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Journal of Thermal Analysis and Calorimetry: An International Forum for Thermal Studies (v.59, #3)

Acknowledgements (pp. 611-612).

Contribution to the Study of the Solid-state Reaction of Mercury With Pure Rhodium by E. Milaré; F. L. Fertonani; A. V. Benedetti; M. Ionashiro (pp. 617-624).
Thermogravimetry (TG) and other analysis techniques (EDX, SEM, Mapping surface, X-ray diffraction, inductively coupled argon plasma emission spectroscopy and atomic spectrometry with cold vapor generation) were used to study the reaction of Hg with Rh. The results permitted the suggestion that, when subjected to heat, an electrodeposited Hg film reacts with Rh to form intermetallic products with different stabilities, as indicated by at least three mass loss steps. In the first step, between room temperature and 160°C, only the bulk Hg is removed. From this temperature up to about 175°C, the mass loss can be attributed to the desorption of a film of metallic Hg. The last step, from 175 to 240°C, can be ascribed to the removal of Hg from a thin dark film of RhHg2 .

Keywords: EDX microanalysis; electrodeposit; mercury; rhodium; SEM; TG

Study of the Crystallization Kinetics. Poly(ethylene oxide) and a blend of poly(ethylene oxide) and poly(bisphenol A-co-epichlorohydrin) by L. E. Cohen; A. M. Rocco (pp. 625-632).
A kinetic study of the crystallization of poly(ethylene oxide) (PEO) and of a blend of PEO+poly(bisphenol A-co-epichlorohydrin) (PBE) was performed by using DSC in a non-isothermal program at constant cooling rates. The curves obtained were analyzed by the Kissinger, Ozawa and Friedman methods, with determination of the kinetic parameters in each case. As a consequence of the presence of PBE, the kinetic parameters were altered, leading to the conclusion that PBE has some influence on the crystallization of PEO, modifying its mechanism.

Keywords: crystallization; non-isothermal kinetics; poly(ethylene oxide)

Kinetic Analysis of the Decomposition of Chelates of Di-alkyldithiocarbamate of Cd(II) by A. Gouveia Souza; M. C. Nóbrega Machado; L. Helker-Carvalho; M. F. Severo Trindade (pp. 633-642).
The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 >Cd(S2 CNPrn 2 )2 >Cd(S2 CNBui 2 )2 >Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.

Keywords: cadmium; dialkyldithiocarbamate; kinetics; thermal decomposition; thermogravimetry

Yeast Intracellular Water Determination by Thermogravimetry by E. B. Alcázar; M. H. M. Rocha-Leăo; J. Dweck (pp. 643-648).
The intracellular water content of a microorganism is an important parameter which is a determinant factor of its physiological properties. It is usually measured by complex and time consuming procedures. Thermogravimetry using infrared balance has been used for this purpose, through the identification of different drying steps occurring during the analysis. This work employs the same method with much smaller samples, using conventional thermogravimetric equipment in a simpler and faster way than other conventional procedures. Commercial yeast (Saccharomyces cerevisiae ) washed samples are analyzed in isothermal procedures which are run in about 30 min. The drying rate curve, when plotted as a function of the residual mass of the cells, allows the identification of the step where the intracellular water is lost and the determination of its content. The obtained values, on extracellular water free basis, are in the range of 65 to 69% and agree with those measured by other techniques.

Keywords: drying; intracellular water; Saccharomyces cerevisiae ; TG

Acid Properties of SiMCM-41 Mesoporous Molecular Sieve by A. S. Araujo; V. J. Fernandes Jr.; S. A. Verissimo (pp. 649-655).
The SiMCM-41 mesoporous molecular sieve was synthesised by the hydrothermal method. The physicochemical characterisation by infrared spectroscopy, X-ray diffraction and thermogravimetry, showed that the material presents a well-defined structure. In this study, the determination of the total acidity and relative strength of the acid sites of the SiMCM-41,was performed by desorption of adsorbed n-butylamine combined with thermogravimetric measurements. The total acidity, determined by means of the amount of amine desorbed normalised by mass of solid, was equivalent to 0.927 mmol g–1, in the temperature range from 96 to 235°C. By using the Flynn and Wall integral kinetic model, at 5, 10 and 20°C min–1 heating rates, it was determined that the activation energy to desorb n-butylamine was 90.7 kJ mol–1, in the same temperature range, evidencing that SiMCM-41 presents only weak acid sites on its surface.

Keywords: acidity; Flynn and Wall model; MCM-41; thermogravimetry

Application of Thermal Analysis in The Characterization of Anti-hypertensive Drugs by R. O. Macêdo; T. Gomes do Nascimento; C. F. Soares Aragăo; A. P. Barreto Gomes (pp. 657-661).
The present work reports studies of the thermal behaviour of some anti-hypertensive drugs. Their purities were determined by DSC and specialized pharmacopeial methods. The activation energy values suggest the following sequence of satability: nifedipine>propanolol hydrochloride>captoril. Analysis of the DSC data indicated that the degrees of purity of nifedipine, captopril and propanolol hydrochloride were similar to those found by pharmacopeial methods BP 93 and USP 23. The simplicity, speed and low operational costs of thermal analysis justify its application in the quality control of pharmaceutical drugs.

