A1416 – Thermal study of some new Ni(II) and Cu(II) complexes with ligands derived from N,N-dimethylbiguanide as potential antimicrobials
The reaction between [M(DMBG)2] nH2O ((1) M:Ni, n = 0; (4) M:Cu, n = 1), ammonia/hydrazine and formaldehyde in methanol resulted in new complexes of type [ML] nH2O ((2) M:Ni, L:L1, n = 0; (3) M:Ni, L:L2, n = 0, (5) M:Cu, L:L1, n = 0 and (6) M:Cu, L:L2, n = 3; HDMBG: N,N-dimethylbiguanide, L1 = ligand resulted from ammonia system and L2 = ligand resulted from
hydrazine system). The features of complexes have been assigned from microanalytical, IR and UV–Vis data. The thermal transformations of compounds are complex processes according to TG and DTG curves including melting, phase transition, dehydration, oxidative condensation of –C=N– units as well as thermolysis processes. The final products of decomposition are the most stable metal oxides.
A1415 – DSC analysis of stengthening precipitates in ultrafine Al–Mg–Si alloys
Equal channel angular pressing (ECAP) was carried out on solution annealed samples of Al–Mg–Si–Zr and Al–Mg–Si–Zr–Sc alloys to achieve a substantial grain refinement of the materials. Post ECAP aging was then investigated on the ultrafine grained alloys by DSC and TEM analyses. DSC scans were carried out with heating rates ranging from 5 to 30°C min–1. Peak identification was performed by the support of literature information and TEM analyses. Precipitation kinetics revealed to be similar for both alloys but the Sc-free alloy showed
a recrystallization peak at temperatures ranging from 310 to 340°C, depending on the strain accumulated during ECAP. On the contrary, the Sc-containing alloy showed a greater grain stability. Analyses of peak positions and of activation energies as a function of ECAP passes experienced by the samples revealed large modifications of precipitation kinetics in the ultrafine-grained alloys with respect to the coarse-grained materials.
A1422 – Thermal decomposition of some biologically active complexes of ruthenium (III) with quinolone derivatives
Aseries of new complexes with mixed ligands of the type RuL2(DMSO)mCl3 nH2O ((1) L: norfloxacin (nf), m = 1, n = 1; (2) L: ciprofloxacin (cp), m = 2, n = 2; (3) L: ofloxacin (of), m = 1, n = 1; (4) L: enrofloxacin (enro), m = 0.5, n = 4; DMSO: dimethylsulfoxide) were synthesised and characterised by chemical analysis and IR data. In all complexes both fluoroquinolone derivative and DMSO act as unidentate. The thermal behaviour steps were investigated in synthetic air flow. The thermal transformations are complex processes according to TG and DTG curves
including dehydration, quinolone derivative and DMSO degradation respectively. The final product of decomposition is ruthenium (IV) oxide.
A1421 – New complexes of Ni(II) and Cu(II) with Schiff bases functionalised with 1,3,4-thiadiazole: spectral, magnetic, biological and thermal characterisation
Schiff bases obtained by the condensation of 2-amino-5-mercapto-1,3,4-thiadiazole with 2,4-pentandione or 1-phenyl-1,3-butandione were synthesized and characterized in order to obtain polydentate ligands HL1 and HL2, respectively. The complexes with these ligands of the type M(L)Cl nH2O [(1) M:Ni, L:L1, n = 0.5; (3) M:Ni, L:L2, n = 0.5]; [(2) M:Cu, L:L1, n = 1; (4) M:Cu, L:L2, n = 0] were also synthesized and characterized. The modifications evidenced in IR spectra of complexes were correlated with the presence of monodeprotonate Schiff bases. The electronic spectra display the characteristic pattern of square-planar stereochemistry. The in vitro qualitative and quantitative antimicrobial activity assays showed that the new complexes exhibited variable antimicrobial activity. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Schiff bases and
complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion removal as well as oxidative degradation of the organic ligands were observed.
A1420 – Thermal study of some new quinolone ruthenium(III) complexes with potential cytostatic activity
A series of new complexes with mixed ligands of the type RuLm(DMSO)nCl3 xH2O ((1) L: oxolinic acid (oxo), m = 1, n = 0, x = 4; (2) L: pipemidic acid (pip), m = 2, n = 1, x = 2; (3) L: enoxacin (enx), m = 2, n = 1, x = 0; (4) L: levofloxacin (levofx), m = 2, n = 2, x = 8; DMSO: dimethylsulfoxide) were synthesized and characterized by chemical analysis, IR and electronic data. Except oxolinic acid that behaves as bidentate, the other ligands (quinolone derivatives and DMSO) act as unidentate. Electronic spectra are in accordance with an octahedral
stereochemistry. The thermal analysis (TG, DTA) in synthetic air flow elucidated the composition and also the number and nature of both water and DMSO molecules. The TG curves show 3–5 well-separated thermal steps. The first corresponds to the water and/or DMSO loss at lower temperatures followed either by quinolone thermal decomposition or pyrolisys at higher temperatures. The final product is ruthenium(IV) oxide.
A1425 – Effect of metal substitution for cobalt on the oxygen adsorption properties of YBaCo4O7
YBaCo4O7 compound is capable to intake and release a large amount of oxygen in the temperature range of 200–400°C. In the present study, the effect of Zn, Ga and Fe substitution for Co on the oxygen adsorption/desorption properties of YBaCo4O7 were investigated by thermogravimetry (TG) method. Due to fixed oxidation state of Zn2+ ions, the substitution of Zn2+ for Co2+
suppresses the oxygen adsorption of YBaCo4–xZnxO7. The substitution of Ga3+ for Co3+ also decreases the oxygen absorption capacity of YBaCo4–xGaxO7. This can be explained by the strong affinity of Ga3+ ions towards the GaO4 tetrahedron. Compared with Zn- and Ga-substituted samples, the drop of oxygen adsorption capacity is smallest for Fe-substituted samples because of the similar changeability of oxidation states of Co and Fe ions.
A1424 – Thermal stability of new vanadyl complexes with flavonoid derivatives as potential insulin-mimetic agents
Aseries of newcomplexes of the typeVO(OH)L nH2O((1) L: fisetin, n = 3; (2) L: quercetin, n = 2; (3) L: morin, n = 4) were synthesised and characterised by analytical as well as IR and electronic data. The modification evidenced in IR spectra was correlated with the presence of flavonoid as bidentate in all complexes. The electronic reflectance spectra showed the
d–d transition characteristic for the square-pyramidal stereochemistry of vanadium (IV) ion. The thermal analysis (TG, DTA) in synthetic air flowelucidated the composition and also
the number and nature of the water molecules. The TG curves show three well-separated thermal events. The first corresponds to the water loss at lower temperatures, which is followed by flavonoid derivative decomposition and pyrolysis at higher temperatures. The final product is vanadium (V) oxide.
A1423 – Thermal behavior of some new triazole derivative complexes
A series of new complexes with mixed ligands of the type [ML(C3H3O2)2]×nH2O ((1) M=Mn, n=1; (2) M=Co(II), n=2; (3) M=Ni(II), n=4; (4) M=Cu(II), n=1.5; (5) M=Zn(II), n=0; L=3-amino-1,2,4-triazole and (C3H3O2)=acrylate anion) were synthesized and characterised by chemical analysis and IR data. In all complexes the 3-amino-1,2,4-triazole acts as bridge while the acrylate acts as bidentate ligand except for complex (5) where it is found as unidentate. The thermal behaviour steps were investigated in nitrogen flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion and 3-amino-1,2,4-triazole degradation respectively. The final products of decomposition are the most stable metal oxides, except for complex (4) that leads to metallic copper.
A1427 – Thermal properties of Nafion–TiO2 composite electrolytes for PEM fuel cell
Thermal analysis has been used to evaluate the stability, glass transition, and water retention of Nafion based polymer–ceramic electrolytes. These electrolytes are envisioned as promising replacement of Nafion in fuel cells operating above 100 °C. The polymeric matrix prepared by casting exhibits lower crystallinity than the extruded Nafion, a feature that affects the water absorption properties. The addition of titania-based nanotubes and nanoparticles to the polymer has enhanced the water retention at high temperatures (*130 °C) and the glass transition temperature, respectively. Such results are important for the design of composite electrolytes for the operation of fuel cells at high temperatures.
A1426 – Carbothermal reduction of the YSZ–NiO solid oxide fuel cell anode precursor by carbon-based materials
The thermal behavior of the yttria-stabilized zirconia (YSZ) and nickel oxide (YSZ–NiO) composite mixtures with the addition of graphite, multiwall carbon nanotubes and functionalized multiwall carbon nanotubes was studied. The YSZ–NiO composite is the precursor of the YSZ–Ni anode of solid oxide fuel cells. The anode exhibits a porous structure, which is usually obtained by the addition of carbon containing pore formers. Thermal analysis and X-ray diffraction evidenced that the properties of carbonaceous materials (C) and atmosphere have a strong
influence on the thermal evolution of the reactions taking place upon heating the anode precursor. The dependence of both the carbon content and the chemical nature of the ceramic matrix on the thermal behavior of the composite were investigated. The discussed results evidenced important features for optimized processing of the anode.
