Simultaneous thermoanalytical investigations of (C6H5)4AsCl and (C6H5)4PCl under air and argon atmospheres

The thermoanalytical curves of (C₆H₅)₄AsCl (I) and (C₆H₅)₄PCl (II) were generated simultaneously by using a Netzsch simultaneous thermal analyser 409 under static air and dynamic argon atmospheres. The ranges of thermal stability of I and II were found to be 145–310°C and 137–365°C, respectively, and their melting points to be 261 and 278°C. The DTA profiles of I and II differ and can be used for their distinction.     

Thermal decomposition of manganese(II)bis(oxalato)nickelate(II)tetrahydrate

Summary A mixed metal oxalate, manganese(II)bis(oxalato)nickelate(II)tetrahydrate, has been synthesized and characterized by elemental analysis, IR spectral and X-ray powder diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to Mn₂O₃, MnO₂ and NiO at ca.1000°C, via. the formation of several intermediates. DSC study in nitrogen upto 500°C showed the endothermic decomposition. The tentative mechanism for the thermal decomposition in air is proposed.     

Thermal analysis of heterocyclic thione donor complexes. Part III. Cobalt(II) complexes of imidazolidine-2-thione

The thermal decomposition of the cobalt(II) complexes of imidazolidine-2-thione (Imdt), Co(Imdt)₂X₂ (X = Cl, Br, and I) have been studied in air and argon by means of TG and DTG as well as in nitrogen by DTA. Decomposition schemes have been proposed for the complexes in both air and inert atmospheres. Reaction enthalpies have been derived from the melting and decomposition endotherms by means of quantitative DTA. A mean coordinate bond dissociation energy, D?, has been estimated for the Co-Imdt bond in the chloro complex. Reaction products in air have been identified by X-ray powder diffraction.     

Thermal Analysis of Cobalt(II) Salts with some Carboxylic Acids

The thermal analysis of CoC₂O₄·2H₂O, Co(HCOO)₂·2H₂O and Co(CH₃COO)₂·4H₂O was carried out with simultaneous TG-DTG-DTA measurements under non-isothermal conditions in air and argon atmospheres. The intermediates and the end products of decomposition were characterised by X-ray diffraction and IR and UV-VIS spectroscopy. The decomposition of the studied compounds occur in several stages. The first stage of dissociation of each compound is dehydration both in air and argon. The next stages differ in air and argon. The final product of the decomposition of each compound in air is Co₃O₄. In argon it is a mixture of Co and CoO for cobalt(II) oxalate and cobalt(II) formate but CoO for cobalt(II) acetate. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of various atmospheres and some metal oxide additives on the thermal decomposition on ammonium chromate

The thermal decomposition of ammonium chromate (AC) in dynamic air, CO₂ and N₂ and in static atmospheres and in the presence of MoO₃, V₂O₅, Fe₂O₃, CuO, MnO₂ and Nd₂O₃ additives was studied by means of TG, DTA, IR spectroscopy and electrical conductivity measurements. It was found that AC decomposes in four stages, forming unstable intermediates which produce Cr₂O₃ as a final product. The presence of the different atmospheres and the oxide additives affected the decompositions of these intermediates and the oxidation state of the chromium ions. Finally, the mechanisms associated with the different decomposition stages are discussed.     

Sol-gel synthesis of hydrous ruthenium oxide nanonetworks from 1,2-epoxides

Hydrous ruthenium oxide (RuO₂·xH₂O) xerogels were synthesized through the addition of a 1,2-epoxide, propylene oxide, to commercial hydrated ruthenium chloride, “RuCl₃·xH₂O,” in ethanol. After a blue-black monolithic gel formed in 4 h, the samples were allowed to age for 24 h and were dried in ambient conditions. The dried samples were then characterized by XPS, XRD, DTA and TGA. XPS showed the Ru(3d_5/2) peak at a binding energy of 281.7 eV, corresponding to that of hydrous ruthenium oxide. XRD data revealed the synthesized material as amorphous. Heating the sample in inert atmospheres caused the complete reduction of the oxide to the zero-valent state, whereas heating the sample in air resulted in both crystalline anhydrous RuO₂ and zero-valent ruthenium, depending on the method of heating. DTA traces showed an endotherm ending at 150 °C, corresponding to the loss of coordinated water, as well as two higher temperature crystallization exotherms when the sample was heated in both inert and oxygen-rich atmospheres. TGA runs also confirmed the complete reduction of the hydrous oxide when heated in nitrogen below 270 °C and the formation of anhydrous ruthenium oxide when heated in air, confirming the XRD results.     

