to investigate more information of the configuration and structural changes in the organoclays with thermal decomposition. There are four different decompositions steps in differential thermogravimetric curves. The obtained TG steps are relevant to the arrangement of the surfactant molecules intercalated in MMT and the thermal analysis indicates the thermal stability of surfactant modified clays. This investigation provides new insights into the properties of organoclays and is important in the synthesis and processing of organoclays for environmental applications.     

Thirty years of thermoanalytical study in Osaka University

During the last three decades, we have developed various types of home-constructed DTA and calorimetric equipments which have been used in clarifying the reciprocal relationship between energy and matter associated with physical and chemical processes both qualitatively and quantitatively. Of the more than one hundred substances surveyed, some interesting results are briefly reviewed here, emphasizing the slightly different aspect of the role of DTA from that of calorimetry.     

A comparative study of the thermal stability of coordination compounds by thermoanalytical methods

The informative capacity of thermal analysis in the evaluation of the thermal stability of coordination compounds involving the evolution of volatile ligands is discussed. The temperature of decomposition under quasi-equilibrium conditions (Q-derivatograph, quasi-isobaric, quasi-isothermal operation) is suitable for characterizing the thermodynamic stability of compounds. The initial temperature of decomposition at linear heating indicates the reaching of a defined value of the rate constant (depending on the sensitivity of the sensing device of the instrument and on experimental conditions). The temperature sequence of increasing thermal stability may not coincide with the sequence of increasing activation energy values, since in the majority of cases it demands on the value of activation enthropy.

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Zusammenfassung Die informative Kapazität der Thermoanalyse bei der Bewertung der thermischen Stabilität von Koordinationsverbindungen in Thermolysevorgängen unter Entwicklung flüchtiger Liganden wird vorgestellt. Die Temperatur der Thermolyse unter Quasi-Gleichgewichtsbedingungen (Q-Derivatograph, quasi-isobare und quasi-isotherme Prozesse) eignet sich zur Charakterisierung der thermodynamischen Stabilität der Verbindungen. Die Temperatur des Beginns der Thermolyse bei linearem Aufheizen zeigt das Erreichen eines definierten Wertes der Geschwindigkeitskonstante an (in Abhängigkeit von der Empfindlichkeit des Fühlers des Gerätes und von den Versuchsbedingungen). Die Temperatursequenz der zunehmenden Thermostabilität stimmt nicht nötigerweise mit der Sequenz der zunehmenden Werte der Aktivierungsenergie überein, da erstere in den meisten Fällen von der Aktivierungsenthropie abhängt.

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Résumé L'aptitude de l'analyse thermique à servir de source de données pour l'évaluation de la stabilité thermique des composés de coordination lors des réactions de décomposition mettant en jeu l'élimination de ligands volatils est discutée. En conditions de quasi-équilibre (Derivatograph-Q, opérations quasi-isobares, quasi-isothermes) la température de la décomposition thermique peut Être utilisée pour caractériser la stabilité thermodynamique des composés. La température du début de la décomposition en chauffage linéaire indique l'obtention d'une valeur définie de la constante de vitesse (qui dépend de la sensibilité du dispositif détecteur de l'appareil et des conditions expérimentales). L'ordre de succession des températures définissant l'augmentation de la stabilité thermique peut ne pas coincider avec celui des valeurs de l'énergie d'activation, puisque dans la majorité des cas il dépend de la valeur de l'entropie d'activation.

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A thermoanalytical study of the catalytic oxidation of carbonaceous residues of nitrocellulose decomposition

Carbonaceous residues of nitrocellulose and doub lebase propellants were collected from TA and combustion experiments and analyzed in air by TG and quantitative DTA. The residues react like charcoal. Burning catalysts like lead and copper salicylates have a strong influence on the reaction interval and kinetic parameters.     