A1430 – Thermal stability and surface structure of Mo/CeO2 and Ce-doped Mo/Al2O3 catalysts
In order to explore the influence of CeO2 on the structure and surface characteristics of molybdena, an investigation was undertaken by using N2 adsorption (BET method), thermal analysis and in-situ diffuse reflectance infrared (DRIFT) techniques. In this work, the Mo/CeO2 and Ce–Mo/Al2O3 samples were prepared by impregnation and co-precipitation methods with high Mo loadings. Combining the results one may notice that the presence of ceria led to the increase of polymerized surface Mo species so as to forming Mo–O–Ce linkages besides the formation of coupled O=Mo=O bonds indicative of polymeric MoO3. From thermal analysis, it can be inferred that Mo/Al2O3 is the thermally most stable material in the temperature range used in the experiment (up to 900°C), whereas Ce–Mo/Al2O3 and Mo/CeO2 samples undergo morphological modifications above 700°C resulting in lattice defects, which motivate the mobility of Mo and Ce ions and thus enhance the possibility of interaction between them. Additionally, their activity towards CO adsorption needs reduced ceria and molybdena containing coordinatively unsaturated sites (CUS), oxygen vacancies and hydroxyl groups to form various carbonate species.
A1429 – Studies on thermal transformation of Na–montmorillonite–glycine intercalation compounds
Thermogravimetric (TG), differential thermal analysis (DTA) and thermal degradation kinetics, FTIR and X-ray diffraction (XRD) analysis of synthesized glycine–montmorillonite (Gly–MMT) and montmorillonite bound dipeptide (Gly–Gly–MMT) along with pure Na–MMT samples have been performed. TG analysis at the temperature range 25–250 °C showed a mass loss for pure Na–
MMT, Gly–MMT and Gly–Gly–MMT of about 8.0%, 4.0% and 2.0%, respectively. DTA curves show the endothermic reaction at 136, 211 and 678 °C in pure Na–MMT whereas Gly–MMT shows the exothermic reaction at 322 and 404 °C and that of Gly–Gly–MMT at 371 °C. The activation energies of the first order thermal degradation reaction were found to be 1.64 and 9.78 kJ mol-1 for Gly–MMT and Gly–Gly–MMT, respectively. FTIR analyses indicate that the intercalated compounds decomposed at the temperature more than 250 °C in Gly–MMT and at
250 °C in Gly–Gly–MMT.
A1428 – Agricultural valorisation of de-inking paper sludge as organic amendment in different soils
The objective of this study is to study the influence of de-inking paper sludge (DPS) and sewage sludge (SL) mixtures addition at different rates (2, 4 and 8%) in two soils. Incubation experiments were performed during 60 days and the influence of treatments in physical soil properties was determined by soil porosity and stability of aggregates. Differential thermal analysis (DTA) of amended soils after incubation was performed. Experimental results show that amendment increased biological soil activity, soil porosity and stability of aggregates. DTA
analysis shows that the first exothermic peak generally increases with the dosage of DPS:SL due to the addition of immature organic matter. Moreover, the second peak enlarges probably due to the humification process during incubation.
A1433 – Lanthanide complexes of 3-methoxy-salicylaldehyde. Thermal and kinetic investigation by simultaneous TG/DTG–DTA coupled with MS
The reaction of a lanthanide(III) nitrate (Ln = Pr, Nd, Gd, Dy, Er) with 3-methoxy-salicylaldehyde(3-OCH3-saloH), afforded neutral complexes of the general formula [Ln(3-OCH3-salo)3], which were characterized by means of elemental analysis, FT-IR spectra, TG-DTA curves, and magnetic measurements. The released products, due to the thermal decompositionwere analyzed by on-line coupling MS spectrometer to the thermobalance in argon, allowed to prove the proposed decomposition stages. In order to confirm the stability scale provided on the basis of the onset decomposition temperature, a kinetic analysis of the three decomposition stages was made using the Kissinger equation, while the complex nature of the decomposition kinetics was revealed by the isoconvertional Ozawa–Flynn–Wall method.
A1432 – Hydrogen production on iron–magnesium oxide in the high-temperature water-gas shift reaction
Fe–Cr–O and Fe–Mg–O catalysts were used for hydrogen production via the water-gas shift reaction. Fe–Cr–O catalysts were synthesized by different methods such as co-precipitation, impregnation and substitution technique. Catalysts were characterized by XRD, TG, BET and TPR. Addition of Mg improved the catalytic activity of Fe–O by favouring the development of small and well dispersed Fe particles (MgFe2O4). As a consequence, MgO prevented iron phase sintering in the presence of a large amount of water in the WGS reaction.
A1431 – The influence of the preparation method on the structural, acidic and redox properties of V2O5-TiO2/SO42- catalysts
The introduction of sulfates into vanadia-titania catalysts and the influence of the preparation method on the properties of the sulfated samples have been studied. Series of V2O5-TiO2/SO42- (VTiS) catalysts were prepared by co-precipitation, sol–gel and mechanical grinding methods and calcined at different temperatures. Their structural properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Co-precipitation was by far the best preparation method in terms ofmaximizing the surface area and the mesoporosity. Temperature-programmed reduction (TPR) revealed that only the vanadia species were reducible. The results from XRD and FT-IR showed that V2O5 was well dispersed on the surface of TiO2. XPS showed that the surface vanadium oxide was composed of stoichiometric V2O4 and V2O5, as well as V2O3 species especially for the samples prepared by mechanical grinding. Meanwhile, titanium was present in its fully oxidized state in all the VTiS samples, and the sulfurcontaining
species presented an oxidation state of +6. The reaction of isopropanol (IPA) conversion in air was used to characterize the surface acid/base and redox properties. The higher activity for the IPA conversion over the VTiS catalysts as compared to TiO2 was possibly due to the generation of redox sites upon the addition of V2O5. Moreover, the surface acidic properties were enhanced and the redox properties weakened upon addition of SO42- species.
A1435 – Thermogravimetric study of the dehydration reaction of LiCl·H2O
The dehydration of LiCl·H2O was studied under inert helium atmosphere by DTA/TG for different heating rates. The dehydration of LiCl·H2O proceeds through a two step reaction between 99–110 and 160–186°C, respectively. It leads to the formation of LiCl·0.5H2O as intermediate compound.
Based on the temperature peak of the DTA signals the activation energies of the two reactions were determined to be 240 kJ mol–1 (step 1) and 137 kJ mol–1 (step 2), respectively.
A1434 – Changes in coal char reactivity and texture during combustion in an entrained flow reactor
Char particle combustion is the slowest step in the combustion of coal, therefore char reactivity and texture have an important influence on this process. In this work, two coals were devolatilised in an entrained flow reactor and the chars obtained were burned under different experimental conditions in order to achieve various degrees of burnoff. Char reactivity was determined by means of non-isothermal thermogravimetric analysis, and the conversion-time data were evaluated by the random pore model proposed by Bhatia and Perlmutter. Char texture was characterised by means of N2 and CO2 adsorption isotherms. The surface areas obtained were used to calculate intrinsic reaction rate parameters. It was found that under chemical controlled conditions, the available surface area during combustion is best represented by the N2 surface area.
A1436 – Nanoscale spinel ferrites prepared by mechanochemical route. Thermal stability and size dependent magnetic properties
Among the many types of preparation and processing techniques, the nonconventional mechanochemical route has been recognized as a powerful method for the production of novel, high-performance, and low-cost nanomaterials. Because of their small constituent sizes and disordered structural state, nanoscale materials prepared by mechanochemical route are inherently unstable with respect to structural changes at elevated temperatures. Taking into account the considerable relevance of the thermal stability of nanoscale complex oxides to nanoscience and nanotechnology, in the present work, results on the response of mechanochemically prepared MgFe2O4 and NiFe2O4 to changes in temperature will be presented. Several interesting features are involved in the work, e.g., a relaxation of the mechanically induced cation distribution towards its equilibrium configuration, a disappearance of the superparamagnetism on heating, an increase of both the saturation magnetization and the Néel temperature with increasing particle size, and a core–shell structure of nanoparticles.