Keywords: anti-hypertensive drugs; quality control; thermal analysis

Solid-state Compounds of 4-chloro-benzylidenepyruvate With Lanthanides. Preparation and thermal studies by N. S. Fernandes; M. A. S. Carvalho Filho; C. B. Melios; M. Ionashiro (pp. 663-668).
Solid-state compounds Ln-4Cl-BP, where Ln represents lighter trivalent lanthanides and 4Cl-BP is 4-chlorobenzylidenepyruvate, were prepared. Thermogravimetry, derivative thermogravimetry (TG and DTG), differential scanning calorimetry (DSC) and other methods of analysis were used to characterize and to study the thermal behaviour of these compounds.

Keywords: 4-chlorobenzylidenepyruvate; lighter trivalent lanthanides; thermal behaviour

Preparation and Thermal Decomposition of Solid-state Cinnamates of Lighter Trivalent Lanthanides by M. A. S. Carvalho Filho; N. S. Fernandes; M. I. G. Leles; R. Mendes; M. Ionashiro (pp. 669-674).
Some new compounds of cinnamic acid with lighter trivalent lanthanides were prepared in the solid state. The compounds have general formula ML3 H2 O, where L is cinnamate (C6 H5 –CH=CH–COO ) and M is La, Ce, Pr, Nd or Sm. Thermogravimetry, derivative thermogravimetry, differential scanning calorimetry, infrared absorption spectra and X-ray diffraction powder patterns were used to characterize and to study the thermal stability and thermal decomposition of these compounds.

Keywords: cinnamate; lanthanides; thermal decomposition

Synthesis And Kinetic Analysis of Poly(2,2'-dymethoxy-4,4'-biphenylenevinylene. A novel conducting polymer by A. M. L. Silva; R. W. C. Li; J. R. Matos; J. Gruber (pp. 675-680).
The title polymer was obtained electrochemically by the reduction of 4,4'-bis(dibromomethyl)-2,2'-dimethoxybiphenyl under very smooth conditions. The DSC and TG/DTG curves registered at four different heating rates showed that the polymer is stable in air up to 150°C, where smooth degradation starts. Above 300°C, decomposition is fast and exothermic (ΔH= –323 J g–1) . The activation energy (116±4 kJ mol–1 ) was determined by Ozawa's method.

Keywords: conducting polymer; DSC; kinetic analysis; PPV; TG

Heat Capacities and Thermal Properties of a Homogeneous Ethylene-1-octene Copolymer by Adiabatic Calorimetry by P. J. van Ekeren; L. D. Ionescu; V. B. F. Mathot; J. C. van Miltenburg (pp. 683-697).
Specific heat capacities of a homogeneous ethylene-1-octene copolymer were measured by adiabatic calorimetry in the temperature range from 5 to 400 K (stepwise heating at averaged rates of approximately 1 to 34 K h–1, after cooling at rates in the range from 8 K h–1 to 4 K min–1). The glass transition takes place from roughly 205 to225 K and is centred around approximately 215 K. At the latter temperature, also the temperature drifts during the stabilisation periods are at maximum. Clearly, with devitrification above 215 K also melting sets in. Using two sets of reference data (one for branched and linear polyethylenes, BPE, and the other for strictly linear polyethylene, LPE)for completely crystalline and for completely amorphous material, the crystallinity of the polymer was calculated as a function of temperature, within the two-phase model. In heating, the crystallinity decreased from 0.254 to zero in the temperature range from 220 to 360 K, confirming earlier DSC heat capacity measurements. During the stabilisation periods, below325 K, negative drifts were observed, related to endothermic effects caused by melting. However, in the temperature range from 325 K up to the end melting temperature, 360 K, positive drifts were measured, reflecting exothermic effects. These are attributed to recrystallisation phenomena. The occurrence and amount of recrystallisation depend on the thermal history of the sample: slower cooling and a longer time spent at a temperature of annealing clearly diminish recrystallisation.

Keywords: adiabatic calorimetry; crystallinity; ethylene-1-octene copolymer; heat capacity; recrystallisation; relaxation

Melt Behaviour of Poly(p-xylylene) (PPX) Coated Gel-spun UHMW-PE Fibers As Revealed by Temperature Modulated DSC by U. Göschel; G. W. H. Höhne (pp. 699-709).
The method of temperature modulated DSC has been applied to obtain additional information about the effect of constraints on the melting behaviour of gel-spun ultra high molecular mass polyethylene (UHMW-PE) fibers coated with a high temperature stable poly(p-xylylene) (PPX) polymer. The underlying signal, corresponding to the normal DSC signal, reveals two endothermic peaks for the coated PE fibers. A shift in the underlying and magnitude signal from 142 to 145°C at 0.1 K min–1 , a relative small magnitude signal, together with a vanishing step-like change in the phase signal with increasing PPX coating layer thickness characterize the constraints in terms of a hindrance of the melting of the unconstrained orthorhombic crystal fraction. The time constant of the melting process can be estimated as larger than the reciprocal angular frequency 1/ω=5 s of the modulation.