Spectrophotometric and thermoanalytical study of cypermethrin/cyclodextrin complexes

Cypermethrin/β-CD complexes were prepared at 1:2 cypermethrin/β-CD molar ratio by different complexation methods: conventional coprecipitation, suspension and kneading methods as well as “melting in solution” technique, which was developed in our laboratory. The complexes were investigated by UV-spectrophotometry and thermal analysis. It was found that complexes made by coprecipitation, suspension and kneading methods contained cypermethrin not only in complexed but also in uncomplexed form. The guest molecule in the complex prepared by “melting in solution” technique showed to be completely complexed, so it was the most effective complexation method studied.Investigating the solubility of cypermethrin with different cyclodextrins (CDs), it was established that the increase of solubility of cypermethrin was the highest in case of methylated cyclodextrins. The equilibrium constants were calculated from solubility isotherms. On the basis of these results, the heptakis(2,6-di-O-methyl)-β-cyclodextrin (DIMEB) complex was the more stable. By UV-irradiation measurements it was found that the photodegradation of cypermethrin was inhibited by methylated β-CDs.     

A thermoanalytical study on some compounds of Zr(IV) with azopyrazolonic derivatives

Thermoanalytical data on six reagents and on their compounds with Zr(IV) are reported. Except for H acid, all reagents were azopyrazolonic derivatives obtained by synthesis. The purpose of this study was to obtain data on the thermal stabilities of the reagents and their zirconium compounds, and to establish the reagent: zirconium: water combination ratio.

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Zusammenfassung Thermoanalytische Daten von 6 Reagenzien und deren Verbindungen mit Zr(IV) werden mitgeteilt. Außer H-Säure waren alle Reagenzien durch Synthese erhaltene Azopyrazolon-Derivate. Zweck der Untersuchung war, Daten über die thermische Stabilität dieser Reagenzien und ihrer Zirkonverbindungen zu erhalten und das Verhältnis Reagens: Zirkon: Wasser festzustellen.

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A thermoanalytical study of the metal nitrate-edta precursors for lead zirconate titanate ceramic powders

Lead zirconate titanate (PZT) ceramic powder has been synthesized from metal nitrate solutions using the EDTA-gel method with different nitric acid/EDTA ratios. It was found that the thermal decomposition of the precursor was strongly affected by the nitric acid/EDTA ratio, the amount of sample, the atmosphere, and the heating rate. Crystallization of the perovskite PZT phase initiated at external temperatures as low as 250°C, as a result of the exothermic decomposition reaction of the nitrate-EDTA complexes. Possible reaction schemes are suggested and discussed to describe the thermal decomposition of PZT-EDTA precursors under different experimental conditions.     

Application of thermoanalytical methods to the study of limestone sulphation

The role that can be played in the elucidation of the limestone sulphation mechanism by thermal analysis methods with some specific procedures is discussed. Contrasting examples of applications of thermoanalytical techniques using the variable conditions are provided. These examples deal with the programmed thermal analysis using different gas sequences, the influence the calcination and sulphation conditions on the capture of SO₂, the effect of catalysts on limestone sulphation and the thermal stability of CaSO₃. Two proposed mechanisms were supported by the phase identification of the solid products.     

Applications of thermoanalytical methods to the study of thin films

Studies of the formation and properties of thin films is a growing area in both science and technology. Characterization of these films and the processes by which they are prepared is a major factor in understanding, controlling, and optimizing their synthesis and usefulness.Thermal methods can play an important role in such studies, provided that they can overcome the difficulties imposed by the massive amount of associated substrate. Unless one is studying the film — substrate interaction, the substrate's presence only serves to decrease the sensitivity by diluting or reducing the thermal effect being measured.The three basic strategies that have evolved are discussed and examples described. One approach is to remove the film from the substrate, when this is appropriate and feasible, and then study the film separately. A second method is to use larger samples and careful measurements in an effort to overcome the reduced sensitivity. The final means is to develop very sensitive and/or selective techniques to investigate the film and its potential interactions with the substrate.