A1438 – Etude expérimentale de la combustion d’ordures ménagères et modélisation d’un four d’incinération
Afin de comprendre et de prévoir l’évolution de polluants tels que les métaux lourds lors de l’incinération des ordures ménagères (OM), il est nécessaire de connaître les conditions physicochimiques et thermiques locales qui gouvernent leur transformation, aussi bien au niveau du lit de déchets circulant sur la grille du four d’incinération d’où ils sont émis, qu’au niveau de la chambre de postcombustion où ces derniers vont progresser, transportés par le courant gazeux ascendant. Pour y parvenir, nous étudions expérimentalement la pyrolyse et la combustion d’échantillons d’OM en utilisant la technique de la thermogravimétrie couplée à la spectrométrie de masse. L’étude expérimentale de la combustion d’un lit de déchets sur grille est abordée au moyen d'une installation pilote, instrumentée de façon à pouvoir suivre en continu l’évolution des températures au sein du lit de combustible ainsi que les concentrations de différentes espèces gazeuses. En parallèle, nous présentons un modèle de combustion du lit d’OM qui prend en compte l'ensemble des étapes de transformation de la charge (séchage, pyrolyse, oxydation du carbone résiduel), les réactions d'oxydation des gaz émis lors de l’étape de pyrolyse ainsi que les transferts thermiques par conduction, convection et rayonnement à l'intérieur du lit, considéré comme un milieu poreux. Enfin, la combustion à l’échelle du four (phase gazeuse située au-dessus du lit et chambre de post-combustion) est simulée à l’aide du code de mécanique des fluides FLUENT.
A1437 – Synthesis of YAP phase by a polymeric method and phase progression mechanisms
The phase formation kinetics of YAP (YAlO3) synthesized through the polymeric precursor method was investigated by thermal analysis, X-ray diffraction and FT-IR spectroscopy. We demonstrated that the YAP synthesis is highly dependent on the heat and mass transport during all stages of the synthesis route. In the first stages, during the preparation of amorphous precursor, ‘‘hot spots’’ need to be suppressed to avoid the occurrence of chemical inhomogeneities. Very high heating rates combined with small amorphous particles are advantageous in the last stage during the formation of crystalline phase. We were able to synthesize nanosized particles of YAP single phase at temperatures around 1100 °C for future preparation of
phosphors or ceramics for optics.
A1440 – Prévision de la corrosion sèche des conteneurs de déchets radioactifs en condition d’entreposage : Etude des mécanismes d’oxydation du fer à basse température et simulation numérique de la croissance d’une couche d’oxyde
Située dans le cadre de recherches sur la corrosion sèche des conteneurs de déchets radioactifs en condition d’entreposage, l’étude présentée ici a pour but d’élucider les mécanismes
de croissance des oxydes de fer à basse température et d’autre part de développer un modèle numérique de croissance d’une couche d’oxyde permettant de faire des extrapolations sur de
très longues durées de résultats acquis en laboratoire.
A1439 – Cation distribution in manganese cobaltite spinels Co32xMnxO4 (0 ? x ? 1) determined by thermal analysis
Thermogravimetric analysis was used in order to study the reduction in air of submicronic powders of Co3-xMnxO4 spinels, with 0 ? x ? 1. For x = 0 (i.e. Co3O4), cation reduction occurred in a single step. It involved the CoIII ions at the octahedral sites, which were reduced to Co2+ on producing CoO. For 0 < x ? 1, the reduction occurred in two stages at increasing temperature with increasing amounts of manganese. The first step corresponded to the reduction of octahedral CoIII ions and the second was attributed to the reduction of octahedral Mn4+ ions to Mn3+. From the individual weight losses and the electrical neutrality of the lattice, the CoIII and Mn4+ ion concentrations were calculated. The distribution of cobalt and manganese ions present on each crystallographic site of the spinel was determined. In contrast to most previous studies that took into account either CoIII and Mn3+ or Co2+, CoIII and Mn4+ only, our thermal analysis study showed that Co2+/CoIII and Mn3+/Mn4+ pairs occupy the octahedral sites. These results were used to explain the resistivity measurements carried out on dense ceramics prepared from our powders sintered at low temperature (700–750 °C) in a Spark Plasma Sintering apparatus.
A1444 – Zinc coatings for oxidation protection of ferrous substrates. Part I. Macroscopic examination of the coating oxidation
The oxidation resistance of ferrous materials at elevated temperatures is limited. For that purpose the performance of zinc coatings deposited with hot-dip galvanizing, pack cementation and thermal spraying was considered. In the present work the oxidation resistance of these coatings at 400°C was estimated with light microscopy, thermogravimetric analysis and X-ray diffraction. From this examination it was deduced that in every coating a scale that was mainly composed of ZnO was formed, while Fe oxides were also detected in galvanized and pack coatings. However, the presence of the Fe/Zn phases inside the galvanized and pack coatings led to the formation of cracks, which could expose the substrate and thus destabilize the coating. This phenomenon was not observed in the thermal sprayed coatings, where the Fe/Zn phases were absent. In any case these cracks are not likely to jeopardize the resistance
of the coating because zinc is anodic to steel. Hence, from the above examination it was deduced that the behavior of zinc coatings would be sufficient at 400°C.
A1443 – Characterization of the thermal degradation and heat of combustion of Pinus halepensis needles treated with ammonium-polyphosphate-based retardants
The thermal degradation behavior of P. halepensis needles treated with two ammonium-polyphosphate-based commercial retardants was studied using thermal analysis (DTG) under nitrogen atmosphere. Moreover, for the same experimental material, the heat of combustion of the volatiles was estimated based on the difference between the heat of combustion of the fuel and the heat contribution of the charred residue left after pyrolysis. The heat of combustion of the volatiles was exponentially related to the retardant concentration of the samples. In the range of
retardant concentrations from 10 to 20% w/w the mean reduction percentage of the heat of combustion of the volatiles, with respect to untreated samples, was 18%
A1442 – Low temperature reactivity in agglomerates containing iron oxide. Studies in the Ca(OH)2–C–Fe2O3 system
In this study, we have attempted to explain the complex reactions that occur during the dehydration of Ca(OH)2, in the presence of solid carbon and Fe2O3, in order to clarify their role as eventual precursors to the reduction and high temperature strength characteristics in feedstock agglomerates of iron and steelmaking by-products. A series of simultaneous thermogravimetric (TG), differential thermal analytic (DTA), and mass spectrometric (MS) tests were performed on agglomerated sample mixes of Ca(OH)2, C, and Fe2O3 to test the influence of heating rate and particle size on the transformations occurring below 1,073 K in inert atmosphere. The overall transformation begins with calcium hydroxide dehydration. Nucleation and growth of CaO grains during dehydration, as well as subsequent gasification of solid carbon, are highly dependent on the governing interstitial particle porosity and mildly dependent on the heating rate in and around agglomerates. The reduction of hematite in current agglomerates is, by association to preceding reactions, partly dependent on porosity and heating rate, but the mechanism of reduction was also found to be highly dependent on the particle size of iron oxides. Furthermore, in areas of intimate contact between CaO and iron
oxide, a calcium ferrite phase appears in the form of angular and calcium-rich particles.
A1441 – Condensation during flue gas cleaning
Nowadays, it is an operational routine to clean the flue gases from glass furnaces to remove noxious air pollutant substances. The established processes are highly effective, however
there are failures caused by the condensation of aggressive fluxes inside the large and expensive flue gas filters. To this day, the process control of the flue gas purification equipment is based on empirical data and on experience. Currently available data do not allow to base process design and control on a solid thermodynamic and kinetic foundation. It is the aim of this work to find out under which conditions condensation really takes place. Therefore, first results of collected kinetic data on the condensation from the system Na2O-H2O-SO2-O2-CO2 are shown to estimate the dew points of liquid and solid condensates as a function of flue gas composition and temperature. The measurements are performed in a self-constructed condensation tube. Investigations are particularly focused on the formation of pyrosulfates and bisulfates
A1446 – Kinetics of thermal degradation of polymers. Complementary use of isoconversional and model-fitting methods
The thermal degradation of polymers has been studied quite extensively using thermogravimetric measurements. For the kinetic description, most of the times single rate heating data and model-fitting methods have been used. Since the thermal degradation of the polymers is a very complex reaction, the choice of a reliable model or a combination of kinetic models is very important. The advantages or the disadvantages of using a single heating rate or multiple heating rates data for the determination of the kinetic triplet have been investigated. Also, the activation energy has been calculated with the isoconversional and model-fitting methods. The reaction model was determined with the model-fitting method. The limits of all these procedures were investigated with experimental data of the thermal degradation of the poly(ethylene adipate) (PEAd).