Keywords: constraints; gel-spun UHMW-PE fibers; hindrance of endothermic transitions; melting behaviour; poly(p-xylylene) (PPX) coating; temperature modulated DSC

DSC and FTIR Analyses of The Curing Behavior of Epoxy/dicy/solvent Systems on Hermetic Specimens by S.-G. Hong; C.-S. Wu (pp. 711-719).
The curing characteristics of adicyandiamide-cured epoxy system under the influence of solvents in a closed environment were studied by means of isothermal differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The DSC analyses revealed that the presence of solvent results in decreases in the curing exotherm, the initial curing rate, the glass transition temperature, the reaction rate and the reaction order of the epoxy resin. The greatest decreases were caused by the solvent with the highest boiling temperature. A change in temperature-dependent curing route due to the heat absorbed during solvent evaporation is responsible for the difference. The FTIR analyses confirmed that the composition of the cured resin is affected by the solvent, the curing temperature and the specimen configuration. As compared with those obtained from open systems, specimens produced in a closed environment have an enhanced curing exotherm, initial curing rate, glass transition temperature, reaction rate and reaction order because of the retention of volatile catalytic by-products.

Keywords: cure; dicyandiamide; DSC; epoxy; hermetic; solvent

Relaxation Transitions in Thermally Treated Polyaniline Films by D. Tsocheva; T. Zlatkov; L. Terlemezyan (pp. 721-727).
Thermally treated films of polyaniline-emeraldine base (PANI-EB) cast from NMP solution were studied by using differential scanning calorimetry. Dependence of the thermodynamic parameters of the relaxation transitions on temperature and annealing period as well as the effect of the thermal history of the samples upon the crosslinking processes were investigated. For the first time DSC analysis of PANI-EB films after prolonged ageing was performed.It was found that relaxation transitions can be registered only for crosslinked PANI-EB. The crosslinking processes proceed both upon short-time heating of the polymer studied over80°C and during long-time storage at room temperature.

Keywords: ageing; annealing; DSC; polyaniline; relaxation transition

Characterization of Silver Flake Lubricants by D. Lu; C. P. Wong (pp. 729-740).
There is a thin layer of organic lubricant on commercial silver (Ag) flakes that are widely used as the fillers in electrically conductive adhesives (ECAs). This lubricant layer highly affects the properties such as conductivity of the ECAs. Therefore, understanding the behavior of Ag flake lubricant layer is essential for developing high performance ECAs. This work is aimed at studying the chemical nature of the lubricant layer, interaction between the lubricant layer and Ag flakes, and thermal behavior of the lubricants during heating. A blank Ag powder is ball-milled into Ag flakes with five fatty acids that have different carbon–hydrogen chain length as lubricants. After lubrication, the Ag flakes are studied using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetry (TG), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). It is found that (i) Ag flakes lubricated with fatty acids of different chain lengths have exothermic DSC peaks and mass losses at different temperatures, (ii) the lubricant layer on the lubricated Ag flake surfaces is a salt formed between the acid and Ag, and (iii) exothermic DSC peaks (in air) of a lubricated Ag flake is probably due to the oxidation of lubricant layer on the Ag flake surface.

Keywords: characterization; fatty acids; interaction; lubricants; silver flakes; thermal behavior

Thermal Degradation of The Poly(m-phenylene Oxadiazole) Molecules in Sulphuric Acid by P. N. Lavrenko; O. V. Okatova; K. A. Andreeva; B. Schulz (pp. 741-746).
Translational diffusion of poly-2,5-(1,3-phenylene)-1,3,4-oxadiazole (PMOD) in solution in 96% sulphuric acid was studied, and intrinsic viscosity was measured at different stages of thermal degradation. Polymer solution has previously been subjected to heating at temperature ranging from 75 to 104°C and then investigated at 26°C. A monotonic decrease in intrinsic viscosity and the molecular mass, M, of degraded products with increasing degradation temperature was detected. The rate constant of the degradation process has been obtained from the change in M of the degradation products with time at a fixed solution temperature, and the activation energy of the process was calculated by using the temperature dependence of the rate constant. The activation energy (E =102±8 kJ–1 ) is close to that obtained previously for the hydrolysis of poly-2,5-(1,4-phenylene)-1,3,4-oxadiazole (PPOD) in sulphuric acid (106 kJ–1 ), the rate constant being approximately twice in the value.

Keywords: activation energy; hydrolytic thermal degradation; poly(meta-phenylene oxadiazole); rate constant

Thermal Dissociation in Dynamic Conditions by Modeling Thermogravimetric Curves Using The Logarithm of Conversion Degree by A. Mianowski (pp. 747-762).
The dependence of conversion degree estimated from the (TG) curve of the mass loss on heating of temperature has been analyzed. It has been shown that dynamic TG curve can be modeled by an equation relating to the logarithm of conversion degree as a function of temperature. A coefficient in the equation developed provides information on the distance from the equilibrium, therefore, the coefficient a 2=0–50 implies equilibrium, while a 2>50 informs about some distance from the equilibrium. Further possibilities for the use of the models of lnα vs. 1/T in the analyses of thermodynamics and kinetics of thermal dissociation of solids has been shown.