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Zusammenfassung Sowohl in Wissenschaft als auch in Technologie gewinnt die Untersuchung von Bildung und Eigenschaften dünner Schichten immer mehr an Bedeutung. Die Beschreibung dieser Schichten und ihres Herstellungsverfahrens ist ein wichtiger Gesichtspunkt zum Verständnis, zur Kontrolle und Optimierung ihrer Herstellung und Nutzbarkeit.In derartigen Untersuchungen können thermische Methoden eine wichtige Rolle spielen, vorausgesetzt es gelingt diejenigen Schwierigkeiten zu überwinden, die durch die beträchtliche Menge assoziierten Substrates verursacht werden. Untersucht man nicht gerade die Wechselwirkung Schicht-Substrat, dann verursacht die Gegenwart des Substrates durch Abschwächung oder Verringerung des gemessenen thermischen Effektes lediglich eine geringere Empfindlichkeit.Es werden die drei bestehenden Grundstrategien diskutiert und Beispiele beschrieben. Eine Lösung ist es, die Schicht, wenn es geeignet erscheint und möglich ist, vom Substrat zu entfernen und dann gesondert zu untersuchen. Eine zweite Methode ist die Verwendung grö\erer Proben und sorgfältiger Messungen, um die verringerte Empfindlichkeit zu überwinden. Die letzte Möglichkeit besteht in der Entwicklung empfindlicher und/oder selektiver Verfahren, um die Schicht und ihre potentiellen Wechselwirkungen mit dem Substrat zu untersuchen.

     

Thermal investigations on yellow wools

Thermal investigations (TG, DTG) were carried out on the wool of Polish Mountain, Polish Lowland, Polish Merino and Polish Long-fleeced sheep in order to find dependences between the yellowing of the wool fibres and their structure. The thermal investigations were made on a single lock, taking into account the upper (yellow) and the lower (white) parts of the staple.

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Zusammenfassung Mittels Thermoanalyse (TG, DTG) wurden Untersuchungen an Fellen von Polnischen Berg-, Flachland-, Merino- und Langfellschafen durchgeführt, um einen Zusammenhang zwischen der Gelbfärbung der Wollfasern und ihrer Struktur festzustellen. Die thermischen Untersuchungen wurden unter Berücksichtigung der oberen (gelben) und unteren (weißen) Rohwollteile an einzelnen Faserbüscheln durchgeführt.

     

Stability and compatibility study on enalapril maleate using thermoanalytical techniques

This paper demonstrates the application of thermal analysis in compatibility and stability studies between an ACE inhibitor (enalapril maleate) and excipients. The results have helped to elucidate the reason of a stability problem observed during the storage of enalapril maleate tablets. Incompatibility between enalapril maleate and colloidal silicon dioxide was detected. Besides, it was confirmed that the reaction between enalapril maleate and NaHCO₃ increases the thermal stability of the drug. This study supports the importance of using thermoanalytical methods in the development of pharmaceuticals.     

A new method for the kinetic study of thermoanalytical data:: The non-parametric kinetics method

A new method, called non-parametric kinetics (NPK), for the treatment of non-isothermal thermoanalytical data has been developed. The most significant feature of this method is its ability to provide a kinetic model that fits the experimental data, without any assumptions either about the functionality of the reaction rate with the degree of conversion or the temperature. The thermal decomposition of dibenzoyl peroxide has been studied in order to validate the NPK method, and the results are compared with those of the traditional ones.     

A comparative study of EDTA-gel derived BSCCO and Pb-BSCCO systems by thermoanalytical and X-ray diffraction techniques

Summary This paper deals with the first investigation concerning the thermal behaviour of Ni(II) complexes with ligands having biguanide moieties. The new complex [NiL(1)](ClO₄)₂·2.5H₂O (1) with the Schiff base resulted in [2+1] condensation of N,N-dimethylbiguanide with pentane-2,4-dione (L(1)) and the complex [Ni₂L(2)](ClO₄)₄ (2), with the Schiff base, L(2), resulted through the oxidative condensation of L(1) have been synthesized and characterised. The bonding and stereochemistry of the complexes have been characterized by IR and electronic spectra. The cyclic voltammograms show the characteristic waves for mononuclear and respectively binuclear Ni(II) complexes and indicate that both complexes exhibit catalytic effects on the CO₂ electrochemical reduction. The thermal behaviour provided confirmation of the complexes composition as well as the number and the nature of water molecules and the intervals of thermal stability. The different nature of the ligands generates a different thermal behaviour for complexes.