A1445 – Zinc coatings for oxidation protection of ferrous substrates. Part II. Microscopic and oxidation mechanism examination
A common phenomenon in the process industries is the oxidation of the exterior surface of steel pipes used in superheated steam or hot oils networks. For their protection different coatings could be used. In the present work the performance of zinc coatings deposited with hot-dip galvanizing, pack cementation and thermal spraying was considered, in order to protect industrial equipment up to 400°C. For that purpose coated carbon steel coupons were exposed at 400°C and their behavior was examined with light microscopy, scanning electron microscopy and X-ray diffraction. Thermogravimetric analysis was also used in order to observe in situ the oxidation phenomena. From this investigation it was deduced that in every coating a scale is formed that is mainly composed of ZnO, while Fe oxides were also detected in galvanized and pack coatings. The growth of this scale took place at the metal/scale interface. Moreover, as far as it regards the kinetics of the oxidation, it was concluded that the increase of the mass of the specimens is a function of the square root of the exposure time, which means that the scale formed is rather protective for the underlying zinc. From the above observation it seems that the behavior of zinc coatings would be excellent at 400°C. However, the presence of the Fe/Zn phases inside the galvanized and pack coatings led to the formation of cracks, which could expose the substrate and thus destabilize the coating. This phenomenon does not take place in the thermal sprayed coatings, where the Fe/Zn phases are absent.
A1448 – Multicyclic study on the carbonation of CaO using different limestones
Different samples of limestones, with small differences in their stoichiometry, have been studied comparatively. The carbonation reaction has been studied for a large area of isothermal temperatures. The conditions for the multicyclic experiments of calcination/carbonation were: isothermal temperature 670°C, heating time 60 min and carrier gas CO2. The final carbonation
conversion depends mainly on the isothermal temperature of the carbonation reaction and the heating time. The final temperature of the calcination reaction depends on the percentage of CaO that it has not been conversed to CaCO3 in the repeated carbonation experiments. The quantity of CaO that has not been carbonated, in the same sample, affects the values of the coefficients of the kinetic model that fit the calcination reaction. In the multicyclic experiments the carbonation conversion for two of the four studied samples, was high enough in comparison to other samples of calcite. At sample A the reduction of the carbonation conversion during the first five cycles is less than it is at other samples from the literature. Under the above experimental conditions – isothermal temperature and heating time – specific samples consisted mainly of calcite can absorb larger quantities of CO2 than samples consisted mainly of dolomite.
A1447 – Novel lanthanide complexes with di-2-pyridylketone-p-chloro-benzoylhydrazone. Thermal investigation by simultaneous TG/DTG-DTA and IR spectroscopy
The reaction of a hydrated nitrate salt of lanthanide(III) (Ln=Er, Ho, Tb, Gd) or yttrium(III) (Y) with the ligand di-2-pyridylketone-p-Cl-benzoylhydrazone (DpkClBH), afforded air stable solid compounds. The new complexes characterized by means of elemental analysis (C, H, N, Ln), magnetic moment determinations and spectroscopic data (IR, MS). It is proposed that they are
cationic of the general type: [Ln(DpkClBH)2(NO3)2]NO3·nH2O, (n=2, 1, 1, 1, 1.5 for Ln=Y, Gd, Tb, Ho, Er, respectively). Their thermal decomposition was studied in nitrogen atmosphere, between 25–980°C, by using simultaneous TG/DTG-DTA technique. The IR spectroscopy used to determine the intermediates and the final products. The anhydrous nitrate complexes decomposed to the intermediates Ln(DpkClBH)(NO3)2, which upon further heating give a carbonaceous residue of Ln2O3 at 980°C. The mass spectra revealed the molecular ions of the complexes and their possible fragmentation pattern.
A1452 – Thermal decomposition kinetics of the synthetic complex Pb(1,4-BDC) (DMF)(H2O)
Pb(1,4-BDC) (DMF)(H2O) (1,4-BDC=1,4-benzenedicarboxylate; DMF=dimethylformamide) has been synthesized and investigated by elemental analysis, FTIR spectroscopy, thermogravimetry (TG), derivative thermogravimetry (DTG). TG-DTG curves show that the thermal decomposition occurs in four stages and the corresponding apparent activation energies were calculated with
the Ozawa–Flynn–Wall (OFW) and the Friedman methods. The most probable kinetic model function of the dehydration reaction of the compound has been estimated by the Coats–Redfern integral and the Achar–Bridly–Sharp differential methods in this study.
A1451 – Thermal degradation kinetics of in situ prepared PET nanocomposites with acid-treated multi-walled carbon nanotubes
A series of PET/acid-treated multi-walled carbon nanotubes (MWCNTs) nanocomposites of varying nanoparticles’ concentration were prepared, using the in situ polymerization technique. TEM micrographs verified that the dispersion of the MWCNTs into the PET matrix was homogeneous, while some relatively small aggregates co-existed at higher filler contents. Intrinsic viscosity of the prepared nanocomposites was increased at low MWCNTs contents (up to 0.25 wt%), while at higher contents a gradual reduction was observed. The surface carboxylic groups of acid-treated MWCNTs probably reacted with the hydroxyl end groups of PET, acting as chain extenders at smaller concentrations, while at higher concentrations, on the other hand, led to the formation of branched and cross-linked macromolecules, with reduced apparent molecular weights. From the thermogravimetric curves, it was concluded that the prepared samples exhibited good thermostability, since no remarkable mass loss occurred up to 320 °C ( .5%). The activation energy (E) of degradation of the studied materials was estimated using the Ozawa, Flynn, and Wall (OFW), Friedman and Kissinger’s methods. Pure PET had an E = 223.5 kJ/mol, while in the PET/MWCNTs nanocomposites containing up to 1 wt% the E gradually
increased, indicating that MWCNTs had a stabilizing effect upon the decomposition of the matrix. Only the sample containing 2 wt% of MWCNTs exhibited a lower E due to the existence of the aforementioned cross-linked macromolecules. The form of the conversion function for all the studied samples obtained by fitting was the mechanism of nth-order auto-catalysis.
A1450 – Oxidation behaviour of precipitation hardened steel: TG, X-Ray, XRD and SEM study
In the present work the oxidation behavior of ageing treated steel was examined up to 1000°C in different environments (O2 and CO2) and with different heating rates. The examination was conducted by means of thermogravimetric analysis, scanning electron microscopy and X-ray diffraction. In this study it was deduced that in the case of O2 an oxide scale is formed on top of the steel. The oxidation is uniform and the growth of the scale is more intent at low heating rate. It consist of different Fe, Mn, Mo and Cr oxides which are adjusted in the form of layers. This phenomenon was explained by the different diffusion coefficients of each metal in the already formed scale. Regarding the oxidation in CO2, the scale formation takes place at a lower temperature than in the case of O2. Hence the examined substrate is more vulnerable in CO2.
A1449 – Urea-formaldehyde resins characterized by thermal analysis and FTIR method
Urea-formaldehyde (UF) resins are the most used polycondensation resins today, in manufacturing particleboards. UF resins possess some advantages such as fast curing, good performance in the panel, water solubility and low price. However, the main chemical bonds of the UF resins macromolecules are hydrolysis sensitive. This causes low water and moisture resistance performance and subsequent formaldehyde release from the UF-bonded panels. A multitude of pathways have been explored for the improvement of UF resins’ behavior relating either to their synthesis procedure or application parameters during panel manufacture. In this study, two UF resins (a conventional and an innovative one produced at very low pH and temperature conditions) were analyzed for their specifications and characterized with TG-DTA technique in dynamic heating conditions and FTIR measurements both in their pre-polymer and cured state.
A1453 – Investigation of thermal behavior of nicotinic acid
The thermal behavior of nicotinic acid under inert conditions was investigated by TG, FTIR and TG/DSC-FTIR. The results of TG/DSC-FTIR and FTIR indicated that the thermal behavior of nicotinic acid can be divided into four stages: a solid-solid phase transition (176–198°C), the process of sublimation (198–232°C), melting (232–263°C) and evaporation (263–325°C) when experiment was performed at the heating rate of 20 K min–1. The thermal analysis kinetic calculation of the second stage (sublimation) and the fourth stage (evaporation) were carried out respectively. Heating rates of 1, 1.5, 2 and 3 K min–1 were used to determine the sublimation kinetics. The apparent activation energy, pre-exponential factor and the most probable model function were obtained by using the master plots method. The results indicated that sublimation process can be described by one-dimensional phase boundary reaction, g(?)=?. And the 'kinetic triplet' of evaporation process was also given at higher heating rates of 15, 20, 25, 30 and 35 K min–1.
A1455 – Catalytic effects of Fe, Al and Si on the formation of NOX precursors and HCl during straw pyrolysis
The catalytic effects of iron, aluminum or silicon on the formation of NOX precursors (HCN, NH3 and HNCO) and HCl during wheat straw pyrolysis were studied using a thermogravimetric analyzer (TG) coupled with a Fourier transform infrared (FTIR) spectrometer in argon atmosphere. The results show that the presence of iron, aluminum or silicon decreases conversion of straw-N into NH3 with the sequence of Fe[Si[Al. The iron or silicon addition suppresses N-conversion into HCN and HNCO, and the aluminum addition has no notable influence on HCN emission during pyrolysis. The share of N-conversion to NH3 and HCN increases, but that to HNCO and NO decreases a little in the presence of added iron, aluminum or silicon. The addition of SiO2 results in the highest HCl removal efficiency.
