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5631 articles

A0296 – Comportement thermique du difluorodioxophosphate ferreux

Difluorodioxophosphates may be used as ceramic phosphate precursor, and their thermal behaviours are very important. In this paper we study by TG and DTA the thermal stability for iron(II) salt. In argon atmosphere, we obtain in a first time the melting of salt at 240°C then the classical breaking up into solid orthophosphate and POF3 exhaust. If the sample of iron(ll) difluorodioxophosphate is heating in air, we do not obtain the melting phenomena, but at the same temperature an exothermic phenomenon that conducts to the formation of iron(Ill). We observe a mass increase. By IR analysis, we can show that this oxidation is obtained without change of difluorodioxophosphate structure.
P. Vast, A. Semmoud, Journal of Thermal Analysis 41 (1994) 1489-1493

A0297 – Cationic distribution and mechanism of the oxidation of V3+ ions in vanadium-substituted magnetites

The thermal behavior in oxygen of Fe(3-x)VxO4 spinels (0 < x < 1) prepared by the ceramic method has been investigated over the temperature range 150-650°C by thermogravimetry and infrared spectroscopy. Below 500°C, iron vanadium spinels are partly oxidized in cation-deficient spinels with a large content of vacancies. A quantitative analysis based on the difference in the reactivity of iron and vanadium in relation to the site occupied (octahedral B site or tetrahedral A site) permits a cation distribution between the sub-lattices to be proposed. Kinetic studies of the oxidation process of V3+ ions at the B sites show that the oxidation reaction is controlled by cation diffusion in a cation-deficient spinel phase of variable composition, with a chemical diffusion coefficient dependent on the vacancy content delta and written: = K0 exp(-Ea/RT) exp( The b constant depends on the temperature. The energy of defect dissociation has been determined.
M. Nohair, P. Perriat, B. Domenichini and B. Gillot, Thermochimica Acta 244 (1994) 223-234

A0300 – Preparation of In- and Ga-modified SAPO materials via a solid state reaction

Ya. Neinska, Ch. Minchev, R. Dimitrova, N. Micheva, V. Minkov, V. Kanazirev, Studies in Surface Science and Catalysis 84 : Zeolites and related microporous materials : State of the art (1994) 989-996

A0299 – Thermal behaviour of graphite intercalation compounds with oxide of difluoride of phosphoryl

We present in this paper the thermal analysis (calorimetry, TG and DSC) of the first stage P2O3F4 graphite intercalate compound in atmospheric pressure and high pressure. By heating we obtain always exfoliation phenomenon. The heating of exfoliated graphite shows an important oxidation resistance in comparison with another exfoliated graphite. This oxidation resistance has been studied also by thermal analysis like TG, in oxygen atmosphere. Carbon foil rebuilding from exfolied graphite keeps these interesting antioxidation properties.
P. Vast, Journal of Thermal Analysis 41 (1994) 1433-1439

A0298 – Carbon from phenolic resins : carbon yield and volatile components – recent studies

On a déterminé le rendement en carbone lors de la pyrolyse de résines phénoliques, avec ou sans oxygène, par comparaison avec les résines furanniques. L'identification des constituants volatils libérés lors de la pyrolyse ne peut se faire qu'à partir d'essais spécifiques. On montre que ces sous-produits de pyrolyse ne sont pas complexes et ont peu tendance à former des hydrocarbures polycycliques. Le rendement en carbone et la qualité dépendent du type de résine pyrolysé, de son taux de réticulation, de l'atmosphère de traitement et de la présence d'éléments en traces.
A. Gardziella, J. Suren, M. Belsue, Interceram. 41 (1992) 461-467

A0303 – The possibility of identification of activation energy by means of the temperature criterion

The influence of the selection of the f(alpha) function, which represents the reaction/process mechanism, on the values of the resulting kinetic parameters is discussed. It has been found that the solutions, in the form of the Arrhenius equation constants, show an isokinetic effect over a wide range of temperature. A special relationship between alpha (degree of conversion), E and T holds for low values of degree of conversion.
A. Mianowski and T. Radko, Thermochimica Acta 247 (1994) 389-405

A0302 – New complexes of copper cinnamates and imidazole or substituted imidazole

We have prepared five new organo-metallic complexes of imidazoles and a dicarboxylate, copper cinnamate, which may be considered as extremely simple models of the active centres in most biocatalysts. The thermal behaviour of the complexes was studied. Using ESR and diffuse reflectance spectra, monomeric or dimeric species were detected.
A. Busnot, F. Busnot, J.F. Hemidy and J.F. Le Querler, Thermochimica Acta 228 (1993) 219-230

A0304 – Formation mechanism of the Bi(2223) phase in Ag-sheathed tapes

J-C. Grivel, A. Jeremie, B. Hensel, R. Flükiger, ICMAS (1993) 359-361

A0305 – Effects of Pb in the first stages of the Bi(2223) phase formation

The reaction of the precursor powders necessary for the formation of the final Bi(2223) phase was investigated with and without the presence of an Ag sheath by means of differential thermogravimetry (DTA/DTG). The nature of the endothermic peaks observed by DTA as well as the influence of Ag on their positions are discussed. By means of X-ray diffraction and energy dispersive X-ray analysis (EDX) on oil-quenched Ag-sheathed tapes it is shown that the Bi(2212) phase originally present in the precursor powders undergoes a structural modification which can be associated with the dissolution of Pb. This transformation occurs at a temperature near 836 degrees C in Ag-sheathed tapes. This work has been essentially focused on the role of Pb and its effects on the Bi(2212) phase in the first stages of transformation.
J-C. Grivel, A. Jeremie, B. Hensel, R. Flükiger, Superconductor Science and Technology 6 (1993) 725-729

A0306 – Thermal decomposition of co-precipitated oxide hydrates of zirconium and manganese

The thermal decomposition of mixed Zr---Mn oxide hydrates containing 0-0.3 mol of manganese was examined by means of simultaneous TG and DTA. When heated, these mixed hydroxides decompose to an amorphous oxide phase and subsequently crystallize to a cubic phase. These changes are accompanied by a broad endothermic peak at around 165-180°C and an exothermic peak between 450 and 700°C. The temperature at which the crystallization occurs depends on the manganese content. A linear increase was observed between manganese content and crystallization (exothermic peak) temperature. The enthalpy of crystallization, however, showed a decreasing trend (from 28.7 to 12.1 kJ mol-1) with increasing manganese content within this range. Since no amorphous manganese oxide was formed when manganese oxide hydrate alone was heated, it is apparent that optimum concentrations of manganese (0.1-0.3 mol) in amorphous zirconia decrease the enthalpy of crystallization, thereby stabilizing zirconia in the cubic phase at low temperatures.
A. Keshavaraja, N.E. Jacob, A.V. Ramaswamy, Thermochimica Acta 254 (1995) 267-275

A0308 – Thermal analysis of montmorillonite-aminotriazole interactions

In the present investigation, DTA and TG techniques were used to study the thermal behaviour of montmorillonite treated with solutions of the pesticide aminotriazole (AMT), in nitrogen flow. These techniques have been complemented by mass spectrometry of the evolved gases (EGA-MS). AMT is adsorbed in the interlamellar space of montmorillonite as a cation. Results obtained in this study show that this provokes a shift of the dehydroxylation peak of montmorillonite to lower temperatures than those of the untreated clay. Montmorillonite protects the adsorbed AMT, delaying its first decomposition step, and catalyseS AMT final decomposition at lower temperatures. The DTA curve of montmorillonite-AMT mechanical mixture differs from the sum of those of the clay mineral and the pesticide heated individually. Montmorillonite dehydroxylation occurs at lower temperature, indicating a complex formation between AMT and the mineral during the heating process.
E. Morillo, J.L. Pérez-Rodriguez, C. Real, P.J. Sanchez-Soto, Journal of Thermal Analysis 44 (1995) 313-327

A0307 – Sulfation of dolomite particles at high CO2 partial pressures

The sulfation reaction of half-calcined dolomite particles at high CO2 partial pressures (around 1 bar) was investigated. The experiments were carried out in two different reactors: (a) a thermogravimetric analysis system (slow heating rates) and (b) a shock-microreactor (rapid heating rates). The experiments were carried out under isothermal conditions at temperatures between 650 and 875°C. A natural dolomite sample was used. Different particle sizes were tested: 26, 128, 256 and 512 µm. Under reaction conditions employed in the experiments (PCO2 ~ 1 atm and T < 900°C), half-calcination of dolomite particles takes place and the sulfation reaction occurs between CaCO3 . MgO and SO2. The CaCO3 is the only active species during sulfation. The particle size and temperature have a strong influence on the variation in extent of conversion with time. Two different stages can be distinguished in the sulfation of half-calcined dolomite particles; chemical control at the onset of reaction and diffusional control at longer reaction times. When the sulfation reaction is carried out under conditions similar to those existing in a boiler (high heating rates and simultaneous calcination and sulfation), the measured reaction rates are higher than those observed from thermogravimetric experiments. At X = 0.1 an activation energy of 34 kcal mol-1 (142 kJ mol-1) was measured. This value suggests that the process is controlled by a solid state diffusion mechanism.
A. Fuertes, G. Velasco, T. Alvarez, M.J. Fernandez, Thermochimica Acta 254 (1995) 63-78

A0310 – Thermogravimetric studies of oxygen stoichiometry and oxygen transport kinetics in La(1-x)Sr(x)MnO(3+d)

J. Kjaer, I.G. Krogh Andersen, N. Mogensen, E. Skou, H. Boye, 14th Riso International Symposium on Materials Science (1993) 281-286