Thermal analysis of manganese(II) complexes of general formula (Bu4N)2[MnBrnCl4−n]

Thermal decomposition of compounds consisting of tetrahalogenomanganese(II) anions, [MnBr_nCl_4?n]^2? (n = 0–4), and a tetrabutylammonium cation has been studied using the DSC, TG-FTIR, TG–MS and DTA techniques. The measurements were carried out in an argon and static air atmospheres over the temperature ranges 173–450 K (DSC) and 300–1073 K (TG). Solid products of the thermal decomposition were identified by FT-FIR spectroscopy as well as X-ray powder diffractometry.     

Thermal analysis of copper(Ii) complexes of general formula [Et<Subscript>4</Subscript>N]<Subscript>2</Subscript>[CuBr<Subscript>n</Subscript>Cl<Subscript>4-n</Subscript>]

Thermal decomposition of compounds consisting of tetrahalogenocuprate(II), [CuBr_nCl_4−n]²⁻ (n=0–4) anions and a tetraethylammonium cation has been studied using TG-FTIR, TG-MS, DTA and DTG techniques. The measurements were carried out in an argon and air atmospheres over the temperature range 293-1073 K. The products of the thermal decomposition were identified by IR and Far Infrared (FIR) spectroscopy as well as X-ray powder diffractometry.     

Double sulfates of some rare earths with tetramethylammonium

Double sulfates of rare earths and tetramethylammonium with empirical formula (CH₃)₄NLn(SO₄)₂ · 3H₂O (Ln=Ce, Pr, Nd, Eu, Gd, Tb and Dy) were synthesized and studied by the methods of TG, DTG and DTA in the temperature range from 20 to 500°C, and by X-ray powder diffraction and chemical analysis. Two isostructural groups were obtained: one from Ce to Eu and another from Gd to Dy. It was found that rare earth sulfates are obtained as final products at 500°C. For comparison, TG, DTG and DTA curves of the thermal decomposition of tetramethylammonium sulfate are given.

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Zusammenfassung Doppelsulfate von Seltenerden und Tetramethylammonium der empirischen Formel (CH₃)₄NLn(SO₄)₂ · 3H₂O mit Ln=Ce, Pr, Nd, Eu, Gd, Tb und Dy wurden synthetisiert und im Temperaturbereich 20–500°C mittels TG, DTG und DTA, weiterhin mittels Röntgenpulverdiffraktion und chemischer Analyse untersucht. Es wurden zwei isostrukturelle Gruppen erhalten, die eine von Ce bis Eu, die andere von Gd bis Dy. Man fand, daß man bei 500°C als Endprodukt die Seltenerdensulfate erhält. Zum Vergleich wurden die TG-, DTG- und DTA-Kurven der thermischen Zersetzung von Tetramethylammoniumsulfat gegeben.

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Financial support by the Research Council of Slovenia is gratefully acknowledged.     

Thermal analysis of heterocyclic thione donor complexes. Part V. Nickel(II) complexes of imidazolidine-2-thione

The thermal decomposition of the nickel(II) complexes of imidazolidine-2-thione (Imdt), Ni(Imdt)₄X₂ (X = Cl and Br), have been studied in air and in argon by means of TG and DTG, as well as in nitrogen by DTA. Decomposition schemes have been proposed for the complexes in air and inert atmospheres. End-products have been identified for the reactions in air by means of X-ray powder diffraction. Quantitative DTA has been used to derive reaction enthalpies (ΔH_R) from the melting and decomposition endotherms of Imdt and the complexes in nitrogen. The factors which govern the reaction enthalpies of these complexes have been discussed.     