A1454 – Removal of VOCs from indoor environment by ozonation over different porous materials
Ozonation of toluene over NaX, NaY and MCM-41 adsorbents was studied targeting for indoor air purification. The combined use of ozone and the various micro- or meso-porous adsorbents aimed to take advantage of the strong oxidizing capability of ozone. At the same time the residual ozone would be minimized due to the enhanced catalytic reaction in the porous structure. To lower the residual ozone level is a crucial issue as ozone is itself an indoor pollutant. The Lewis acid sites in the adsorbents were believed to decompose ozone into atomic oxygen, and the subsequent reactions would then convert the adsorbed toluene into CO2 and H2O. In the dry conditions, the MCM-41 required the smallest amount of material to achieve the 90% reduction target, followed by NaY and NaX. In the more humid environment (50% RH), extra amounts of MCM-41 and NaX adsorbents were required to reach the target as compared with the dry conditions. Desorption experiments were also conducted to study the amounts of various major species held in the adsorbents during the catalytic process. A material balance analysis of the major species in both the effluents and the adsorbents showed that within our experimental conditions, about 20–40% of the removed toluene was carried out via catalytic ozonation while
adsorption covered the rest. Trace amount of intermediate species such as aldehydes and organic acids were identified in the desorbed gas indicating that they were withheld by the adsorbents during the air purification process and those in the effluent were below detection levels.
A1457 – Thermal analysis of gel-derived support for metallic catalyst .Part II. Al2O3–SnO2 system in reductive atmosphere
A series of Al2O3–SnO2 catalysts with the molar ratio of Al2O3 to SnO2 between 1:0 and 0:1 have been characterized by thermal analysis in reductive conditions, TPR and XRD methods. In the reductive conditions in temperatures up to about 1000 K, no reduction of the tin component to the metallic form takes place in the binary gel Al2O3–SnO2. In the temperatures characteristic of the reforming process, only a reduction to SnO occurs in the above binary support. Thermal analysis of the gels in the reductive conditions and TPR results indicate stabilisation of the tin oxide species even in the systems of the molar ratio of Al2O3 to SnO2 of 1:1. The metallic tin appears in the binary gel only after its reduction in the hydrogen atmosphere at temperatures close to ~1100 K.
A1456 – Thermal investigation of strontium acetate hemihydrate in nitrogen gas
The thermal decomposition of strontium acetate hemihydrate has been studied by TG-DTA/DSC and TG coupled with Fourier transform infrared spectroscopy (FTIR) under non-isothermal conditions in nitrogen gas from ambient temperature to 600°C. The TG-DTA/DSC experiments indicate the decomposition goes mainly through two steps: the dehydration and the subsequent decomposition of anhydrous strontium acetate into strontium carbonate. TG-FTIR analysis of the evolved products from the non-oxidative thermal degradation indicates mainly the release of water, acetone and carbon dioxide. The model-free isoconversional methods are employed to calculate the Ea of both steps at different conversion a from 0.1 to 0.9 with increment of 0.05. The relative constant apparent Ea values during dehydration (0.5< 0.9) of strontium acetate hemihydrate and decomposition of anhydrous strontium acetate (0.5<0.9) suggest that the simplex reactions involved in the corresponding thermal events. The most probable kinetic models during dehydration and decomposition have been estimated by means of the master plots method.
A1458 – Synthesis, characterization and thermal behaviour of hemimellitic acid compexes with lanthanides (III)
The complexes of lanthanides(III) with hemimellitic acid (1,2,3-benzenetricarboxylic acid, H3btc) of the formula Ln(btc)·nH2O, where Ln=lanthanide(III) ion and n=2–6 were prepared and characterized by elemental analysis, infrared spectra, X-ray diffraction patterns and thermal analysis. The IR spectra of the complexes indicate coordination of lanthanides(III) through all carboxylate groups. The complexes of La(III), Ce(III), Pr(III) and Er(III) are amorphous. On heating in air atmosphere all complexes lose water molecules and next anhydrous compounds decompose to corresponding metal oxides.
A1461 – Mesoporous micelle templated silica with incorporated C8 and C18 phase
Mesoporous silica material of MCM-41 type was synthesized by co-condensation of highly concentrated octyltriethoxysilane (OTEOS), octadecyltriethoxysilane (ODTEOS) and tetraethoxysilane (TEOS). The obtained hybrid materials were characterized using XRD, TG-DSC and low temperature adsorption/desorption of nitrogen. It was shown that the applied method of synthesis allows to obtain silica of MCM-41 type with a high degree of hydrocarbon saturation
A1460 – Sorption on AS-synthesized MCM-41
Mesoporous materials MCM-41 with the hexagonal arrangement of pores were obtained using dodecyltrimethylammonium bromide and octadecyltrimethylammonium bromide as templating surfactants. Adsorption of toluene and propan-1-ol on the as-synthesized MCM-41 silica samples was investigated using the TG-DTG, DTA and DSC techniques. The sorption mechanism of used adsorptives is discussed in terms of hydrophobicity of pore interior filled with template as well as pore dimensions.
A1459 – Comparison of thermal properties of lanthanide trimellitates prepared by different methods
By diffusion in gel medium new complexes of formulae: Nd(btc)·6H2O, Gd(btc)·4.5H2O and Er(btc)·5H2O (where btc=(C6H3 (COO)33– ) were obtained. Isomorphous compounds were crystallized in the form of globules. During heating in air atmosphere they lose stepwise water molecules and then anhydrous complexes decompose to oxides. Hydrothermally synthesized polycrystalline lanthanide trimellitates form two groups of isomorphous compounds. The light lanthanides form very stable compounds of the formula Ln(btc)·nH2O (where Ln=Ce–Gd and n=0 for Ce; n=1 for Gd; n=1.5 for La, Pr, Nd; n=2 for Eu, Sm). They dehydrate above 250°C and then immediately decomposition process occurs. Heavy lanthanides form complexes of formula Ln(btc)·nH2O (Ln=Dy–Lu). For mostly complexes, dehydration occurs in one step forming stable in wide range temperature compounds. As the final products of thermal decomposition lanthanide oxides are formed
A1464 – Preparation and characterization of uranyl complexes with phosphonate ligands
The preparation, spectroscopic characterization and thermal stability of neutral complexes of uranyl ion, UO22+, with phosphonate ligands, such as diphenylphosphonic acid (DPhP), diphenyl phosphate (DPhPO) and phenylphosphonic acid (PhP) are described. The complexes were prepared by a reaction of hydrated uranyl nitrate with appropriate ligands in methanolic solution. The ligands studied and their uranyl complexes were characterized using thermogravimetric and elemental analyses, ESI-MS, IR and UV–Vis absorption and luminescence spectroscopy as well as luminescence lifetime measurements. Compositions of the products obtained dependent on the ligands used: DPhP and DPhPO form UO2L2 type of complexes, whereas PhP forms UO2L complex. Based on TG and DTG curves a thermal stability of the complexes was determined. The complexes UO2PhP 2H2O and UO2(DPhPO)2 undergo one-step decomposition, while UO2PhP 2H2O is decomposed in a two-step process. The thermal stability of anhydrous uranyl complexes increases in the series: DPhPOPhPDPhP. Obtained IR spectra
indicate bonding of P–OH groups with uranyl ion. The main fluorescence emission bands and the lifetimes of these complexes were determined. The complex of DPhP shows a green uranyl luminescence, while the uranyl emission of the UO2PhP and UO2(DPhPO)2 complexes is considerably weaker.
A1463 – Modified Pechini synthesis of Na3Ce(PO4)2 and thermochemistry of its phase transition
Effect of the synthesis conditions of Pechini technique on crystallinity and purity of Na3Ce(PO4)2 compound was investigated. Nano-sized cerium–sodium phosphate obtained when EDTA was used as an additional chelating agent for Ln3+. The total enthalpy change of Na3Ce(PO4)2 phase transition was determined as 14.2 ±0.7 kJ mol–1 for sample synthesized by conventional solid–solid reaction. The phase transition process was confirmed to occur at 1060°C or in temperature range 920–1060°C depending on thermal treatment of powders.
A1462 – Thermal properties of tetraethylammonium tetrachloro-, bromotrichloro- and tribromochloroferrates (III)
Thermal decomposition of tetraethylammonium tetrachloro-, bromotrichloro- and tribromochloroferrates(III), of general formula [(C2H5)4N][FeBr4–nCln] (n=1, 3, 4), has been studied using the TG-MS, DTA and DTG techniques. The measurements were carried out in an argon atmosphere over the temperature range 293–1073 K. Solid products of the thermal decomposition were identified by Mössbauer spectroscopy.