A0309 – Studies on the thermal decomposition of dipotassium trans-diaquabis(oxalato-O,O’)nickelate(II) tetrahydrate

The thermal behaviour of the compound K2[Ni(C2O4)2(H2O)2].4H2O has been studied by thermogravimetry and differential thermal analysis. Experiments were carried out in dynamic atmospheres of argon-oxygen and argon, respectively, over the temperature range 20-600°C.Thermoanalytical data show that the surrounding atmosphere significantly influences the dehydration process as well as the final products. In the oxidative atmosphere, the six water molecules are released during two almost overlapping endothermic steps, whereas in the inert atmosphere, the free water molecules and the coordinated ones are lost in separate stages. In both cases, dipotassium carbonate has been found as the final product, together with NiO in the oxidative environment and metallic nickel in the inert atmosphere.
P. Roman, C. Guzman-Miralles, A. Luque, M.L. Seco, Thermochimica Acta 257 (1995) 67-73

A0313 – Comportement thermique de quelques végétaux méditerranéens

Thermal analysis can be used for the study of the behaviour of plants during heating, and most particularly in the risk prevention of forest fire. Simultaneous thermal analysis (DTA-TG) of some mediterranean vegetals (needles of Pinus halepensis, leaves of Quereus eoeeifera; leaves of Rosmarinus offieinalis; prickles, flowers and branehs of Ulex parviflorus; leaves and branehs of Acacia dealbata; leaves of Cistus albidus) shows the presence of several exotherrnie peaks. The first one, about 300°C is responsible for a brutal ignition of the evolved gas. We compare the different samples by using the DTA and DTG peak temperatures and the weight loss by volatilization at 300°C
J. Kaloustian, A.M. Pauli, J. Pastor, JCAT (1995) 70-75

A0312 – Identification par analyse thermique de quelques excipients pharmaceutiques

J. Kaloustian, A.M. Pauli, J. Pastor, JEEP (1995) 248-251

A0311 – On the low- and high-temperature interactions of ammonia with AlPO5

Results are presented on the low-temperature interaction of ammonia with A1PO-5, the TPD of the adsorbed ammonia and the high-temperature interaction of ammonia with the A1PO-5 framework.
E. Segal, I. Iranova, E.G. Derouane, Journal of Thermal Analysis 44 (1995) 1079-1085

A0315 – Décomposition thermique des grignons d’olive. Influence des différents paramètres

A. Bacaoui, A. Dahbi, C. Bennouna, A. Yaacoubi, 26th vacuum technique 38-43

A0314 – Etude par thremogravimétrie du comportement vis-à-vis de l’oxygène de quelques oxydes à base de manganèse de structure spinelle : CoMnxFe2-xO4 (0

M. Laarj, S. Kacim, B. Gillot, P. Tailhades, T. Battault, R. Legros, A. Rousset, 26th vacuum technique 183-188

A0318 – Synthèse, cristallochimie et comportement thermique de VOPO4,2H2O,NbOPO4,3H2O et (Nb1-xVx)OPO4,nH2O

A. Benardia, A. Legrouri, A. Barroug, M.E. De Roy, J.P. Besse, 26th vacuum technique 76-79

A0317 – Caractérisation par analyse thermique de l’eau dans des coacervats et gels à base de polyphosphates

F. Gomez, P. Vast, A.M. Bera, F. Barbieux, Ph. Llewellyn, F. Rouquerol, T. Miyajima, JCAT (1995) 357-362

A0316 – Bismuth and mixed bismuth-lanthanide carboxylates as precursors for pure and Ln-promoted bismuth molybdate catalysts

Several bismuth(III) carboxylates (formate, acetate, propionate, oxalate, lactate) and the analogous tervalent lanthanum, samarium and praseodymium formates and acetates were synthesized and characterized in view of their use as precursors for the formation of bismuth- or lanthanide-based molybdate catalysts upon controlled thermal decomposition on MoO3 support. Mixed Bi-Ln carboxylates were prepared and used in parallel as precursors for Ln-promoted bismuth molybdate catalysts. Both the nature of the lanthanide element and the calcination temperature were found to determine the formation of specific molybdate-type phases on the support. Detailed examination of these catalysts by X-ray diffraction and FTIR spectroscopy identified alpha-M2Mo3O12 phases in Bi- and Pr-containing samples calcined at 823 K, and hexamolybdate phases M2Mo6O21 in La- or Sm-containing catalysts calcined at 973 K.
M. Devillers, F. De Smet, O. Tirions, Thermochimica Acta 260 (1995) 165-185

A0320 – An automatic micro-gravimetric water sorption apparatus

A. Raoof, J-P. Guilbaud, A. Dupas, N.L. Tran, 26th vacuum technique 207-218

A0319 – Influence de la pression d’oxygène sur les phénomènes d’oxydo-réduction observés avec les ferrites et le manganite de nickel de formules : Mn(x)Fe(3-x)O4 ; Mn(x)Zn(1-x)Fe2O4 ; NiMn2O4 (0

M. El Guendouzi, K. Sbai, B. Gillot, 26th vacuum technique 116-122

A0321 – Mesures thermogravimétriques de la cinétique de vaporisation des sulfures de fer

N. Abdenouri, A. Belghit, R. Berjoan, G. Flamant, G. Peraudeau, 26th vacuum technique 26-31

A0324 – Thermal analysis of the crystallization of SAPO-5

The crystallization of microporous silicoaluminophosphate structure type 5 (SAPO-5) is studied by thermal analysis. The results obtained are compared with X-ray powder diffraction and IR spectroscopy data. The thermal effects determining the structure directing agents in the initial gel, in the intermediate X-ray powder diffraction amorphous product and in the final crystalline material are investigated.
Chr. Minchev, V. Valtchev, S. Mintova,Thermochimica Acta 264 (1995) 59-66

A0323 – Kinetic study of a way of solid state synthesis of barium titanate

The aim of this work is to study a way of solid state synthesis of barium titanate, from barium nitrate and titanium dioxide. The reaction path has first been identified, i.e. the intermediate phases that can appear during the reaction, from a thermodynamical and experimental point of view. Experimental conditions of temperature and partial pressures of nitrogen monoxide and oxygen (which are the main gases released during the reaction) have been chosen such as BaTiO[3] is the stable phase. The experimental kinetic curves have been obtained using thermogravimetry, in isothermal conditions, under controlled partial pressures of nitrogen monoxide and oxygen. These gases have an inhibiting effect on the reaction. A qualitative interpretation of the transformation is proposed, as well as a geometrical modeling that leads to the variations of the fractional conversion with time.
F. Valdivieso, M. Pijolat, M. Soustelle, Chemical Engineering Science 51 (1996) 2535-2540

A0322 – Synthesis of barium titanium oxide from barium sulphate and anatase – Study of equimolar mixtures under different atmospheres

To enable the ceramization of a barium sulphate-rich radioactive waste the synthesis of barium titanium oxide is studied by using anatase and barium sulphate. As a function of the calcination atmosphere, helium (or air) and Ar/H[2], two reactions are studied. A mechanism of barium titanium oxide synthesis in helium (or in air) is proposed.
F. Lebeau, F. Valdivieso, M. Pijolat, J.C. Thiéblemont, J.F. Baumard, Solid State Ionics 95 (1997) 151-154

A0326 – Contribution à l’étude des systèmes Sm-Co-Zr et Sm-Co-Zr-Cu en vue de l’élaboration des aimants permanents de type Sm2Co17.

A. Lefèvre, L. Cataldo, M.Th. Cohen-Adad, JEEP (1996) 83-86

A0325 – Diagramme de phases du système Bi-Pb-Sr-Ca-Cu-O : règle des phases et stabilité des phases.

P. Satre, M. Mansori, A. L'Honoré, A. Sebaoun, JEEP (1996) 63-66

A0328 – Cinétiques de transformation à haute température des structures polytypiques du diagramme Al2O3-ALN.

P. Tabary, C. Servant, JEEP (1996) 221-224

A0330 – 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.
E. Marceau, D. Busatto, G. Papin, M. Michaud, Journal of Thermal Analysis 46 (1996) 27-37

A0329 – Caractérisation par analyse thermique de la lignine, de la cellulose et de quelques uns de ses dérivés éthérifiés.

Cellulose and its derivatives (methyl cellulose, sodium carboxymethyl cellulose, hydroxymethyl cellulose and hydroxypropyl cellulose) used as excipients in pharmaceutical industry can be characterised by simultaneous thermoanalytical (DTA and TG) methods, based on the temperatures of exothermic peaks. Lignine cellulose can be identified by taking into account the difference in temperature between the first exothermic DTA peak and the corresponding DTG peak.
J. Kaloustian, A.M. Pauli, J. Pastor, Journal of Thermal Analysis 46 (1996) 91-104

A0332 – The effect of C3S on the early hydration of C3A.

The hydration of C3A, C3S and C3A+C3S mixtures was examined by thermogravimetry, differential thermogravimetry and ealorimetry. The results showed the early hydration (15 min) of C3A+C3S is of two types: If the content of C3S<40%, then C3A hydrates as it does alone, but if the content of C3S>40%, then the hydrate with the lowest temperature and the cubic one do not appear together up to 15 min.
E. El Aouni, Journal of Thermal Analysis 45 (1995) 1349-1357

A0331 – Thermoanalytical study of the pesticide 3-amino-1,2,4- triazole.