Keywords: calcium carbonate; conversion degree; dependence on temperature; equilibrium conversion degree

Kinetic Study on Pyrolysis of Extracted Oil Palm Fiber. Isothermal and non-isothermal conditions by J. Guo; A. C. Lua (pp. 763-774).
Pyrolysis of extracted oil palm fibers under isothermal and non-isothermal conditions was carried out in a thermogravimetric analyzer. Isothermal curves showed that increasing pyrolysis temperature resulted in a faster pyrolysis and a higher conversion of oil palm fibers into gaseous products. Raw material sizes (below 1.0 mm) had insignificant effects on the isothermal pyrolysis, but the fibers with a size fraction of 1.0 to 2.0 mm resulted in a lesser conversion. Two-step reactions were found in the non-isothermal pyrolysis as evidenced by the presence of two peaks in the derivative thermogravimetry curves. Raw material sizes had no obvious effects on the temperature at which the maximum rate of pyrolysis occurred, but affected the rate of sample mass loss. For the low and high temperature regimes, a three-dimensional diffusion mechanism and a first-order of reaction mechanism respectively were used to describe the non-isothermal pyrolysis kinetics of extracted oil palm fibers.

Keywords: extracted oil palm fiber; kinetic parameter; pyrolysis; TG

Thermal Behavior of Galena Ore in Chlorine Atmospheres by M. A. Luengos; E. Ambrosio; A. E. Bohé; D. M. Pasquevich (pp. 775-789).
The thermal behavior of a purified galena in a chlorine surrounding was determined. The kinetic of the chlorination of galena and the stoichiometry of this reaction between 723 to 973 K (450 to 700°C) were measured by thermogravimetry. The microstructural characterization of the solid residues were determined by SEM, EDXS and XRD. The ΔH vap of the produced lead chloride volatilization was obtained by the application of Clausius-Clapeyron equation considering the process in an equilibrium state.

Keywords: galena ore; kinetic of the chlorination

Synthesis, Characterization and Thermal Decomposition of M1[M2(C2O4)2]xH2O (x=5 for M1=Co and x=4 for M1=Cd; M2=Ni) by N. Deb; S. D. Baruah; N. N. Dass (pp. 791-797).
Cobalt bis(oxalato)nickelate pentahydrate, Co[Ni(C2O4)2]5H2O and cadmium bis(oxalato)nickelate tetrahydrate, Cd[Ni(C2O4)2]4H2O have been synthesized and characterized by elemental analysis, reflectance and IR spectral studies. Thermal decomposition studies (TG, DTG and DTA ) in air showed that both the compound of cobalt and cadmium produced the oxide, MNiOx (x=3 for M=Co; x=2 for M=Cd ) at 325 and 360°C respectively. DSC studies in nitrogen attributed only the mixture of both the metal at the end.

Keywords: IR; oxalato complexes; thermal decomposition

Spectral and Thermal Studies of Rare Earth Complexes With 2,4,6-trimethylbenzoic Acid by W. Brzyska (pp. 799-806).
The rare earth element 2,4,6-trimethylbenzoates were prepared as solids with the general formula Ln(C10 H11 O2 )3 ×n H2 O, where n =2 for Ln =Y, La–Nd, and n =1 for Ln =Sm–Lu. The IR spectra of the complexes prepared were recorded and their solubilities in water and thermal decomposition in the air were investigated. During heating the hydrated complexes lose all the crystallization water molecules in one (Y, Ce–Lu) or two steps (La) and then the anhydrous complexes decompose either directly to oxides (Y, Ce, Pr, Sm–Lu) or with intermediate formation oxocarbonates Ln2 O2 CO3 (La, Nd). The carboxylate groups in the complexes prepared act probably as mono- and bidentate.

Keywords: DTA; IR; rare earth complexes; 2,4,6-trimethylbenzoates

Kinetic and Thermodynamic Studies of Facial and Meridional uns-cis-[Co(eddp)gly] Complexes by N. Petranović; D. Minić; T. J. Sabo; D. Doković (pp. 807-814).
Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed.

Keywords: facial and meridional Co(III) complexes; kinetics; thermodynamics

Synthesis, Characterization and Thermal Studies of Some Iron(III) Complexes of o-Vanillin Oxime by M. R. P. Kurup; E. Lukose; K. Muraleedharan (pp. 815-825).
Iron(III) complexes of o-vanillin oxime have been synthesized and characterized by different physicochemical techniques. The complexes containing thiocyanate, iodide and sulphate ionshave been subjected to non-isothermal decomposition studies in N2 using TGand DTG techniques. The kinetic parameters for both stages of decomposition of these complexes were evaluated by weighted least-squares method using the general approach as well as the Coats–Redfern and Horowitz–Metzger equations. The results indicate that the values of kinetic parameters obtained by these three different approaches agree well.