A1467 – Zinc(II) and cadmium(II) complexes with o-hydroxybenzoic acid or o-aminobenzoic acid and 2-methylimidazole. IR spectra, X-ray diffraction studies and thermal analysis
Mixed complexes of the type: Zn(Hsal)2(2-MeHim)2, Zn(Han)2(2-MeHim)2, Cd(Hsal)2(2-MeHim)2, Cd(Han)2(2-MeHim)2, where Hsal=OHC6H4COO–, Han=NH2C6H4COO–, 2-MeHim=2-methylimidazol) have been synthesized and characterized by IR spectroscopic and X-ray diffraction studies. Single-crystal X-ray structure of Cd(Hsal)2(2-MeHim)2 has been obtained. Thermal behaviour of the compounds was investigated by thermal analysis (TG, DTG, DTA). A coupled TG-MS system was used to analyse the principal volatile products of complexes. Thermal decomposition pathways have been postulated.
A1466 – Thermal parameters of phenylcarbamic acid derivatives using calculated molecular descriptors with MLR and ANN. Quantitative structure-property relationship studies
The aim of this work was to build MLR and ANN models for predicting certain thermal parameters of phenylcarbamic acid derivatives. For 66 compounds belonging to this group DSC analysis was performed. Based on the DSC curves, nine thermal parameters were calculated. The chemical structure of newly synthesized local anaesthetic drugs was encoded in calculated theoretical descriptors. To build the QSPR models Multiple Linear Regression and Artificial Neural Networks were applied. The variable reduction in the case of MLR was performed by means of visual inspection of the significant loading plots obtained by Principal Component Analysis, but using forward selection. Two models of ANN were built: linear and non-linear, but for the reduction of the variables the genetic algorithm was applied. As a result, MLR and ANN models for predicting some thermal parameters of phenylcarbamic acid derivatives were obtained.
A1465 – Thermal, spectroscopic and structural studies of zinc(II) complex with nicotinamide
The zinc(II) complex with nicotinamide (ncam) was prepared and investigated by single-crystal X-ray diffraction, infrared spectrum (FTIR), conductivity and thermal analysis techniques. The formula of complex is [Zn(ncam)2(H2O)4](NO3)2·2H2O. The nicotinamide molecule has three following donor sites: pyridine ring nitrogen, aminonitrogen and carbonyl group oxygen. In this
monomeric complex, the Zn(II) ion is six-coordinated by two pyridine ring N atoms and four water O atoms in a slightly distorted octahedral arrangement. In the crystal structure, intermolecular O–H…O and N–H…O hydrogen bonds link the molecules to form a supramolecular structure. The complex is stable up to 323 and above 360 K it dehydrates in one step losing six water molecules. The dehydration proceeds in the range of 360–438 K, and its enthalpy value is equal to 62.6 ±1.5 kJ mol–1.
A1468 – DSC analysis of Al6061 aluminum alloy powder by rapid solidification
Differential scanning calorimetry (DSC) is a powerful technique that measures the heat evolution from a sample under a controlled condition and studies the phase transformation, precipitation, and dissolution activities. In this work, we investigated the influence of admixed silicon and silicon carbide and the effect of different atmospheres on the heat flow properties and microstructure of atomized Al6061 powder using DSC and scanning electron microscopy. The DSC analysis revealed the addition of silicon considerably decreased the temperature of first endothermic peaks. With an increase in silicon content the enthalpy for the first endothermic peak increased, whereas the second endothermic peak decreased. An endothermic peak,
indicating the formation of AlN, was observed for powders without the silicon addition, but was noticeably absent in the case of alloys with Si addition. The SiC addition has no influence on changing the enthalpy of the systems we investigated. The reason for this behavior is analyzed and presented in this article.
A1471 – Study by DTA/TG of the formation of calcium aluminate obtained from an aluminium hazardous waste
A Spanish hazardous waste from tertiary aluminium industry was used as a raw material for the synthesis of calcium aluminate. An amorphous precursor was obtained by a hydrothermal method at different values of pH. The transformation of the precursor in a crystalline aluminate was followed by TG/DTA up to 1300 °C. At temperatures between 719 and 744 °C, the precursors evolve towards the formation of C12A7 which becomes CA at circa 1016 °C. Mass spectrometry coupled to thermal analyser allowed the identification of the decomposition
A1470 – Application of thermogravimetric analysis to the evaluation of aminated solid sorbents for CO2 capture
In this work a series of solid sorbents were synthesized by immobilizing liquid amines on the surface of a mesoporous alumina. The samples were chemically characterized and BET surface areas calculated from the N2 adsorption isotherms at 77 K. The CO2 capture performance of the sorbents and their thermal stability was studied by thermogravimetric methods. The effect of amine loading on the CO2 capture performance of the prepared sorbents was also evaluated. Analysis of TG-DTG curves showed that thermal stabilization of the amines is significantly improved by immobilizing them on an inorganic support. Temperature-programmed CO2 adsorption tests from 298 K up to 373 K at atmospheric pressure, proved to be a useful technique for assessing the capacity of sorbents for CO2 capture. Alumina impregnated with diethylenetriamine presented the highest CO2 adsorption capacities throughout the tested temperature range.
A1469 – Thermal dehydration of CeP3O9×3H2O by controlled rate thermal analysis
The aim of this work is to highlight the importance of controlling the residual water vapour pressure above the sample as well as the rate of the thermal decomposition during the thermal dehydration of cerium cyclotriphosphate trihydrate CeP 3O9×3H2O. For this reason, the dehydration of the titled compound was followed by both techniques: the constant rate thermal analysis at PH2O=5 hPa and the conventional TG-DTA in air. It has been shown that the pathway of the thermal dehydration depends strongly on the nature of atmosphere above the
sample. However, in air atmosphere CeP3O9×3H2O decomposes in two well defined steps to give first an amorphous, phase in the temperature range 440–632 K, then the cerium polyphosphate Ce(PO3)3 crystallizing in orthorhombic system (C2221) at T>632 K. Whereas decomposition carried out at 5 hPa water vapour pressure, also occurring in two steps, leads first to a crystallized intermediate monohydrate at 259
A1473 – Thermal behavior and other properties of Pr(III), Sm(III), Eu(III), Gd(III), Tb(III) complexes with 4,40-bipyridine and trichloroacetates
A novel mixed-ligand complexes with empirical formulae: Ln(4-bpy)1.5(CCl3COO)3 nH2O(where Ln(III) =Pr, Sm, Eu, Gd, Tb; n = 1 for Pr, Sm, Eu and n = 3 for Gd, Tb; 4-bpy = 4,40-bipyridine) were prepared and characterized by chemical, elemental analysis and IR spectroscopy. Conductivity studies (in methanol, dimethylformamide and dimethylsulfoxide) were also described. All complexes are crystalline. The way of metal–ligand coordination was discussed. The thermal properties of complexes in the solid state were studied under non-isothermal conditions in air atmosphere. During heating the complexes decompose via intermediate products to the oxides: Pr6O11, Ln2O3 (for Sm, Eu, Gd) and Tb4O7. TG-MS system was used to analyze principal
volatile thermal decomposition and fragmentation products evolved during pyrolysis of Pr(III) and Sm(III) compounds in air.
A1472 – Estimate of firing temperatures through bone-based chalcolithic decorated pottery
Guadiana River Chalcolithic middle basin (Badajoz, Spain) pottery was in many cases decorated with bone, which suffers a hydroxyapatite to b tri-calcium phosphate transformation while firing. The evolution of physico-chemical characteristics of bone decorations and experimentally heated fossil bone as a function of temperature through 1) major XRD planes, and 2) OH librational mode at 630 cm–1 in the FTIR spectra let us establish a correlation between the physico-chemical features and firing temperature, allowing the estimate of firing temperatures for bone decorated pottery. What is a reliable criterion to differentiate over potters behavior and skill during the pottery production.
A1476 – Investigation of clinoptilolite rich natural zeolites from Turkey: a combined XRF, TG/DTG, DTA and DSC study
Turkey clinoptilolite-rich tuffs from Gördes and Bigadic¸ regions of western of Anatolia and their exchanged forms (K?, Na?, Mg2? and Ca2?) were characterized by TG/DTG-DTA, DSC and XRF methods and the surface areas were also determined for both tuffs. TG-DTG and DTA curves of all clinoptilolite samples were measured in the temperature range 30–1000 °C. All clin-
optilolite samples had major, rapid mass losses between 30 and 200 °C, with slower and less significant mass losses at higher temperatures. The mass loss of the Natural-G is 9.54% while that of the Natural-B sample is 10.50%. Water content increases in the order of KNaCaMg for Bigadic¸ clinoptilolite samples and in the following sequence KNaMgCa for Gördes clinoptilolite samples. One mass loss step for all clinoptilolite samples was observed using differential scanning calorimeter (DSC) in the range of 30–550 °C.