Thermoanalytical study of the pesticide 3-amino-1,2,4-triazole (ATA) has been carried out, using simultaneous DTA-TG in nitrogen flow, in order to know its thermal behaviour and stability. These techniques have been further complemented using evolved gas analysis and mass spectroscopy (EGA-MS). Two different stages of ATA decomposition were observed: after the first decomposition step, a mixture of compounds is obtained, according to MS data, being the principal component a compound of molecular weight 126. It is formed by a first order reaction mechanism, according to the kinetic study, with Ea= 124 ± 8 kJ.mol-1. The second decomposition step takes place about 735°C with evolution of HCN and NH3, being the final weight loss 96%.
P.J. Sanchez-Soto, E. Morillo, J.L. Perez-Rodriguez and C. Real, Journal of Thermal Analysis 45 (1995) 1189-1197

A0334 – Thermal behaviour of cotton-modacrylic fibre blends : kinetic study using the invariant kinetic parameters method.

This work studies the thermooxidative degradation of cotton and modacrylic fabrics and of a cotton-modacrylic blend. The association in a blend of modacrylic with cotton fibres is used to improve the fire behaviour of the latter. Using the IKP method which allows the degradation of the material to be modelled, we demonstrate that better thermal stability does not imply better fire-proofing properties, but that these are controlled by the fuel flow rate feeding the flame.
L. Richard-Campisi, S. Bourbigot, M. Le Bras, R. Delobel, Thermochimica Acta 275 (1996) 37-49

A0333 – Influence of oxygen pressure on oxidation-reduction phenomena observed with submicrometre-sized manganese-substituted magnetites

Over the temperature range 250-600°C, the oxidation of submicrometre-sized manganese-substituted magnetites depends on oxygen pressure because the presence of manganese ions leads to redox phenomena. Below 400°C, within the single-phase region of the cation-deficient spinel, a quantitative analysis by DTG of oxidizable cations allows the defect concentration associated with partial oxidation of manganese ions in tetrahedral sites to be related to oxygen pressure. Above 550°C, the oxidation of manganese ions not oxidized previously is accompanied by a structural change, but the nature of the inversion products again depends markedly on oxygen pressure.
B. Gillot, M. El Guendouzi, Thermochimica Acta 162 (1990) 265-275

A0336 – Investigation of catalytic activities by differential thermal analysis.

A calorimetric method is proposed to evaluate the catalytic activity of a solid catalyst with respect to the exothermic oxidation of Volatile Organic Compounds (VOC).This method employs a differential thermal analyzer in which an inert reference and a catalytically active sample are both fluxed at a constant rate with a reactive gaseous mixture composed of an inert gas (N2 90% vol.), oxygen and VOC, the last typically 900 to 5000 ppm. While the temperature is varied according to a predefined cycle, the output signal due to the exothermic reaction on the catalyst is continuously recorded. The design of the test chamber, the amount of catalyst, the shape of the holders and finally the flow rate and composition of the gaseous mixture should be carefully selected in order to achieve reproducible results.
D. Mazza, M. Lucco-Borlera, E. Lepore, S. Ronchetti, Journal of Thermal Analysis 46 (1996) 1625-1632

A0335 – Etude par analyse thermique de quelques végétaux méditerranéens.

Thermal analysis can be used for the study of the behaviour of plants during heating, and most particularly in the risk prevention of forest fire.Simultaneous thermal analysis (DTA-TG) of some mediterranean vegetals (needles of Pinus halepensis, leaves of Quercus coccifera; leaves of Rosmarinus officinalis; prickles, flowers and branchs of Ulex parviflorus; leaves and branchs of Acacia dealbata; leaves of Cistus albidus) shows the presence of several exothermic peaks. The first one, about 300°C, is responsible for a brutal ignition of the evolved gas. We compare the different samples by using the DTA and DTG peak temperatures and the weight loss by volatilization at 300°C.
J. Kaloustian, A.M. Pauli, J. Pastor, Journal of Thermal Analysis 46 (1996) 1349-1365

A0337 – Studies on the dehydration and decomposition of calcium and dicalcium magnesium aconitate hydrates.

The thermal decomposition of calcium and dicalcium magnesium aconitate hydrates were studied by TG/DTG, DTA, EGA, SEM and other physico-chemical techniques. The decomposition proceeds in four stages: dehydration; oxidation of the carboxylic acid portion of the salt; complete fragmentation of the hydrocarbon portion; and finally, decarboxylation of the metal carbonate to the oxide. The crystal morphologies of the hydrate and anhydrous salts of each compound are very similar. Tricalcium aconitate consists of well-developed twinned crystals and stellate clusters intergrown with flat platy crystals. On the other hand, dicalcium magnesium aconitate crystals are monoclinic with well-developed pinacoidal faces.The activation energy,E d (43±2 kJ mol-1 water), calculated from Borchardt and Daniels' method, for the dehydration process of calcium aconitate trihydrate is of the same order of magnitude as some simple metal salt hydrates. The rate constant, kd increased from 0.04/min at 238°C to greater than 0.86/min at 295°C. It is concluded that the dehydration process is due to cation bound water.
W.O.S. Doherty, O.L. Crees, C. Cuff, E. Senogles, Journal of Thermal Analysis 46 (1996) 1201-1213

A0338 – The emanation thermal analysis of kaolinite clay minerals.

Emanation thermal analysis (ETA) is based on the measurement of the rate of release of radon from solid samples previously labelled with trace concentrations of an inert radioactive nuclide (Thorium-228 or Ra-224). This method enables pointing out of the different steps that occur during the heating of kaolinite: pre-dehydroxylation, dehydroxylation, evolution of structural disorder in metakaolinite, segregation of amorphous silica and formation of precursors of high-temperature phases, crystallization and sintering of both mullite and cristobalite. The investigations of two kaolinite samples of quite different crystallinity demonstrates the role of the structural disorder of the mineral in the manifestation of these structural changes. The differences observed between the behaviour of the two samples are reflected by different diffusivities of radon which can be related to different morphology changes taking place in kaolinite during heating. The results obtained demonstrate the potential of ETA as a complementary method of conventional thermoanalysis and XRD methods.
V. Balek, M. Murat, Thermochimica Acta 282/283 (1996) 385-397

A0339 – Reduction of tungsten oxides with carbon. Part 1 : Thermal analyses.

The kinetics and mechanism of the reduction of WO3 with carbon (in the form of graphite and of lamp black) were studied using isothermal thermogravimetry of small sample masses (< 50 mg) in the temperature range 935 to 1100°C. Two stages were observed in the reduction. The first stage corresponds approximately to the formation of WO2 and the final product of the reduction was tungsten. The CO/CO2 ratio in the gaseous products had a considerable influence on the reactions occurring.The rate of the first stage of the reduction under isothermal conditions could be described by diffusion models, and is proposed to involve diffusion of CO(g) and CO2(g) through the pores of the reacting tungsten oxides. The activation energies of the graphite and lamp black systems differed significantly for this first stage of reduction (386 compared to 465 kJ mol-1). These activation energies are high for a diffusion process and may be inflated by changes in the structure of the product and the CO/CO2 equilibrium ratio as the temperature increases. The rate of the second stage of reaction can be described by a first-order rate equation, and it is proposed that the second stage of reaction is limited by the reaction of carbon with carbon dioxide, rather than by the reduction of a tungsten oxide. The measured activation energy of 438 kJ mol-1 is slightly higher than the reported values for the carbon-carbon dioxide reaction (up to 400 kJ mol-1
D. Venables, M.E. Brown, Thermochimica Acta 282/283 (1996) 251-264

A0342 – Analyse thermique de la cellulose et de quelques dérivés etherifiés et estérifiés.

The cellulose and its derivatives are used more and more, especially like excipients in pharmaceutical industry.The identification of cellulose and some of its derivatives: cellulose acetophthalate, hydroxy-propylmethylcellulose acetosuccinate, sodium carboxymethylcellulose, hydroxysthylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, methylcellulose, hydroxypropylmethyl-cellulose phthalate, is possible by thermal analysis (simultaneous DTA-TG). For that reason, one consider the temperature of the DTA maximum peaks and the DTG minimum peaks. This identification is easy when these products are a majority in pharmaceutical specialities.
J. Kaloustian, A.M. Pauli, J. Pastor, Journal of Thermal Analysis 48 (1997) 791-804

A0341 – A study of the self-heating of fresh and oxidized coals by differential thermal analysis.

Differential thermal analysis (DTA) has been used as a method to study the self-heating behaviour of fresh and oxidized coals. Oxidation was performed in air at 200°C for periods of up to 72 h. Six coals ranging from a High A Bituminous coal to a semi-anthracite were used. As the rank of the coal increases, both the self-heating and the end of combustion temperatures also increase. The total heat loss (area under the DTA curve) increases with the rank of the coal. An increase in the self-heating temperature, a decrease in the temperature of the end of combustion and a decrease in total heat flow were observed as a consequence of coal oxidation. A relationship between the total heat loss and the calorific value as determined using the ASTM standard method is pointed out.
J.J Pis, G. de la Puente, E. Fuente, A. Moran, F. Rubiera, Thermochimica Acta 279 (1996) 93-101

A0340 – The effect of metallic salt additives on direct sulfation of calcium carbonate and on decomposition of sulfated samples.