Keywords: iron(III) complex; kinetic parameters; non-isothermal decomposition; o-vanillin oxime

Synthese Basse Temperature Du Gallate De Zinc by C. Beauger; P. Grosseau; B. Guilhot; D. Huguenin; P. Iacconi (pp. 827-835).
The dependence of the firing conditions on the crystal structure formation of ZnGa2 O4 has been investigated. The effects of temperature and atmosphere were examined and gave evidence of the instability of the zinc gallate under a reducing atmosphere at temperatures above 600°C. A new preparation route has allowed to synthesize ZnGa2 O4 at low-temperature, right from 300°C, avoiding the decomposition of the matrix during the annealing.

Keywords: DTA; synthesis route; zinc gallate

The Effects of γ-Irradiation on the Electrokinetic and Thermal Behaviour of Zirconium Hydroxide by S. Musić; G. Štefanić; N. Vdović; A. Sekulić (pp. 837-846).
Zirconium hydroxide particles produced by rapid precipitation at pH 10.4, 7 or 2 were subjected toγ-irradiation up to a final dose of 20 MGy. The effects of the γ-irradiation were examined by X-ray powder diffraction, laser Raman spectroscopy, differential scanning calorimetry and microelectrophoretic measurements. It was found that γ-irradiation had no influence on the behaviour of zirconium hydroxide during calcination and subsequent cooling. The results of microelectrophoretic measurements showed that γ-irradiation influences the surface properties of zirconium hydroxide as a function of the precipitation pH. Zirconium hydroxide precipitated at pH 2 proved to be the most susceptible to γ-irradiation, while the sameγ-irradiation had very little (if any) effect on the surface properties of zirconium hydroxide precipitated at pH 10.5. After γ-irradiation, the electrophoretic mobility of zirconium hydroxide precipitated at pH 2 was increased at both low and high pH, thereby indicating an increase in its adsorption capacity. The analogy observed between the pH-dependence of the effects of γ-irradiation on the electrokinetic behaviour of zirconium hydroxide and the influence of ball-milling on the thermal behaviour of zirconium hydroxide [8] suggested that the susceptibility of amorphous zirconium hydroxide increases with decrease of the precipitation pH.

Keywords: DSC; γ-irradiation; laser Raman; microelectrophoresis; XRD; zeta-potential; zirconium hydroxide; ZrO2

Modeling of the DTG Curves for Oxidation of a Nanosized Molybdenum Ferrite Coupling Mechanics and Diffusion by V. Nivoix; P. Perriat; B. Gillot (pp. 847-858).
From a model for isothermal oxidation kinetics in nanosized ferrite spinels based on a diffusion-induced stress effect, the authors present a modeling of the DTG curves for the oxidation of Fe2+ and Mo3+ cations on octahedral sites of a molybdenum ferrite. This has been made by considering that the chemical diffusion coefficient is given by the relation $$ ilde D = D_o exp left( {frac{{E'_{ ext{a}} + pV_{ ext{a}} }}{{RT}}} ight)$$ , when D o is a pre-exponential factor, E a an activation energy and V a an activation energy induced by the oxidation.

Keywords: derivative thermogravimetry; diffusion-induced stress; modeling; molybdenum ferrite; oxidation kinetics

Synthesis, Characterization and Thermal Decomposition of the Pyridine Adducts of Co, Ni, Cu and Zn Sulfate by V. Jordanovska; P. Naumov; B. Boyanov; R. Trojko (pp. 859-868).
Pyridine adducts of Co, Ni, Cu and Zn sulfate were obtained by refluxing the corresponding sulfate with pyridine in chloroform. The compounds were characterized by elemental analysis, X-ray powder diffraction and FTIR spectroscopy. The thermal decompositions (TG/DTG/DTA) of the complexes in the interval 20–1000°C were also studied.The elemental and thermal analysis results revealed that the formulae of the complexes are M2(SO4)2 xC5H5NyH2O, where x=2, 3, 2 and 1 and y=6, 4, 6 and 4 for the Co, Ni, Cu and Zn compound, respectively. The complexes were not found to be isostructural, but certain structural similarities were observed between the Zn and Co compounds. Although the thermal decomposition pathways of the various compounds were quite different and each consisted of several steps, in all cases the dehydration preceded the depyridination. Metal oxide was always obtained as final product.The spectral data are discussed with regard to the thermal behaviour. Appreciably stronghydrogen-bonding and pronounced structural differences relating to the sulfate ions were presumed for the Cu compound.

Keywords: M(II) sulfates; pyridine adducts; thermal decomposition

Kinetics of Thermal Decomposition of Plumbo-jarosite by M. Ózacar; A. Alp; A. O. Aydin (pp. 869-875).
An investigation was carried out on the kinetics of thermal decomposition of plumbo-jarosite. The kinetic models of dissociation of the compounds in the ore were identified. The results of the kinetic studies and the mechanism of the process are discussed. The thermal decomposition of plumbo-jarosite occurs in three stages: the first up to 763, the second up to 1023 and the third up to 1223 K, the corresponding activation energy values being 62.2, 60.3 and 98.0 kJ mol–1 , respectively.