Thermal behavior of aluminum powder and potassium perchlorate mixtures by DTA and TG

In this work the thermal decomposition characteristics of micron sized aluminum powder + potassium perchlorate pyrotechnic systems were studied with thermal analytical techniques. The results show that the reactivity of aluminum powder in air increases as the particle size decreases. Pure aluminum with 5 μm particle size has a fusion temperature about 647 °C, but this temperature for 18 μm powder is 660 °C. Pure potassium perchlorate has an endothermic peak at 300 °C corresponding to a rhombic-cubic transition, a fusion temperature around 590 °C and decomposes at 592 °C. DTA curves for Al₅/KClO₄ (30:70) mixture show a maximum peak temperature for thermal decomposition at 400 °C. Increasing the particle size of aluminum powder increases the ignition temperature of the mixture. The oxidation temperature increased by enhance in the aluminum content of the mixture.     

Determination of the kinetic parameters of thermal decomposition of [Co(NH3)6]2(C2O4)3· 4H2O by Kissinger's method

The values of the kinetic parametersE andA were determined by Kissinger's method on the basis of the DTA, DTG and DSC curves of particular stages of the thermal decomposition of [Co(NH₃)₆]₂(C₂O₄)₃· 4H₂O in air and argon atmospheres. It is shown that the use of Kissinger's method for different kinds of experimental curves (DTA, DSC, DTG) leads to close results.

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Zusammenfassung Für verschiedene Schritte der thermischen Zersetzung von [Co(NH₃)₆]₂(C₂O₄)₃· 4H₂O in Luft bzw. Argon wurden nach dem Kissinger-Verfahren auf der Basis von DTA-, DTG- und DSC-Kurven Werte für die kinetischen ParameterE undA ermittelt. Es wurde gezeigt, daß das Kissinger-Verfahren für die verschiedenen Arten von experimentellen Kurven (DTA, DSC, DTG) genaue Ergebnisse liefert.

     

Thermal behaviour and S-O bonding state of alkaline-earth metal sulfites

The thermal behaviours of magnesium sulfite, strontium sulfite and barium sulfite were investigated in the atmospheres of argon and air. the thermal behaviours of magnesium sulfite were different from those of the other two sulfites. The oxidation of magnesium sulfite in air does not occur.The bonding state of the SO ₃ ^2– in each sulfite was compared. The SO ₃ ^2– in magnesium sulfite was coordinated through the sulfur, while those in the other sulfites were coordinated through the oxygen.It appears that the difference in thermal behaviour between magnesium sulfite and the other sulfites depend upon the difference in bonding state of the SO ₃ ^2– We wish to thank Mr. K. Takahashi of MAC Science Inc. for TG and DTA measurements, mass spectra in Ar and his valuable discussions.     

Study of the temperature effect on the process of rubidium hexachlorotellurite decomposition

Thermal dissociation of rubidium hexachlorotellurite in inert atmosphere (argon) and in atmosphere with air access was studied. The DTG and DTA curves for the process of rubidium hexachlorotellurite thermal dissociation in the argon atmosphere are given. Their character is defined by the behavior of TeCl₄, which is liberated on the decomposition of samples.     

Kinetic and thermodynamic studies of the nonisothermal decomposition of anhydrous copper(II) formate in different gas atmospheres

The thermal decomposition of anhydrous (orthorhombic) copper(II) formate was studied by programmed rising-temperature methods (TG, DTG, DTA and DSC) to about 250 °C in flowing gas atmospheres of nitrogen (inert), hydrogen (reducing) and air (oxidizing). The degradation reaction, anion breakdown, proceeded to completion in two distinct, but partially overlapping, rate processes and apparent Arrhenius parameters, calculated by the Ozawa nonisothermal kinetic method, agreed satisfactorily with the literature results. It was concluded that the two consecutive processes, contributing to the overall reaction, involved stepwise cation reduction: Cu²⁺→Cu⁺→Cu⁰, with copper(I) formate as intermediate. This mechanism is similar to that proposed in previous studies of the decompositions of copper(II) oxalate, malonate, maleate, fumarate, mellitate and squarate. For all of these reactants, the Cu⁺ salt has been identified as an intermediate, exhibiting a (slightly) lower relative reactivity than the corresponding Cu²⁺ salt. For copper(II) formate the response curves in the three different gaseous atmospheres were generally similar, showing that neither oxidizing nor reducing conditions caused a marked change in reactivity. The temperature of reaction initiation in H₂ was slightly diminished and the temperature of the second stage of reaction in O₂ was raised appreciably. It is believed that electron transfer contributed to the control of reactivity and that the gases present appreciably influence the rates of the contributory reactions occurring.     