The effect of different types of metallic salt additives (Na2CO3, Li2CO3, K2CO3, Na2SO4, NaF, NaCl, ZnSO4, Ca(NO3)2, Cs2CO3 and Al2(SO4)3) on direct sulfation of calcium carbonate is investigated. The experiments were carried out in a thermogravimetric analyzer under isothermal conditions at temperatures between 700 and 875°C. An ultrapure calcium carbonate sample with a mean size of 17 µm and a specific surface area of 0.43 m2 g-1 was used. From the sulfation tests some additives (Na2CO3, Li2CO3, K2CO3, Na2SO4, NaF, NaCl) enhanced the sulfation capacity and sulfation rate with respect to the undoped sample. All these additives correspond to alkaline compounds. The effect of additives on the decomposition of CaSO4 in sulfated samples was also investigated. In this case nonisothermal experiments with a heating rate of 4 K min-1 were performed in a CO2 atmosphere. The results indicate that presence of some additives has a catalytic effect on sulfate decomposition.
A.B. Fuertes, M.J. Fernandez, Thermochimica Acta 276 (1996) 257-269

A0345 – Synthesis and characterization of high temperature superconductors. System Bi-Pb-Sr-Ca-Cu-O.

The high temperature superconductors of the system Bi-Pb-Sr-Ca-Cu-O show promising properties and large scale applications can be considered. The (Bi,Pb)2Sr2Ca2Cu3O(10+d) (Bi,Pb(2223)) phase is attractive because of its high superconducting temperature (110 K) and high current transport capabilities.Simultaneous DTA/TG has proved an excellent tool for synthesizing, characterizing these high temperature superconductors, confirming phase diagrams and finding the optimal annealing temperature for Bi,Pb(2223)/Ag tapes in order to obtain high critical current densities around 30 kA cm-2 at 77 K and 0T. The identification of the main DTA peaks of measurement of different phase mixtures made it possible to observe the formation of an intermediate phase Bi,Pb(2212) during the formation of Bi,Pb(2223).
A. Jeremie, G. Grasso, R. Flükiger, Journal of Thermal Analysis 48 (1997) 635-645

A0344 – Valence states of copper in copper ferrite spinels CuxFe(3-x)O4 (O

The oxidation in cation deficient spinels of copper iron spinels CuxFe3-xO4 (0 < x < 1) synthesized by soft chemistry with a grain size < 50 nm has been investigated by thermal measurements (DTG and DSC). For stoichiometric synthesized spinels when the copper content determines the number of oxidizable cations 1-x per mole of ferrite, three oxidation phenomena corresponding to Cu+ at B-sites (130°C), Fe2+ at B-sites (180°C) and Cu+ at A-sites (240°C) have been found in close relation with the cation-oxygen distance of each oxidizable cation. For nonstoichiometric synthesized spinels CuxFe3-xO4+d with d < 0 when the oxidation reveals a mass gain larger than that calculated with 1-x, the presence of additional interstitial Cu+ ions has been envisaged. The oxidation temperature of these interstitial ions ( > 300°C) is higher than that for Cu+ ions at Asites suggesting that interstitial copper ions also essentially reside in A-sites.
E. Kester, B. Gillo, C. Villette, Ph. Tailhades, A. Rousset, Thermochimica Acta 297 (1997) 71-78

A0343 – Phase diagram in the Bi-Pb-Sr-Ca-Cu-O system

TG-DTA and X-ray diffraction measurements at different temperatures and under different oxygen partial pressures were carried out on the species Bi1.6Pb0.4Sr2CuO6±x, Bi1.6Pb0.4Sr2CaCu2O8±y and Bi1.6Pb0.4Sr2Ca2Cu3O10±z to analyse the influence of the oxygen chemical potential on the phase transformations. A new phase was found at isobaric invariant equilibrium for 0.5 < P(O2)/P(Tot) < 1 at 884°C. This new phase presents a buffer effect towards oxygen exchange between superconducting oxides and the gas phase.
A. Sebaoun, P. Satre, M. Mansori, A. L'Honore, Journal of Thermal Analysis 48 (1997) 971-980

A0347 – Characterization of polyphosphate glasses preparation using CRTA.

We used CRTA for the study of both the elaboration and characterization of several polyphosphate glasses. We show that controlled transformation rate thermal analysis is able to remove a systematic error present in classical thermal analysis, in the study of the precursor of the phosphate glass. We show too that in CRTA, water release in the phosphate glasses can take place by diffusion phenomena at low temperature and that it is not due to the crystallization. These two examples illustrate some interests of this inverse method in the study of the decomposition of inorganic compounds with water release.
F. Gomez, P. Vast, Ph. Llewellyn, F. Rouquerol, Journal of Thermal Analysis 49 (1997) 1171-1178

A0346 – DTA/TG study of the formation of the (Bi,Pb)2Sr2Ca2Cu3O(10+d) superconductor.

In order to get insight in some of the yet unanswered questions about the formation process of the (Bi,Pb)2Sr2Ca2Cu3O(10+d) superconducting compound, coupled DTA-TG measurements have been performed in parallel with other techniques such as X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Microanalysis. The path leading to the formation of the (Bi,Pb)2Sr2Ca2Cu3O(10+d) compound, starting from coprecipitated oxalates powders was studied. The activation energy of some of the involved transformation processes were determined. Relationships between the differences induced in the DTA traces by various sample nominal compositions and the intergranular magnetic properties of the superconductor will be discussed.
J.C. Grivel, F. Kubel, I. Flükiger, Journal of Thermal Analysis 48 (1997) 665-674

A0348 – Décomposition thermique de quelques oxalates de zirconyle.

Les complexes oxalatozirconyles de cobalt, de cadmium, de nickel et de cuivre ont été préparés et caractérísés par analyse chimique et par diffraction X. Leur évolution thermique a étéétudiée par différentes techniques: ATD-ATG couplées, spectrométrie de masse et spectrométrie infra-rouge à température variable. Dans tous les cas, la décomposition thermique s'effectue en quatre étapes: deshydration décomposition des oxalates en oxycarbonates, en carbonates, puis en oxydes. L'étape finale conduit à un mélange d'oxydes simples, sauf dans le cas du cadmium oú le terme ultime est le trioxyde de cadmium et de zirconium CdZrO3
Y. Saikali, J-P. Deloume and M. Roubin, Thermochimica Acta 298 (1997) 169-177

A0350 – Thermal analytical study of steels at high temperature including the range of melting.

Measurements with a plate transducer, up to 1600°C, are investigated in the current paper. The calibration of the transducer, comparative measurements concerning the accuracy of specific heat capacity determination, the modelling for the high-temperature range and results for three steels are presented. The results are used to develop the database dbs for thermal simulation computations.
A. Lindemann, J. Al-Karawi, J. Schmidt, Thermochimica Acta 310 (1998) 133-140

A0349 – Etude comparative par analyses thermique et chimique de quelques végétaux méditerranéens.

Thermal analysis can be used for the behaviour of plants during heating and most particularly in the risk prevention of forest fire. Cellulose, holocellulose and lignin are the most important compounds determinated by analytical procedures in six mediterranean vegetals: Acacia dealbata, Pinus halepinsis, Quercus coccifera, Rosmarinus officinalis, Thymus vulgaris, Ulex parviflorus. TG-DTA is applied to the powders obtained after drying (110°C), pounding and sifting. The rate of pyrolysis about 300°C allows a semi-quantitative estimate of the cellulose present in the vegetal and its flammability.
J. Kaloustian, A.M. Pauli, J. Pastor, Journal of Thermal Analysis 50 (1997) 795-805

A0352 – Application de la spectroscopie infra rouge à l’étude du comportement thermique de la cellulose. Partie I

In this work, we describe and evaluate the use of the Fourier transform infra red (FTIR) spectroscopy in DRIFT mode (diffuse reflectance infra red Fourier transform) in an environmental device to follow the functional evolution of cellulose during thermal treatments. The potentialities (and difficulties) of the technic are given.
J.V. Weber, A. Koch, D. Robert, Journal of Thermal Analysis 53 (1998) 11-17

A0351 – The Al-Zn-Ga phase diagram. Part I

The Al-Zn-Ga ternary phase diagram was earlier established by thermodynamic modellization [1], but no experimental study appears to have been carried out on this system, except for measurements of mixing enthalpies in the liquid [2].The present experimental study was carried out by thermal analysis and X-ray diffraction at various temperatures, using the isopletic cuts method.Four isopletic cuts were established and two others were partly studied in the Al-rich corner of the diagram. On these cuts, two isobaric ternary invariant reactions were determined: a eutectic reaction at 23±1°C, and a metatectic reaction at 123±1°C. Evidence was found for the existence of a retrograde miscibility of Ga in a solid solution SS which protrudes into the ternary system starting from the Al-Zn binary up to a Ga concentration of about 30%*.
E. Aragon, K. Jardet, P. Satre, A. Sebaoun, Journal of Thermal Analysis 53 (1998) 769-784

A0353 – Etude comparative de cinq végétaux méditerraneens par analyses thermique et chimique

The comparative thermal and chemical study was done on five mediterranean plants: Acacia dealbata, Quercus coccifera, Rosmarinus officinalis, Thymus vulgaris, Ulex parviflorus. Results were independent of the drying way of samples (110°C, 60°C or lyophilisation). The correlation between the maximum decomposition rate at about 300°C and the content of cellulose was confirmed. The samples cut on the same foot of Ulex parviflorus, in spring, produced, for the thorns and sprigs, a minimum in cellulose content, and a maximum in lignine content. The results were inverse in winter.
J. Kaloustian, A.M. Pauli, J. Pastor, Journal of Thermal Analysis 53 (1998) 57-69

