Use of thermomagnetometry in the study of iron-containing pyrotechnic systems

Thermal analysis is routinely used to characterize pyrotechnic fuels, oxidants and fuel/oxidant mixtures [1]. Thermomagnetometry (TM) can provide additional information if the magnetic properties of the materials change during reaction. TG, TM and DTA results for the iron/potassium permanganate, iron/barium peroxide, and iron/strontium peroxide systems as loose powders or pressed pellets indicate predominantly solid-gas mechanisms for reactions in these systems.     

Application of thermomagnetometry to corrosion studies of archaeological iron

Summary Thermomagnetometry has been applied to mineralized archaeological iron samples and samples from accelerated corrosion tests. It has successfully quantified the degree of corrosion, measured by the loss of iron, as well as the amount of magnetite formed and water held in the corrosion and adhered soil layers. Thermomagnetometry, thermogravimetric analysis and differential scanning calorimetry have been applied to the reported corrosion products from archaeological iron. Fourier transform infra-red and Raman spectroscopies and X-ray diffraction analyses were undertaken on the residues and at intermediate heating stages, where the thermal analyses indicated, to identify the reaction products.     

Some applications of thermal analysis to the coordination chemistry

The behaviour of complexes of the type MeD2I2 (Me=Co,D = acetylacetone or benzoylacetone,I = imidazole and derivatives in the course of the stepwise thermal degradation is different. In the case ofD = acetylacetone in the first step acetylacetone is split off. At D = benzoylacetone the decomposition starts with the partial elimination of the heterocyclic ligands.In-position unsubstituted nickelacyclic complexes from type (bipy)Ni(CH₂CH₂CH₂COO) decompose by a reductive elimination and separating of CO₂ forming a (bipy)Ni-intermediate. A single reductive decoupling is hindered by blocking up the-position.Opposite to the high thermal stability of the trimesityl aluminium the intermediates Almes₂Cl and AlmesCl₂ show with decreasing amounts of mesityl groups and increasing content of halogene, respectively, a significant decreasing thermal stability.The thermal degradation of nickelchelates of alkylsubstituted chinolin-8-ol starts with the dehydration followed by a different separation of the ligands as a function of the chain-length and the position of the substituents of the ligands.

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Zusammenfassung Das Zersetzung Verhalten der Komplexverbindungen vom Typ C0D2I2 (P = acetylaceton, Benzoylaceton;I = Imidazol oder Derivate) erfolgt stufenweise. Im Falle vonD = Acetylaceton erfolgt zuerst eine Eliminierung von Acetylaceton wärend beiD = Benzoylaceton zuerst ein Heteroligand eine Abspaltung erfährt.Bei einer unsubstituierten-Position von Nickelacyclen des Typs (bipy)Ni(CH₂CH₂CH₂COO) erfolgt eine thermisch induzierte-Hydrideliminierung unter Ringspaltung und Freisetzung von CO₂.Im Gegensatz zur hohen thermischen Stabilität des Trimesityl Aluminium erfahren die Zwischenverbindungen Almes₂Cl und AlmesCl₂ mit abnehmenden Mesityl- bzw. zunehmenden Chlorgehalt einen wessentlich früheren thermischen Zerfall. Bei zunehmenden Kovalenzgrad ist hier ein Einfluss der veränderten Polarisation anzunehmen.Der thermische Abbau der prinzipiell wasserhaltig kristallisierenden Nickelchelate von alkylsubstituierten Chinolin-8-ol beginnt jeweils mit der Dehydratisierung. In Abhängigkeit von der Kettenlänge und der Position der Substitution am Chinolin schliesst sich der thermische Abbau der Chelatliganden ein- bzw. mehrstufig an.

     

Some applications of thermal analysis to fullerenes

Thermal analysis is a convenient means of characterizing the soot used as a source of the carbon clusters, the extracted mixture of fullerenes, and the individual clusters themselves. TG in an inert atmosphere will rapidly assay the volatile fractions, presumably the lower molecular weight clusters. TG in oxygen indicates — a slight weight gain for the soots and clusters prior to their combustion.DSC in oxygen is used to determine the heat of combustion for the separated C₆₀ and C₇₀ materials. The combustion occurs around 300°C for the clusters. There is a small exothermic peak before this which is attributed to the oxidation associated with the slight weight gain. The heats of combustion measured are –18.7 and –21.0 kJ·mol^–1 for the C₆₀ and C₇₀ respectively.MS-EGA indicates the loss of small amounts of water and argon at temperatures around 250°C in vacuum and of solvent at about 350°C prior to sublimation.