A1475 – Kinetics of combustion of oil shale with polystyrene
The combustion kinetics of Göynük oil shale, polystyrene and several polystyrene–oil shale blends were investigated by thermogravimetric analysis in the present study. Experiments were conducted at non-isothermal conditions with a heating rate of 5, 10 and 20 K min–1 in the 298–1173 K temperature interval under an air atmosphere. Differential thermogravimetric data were analyzed by two different models. Effects of blending ratio of oil shale and polystyrene and heating rate on the combustion kinetics were investigated. Kinetic parameters were determined and the results were discussed.
A1474 – Kinetic analysis of thermal decomposition of some Co-complexes of three unsymmetrical Vic-dioximes ligands. Model fitting and model-free method
The thermal decomposition of three new reagent cyclohexylamine-p-tolylglyoxime (L1H2), tertiarybutyl amine-p-tolylglyoxime (L2H2) and secondary butylamine-p-tolylglyoxime (L3H2 and their Co-complexes were studied by both isothermal and nonisothermal methods. As expected, the complex structure of Co-complexes, different steps with different activation energies were realized in decomposition process. Model-fitting and model-free kinetic approaches were applied to nonisothermal and isothermal data. The kinetic triplet (f( ), A and E) related to nonisothermal model-fitting method can not be meaningfully compared with values obtained from isothermal method. The complex nature of the multi-step process of the studied compounds was more easily revealed using a wider temperature range in nonisothermal isoconversional method.
A1478 – Thermal behavior and immersion heats of selected clays from Turkey
Four clays (two bentonites and two kaolinites) from Turkey were investigated by X-ray diffraction (XRD), thermal analysis (DTA/TG-DSC) and surface area measurement techniques. Mineralogically bentonite samples were characterized low concentration of montmorillonite and high level of impurities. Both kaolinite samples mainly contained kaolinite and quartz as major mineral. TG-DTA curves of all clay samples were measured in the temperature range 30–1200 °C. The total % weight losses for the bentonite samples (B1 and B2) and the kaolinite
samples (K1 and K2) were determined as 14.50, 13.42, 5.55 and 11.85%, respectively. Differential Scanning Calorimeter (DSC) analyses of samples were carried out by heating the samples from 30 to 550 °C. The immersion heats of clay samples were measured using with a Calvet-type C-80 calorimeter. The higher exothermic Qimm values were determined for bentonite samples compared to kaolinite samples.
A1477 – Thermal treatment of zeolitic tuff
In this study, the zeolitic tuffs having clinoptilolite obtained from Bigadic region of western of Anatolia, Turkey were investigated as regards to whether it is possible to be transformed into amorphous phase from them. At first, the zeolite tuffs rich in clinoptilolite were characterized using XRD, DTA, TG, DSC, and FTIR standard methods. All the samples were heated at 110 °C
for 2 h and then were expanded within 5 min between the temperatures 1200 and 1400 °C. In addition, porosity and density were determined. The resistance values of all the samples were measured in acidic and basic media. These samples were also analyzed. As a result of this study, zeolitic tuffs in clinoptilolite were transformed into amorphous phase, and especially in chemical industry were found convenient.
A1479 – Nanocomposites based on gelatin and montmorillonite. Morphological and thermal studies
Model gelatin/montmorillonite (Ge/MMt) composites were obtained for a variety of unmodified clay concentrations and in the absence of additives, with the main goal of evaluating the effect of the morphologies developed on the composites thermal stability. Morphologies turned form partially exfoliated to exfoliate/intercalated and eventually agglomerated with increasing clay
loading, as was observed by atomic force microscopy. Formulations containing 3–10 mass% montmorillonite resulted in an enhancement of composites thermal stability due to stabilizing interactions between co-components, such as strong hydrogen-type bonds, in agreement with the partially exfoliated/intercalated morphologies. Higher clay concentrations showed lower stabilizing effect in agreement with the agglomerated structures developed and the less effective interactions between co-components.
A1482 – Mechanistic investigations of photo-driven processes over TiO2 by in-situ DRIFTS-MS: Part 1. Platinization and methanol reforming
There is growing interest in the reforming of methanol and other bio-oxygenates as high-density, CO2-neutral, renewable sources of H2. Photocatalysis is worthy of investigation as a potentially economic means to drive such endothermic processes. In this study, in-situ DRIFTS, adapted for optical pumping and coupled to on-line MS, was used to observe the surface of TiO2 (Degussa P25) during photo-metallization from pre-sorbed hexachloroplatinate, at a nominal Pt loading of 1 wt%, and to evaluate photo-reforming of methanol over the resulting Pt/TiO2 composite. The irreversible growth of a quasi-continuum absorption, characteristic of the surface plasmon resonance of zerovalent Pt nanoparticles, along with bands at 2050 and 1830 cmÿ1 typical of metal-adsorbed CO, indicated that photo-metallization was complete typically within 2 hours. Methanol reforming was photocatalyzed at room temperature but in low quantum efficiency, fz0.01. However, this was raised substantially, to fz 0.07, simply by the application of mild heating (T # 70 C). Photo-reforming proceeded at a fixed rate but the H2/CO2 ratio generally exceeded that of the reforming stoichiometry, suggesting some retention of CO2. The photo/thermal synergy was rationalized by model DRIFTS studies, starting from formalin (hydrated formaldehyde), which revealed key features of the mechanism. TiO2 promoted the Cannizzaro disproportionation in the dark, yielding formate and methoxy species already at 40 C.
While methoxy was effectively cycled back to the initial photo-dehydrogenation stage, the slow step was identified as formate decomposition to H2 and CO2. The low value measured for the apparent activation energy ( 40 kJ molÿ1) was taken as supporting evidence for ‘water-assisted destabilization’ of formate, as originally reported by Shido and Iwasawa. No evidence was found for an alternative thermal- or photo-reforming mechanism involving the Pt–COad species.
A1481 – Thermal characterization of the clay binder of heritage Sydney sandstones
Thermal analysis has been employed in a study of the degradation of heritage Sydney sandstone used in St Mary’s Cathedral in Sydney, Australia. TG and DSC have been used to characterise the clay components removed from weathered and unweathered sandstone. Two types of kaolin clays – kaolinite and its polymorph, dickite – have been identified. A higher amount of dickite present in the clay of weathered sandstone indicates that a kaolinite-to-dickite transformation occurs upon weathering. XRD hot stage analysis was also used to demonstrate the presence of a more thermally stable polymorph of the kaolinite.
A1480 – TG-MS analysis of the thermal decomposition of pig bone for forensic applications
In order to investigate the potential of thermal analysis for the determination of post-mortem age, rib bone specimens were collected from the remains of a number of slaughtered pigs that were allowed to decompose in the Australian bush in a controlled site under a range of conditions for time periods ranging from 1 to 5 years. The bone specimens were cut in cross-section with the compact bone collected for analysis. TG-MS curves were collected by heating bone samples to 1100°C in an argon atmosphere. The TG-MS data showed significant differences for the pig bone specimens derived from the different environments and showed trends in peak size correlating with age. The reported data suggest that TG-MS has significant potential for the identification of origin as well as the ageing of skeletal remains in a forensic context.
A1484 – TGMS analysis of archaeological bone from burials of the late Roman period
The use of thermogravimetric analysis–mass spectrometry (TGMS) to study the state of preservation of archaeological bones has been investigated. As part of a collaborative multi-analytical study, bones exhumed from graves of the late Roman period in France and Italy were examined. A decrease in organic matter for the archaeological bones compared to that for new bone was confirmed, demonstrating that diagenesis of aged bones can be detected using TGMS. Different amounts of collagen were determined for bones from different graves and could, for the
majority of specimens, be correlated with the visually observed preservation states.
A1483 – Dehydroxylation kinetic and exfoliation of large muscovite flakes
The thermal transformations of muscovite flakes are a key point in many applications because besides dehydroxylation a significant exfoliation process occurs. Dehydroxylation kinetic is experimented by isothermal TG analyses in the 700–850°C temperature range and described with the Avrami theory. Hydroxyl condensation predominates at the onset of the process, but water diffusion is the most important process when the transformed fraction is high. The progressive transition between the two transformation stages contrast with the more accentuated transition for a ground muscovite. The activation energy varies weakly (190–214 kJ mol–1) in the whole transformation process that supports the co-existence of hydroxyl condensation and diffusion phenomena. Dehydroxylation kinetic increases strongly with temperature and decreases with the reaction advancement. Exfoliation is correlated with dehydroxylation kinetic and occurs in a narrow transformation and temperature ranges. An in-situ combination process of hydroxyls occurs and water vapor favors the layer expansion.