A0355 – Etude de la dégradation thermique du polystyrène choc ignifugé

The authors studied the ignifugation and the kinetic of thermal degradation of the Styrene-Butadiene copolymer with an intumescent system Ammonium polyphosphate-Pentaerythrinol-Melamine. For that, they used the thermogravimetric and oxygen index techniques. The best formulation of intumescent system which can give the optimum results is proposed.
L. El Watik, P. Antonetti, Y. Claire, H. Zineddine, J. Kaloustian, C. Rossi, A. Périchaud, Journal of Thermal Analysis and Calorimetry 53 (1998) 297-308

A0354 – Thermogravimetric analysis of vanadium phosphorus oxide catalysts doped with cobalt and iron

The transformation of VOHPO4.0.5H2O (VPO) precursor doped with cobalt or iron for n-butane oxidation to maleic anhydride was investigated by thermogravimetric analysis under air and nitrogen, with and without n-butane in the flow. While almost no effect was observed in nitrogen or air, a strong influence of the doping was observed when n-butane was added to the nitrogen or air. This resulted in a delay of the decomposition of the precursor and a further reoxidation of the VPO catalyst, particularly for doping with cobalt at low percentage (1%). This shows that doping can change the oxidation state of vanadium phosphorus oxide catalysts, which can explain differences in their catalytic performances and the favourable effect of doping by cobalt.
V. Martin, J.M.M. Millet, J.C. Volta, Journal of Thermal Analysis 53 (1998) 111-121

A0356 – Comportement thermique du polypropylene au cours du vieillissement

Several samples of polypropylene were studied by thermal analysis. The photo-oxidation and the aging of polypropylene films showed a mass loss more than 7% in heating from 20 to 220°C (5°C min-1), cooling to 20°C and reheating to 220°C. The authors observed also a decrease of the melting and crystallization temperatures. The non aged samples or these ones with preservatives are thermo-oxidised and presented an exothermic peak at about 200°C in DTA heating.The DTA-TG simultaneous apparatus is very useful in the study of polypropylene oxidation by making comparative trials according to a well definite procedure
J. Kaloustian, P. Antonetti, A. Berrada, Y. Claire, A. Perichaud, Journal of Thermal Analysis 52 (1998) 327-340

A0358 – Experimental set up for determining the temperature-oxygen partial pressure conditions during synthesis of spinel oxide nanoparticles

Nanometric spinel oxide powders, Fe(3-x)MxO4, where M is a transition element, have been synthetized by soft chemistry. This method generally leads to a non-stoichiometric phase, Fe(3-x)MxO(4+d) where d is the deviation from stoichiometry so that further annealing at low temperatures around 450°C and low oxygen partial pressure around 10^(-25) Pa given by N2/H2/H2O gas mixtures is required: this enables a stoichiometric compound to be obtained and a nanometric size to be maintained. The complete set up consisting of a gas mixer, a thermogravimetric apparatus and a preparative furnace is described. Some results concerning the conditions of temperature and oxygen partial pressure leading to stoichiometry are given in the case of vanadium ferrites containing or without Co.
D. Aymes, N. Millot, V. Nivoix, P. Perriat and B. Gillot, Solid State Ionics 101-103 (1997) 261-264

A0357 – Burnout of organic components of glass ceramic composite tapes. Thermoanalytical investigations

Glass ceramic composite tapes are composed of inorganic raw materials (borosilicate glasses and inert fillers) and organic additives (polymer binder, plasticizer, dispergent, residues of solvent from the tape casting process). Burnout of organics in air is a complex process of vaporization, depolymerization and oxidation. Conditions of this process can be simulated by thermal analysis of plasticizer, various binders and binder/plasticizer mixtures with alumina, prepared by impregnation of alumina powder with corresponding solutions and subsequent drying. This allows a quantitative interpretation of the results of burnout of tapes
D. Schultze, W.A. Schiller, Journal of Thermal Analysis 52 (1998) 211-219

A0359 – Thermal behavior of neopentylpolyol esters. Comparison between determination by TGA-DTA and flash point.

In the course of an investigation on the properties of neopentylpolyol esters, we examined their behavior at high temperatures using two different methods: thermogravimetry with differential thermal analysis (TGA-DTA) and measurement of flash point (ASTM D-93). Thermal behavior of the neopentylpolyol esters was found to be related to the length of acyl chain (C9 : 0, C12 : 0, C14 : 0, C18 : 1, C22 : 1) and nature of the polyol (PE, TMP, NPGHP).We also examined the thermal behavior of the partial esters of pentaerythritol in both, helium and air. The TGA-DTA technique appeared to be a suitable replacement for the flash-point methodology (ASTM D-93), especially for studying the thermal behavior of small amounts of the sample.
V. Eychenne, Z. Mouloungui, A. Gaset, Thermochimica Acta 320 (1998) 201-208

A0361 – Dehydroxylation and structure of alumina gels prepared from trisecbutoxyaluminium.

The dehydroxylation of alumina gels prepared from the hydrolysis of trisecbutoxyaluminium has been studied using a combination of differential thermal analysis and infrared emission spectroscopy. Trisecbutoxyaluminium was hydrolysed in water at both 25°C and 90°C. The alumina phase in the gel was found by both DTA and FTIR absorption and FTIR emission spectroscopy to be gibbsite. The 25°C hydrolysed gel showed endotherms at 82°C, 168°C and 244°C which were attributed to the dehydration of adsorbed and surface coordinated water, and to the dehydroxylation of the gibbsite in the alumina gel. The weight loss in the first two endotherms was 23% and 10% showing that the gel had a high water content. The gel formed at 90°C shows endotherms at 62°C, 251°C, 277°C, 404°C and 538°C. The first endotherm was attributed to the loss of adsorbed water, the 251°C and 277°C endotherms to the dehydroxylation of the gibbsite and the endotherms at 404°C and 538°C to the dehydroxylation of boehmite in the gel. The structure and dehydroxylation of the gel was determined by both infrared absorption and emission spectroscopy.
R.L. Frost, Thermochimica Acta 329 (1999) 47-56

A0360 – Mechanism of carbothermal synthesis of aluminium nitride.

The reaction between Al(OH)3 and carbon black powders under flowing nitrogen atmosphere was investigated by a dynamic thermogravimetric method. In the temperature range 1300-1700°C, the reaction can be divided into two steps: the first includes the direct reaction between Al2O3 and C particles and partial gas-solid reaction at relatively low temperature. The second is the gas-solid reaction between CO-N2 and Al2O3 where the gaseous phase transfers through the cracks in the product layer of AlN to the surface of the un-reacted core of Al2O3. The apparent activation energy of the two reactions are 486 and 592 kJ mol-1, respectively. The reaction rates of the two reactions can be expressed as:
P. Wei, Y. Qing, C. Juan, Thermochimica Acta 325 (1999) 89-93

A0362 – Thermogravimetric analysis for acidity determination in pillared clays.

Thermogravimetric analysis of pyridine adsorption was applied to study the acidity at different temperatures of clays pillared with Al pillars and mixed Al-Ga pillars, in relation to the starting montmorillonite. These results were compared with those obtained by means of a pulse-chromatographic technique. The pillaring process produces a large number of acid centers in the samples. Al-Ga-PILC has a higher acidity than Al-PILC.
I. Benito, C. Blanco, M. Martinez, A. del Riego, F. Gonzalez, C. Pesquera, Journal of Thermal Analysis and Calorimetry 55 (1999) 461-466

A0364 – The synthesis and thermal stability of superconducting HgBa2CaCu2O6+d

HgBa2CaCu2O6+ delta has been synthesized through a two-step route, via a precursor but under controlled Hg vapour pressure during the second step. A calculated excess quantity of HgO was put along the precursor, whereon the latter reacted with a stoichiometric amount of the former. Annealing raised the superconducting critical temperature from 97 to 127 K, according to susceptibility measurements. Correspondingly, the lattice parameters also increased. Microwave non-resonant absorption experiments indicated a minute presence of Hg-1223. The thermal stability of Hg-1212 was studied with the help of thermogravity, differential thermal analysis, mass spectroscopy, and X-ray diffractometry. Decomposition became significant above 600 degrees C, but the out-diffusion followed by evaporation of Hg proceeded more slowly; the enthalpies of these two processes were approximately 43 and 130 kJ mol-1.
Q. Xu, T.B. Tang, Z. Chen, Superconductor Science and Technology 7 (1994) 828-831.

A0363 – Thermal and surface analytical study of flame retarded polyolefins.

Pentaerythritol may react with tetraethoxy-silane and ammonium-polyphosphate in flame retarded polyolefins and an interfacial layer can be formed around the ammonium-polyphosphate particles. It is advantageous to study such systems using methods of thermal and surface analysis together.
Gy. Marosi, I. Csontos, I. Ravadits, A. Tohl, P. Anna, F. Sommer, M. Botreau, M.D. Tran, Journal of Thermal Analysis and Calorimetry 56 (1999) 1071-1080

A0366 – Controlled transformation rate thermal analysis:an inverse method allowing the characterisation of the thermal behaviour of polyphosphate glasses

Polyphosphate glasses are generally obtained from condensation of hydrogenophosphates. They contain important amounts of water (P-OH groups). We used the coacervation process to obtain a calcium-sodium polyphosphate glass. This technique permits the development of more polymerised products. The decomposition of residual P-OH groups was analysed by controlled transformation rate thermal analysis (CRTA) for a sample calcium-sodium polyphosphate glass and for a commercial sodium polyphosphate. It was found that dehydration takes place by diffusion from the sample in the solid state. Differential thermal analysis of glasses obtained from usual melting or by CRTA indicated an important increase in the devitrification temperature and a decrease of the melting temperature when P-OH groups are eliminated.
F.Gomez, P.Vast, F. Barbieux, P. Llewellyn, F. Rouquerol, High Temperatures - High Pressures 30 (1998) 829-834

A0365 – Dynamic thermal analysis of solid-state reactions. The ultimate method for data analysis ?