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Zusammenfassung Thermoanalyse ist ein praktisches Hilfsmittel zur Charakterisierung von Ruß als Quelle für Kohlenstoffcluster, extrahierte Gemische von Fullerenen und die individuellen Cluster an sich. TG in einer inerten Atmosphäre ergibt schnell die flüchtigen Fraktionen, wahrscheinlich die niedermolekularen Cluster. TG in Sauerstoff zeigt einen leichten Gewichtszuwachs für Ruß und Cluster vor ihrer Zersetzung.DSC in Sauerstoff wurde angewendet, um die Verbrennungswärme der getrennten C₆₀ und C₇₀ Materialien zu ermitteln. Die Verbrennung erfolgt für die Cluster bei etwa 300°C. Davor kann ein kleiner exothermer Peak beobachtet werden, welcher der Oxidation in Verbindung mit dem geringen Gewichtszuwachs zugeschrieben wird. Die gemessenen Verbrennungswärmen betragen –18.7 und –21.0 kJ·mol^–1 für C₆₀ bzw. C₇₀.MS-EGA zeigt den Verlust von geringen Mengen an Wasser und Argon bei Temperaturen von etwa 250°C in Vakuum und von Lösungsmittel bei etwa 350°C, bevor die Sublimation eintritt.

     

A study of the effect of purity on the use of nickel as a temperature standard for thermomagnetometry

Samples of nickel, varying by four orders of magnitude in their purity, were studied by thermomagnetometry (TM), to determine if the extrapolated end point (T _C ) changes.T _C is virtually identical for the 99.99 and 99.999% samples. Samples of less purity did show changes. Simultaneous DTA/TM can accurately defineT _C by comparing with the melting points of pure metals determined simultaneously. The melting points of lead and zinc bracket theT _C for nickel. They were added to the sample pan prior to TM of nickel. Experiments were performed at heating rates in the range from 1 to 20 deg·min^?1. It serves as a pilot study for the ICTAC Committee for Standardization to more accurately define the recommended values ofT _C .     

New data obtained by thermomagnetometry,on the phase transitions in Ni,Co, Pt,Cu and Fe-C alloys

On the basis of thermomagnetic and DTA measurements, together with data from the literature, it may be concluded that in some f.c.c. metals a phase transformation occurs just before melting.

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Zusammenfassung Auf Grund thermomagnetischer und differentialthermoanalytischer Messungen sowie Literaturangaben wird geschlossen, dass in manchen kubisch-flächenzentrierten Metallen wenig unterhalb der Schmelztemperatur eine reversible Phasenumwandlung, wahrscheinlich in eine kubischraumzentrierte oder amorphe Phase, stattfindet.

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A new simple instrument for thermomagnetometry. Applications to simultaneous thermomechanical measurements

A new instrument has been set up to study magnetic materials. Curie points measured by means of this simple apparatus are in perfect agreement with those given by a conventional magnetic balance. The apparatus may be used alone, but also combined with an electronic thermodilatometer. Curie points are emphasized simultaneously by the thermodilatometric and impedance curves. It appears that the sensitivity and reliability of the apparatus demonstrate magnetic phenomena of very low intensity such as the order point of α-Fe₂O₃.     

Some applications of thermal methods of analysis to polymers

Some examples are given of the application of thermogravimetry, differential scanning calorimetry, thermomechanical analysis, torsional braid analysis, stress relaxometry and dynamic viscoelastometry to the study of cross-linked polymer systems. The information derived by the use of each technique is outlined and the advantages and disadvantages of the different methods are compared.

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Zusammenfassung Einige Beispiele der Anwendung der Thermogravimetrie, Differential Scanning Kalorimetrie, thermomechanischen Analyse, Torsionsfadenanalyse, Streßrelaxometrie und dynamischen Viscoelastometrie zur Untersuchung quervernetzter Polymersysteme werden gegeben. Die an Hand des Einsatzes der einzelnen Techniken erhaltenen Informationen werden beschrieben und die Vor- und Nachteile der verschiedenen Methoden miteinander verglichen.

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Résumé On donne quelques exemples de l'application de la thermogravimétrie, de l'analyse calorimétrique différentielle (DSC), de l'analyse thermomécanique, de l'analyse au fil de torsion, de la mesure de la relaxation des tensions, de la viscoélastométrie dynamiques, à l'étude des polymères à réseau tri-dimensionnel. On souligne les renseignements obtenus en utilisant chacune de ces techniques et on compare les avantages et les inconvénients de ces différentes méthodes.

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Some applications of the ultramicrobalance to power station of flue gas research

Mechanisms of formation and emission of acid smuts have been investigated using an apparatus based on an ultramicrobalance. Conclusions drawn from the experimental results are that, of the three potentially most significantly smut-forming processes, condensation of sulphuric acid is most important whilst catalytic adsorption of sulphur dioxide and sulphuric acid adsorption above the acid dewpoint play minor roles.     

Some applications of the partial least-squares method

The philosophy of the applications of the partial least-squares method in chemistry is outlined. The method is compared with multiple regression and illustrated by means of examples in various fields of chemistry.     