Synthesis of γ-Fe2O3 by Thermal Decomposition of Ferrous Gluconate Dihydrate

Ferrous gluconate dihydrate (FeC₁₂H₂₂O₁₄⋅2H₂O), was prepared and its thermal decomposition was studied by means of simultaneous thermal analysis, supplemented with a two probe d.c. electrical conductivity measurements under the atmospheres of static air, dynamic air and dynamic nitrogen. Under all the atmospheres final product was found to be α-Fe₂O₃ with FeO, γ-Fe₂O₃, Fe₃O₄ etc. as probable intermediates. γ-Fe₂O₃ was formed under the atmosphere of dynamic air containing water vapour. γ-Fe₂O₃ thus synthesised was characterised for its structure, morphology, thermal and magnetic behaviour. This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies on antimony oxides: Part I

Thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction studies of antimony(III) oxide, (Sb₂O₃), in air, nitrogen and argon atmospheres have been made. In air Sb₂O₃ becomes oxidized to Sb₂O₄ above 510°. The oxidation reaction proceeds in two stages as revealed by the TG and DTA curves. The behaviour of Sb₂O₃ is similar in both N₂ and Ar. Sb₂O₃ remains unaffected up to 430°, above which there is a slow, and continuous mass loss up to 550°. Above 550° Sb₂O₃ volatilizes resulting in an enormous weight loss. X-ray studies of the sublimate and the residue indicate the former to be the cubic form of Sb₂O₃ (Senarmontite) while the residue is the orthorhombic (Valentinite) structure. From the DTA curves in air, N₂ and Ar, the transition temperature for the cubic to the orthorhombic modification has been estimated to be around 610°.     

Thermal analysis of lanthanide polyphosphates

Summary A study of thermal analysis of some lanthanide polyphosphates has been reported. The DTA curves of Ce, Pr and Sm polyphosphates were of similar nature. They exhibited a sharp exothermic peak indicating crystallization temperature (T _c) around 520 °C. However, no peak indicatingT _m was observed upto 800 °C. TG curves of Ce, La, Pr, Sm, Y polyphosphates indicated weight loss occurring in three stages. The integral procedural decomposition thermal analysis (ipdt) indicated that these materials had refractory nature.With 4 figures and 2 tables     

Thermal decomposition of silver cyano complex and characterization its decomposition products by ETA,DSC, DTA and TG

It was found by DTA and TG that [Phenyl₂I][Ag(CN)₂] in the solid state is chemically stable on heating in argon up to 160°C. During heating to higher temperatures it decomposes, forming volatile products such as [Phenyl]I, [Phenyl]NC and (CN)₂ [1]. After heating the sample to 500°C metallic silver resulted. The volatile and intermediate solid products were analysed by IR-spectroscopy.It was found by means of DTA and ETA that an isophase reversible transition takes place when the sample is heated and cooled, not higher than 100°C. At heating higher than 100°C the sample melts (melting pointT _m=135°C). The enthalpy melting was determined by means of DSC (H=–28 kJ·mol^–1).By means of ETA the disorder degree of the final decomposition product was estimated. The value of the activation energy of radon diffusion in the temperature range 720°–500°C equals 32.6 kJ·mol^–1.Dedicated to Prof. I. N. Bekman Moscow State University at the occasion of his 50th birthday     

Synthesis and thermal decomposition of antimony(III) oxide hydroxide nitrate

The thermal decomposition of the only known antimony nitrate antimony(III) oxide hydroxide nitrate Sb₄O₄(OH)₂(NO₃)₂, whose synthesis routes were reviewed and optimized was followed by TG-DTA under an argon flow, from room temperature up to 750°C. Chemical analysis (for hydrogen and nitrogen) performed on samples treated at different temperatures showed that an amorphous oxide hydroxide nitrate appeared first at 175°C, and decomposed into an amorphous oxide nitrate above 500°C. Above 700°C, Sb₆O₁₃ and traces of -Sb₂O₄ crystallized.Author to whom all correspondence should be addressed