There are many reactions of interest in which one or more of the reactants belong to some solid phases. Modern thermoanalytical instruments can conveniently provide reaction kinetic data of high precision and accuracy, from which the underlying activation energyE may be derived in principle. Unfortunately, no best method yet exists for the derivation when the data have been collected with a programmed linear increase in sample temperature, unlike the case of isothermal measurements, which however suffer from experimental limitations [1]. Here we propose a method for extractingE from non-isothermal data, that promises general validity.
C-R. Li, T.B. Tang, Journal of Thermal Analysis 49 (1997) 1243-1248

A0368 – Dégradation thermique d’un polystyrène choc ignifugé par un mélange intumescent.

The study of the thermal degradation of the fireproof polystyrene-butadiene copolymer by an intumescent system: ammonium polyphosphate (APP)-pentaerythritol (PER)-talc (TAL), was done through an experimental process. Thermogravimetry under air sweeping was used. We observed for the degradation rate of the mixture with fireproofing agents, in the field of 20 to 50% mass loss, a better linear increasing when this mixture contains more TAL and the ratio APP/PER is smaller.
L. El Watik, Y. Claire, H. Zineddine, C. Rossi, J. Kaloustian, M. Sergent, A. Périchaud, Journal of Thermal Analysis and Calorimetry 58 (1999) 19-28

A0367 – Thermogravimetric analysis of two Chinese used tires.

Two Chinese used tire samples' components have been measured by using TGA technique. In general, a tire contains approximately 65% organic materials, 32% carbon black and less than 4% ash. The most commonly used tire rubbers, such as natural rubber (NR), styrene-butadiene rubber (SBR) and polybutadiene rubber (BR), were also investigated separately under the same conditions. NR is distinguished from BR or SBR in the tires' TG/DTG curves because that the NR in tires decompose mainly at lower temperature than SBR or BR. The similar TG/DTG patterns of SBR and BR result in a difficulty in identification of these two types of tire rubber.
H. Cui, J. Yang, Z. Liu, Thermochimica Acta 333 (1999) 173-175

A0369 – Oxidation behaviour of TaxTi1-xC and TaxTi1-xCyN1-y whiskers

TaxTi1-xC and TaxTi1-xCyN1-y (0 = x = 1, 0 = y = 1) whiskers have been oxidised under non-isothermal as well as isothermal conditions. The non-isothermal oxidation experiments were carried out in a combined thermogravimetric - differential thermal analysis set-up (TG-DTA), using oxygen atmosphere, with a heating rate of 5°C/min. It was found that the oxidation onset temperature (Ton) increased with increasing x-value within the temperature range 375-550°C for both TaxTi1-xC and TaxTi1-xCyN1-y whiskers and also that Ton is higher for carbonitrides compared to carbides. Scanning and transmission electron microscopy studies (SEM and TEM) showed that whiskers with a diameter exceeding 0.3 µm were split into two halves along the length of the whisker when oxidised, whereas whiskers with a diameter less than 0.3 µm retained their morphology after oxidation. Isothermal oxidation experiments were performed with TaxTi1-xC whiskers in the temperature range 400-1200°C, and it was found that the size of TiO2 particles formed from mixed transition-metal carbide precursors was substantially smaller compared to the particle size resulting from oxidation of TiC. However, the size of Ta2O5 particles were found to be small and of the same size independently if TaC or TaxTi1-xC were oxidised.
N. Ahlén, M. Johnsson, M. Nygren, Thermochimica Acta 336 (1999) 111-120

A0370 – Characterization of sulfated zirconias by DTA-TG and drift spectroscopy.

Sulfated zirconias were prepared either by impregnation of zirconia with sulfuric acid or by a one step sol gel process by using different solvents. Solids prepared under closely similar conditions in different solvents show different amounts of sulfur and surface areas, thus demonstrating that the crystallization is different. Clear differences occur in the DTA-DTG curves with the appearance of a composite peak for the sol-gel catalysts, whereas the solid obtained by the classical two-step technique shows only one peak. The number of acid sites of these samples is changed by a factor of 3 depending on the preparation. Two types of hydroxyls are observed by infrared spectroscopy: one with bands at 3640 and 3585 cm-1, associated with protons of moderate acidity, and a second at about 3300 cm-1 able to exchange D with C6D6. Moreover, the infrared band of sulfates also contains two components: one at 1405 cm-1 more intense for the most acidic solids and a second one at 1380 cm-1. After activation, these solids are as active as zeolite beta for the acylation of anisole with acetic anhydride
K. Biro, F. Figueras, C. Marquez Alvarez, S. Békassy, J. Valyon, Journal of Thermal Analysis and Calorimetry 56 (1999) 345-353

A0371 – Dehydration and dehydroxylation of nontronites and ferruginous smectite.

Differential thermal analysis and thermogravimetry have been used to compare the dehydration and dehydroxylation behaviour of a series of nontronites including two newly discovered nontronites from Uley, South Australia. A comparison is made with the thermal behaviour of ferruginous smectite. Three dehydration endotherms were found at around 60°C, 100°C and 160°C. A strong dehydroxylation endotherm for all samples was found at 430°C. The nontronites from Hohen-Hagen and Garfield show well-defined steps for dehydroxylation whereas the two Uley nontronites showed continuous dehydroxylation. The intensities of the infrared spectra of the hydroxyl-stretching region showed excellent correlation with the nontronite dehydroxylation endotherms. The infrared spectra of the water bending region showed two bands centred at 1630 and 1670 cm-1. These bands are attributed to adsorbed water and coordinated water.
R.L. Frost, H. Ruan, J.T. Kloprogge, W.P. Gates, Thermochimica Acta 346 (2000) 63-72

A0372 – Thermal transformations of titania hydrolysates prepared from tetraisopropoxytitanium (iv).

Titania hydrolysates prepared from the hydrolysis of both unmodified and modified tetraisopropoxytitanium(iv) are shown by both FT-Raman spectroscopy and X-ray diffraction to be amorphous with no long range ordering. The Raman hydrolysate spectra show three broad bands, consisting of multiple components, at Raman shifts of 210, 440 and 570 cm-1. These bands do not correspond with any known phase of titania. Thermal analysis shows broad endothermic peaks centred at 106-136°C and extending to =200°C for each of the hydrolysates and is attributed to dehydration and loss of water. Strong, broad exothermic peaks are observed in the modified hydrolysate curves, in the 310-340°C temperature range and are attributed to the combustion of the residual surface adsorbed organics. Weight loss occurred during these exotherms. Crystallisation of the disordered hydrolysates into anatase occurs in the 500-600°C temperature range. The anatase --> rutile phase transition was found between 665°C and 691°C.
P.A. Venz, J.R. Bartlett, J.L. Woolfrey, J.T. Kloprogge, Thermochimica Acta 346 (2000) 73-82

A0373 – Phase relation in Li2MoO4-Li2WO4 system.

The compounds Li2MoO4 and Li2WO4 have the phenacite structures with almost the same lattice constants. It is expected and was actually reported that the Li2MoO4-Li2WO4 quasi-binary system forms a complete solid solution. In the present study, however, we found by differential thermal analysis (DTA) that the system actually forms a partial solid solution with the peritectic reaction.
T. Nagasaki, S. Inui, T. Matsui, Thermochimica Acta 352-353 (2000) 81-85

A0375 – Investigation of a new methodology in high temperature oxidation application to commercial austenitic steels

Avesta Sheffield R&D has evaluated a scaling temperature for heat resistant steels from laboratory gravimetric measurements of cyclic exposures. In this paper, this old method is described. A new methodology, based on the results of isothermal and cyclic tests, is proposed and discussed. It includes isothermal and cyclic oxidation kinetics of different commercial austenitic steels. Oxidation of Avesta Sheffield 153MA, 253MA and 353MA and standard commercial heat resistant steels 309S, 310S and A800 have been investigated under isothermal and cyclic conditions, in air, in the temperature range 800-1200°C. For all alloys, oxidation rates obey a parabolic law below a critical temperature. The activation energies have been calculated. Kinetics of the cyclic tests show that a critical mass change corresponding to a critical thickness of the oxide scale is responsible for the spallation start. This thickness depends on the composition of the alloys, and is very much increased by alloying minor elements like Ce.
P. Vangeli, B. Ivarsson, Materials Science Forum vol.369-372 (2001) 785-792

A0374 – Decomposition of bio-polymers of some mediterranean plants during heating.

Forest fires are a plague for all countries in the world. Many factors can induce them. The organic matter (fuel) in the plant, is often responsible for the start of the fire. The bio-polymers and mainly the cellulose decompose at about 300°C with flammable evolved gas. This decomposition is first order, and the activation energy is about 180 kJ mol-1. On the other hand, the degradation of the lignin seems more complex, but we observed on many samples, a linearly decomposition of the lignin vs. the heating rate (in the interval close to the start of the forest fire, 300 to 3000°C h-1). The decomposition of the plant during the heat is mainly dependent on the cellulose level. This degradation is also slightly dependent on the lignin level mainly if the lignin present in this plant is less stable
J. Kaloustian, A.M. Pauli, J. Pastor, Journal of Therm Analysis and Calorimetry 61 (2000) 13-21

A0376 – Non-isothermal modelling of hydrocarbon adsorption on a granulated active carbon.