Keywords: decomposition; kinetics; plumbo-jarosite

Effect of Copper on Thermomechanical Characteristics of Amorphous AsSeyIz by F. Skuban; D. M. Petrović; S. R. Lukić; M. M. Garić; I. O. Gúth (pp. 877-883).
The paper describes results of a study of glasses of the type Cux (AsSe1.4 I0.2 )100–x for x =0, l, 5, 10, 15, 20 and 25 at% Cu, by the methods of thermomechanical analysis. Values of the thermal coefficients of linear expansion in solid and visco-plastic phase were determined and the dependence of this parameter on copper concentration was established. The experimental method used enabled the determination of characteristics glass transition temperature and the temperature of the beginning of deformation, and it was found that these parameters increase with increase in the copper content.

Keywords: amorphous chalcogenides; glass transition temperature; temperature of beginning of deformation; thermal coefficient of linear expansion

Solid–liquid Equilibria in the Quaternary System Na+, Mg2+//Cl–, SO2–4–H2O at 25 and 30°C by L. Zayani; R. Rokbani (pp. 885-892).
The isoplethic sections in the diagram of the quaternary system Na+ , Mg2+ //Cl , SO2– 4 –H2 O were established at 25 and 30oC by analytical and conductometric measurements. Three compounds can be observed in the isoplethic sections: NaCl, Na2 SO4 and MgNa2 (SO4 )2 4 H2 O. Seven fields are determined, relating to the precipitation of one, two or three salts. The solubility range of MgNa2 (SO4 )2 4 H2 O is wide, while the liquidus curve of Na2 SO4 is very short. The compositions, expressed in Jänecke coordinates, at the eutonic and peritonic points, respectively, were:42.70% Cl and 745% H2 O; 79.47% Cl and 787% H2 O; 71.6% Cl and 744% H2 O at 25°C; and 48.80% Cl and 715% H2 O; 80.20% Cl and 778% H2 O; 70.14% Cl and 707% H2 O at 30°C.

Keywords: brine; sea water; sodium sulphate; solubility diagram; quaternary system

Diagramme Polythermique Du Systeme Ternaire KCl–FeCl2–H2O Entre 0 Et 70°C by A. Atbir; L. Aneflous; A. Marrouche; M. El Hadek; R. Cohen-Adad; M.-Th. Cohen-Adad (pp. 893-900).
Polytherm diagram of the ternary system KCl–FeCl2 –H2 O between 0 and 70°C. Phase equilibria in the KCl–FeCl2 –H2 O system were studied over the temperature range 0–70°C by conductimetric and analytical methods.A solubility polytherm of the system was constructed. We have observed the crystallization fields of the KCl and FeCl2 6H2 O (at 0°C), KCl and FeCl2 4H2 O (at 15, 30 and 40°C) and KCl, FeCl2 4H2 O and of a double salt KClFeCl2 2H2 O are obtained at 70°C.

Keywords: FeCl2 ; phase diagram; potassium chloride; ternary system

The Decomposition of Hydrogen Peroxide. A non-linear dynamic model by B. Khoumeri; N. Balbi; E. Leoni; N. Chiaramonti; J. H. Balbi (pp. 901-911).
All thermal systems are subject to problems of thermal regulation. These can be understood through the use of thermochemical systems, in particular for those in the liquid phase. A dynamic linear model was earlier applied to obtain both the reaction enthalpy and the rate constant at constant temperature for the catalytic decomposition of hydrogen peroxide. This first model did not yield a good fitting between the calculated and experimental data. The hypothesis that the rate constant was independent of temperature was too strong.In the present study, a more elaborate, non-linear model was developed, which takes into account the rate constant variations as a function of temperature (Arrhenius law). This model allowed the activation energy to be determined. The calculated data then successfully fitted the experimental data. The literature indicates that the first-order rate law is not valid for a certain range of concentrations; the present model verified this.The results of dynamic modelling confirm and increase the precision of results obtained in different ways. The developed model is validated through these comparisons.

Keywords: dynamic modelling; hydrogen peroxide; kinetic; thermodynamic

Thermodynamic Parameters of Some Schiff Bases Derived From 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one by O. E. Sherif; Y. M. Issa; S. M. Abbas (pp. 913-926).
Potentiometric studies on Schiff bases derived from5,7-dihydroxy-6-formyl-2-methylbenzopyran- 4-one were carried out at different ionic strengths (0.02, 0.04, 0.06, 0.10 and 0.14 M NaCl), at different temperatures (25, 35, 45 and55°C) and in ethanol-water media of varying compositions (60, 70, 80 and 90% v/v). The ionization constants of the Schiff bases were investigated in the presence of different organic solvents (70% v/v), e.g. methanol, ethanol, n-propanol, isopropanol, acetone, DMSO and DMF-water media. The thermodynamic parameters (ΔG, ΔH and ΔS) were also calculated.