Some applications of the use of the reflectance photodensitometer to spot test analysis

Summary The colour developed during certain spot tests has been measured using a reflectance photodensitometer. In this way a quantitative estimation of the amount of substances present in the test solution has been made. The relationship between densitometer reading and concentration of test substance, and the best method of obtaining uniform colour in the spots are discussed. Several substances have been analysed by this method, for which only 5 to 10l of solution are required. 5 to 0.2 g of metallic ions, 100 to 5g of polyamide and 1 to 0.05 micro-equivalents of amino nitrogen can be determined. Precision compares well with other colorimetric methods.

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Zusammenfassung Die bei einigen Tüpfelreaktionen entwickelte Farbe wurde mit einem Reflexions-Photodensitometer gemessen. Dies ermöglicht eine quantitative Beurteilung der in der Probelösung vorhandenen Menge Substanz. Das VerhÄltnis zwischen den Densitometerablesungen und der Konzentration der Probelösung sowie die beste Methode der Herstellung gleichmÄßig gefÄrbter Tüpfelflecke werden besprochen. Mehrere Substanzen wurden mit Hilfe dieser nur 5 bis 10l benötigenden Methode untersucht. 5 bis 0,2g eines Metall-Ions, 100 bis 5g eines Polyamids und 1 bis 0,05 Mikro-Val Amino-Stickstoff können bestimmt werden. Ein Vergleich der Genauigkeit der Methode mit der anderer kolorimetrischer Methoden fÄllt vorteilhaft aus.

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Résumé A l'aide d'un photodensimètre à réflexion, on a mesuré la couleur qui apparaÎt au cours de certains essais à la touche. Il a été ainsi possible d'estimer quantitativement les teneurs de substances présentes dans des solutions soumises à l'étude. Les relations existant entre les lectures densitométriques et les concentrations des substances étudiées sont discutées par l'auteur ainsi que la meilleure méthode d'obtention de taches de couleurs uniformes. Plusieurs substances ont été analysées à l'aide de cette méthode qui ne nécessite que 5 à 10l de solution; on peut ainsi doser 5 à 0,2g d'ions métalliques, 100 à 5g de polyamides et 1 à 0,05 microéquivalents d'azote aminé. La précision obtenue est comparable à celle des autres méthodes colorimétriques.

     

Some applications of silica aerogels

Silica aerogels are very highly divided materials which are synthesised through the association of a chemical step, the so-called sol–gel chemistry, with a physical step which is a particular way of drying the wet gel, namely under supercritical conditions with respect to the liquid phase filling its porosity. This drying process preserves the texture of the dry material: in practice it strongly reduces the pore collapse. The resulting hyperporous solids that have bulk densities of the same magnitude as air develop new and very interesting physical and even chemical properties. Owing to their poor chemical reactivity, very large surface areas (of the order of 1,000 m ²/g), unusual porous volumes (greater than 95%), morphologies (monoliths or powders), optical properties (transparent, opaque or translucent), and very low thermal conductivity, they find high added-value applications in the physics of high-energy particles (Cherenkov emitters), transparent and superinsulating double windows, life and space science as well.     

Some applications of bonded-phase high-performance liquid chromatography to the analysis of pharmaceutical formulations

Chromatographic procedures are presented for the determination of guaiphenesin, phenylephrine hydrochloride, phenylpropanolamine hydrochloridfe, pholcodine, methyl and propyl 4-hydroxybenzoates, and tyrothricin in some pharmaceutical products. An investigation of the contamination of lozenges with aspirin, paracetamol, phenacetin, prednisone and prednisolone is reported, together with the preparation of a novel bonded weak cation-exchange packing used.     

Some applications of local density functional theory to the calculation of reaction energetics

Summary We report the results of a local density functional investigation of the energetics of some isomerization reactions, involving the conversions of several unsaturated systems to highly strained molecules related to triprismane and tetrahedrane. The program DMol was used at the DNP level to compute the activation barriers and total energy changes associated with these processes. We also show, for more than 70 first- and second-row atoms and molecules, that the errors (non-local corrections) in their energies correlate very well with the number of electrons, within isonuclear series. This should provide a useful empirical means for improving dissociation energies obtained within the local approximation.     

Analysis of the phase composition and homogeneity of ferrite lithium-substituted powders by the thermomagnetometry method

In the present work, the possibilities of application of the thermomagnetometry TG(M)/DTG(M) method for estimation of the phase homogeneity of end products of synthesis at different stages of ferritizing annealing are considered on the example of solid-state synthesis of Li_0.5(1?x)Fe_2.5?0.5xZn_xO₄ and Li_0.5(1 + x)Fe_2.5?1.5xTi_xO₄ (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) lithium-substituted ferrospinels. Results of thermomagnetometric analysis are compared with XRD data. It is shown that the resolution of the TG(M)/DTG(M) method on two orders exceeds capabilities of the traditional XRD method. Considerable influence of both intermediate grinding and mixing of samples and concentration of an inducted impurity on the homogeneity of the synthesized powders is confirmed.