The adsorption of n-butane on extruded cylindrical activated carbon grains is studied providing two kinds of information: the influence of the temperature and the hydrocarbon partial pressure on the adsorption dynamics (kinetic study) and on the adsorption capacities (thermodynamic study). The thermodynamic aspect could be interpreted by a Langmuir model. From a kinetic point of view, we have experimentally proved that strong temperature variations occur inside the particles during the adsorption. In this paper, a kinetic model including both mass and heat transfer phenomena is proposed. Good agreement is found between the kinetic model predictions and the experimental mass and temperature variations inside the grain during the hydrocarbon adsorption
E. Fiani, L. Perier-Cambry, G. Thomas, Journal of Thermal Analysis and Calorimetry 60 (2000) 557-570

A0377 – Dehydration and dehydroxylation of alumina gels prepared from tri-sec-butoxyaluminium modified with short chain aliphatic acids

The dehydration and dehydroxylation of alumina gels prepared from the hydrolysis of tri-sec-butoxyaluminium (ASB) at both 25 and 90°C, unmodified and modified with short chain aliphatic acids has been studied using a combination of differential thermal analysis (DTA) and thermogravimetry. The alumina phase in the gel was found to be dependent upon the temperature of hydrolysis and the modifying acid. The gels formed at 25°C from unmodified ASB contained alumina as gibbsite and at 90°C from the unmodified ASB a mixture of gibbsite and boehmite, whereas those gels formed from ASB at 25°C and modified with short chain aliphatic acids were amorphous. In DTA of the modified gels, the exotherms from the combustion of the aliphatic acid groups masked the endotherms of dehydration and dehydroxylation of the gels. Neither DTA nor thermogravimetric analysis (TGA) could determine the dehydroxylation temperature range. The application of differential thermogravimetric analysis (DTGA) enabled these temperatures to be obtained. DTGA of the gels formed from the acid modified ASB showed complex 'endograms'. Infrared spectroscopy was used to determine the molecular structures of the acetic acid modified gels.
J.L. Szetu, R.L. Frost, J.T. Kloprogge, S.C. Russell, W. Martens, Thermochimica Acta 362 (2000) 37-48

A0378 – Polyimide films from linear and network precursors.

Pyromellitic anhydride-4,4'-diaminodiphenyl ether (PMDA-DDE) polyimide precursor was blended with mellitic acid hexamethyl ester-4,4'-diaminodiphenyl (MAHE-DDE) precursor to obtain polyimide films. The films from blends required higher temperatures for complete imidisation than those necessary for either of the pure constituents. Storage moduli and secondary glass transition temperatures improved with increase of imidisation temperature and amount of the network constituent, indicating that the latter provided some reinforcement to the mixed films. Differential thermal analysis (DTA) of the blends and the changes in morphology with composition observed by scanning electron microscopy suggested that the two constituents may be cross-linked.
J. Wang, M.P. Srinivasan and S-C. Ng, Journal of Materials Chemistry 9 (1999) 655-659

A0380 – Cu0/Fe3O4 nanocomposites in an aqueous media

G. Pourroy, A. Valles-Minguez, T. Dintzer, J.OX.MAG (2000)

A0379 – Conductive composite films of polyimide and poly (3-dodecylthiophene).

A new method of making polymer films with conductive surfaces by permeation of the conducting guest species into the host is reported. A layer of poly(3-dodecyl thiophene) (p3ddt) is embedded at the surface of polyimide by permeation of the polythiophene (in solution in tetrahydrofuran (THF)) into a solution of polyamic acid in n-methyl pyrrolidinone (NMP) or dimethyl acetamide (DMAc). The resulting composite could be imidised chemically and the conducting polymer was stable in the composite even after solvent extraction. The sheet resistance of the composite decreased rapidly upon exposure to iodine; this effect was similar to, though slower than that observed for pure dodedcyl thiophene. Also, the composite recovered conductivity after a few hours of exposure to the dopant subsequent to de-doping. The higher mobility afforded by contact in the liquid state may contribute to the entanglement between the constituents leading to greater thermal and solvent resistance of the conducting constituent
J. Wang and M. P. Srinivasan, Synthetic Metals 105 (1999) 1-7

A0381 – Synthesis and thermal properties of 4,4′-bipyridine adducts of Mn(II), Co(II), Ni(II) and Cu(II) monochloroacetate

The complexes with the empirical formula M(4-bipy)(ClCH2COO)2.nH2O (where: 4-bipy=4,4'-bipyridine, L=ClCH2COO-, M(II)=Mn, Co, Ni, Cu) were prepared and characterized via the IR and electronic (VIS) spectra and conductivity measurements. Thermal decomposition of these compounds was studied. During heating in air dehydration processes occur. The anhydrous compounds decompose at high temperature to oxides. The principal volatile mass fragments correspond to: H2O, CO2, CH3Cl, HCl, Cl2 and other.
D. Czakis-Sulikowska, A. Czylkowska, J. Radwanska-Doczekalska, Journal of Thermal Analysis and Calorimetry 63 (2001) 387-395

A0384 – Thermal transformation of alumina hydrolysates and gels synthesized from secbutoxyaluminium (III) modified with short-chain aliphatic acids dissolved in butyl ether

A combination of X-ray diffraction and thermal analysis was employed to characterise alumina hydrolysates synthesised from the hydrolysis of anhydrous trisecbutoxyaluminium (III). X-ray diffraction showed that the alumino-oxy(hydroxy) hydrolysates were boehmite. For boehmite the lamellar spacings are in the b direction and multiple d(0 2 0) peaks are observed for the unaged hydrolysate. After 4 h of ageing, a single d(0 2 0) peak is observed at 6.53 Å. Thermal analysis showed five endotherms at 70, 140, 238, 351 and 445°C. These endotherms are attributed to the dehydration and dehydroxylation of the hydrolysate.Alumina oxy(hydroxy) gels were formed from the hydrolysates of anhydrous aliphatic acid modified trisecbutoxyaluminium(III). X-ray diffraction shows the gels were expanded above the (0 2 0) spacing of boehmite due to the incorporation of acid in the interlamellar space. The thermal analysis patterns of the acid modified gels were significantly different from that of the unmodified gel.
W.N. Martens, R.L. Frost, J. Bartlett, J.T. Kloprogge, Thermochimica Acta 374 (2001) 31-43

A0383 – FTIR study of the thermal degradation of poly(vinyl alcohol)

The degradation of poly(vinyl alcohol) was investigated using TG analysis and Fourier transform infrared spectroscopy to determine the effect of atmosphere on the process of degradation. In the spectra, four vibrational modes were identified that characterised the major steps of the degradation process. These were the O-H, C-H, C=O and C=C stretching modes. The mechanism observed for degradation in an inert atmosphere was in accordance with the accepted mechanism of elimination followed by pyrolisation. Evidence of conjugated polyenes, however, was not observed. For the air atmosphere, oxidation in both steps of the degradation process was observed.
P.S. Thomas, J-P. Guerbois, G.F. Russell, B.J. Briscoe, Journal of Thermal Analysis and Calorimetry 64 (2001) 501-508

A0382 – Kinetic study of the thermal decompositions of biopolymers extracted from various plants

A knowledge of the kinetics of decomposition of biopolymers on heating is important mainly in two domains: forest fires and the incineration of biomass for the production of electric energy. For the study by thermogravimetry of biopolymers (cellulose, holocellulose and lignin), samples of several Mediterranean plants were used.
J. Kaloustian, A.M. Pauli, J. Pastor, Journal of Thermal Analysis and Calorimetry 63 (2000) 7-20

A0390 – Short-term high temperature oxidation of lamellar cast iron

The present study is focused on the oxidation behavior, at temperatures above 900°C, of lamellar cast irons containing various amounts of species commonly present in these alloys (mainly P, S and Si) and less common metallic impurities (Cu and Cr). Oxidation kinetics were investigated from TGA tests performed in flowing air for four hours. The morphology, microstructure and composition of oxide scales were investigated by means of SEM and XRD. It was found that the oxidation kinetics and the microstructure of oxide scales strongly depend on composition and temperature. Slower oxidation kinetics is associated with the growth of oxide scales showing a two-layered microstructure consisting in an outer scale of hematite and magnetite and an inner scale of wustite and fayalite. Faster oxidation kinetics, usually linear, relates to the growth of a single stratified scale primarily composed of hematite, with a small amount of magnetite and a dispersion of silicon-rich precipitates, most likely amorphous silica.
R. Durham, J. Lacaze, D. Monceau, B. Pieraggi, Materials Science Forum vol.369-372 (2001) 181-188

A0388 – In situ high temperature X-Ray characterization of yttrium implantation effect on pure iron oxidation at 700°C

Yttrium implanted and unimplanted pure iron oxidation behaviour were studied by thermogravimetry, scanning electron microscopy (SEM) and in situ X-ray diffraction at T=700°C and P[O2]=0.04 Pa for 24h to determine the yttrium implantation effect on sample oxidation resistance at high temperature. In situ X-ray diffraction analyses performed on unimplanted pure iron allow to observe the initial nucleation stage of FeO (wustite), Fe[3]O[4] (magnetite) and Fe[2]O[3] (hematite) whereas two other compounds (i.e. FeYO[3] and Fe[2]YO[4]) were detected in combination with iron oxides in the case of yttrium implanted pure iron. These two yttrium-iron mixed oxides seem to be responsible for the low oxidation rate observed by thermogravimetry. This paper shows that in situ high temperature X-ray diffraction technique provides a better understanding of yttrium implanted and unimplanted pure iron oxidation mechanisms.
E. Caudron, H. Buscail, R. Cueff, V.A.C. Haanappel, Y.P. Jacob, F. Riffard, M.F. Stroosnijder, Materials Science Forum vol.369-372 (2001) 817-824