Keywords: benzopyran-4-one; chromone; ionic strength; potentiometry; Schiff bases; temperature and solvent

Reactions Invariantes Induisant La Densification Des Varistances ZnO by N. Achard; J. J. Counioux; G. Marichy; A. Marchand (pp. 927-934).
The electrical properties of ZnO varistors are induced by a sintering step. The phenomena occurring during this thermal treatment have been studied through model systems whose nature and composition are well defined. The pure BiSbO4 and Bi3 Zn2 Sb3 O14 phases have been synthetised by Direct Oxidation of a Precursory Alloy (DOPA) and characterized using XRD method. Each one of these phases can react with zinc monoxide through an invariant isobaric reaction in the ZnO–Bi2 O3 –Sb2 O3 system:– at 998°C 17/3+2/33 Zn2 Sb3 O14 > arrow 7 Sb2 O12 > + ((Bi2 O3 ))– at 1058°C 7+24 > arrow 7 Sb2 O12 >+((Bi2 O3 ))These thermodynamic considerations can explain the thermal domain of the sintering reaction described in the literature.

Keywords: binary and ternary oxides; DOPA; sintering reaction; ZnO varistors

Study of The Mechanism and Kinetic Parameters of The Thermal Decomposition of Cobalt Sulphate Hexahydrate by J. Straszko; M. Olszak-Humienik; J. Możejko (pp. 935-942).
Thermogravimetry (TG-DTG), and differential thermal analysis (DTA) were used in the study of the kinetics of decomposition of cobalt sulphate hexahydrate under an air atmosphere.The kinetics of the particular stages of CoSO4 6H2 O decomposition were evaluated from the dynamic mass loss data. The values of the kinetic parameters for each stage of the thermal decomposition were calculated from the α(T) data by using the integral method, applying the Coats-Redfern approximation.

Keywords: CoSO46H2O; kinetics; thermal decomposition

Vacancy Contents in MnZn Ferrites From TG Curves by O. E. Ayala; D. Lardizábal; A. Reyes; M. I. Rosales; J. A. Matutes; A. González Arias (pp. 943-949).
Expressions for calculating the cation vacancy contents of MnZn ferrites from thermogravimetric curves are presented together with some experimental data. In a single-phase MnZn ferrite synthesized by conventional ceramic procedures, the O2 evolution accompanying ferrite formation follows the formal equation.Mn2+ σα Znσβ Fe3+ 2σ(1–γ) [V ]σ/4(1–2γ) O4 =σ'/σ Mn2+ σ(α–2ϕ) Znσβ Fe2+ 2σθ Mn3+ 2σϕ Fe3+ 2σ(1–γ–θ) [V ]σ/4(1–2γ–3ϕ) O4 +σ'φ/2O2 (g)where α and β denote the MnO and ZnO mole fractions in the primary mixture γ=α+β, θ and ϕ depend on the quantities of Fe2+ and Mn3+ formed, respectively, φ=θ–ϕ and σ'/σ is a function of the former parameters. Even though the relative amounts of Fe2+ /Fe3+ and Mn2+ /Mn3+ remain uncertain, the vacancy content [V ] of the ferrite can be determined because it depends on φ alone, which is related to the change in mass of the sample as the synthesis takes place through the equationφ=(1.5–γ) µβO2 (1–m f /m i )Here, m i and m f are the masses of the sample before and after O2 evolution, µB is the formula mass of the ferrite and µO2 is the O2 molar mass. Practically vacancy-free single-phase MnZn ferrite samples were obtained by sintering in air at 1250°C and cooling in pure N2 .

Keywords: MnZn ferrite; TG

Complex Formation Between Erythritol and 4-hexylresorcinol by L. M. Zhou; J. Sirithunyalug; E. Yonemochi; T. Oguchi; K. Yamamoto (pp. 951-960).
The interaction between erythritol and 4-hexylresorcinol during heating was investigated by thermal analysis, powder X-ray diffractometry and infrared spectroscopy. A phase diagram was constructed by measuring the thermal behaviour of various resolidified physical mixtures of erythritol and 4-hexylresorcinol. The phase diagram revealed complex formation between erythritol and 4-hexylresorcinol with incongruent melting at 84°C; the stoichiometry was a molar raio of 1:2 erythritol:4-hexylresorcinol. The complex gave diffraction peaks at 2θ=5.6° and 11.2° in the X-ray powder diffraction pattern. In the infrared spectrum, a new peak due to the complex was observed at 3504 cm–1. The complex prepared by grinding and evaporation had the same molecular arrangement as the complex prepared by sealed heating.

Keywords: complex formation; erythritol; 4-hexylresorcinol; incongruent melting point; phase diagram

Thermal Decompositions of Pure and Mixed Manganese Carbonate and Ammonium Molybdate Tetrahydrate by W. M. Shaheen; M. M. Selim (pp. 961-970).
The thermal decompositions of pure and mixed manganese carbonate and ammonium molybdate tetrahydrate in molar ratios of 3:1, 1:1 and1:3 were studied by DTA and TG techniques. The prepared mixed solid samples were calcined in air at 500, 750 or 1000°C and then investigated by means of an XRD technique. The results revealed that manganese carbonate decomposed in the range 300–1000°C, within termediate formation of MnO2, Mn2O3 andMn3O4. Ammonium molybdate tetrahydrate first lost its water of crystallization on heating, and then decomposed, yielding water and ammonia. At 340°C,MoO3 was the final product, which melts at 790°C. The thermal treatment of the mixed solids at 500, 750 or 1000°C led to solid-solid interactions between the produced oxides, with the formation of manganese molybdate. At 1000°C, Mn2O3 and MoO3 were detected, due to the mutual stabilization effect of these oxides at this temperature.