A0385 – Effects of bond-coat preoxidation and surface finish on isothermal and cyclic oxidation, high temperature corrosion and thermal shock resistance of TBC systems

A systematic study of the effects of bond-coats surface modifications prior to ceramic deposition is presented. TBC systems have been made and tested with most combinations of the following parameters: 1/substrate: IN 100 or AM3 (single crystal) Ni-based superalloys; 2/ bond-coat: VPS NiCoCrAlYTa or CoNiCrAlY, (Ni,Pd)Al, (Ni,Pt)Al; 3/ bond-coat surface finish: as deposited, machined, grit blasted, preoxidized; 4/ top coat: APS or EB-PVD Y[2]O[3] stabilized ZrO[2]. The preoxidation treatments of bond-coats were determined from the results of a study (TGA-GIXRD-SEM-SIMS) of their short-term (6 hours) isothermal oxidation behavior as a function of temperature (900 to 1100°C), oxygen partial pressure and heating rate. Under these conditions all bond-coats are alumina formers, but depending on the oxidation conditions, transition aluminas may be formed. The characterization of complete TBC systems was also performed, including isothermal oxidation (TGA), cyclic oxidation at 1100°C, cyclic corrosion at 900°C and thermal shock (fast cooling from 1200°C).
D. Monceau, F. Crabos, A. Malié, B. Pieraggi, Materials Science Forum vol.369-372 (2001) 607-614

A0393 – Oxidation behaviour of beta-FeAlCr coating produced by close-field unbalanced magnetron sputter deposition

beta-FeAl coatings containing 5.7at.% Cr were produced with a close-field unbalanced magnetron sputter (CFUMS) deposition technique. Cyclic oxidation test at 1100°C in air for 100 1-h cycles and isothermal exposures from 1000°C through 1200°C in pure O[2] for 100 hours were carried out with the coatings. The coating showed better scale spallation resistance during cyclic oxidation test than the cast FeAl. After the isothermal oxidation at 1000°C and 1100°C, fine-grained ridge-type oxide scales were formed on the coatings, while at 1000°C, the oxide scale formed on the cast FeAl showed a large quantity of ?-Al[2]O[3] blades, and big interfacial voids on the base alloy surface were observed. The transformation from 6 to alpha-Al[2]O[3] was accelerated due to the presence of Cr in the coatings, and suppressed the fast outward Al diffusion for the growth of ?-Al[2]O[3]scale and eliminated the formation of interfacial voids that deteriorated the oxide scale spallation resistance. After the isothermal exposure at 1200°C, however, the oxide scale on the coating was greatly buckled and spalled, and did not show much improvement over the cast FeAl.
Z. Liu, W. Gao and F. Wang, Materials Science Forum vol.369-372 (2001) 295-302

A0391 – Evolution of scale microstrusture as a function of scale oxide thickness during oxidation of nickel at 700°C

The oxidation of high purity polycrystalline nickel was studied at 700°C under flowing oxygen. For 1 ?m thick oxide scale, the microstructure is cellular. For 3 to 30 ?m thick oxide scales, rounded oxide platelets are observed on the scale surface. There is a large effect of substrate orientation. The scale is duplex, i.e. composed of an external scale of columnar grains and an inner subscale of equiaxed microstructure. The ratio external scale thickness/internal scale thickness is constant (? 2) and does not depend on total oxide scale thickness. The interface between internal scale and external scale corresponds to the initial surface of the metal. To explain these microstructural features, the mechanisms of scale growth proposed in the literature are critically reviewed. The relative position of the duplex oxide scale and the initial surface of the metal, and the relative growth of the outer and inner scales permits to conclude that NiO growth does not proceed only by the outward diffusion of cationic species in a dense scale. The duplex scale formation seems to be associated with the growth of the inner scale by inward transport of oxygen.
R. Peraldi, D. Monceau, B. Pieraggi, Materials Science Forum vol.369-372 (2001) 189-196

A0394 – Abnormal oxidation of stabilized ferritic stainless steels in water vapor

The influence of water vapor on the high temperature oxidation of several stabilized ferritic stainless steels with various Si and Cr contents has been studied by thermogravimetry at 900°C in pure water vapor or dry oxygen, followed by the characterization of the oxide scales formed. Oxidation of Fe-Cr steels in pure water vapor was characterized by a non-protective breakaway oxidation due to the formation of iron oxide nodules on the sample surface. Decreasing the H[2]O partial pressure or increasing the Si or Cr content enhanced the oxidation resistance of the alloy by delaying the breakaway appearance. This abnormal oxidation is thought to be initiated by the arrival of oxygen- and hydrogen-containing species on the chromium depleted metal/oxide interface. The mechanism of the effect of water vapor is discussed and some assumptions proposed.
S. Henry, A. Galerie, L. Antoni, Materials Science Forum vol.369-372 (2001) 353-360

A0395 – Formation and mechanism of carbon-containing oxide scales by oxidation of carbides (ZrC, HfC, TiC)

The isothermal oxidation of carbide single crystals (ZrC, HfC, TiC) with the 200 or 220 face was carried out at 700 to 1500°C and at oxygen pressures of 0.08 to 80 kPa. The oxidation, which was determined from the weight changes, was described by linear kinetics. The preferred {200} or {220 orientation of ZrO[2], HfO[2], and Ti[3]O[5]was detected by XRD. The duplex oxide scale was found to consist of an almost compact, pore-free scale (zone 1) and a porous, cracked scale (zone 2). Zone 1 contained 20 - 25 at. % elemental carbon and zone 6 to 11 at.% carbon. Zone 1 grew parabolically and zone 2 thickened linearly. The interface between zone 1 and the carbide was observed by SEM and HRTEM to reveal the microstructure and morphology of zone 1. The formation mechanism of carbon-containing scales (zones 1 and 2) was derived from kinetic considerations and interfacial observations.
S. Shimada, Materials Science Forum vol.369-372 (2001) 377-384

A0396 – The influence of water vapor on the oxidation of MoSi2 at 450°C

The oxidation of a MoSi[2] composite was studied in dry air, oxygen and oxygen saturated with 10% water vapour at 450°C. The kinetics were investigated using TGA as well as oxide thickness measurements. Detailed analyses were performed on the morphology and composition of the oxide using XRD, ESEM, SEM, and EDX. It is shown that the oxidation rate increases drastically in the presence of water vapour, and the growth of MoO[3] crystals on the oxide surface increases considerably. The different regions in the oxide cross-section are Mo-depleted compared with the corresponding regions in the bulk when oxidised in oxygen saturated with 10% water vapour. However, the samples oxidised in dry oxygen only shows Mo-depletion in some outer parts of the oxide. Accelerated growth of the MoSi[2]-oxide layer during exposure in O[2]+10%H[2]O compared to that in O[2] can be related to the fact that more volatile Mo-species form in the presence of water vapour, resulting in a substantial loss of MoO[3] from the inner part of the oxide. The voids left behind are not healed by the silica at this low temperature, which leaves the oxide with an open structure. As a result, the oxidation rate increases.
K. Hansson, J-E. Svensson, M. Halvarsson, J.E. Tang, M. Sundberg, R. Pompe, Materials Science Forum vol.369-372 (2001) 419-426

A0397 – Mechanical, kinetic and morphological correlations during the scale growth of nobium and zirconium oxides

Oxidation of niobium at 700°C and zirconium at 850°C, in air or oxygen pressures from 20 to I 000 hPa, lead to the formation in one case of a stratified Nb[2]O[5] oxide scale and in the other case a more compact ZrO[2] oxide scale. Analyses of the evolutions of phases, crystalline textures and mechanical stresses during oxidation are determined by X-ray diffraction techniques. Interactions between chemical processes, crystalline building and mechanical processes constitute together the driving force of the reaction and can explain the differences in morphologies of oxide scales.
D. Ciosmak, C. Valot, M. Lallemant, G. Bertrand, Materials Science Forum vol.369-372 (2001) 523-530

A0398 – A study of solid state reaction between strontium carbonate and ruthenium dioxide

R.K. Mishra, J.G. Shah, R.G. Yeotikar, S.R. Dharwadkar, Thermans (2000) 129-132

A0400 – Synthesis and characterization of metal oxide nano particles through PVA route

P.C. Mohan, H. Subramanian, P.K. Ajikumar, M.P. Srinivasan, M. Kamruddin, S. Velmurugan, S.V. Narasimhan, Thermans (2002) 227-229

A0399 – Application of differential thermal analysis for uranium oxide powders characterisation

Y. Balaji Rao, H.R. Ravindra, R.B. Yadav, B. Gopalan, S. Syamsundar, Thermans (2000) 158-160

A0402 – Preparation of NiO through NaNO3-KNO3 eutectic melt and its catalytic activity during the decomposition of polystyrene

The decomposition of basic nickel carbonate in the presence and absence of NaNO3 (sodium nitrate)-KNO3 (potassium nitrate) eutectic melt has been studied by employing isothermal TG and dynamic TG-DSC techniques. The rate constants for the decomposition in the presence of eutectic melt were found to be higher than when carbonate alone was heated. In both cases, nickel oxide was found to be the end product. Catalytic activities of nickel oxide obtained by the two methods were tested for their efficiency in decomposition of polystyrene (PS). It was found that at higher temperature (330 and 360°C), the nickel oxide obtained from eutectic melt was more active than that obtained by direct decomposition.
N.B. Singh, A.K. Ojha, Thermochimica Acta 378 (2001) 87-96