Keywords: solid–solid interactions; thermal decomposition; transition metal oxides

Thermal Properties of Polycrystalline ZnIn2Se4 by L. I. Soliman; M. H. Wasfi; T. A. Hendia (pp. 971-976).
A pulse method was used to measure the thermal conductivity, specific heat capacity C p and thermal diffusivityξ of polycrystalline ZnIn2Se4 in the temperature range 300–600 K. The temperature dependence of λ, C p and ξ demonstrated a light decrease for this material in the temperature range 300–600 K, indicating that there is not a significant change in the structure in this temperature range; this was confirmed by DTA measurements. The results showed that the mechanism of heat transfer is due mainly to phonons; the contributions of electrons and dipoles are very small.

Keywords: heat capacity; polycrystalline ZnIn2Se4 ; thermal conductivity; thermal diffusivity

Thermal Stability and Non-isothermal Decomposition Kinetics. Heteropolynuclear compounds of Cu(II) by M. Badea; R. Olar; E. Cristurean; D. Marinescu; M. Brezeanu; C. Calina-Soradi; E. Segal (pp. 977-984).
Data concerning the thermal behaviour of four heteropolynuclear compounds with the general formula [CuML(CH3COO)3] whereM=Ni(II), Zn(II), Mn(II) and Co(II); LH=2-amino-5-mercapto-1,2,3-thiadiazole were obtained. For the kinetically workable decomposition steps the values of the kinetic parameters were estimated.

Keywords: coordination compounds; non-isothermal kinetics; thermal stability

New Microthermogravimetric Apparatus. Kinetics of metal sulphidation and transport properties of transition metal sulphides by Z. Grzesik; S. Mrowec; T. Walec; J. Dabek (pp. 985-997).
A novel microthermogravimetric apparatus to study the kinetics of metal sulphur reactions and transport properties of transition metal sulphides has been described. The main feature of this arrangement includes the application of the carrier gas for sulphur vapour transportation and the protection of the balance chamber from sulphur attack. As a consequence, the helix balance could have been replaced by an automatic electronic microbalance and the accuracy of the mass change measurements increased more than two orders of magnitude, up to 10–7 g. The application of two liquid sulphur reservoirs created very stable, strictly defined reaction conditions, and enabled to make rapid changes of sulphur partial pressure in the reaction chamber. It has been demonstrated that all these innovations make it possible to study not only the kinetics of very slow sulphidation processes but also to determine deviations from stoichiometry and defect mobility in transition metal sulphides.

Keywords: chemical diffusion; microthermogravimetric apparatus; Mn1–yS

A New Software to Show the Behaviour of the PID Controller. Influence of the setting parameters of DSCs. Part I by D. Brunel; L. Elegant (pp. 999-1015).
Some DSC calorimeters such as the model Setaram DSC 111 allow the user to set the parameters of temperature programming. Default values furnished by the constructor are often used, but it is very interesting to study the thermal behaviour of the regulation of the calorimeter under different conditions and kinds of set point temperatures.For this research we have developed in C a set of softwares in order to show the behaviour of the proportional integral derivative (PID) controller of the DSC. It can help the user to choose correct values for P, I and D parameters according to the kind of experiment conducted. The software allows studies for extra parameters such as the sampling rate of the computerized PID controller or the determination of filtering of the correction.

Keywords: DSC; PID controllers; tuning PID parameters

Thermal Properties of Mechanochemically Pretreated Precursors of BaTiO3 Synthesis by P. Baláž; B. Plešingerová (pp. 1017-1021).
The changes of physico-chemical properties of mechanochemically pretreated (BaCO3 +TiO2 +PbO) powders were investigated. The values of apparent activation energy of BaTiO3 formation calculated by the Freeman and Carroll method decrease with milling time. The changes of precursors density may be interpreted as a consequence of mechanochemical reactions during milling.

Keywords: barium titanate; density; DTA; mechanochemistry; TG

Thermal Measurements on Poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] Fibers by J. D. Menczel (pp. 1023-1027).
Fibers drawn form poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI) were studied by DSC and DMA. PBI is a high temperature polymer T g is between 387 and450°C depending on the measurement technique used. The as-spun fiber is free of orientation. The oriented fiber exhibits considerable dependence on whether the DSC measurements were carried out in free-to-shrink or fixed-length modes. The β-relaxation is at 290°C, and was associated with loss of water. The γ-transition at 20°C was not identified, while theδ-transition at –90°C seems to correspond to rotation of the m-phenylene ring.

Keywords: DMA; DSC; fibers; polybenzimidazole; secondary transitions

Obituary (pp. 1029-1030).
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