A1486 – Influence of the processing parameters of slurries for the deposit of nickelate thick films
Thick films cathodes for Solid Oxide Fuel Cells (SOFC) are prepared by dip-coating slurries made of several lanthanum nickelate oxide powders onto yttria stabilized zirconia (YSZ) substrates. The processing parameters for the slurries preparation and the multilayers coating have been optimized to obtain homogeneous, crack-free, thick and adherent films after heat treatment
A1485 – Thermal ignition and self-heating of carbon nanotubes: From thermokinetic study to process safety
A comprehensive investigation on the kinetics of combustion of multiwall carbon nanotubes (MWCNTs) produced by vapour chemical deposition has been undertaken. The kinetics parameters were determined from isothermal and non-isothermal combustion tests i.e. by both thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The activation energy of CNT combustion was found to be about 150 kJmol?1. The oxidation of carbon nanotubes (CNTs) appears to be a single step reaction well represented by a cylindrical shrinking core model. The consistency of this model was assessed both by comparing the activation energy extracted from TGA and DSC, and by theoretical considerations on the geometrical development of CNT oxidation. The influence of oxygen concentration on CNT combustion was also studied. Finally, these results combined with those obtained by self-ignition tests in baskets lead
to recommendations for a safe handling and storage of CNTs.
A1489 – Thermal study of phenol–formaldehyde resin modified with cashew nut shell liquid
In this study, an experimental phenol–formaldehyde resin with 20% phenol replacement by cashew nut shell liquid (CNSL) was studied and compared with a conventional phenol–formaldehyde resin synthesized totally from petrochemical raw materials. The resins were characterized with standard lab analysis for their physicochemical specifications, while their thermal properties were studied with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). For comparison reasons pure CNSL and wood were also included in the TGA study. A DSC study conducted both for the neat resins and the system wood–resin as to examine the effect of wood on the curing performance of the resins in the real time conditions of their usage at the wood-based panels industry.
The adhesion strength of these resins was investigated by their application in plywood production. The plywood panels were tested for their shear strength and wood failure performance while their free formaldehyde emissions were determined with the desiccator method. It was proved that although the neat CNSL modified PF resin (PCF) cures at longer time and higher temperature than a conventional PF resin, wood affects it more significantly, resulting in the evening of their curing performance. This is a novel finding that manifests the possibility of replacing a convention PF resin by a CNSL modified one in the plywood production, without changing any of their production conditions and with improvement to their overall properties.
A1488 – In situ prepared PET nanocomposites: Effect of organically modified montmorillonite and fumed silica nanoparticles on PET physical properties and thermal degradation kinetics
In the present study a series of PET nanocomposites were prepared by in situ polymerization using different amounts of organically modified montmorillonite (OMMT) with a triphenylphosphine compound and fumed silica nanoparticles (SiO2). As verified by TEM micrographs, the dispersion of both nanoparticles into the PET matrix was homogeneous while montmorillonite was dispersed in the exfoliated form. The intrinsic viscosities of the prepared nanocomposites were affected by the addition of the nanoparticles and in both cases a slight increase was observed. Tensile strength was also increased by increasing nanoparticles content while both types of nanoparticles act as nucleating agents, enhancing the crystallization rates of PET. From the thermogravimetric curves it was concluded that PET and the samples with different nanoparticles presented good thermostability, since no remarkable mass loss occurred up to 320 °C (<0.5%). The activation energy (E) of degradation of the studied samples was estimated using the Ozawa, Flynn and Wall (OFW) method. Pure PET had an E = 223.5 kJ/mol while the activation energy of PET/SiO2 2 wt.% nanocomposites was almost identical (222.1 kJ/mol). However, PET/OMMT 2 wt.% nanocomposites exhibited a higher activation energy (228.3 kJ/mol), indicating that OMMT incurred a stabilizing effect upon the decomposition of the matrix. The form of the conversion function for all the studied samples obtained by fitting was the mechanism of nth-order auto-catalysis.
A1487 – Influence of Ni substitution on redox properties of In2(1?x) Ni2xTiO5?? oxides
The thermal behavior of mixed metal oxides with nominal compositions of In2(1?x)Ni2xTiO5?? where 0.0 ? x ? 0.2, were investigated by recording their temperature programmed reduction (TPR). The samples were synthesized by ceramic route and analyzed for phase composition using powder X-ray diffraction. The TPR profile of pristine In2TiO5 indicated the reduction of In3+, which takes place predominantly over the other species Ti4+ in In2TiO5 sample. Ni substitution at In3+ site induced ease in reducibility as indicated by lowering of onset reduction temperature and Tmax. Moreover, it also facilitated the reduction of otherwise non reducible cation, Ti4+. Ni metal initially formed by reduction, dissociates and activates hydrogen which then reacts and reduces the oxide (even Ti4+), a case of hydrogen spillover. The metallic Ni forms an alloy Ti2Ni with reduced Ti metal and ?In3Ni2 alloy with the reduced In metal as evident by XRD and XPS results of the reduced residue of 20% Ni doped (In1.6Ni0.4TiO5??) sample. Due to formation of new alloy phases of ?In3Ni2 and Ti2Ni, the rate of hydrogen adsorption diminishes which slows down further hydrogen activation and consequent further Ti4+ reduction.
A1490 – Determination of standard enthalpy of vaporization and thermal decomposition reactions from derivative thermogravimetric (DTG) curves
The paper proposes the use of the derivative thermogravimetric (DTG) curve for the acquisition of equilibrium vapor pressure and dissociation pressure for the materials and derivation of their standard enthalpy of formation from single DTG curve recorded under optimum experimental conditions, such as heating rate and the sweep rate of the carrier gas passed over the sample. The vapor pressure and the standard enthalpy of sublimation (?subH ° 298.15) of CdI2 and the dissociation pressure and the standard enthalpy of formation of CaCO3 derived from their DTG curves are found to be in good agreement with the best assessed values reported in the literature.
A1493 – Arrhenius parameters determination in non-isothermal conditions for the uncatalyzed gasification of carbon by carbon dioxide
Non-isothermal thermogravimetric data were used to evaluate the Arrhenius parameters (activation energy, E, and pre-exponential factor, A) for the uncatalyzed gasification by carbon dioxide of two carbons, select as steam activated carbon (BPL) and SP-1 spectroscopically pure graphite. The paper reports on the application of the model-free isoconversional method (KAS/Vyazovkin linear method) for evaluating the activation energy of the gasification process. Activation energies have been calculated by this method were in good agreement with literature data for similar carbons. On the other hand, by means of the kinetic compensation relation between E and ln A, which was established by the model-dependent Coats–Redfern method, the value of the pre-exponential factor was estimated from the known value of the model-independent activation energy.
A1492 – Detail kinetic analysis of the thermal decomposition of PLA with oxidized multi-walled carbon nanotubes
Nanocomposites of poly(l-lactic acid) (PLA) with oxidized multi-walled carbon nanotubes (MWCNTs-COOH) were prepared by solved evaporation method containing 2.5 wt% MWCNTs-COOH. From the thermogravimetric curves it can be seen that PLA/MWCNTs-COOH nanocomposite present a relatively better thermostability than PLA. The activation energy was calculated with the isoconvertional Ozawa–Flynn–Wall and Friedman's methods. For all the mass conversions, PLA has lower values than the nanocomposite. From the variation of the activation energy (E) with increasing degree of mass conversion, especially for the PLA, it was concluded that the decomposition of all the samples is taking place with a complex reaction mechanism with the participation of at least two different mechanisms. The best fitting of experimental data with theoretical models for PLA and PLA–2.5 wt% MWCNTs-COOH give nth-order for the first mechanism and nth-order with autocatalysis (Fn–Cn) for the second mechanism with different activation energies.
A1491 – The stress corrosion cracking behavior of ZIRCALOY-4 fuel claddings with different rates of oxidation
With the aim to study the Zircaloy-4 Stress Corrosion Cracking (SCC) susceptibility several samples with different levels of thickness of the oxide layer (2.7µm, 4.5µm and 8µm) were prepared using a thermo-analyzer SETARAM SETSYS EVOLUTION 24. The mode of stressing chosen in this work was according to the C-ring method. In this case, the value of the stress was estimated at 480 MPa using the ANSYS code. The oxidized C-rings were tested by electrochemical methods in KI 0.55g/l + LiOH solution (pH=10.5) at 850C. The metallographic method emphasized some pits and incipient cracks on the inner surface of the tested samples. The number of pits increases with the oxide thickness. Only for the samples having an oxide layer thickness of 8µm the cracking of the external oxide layer consisting of monoclinic zirconium oxide was put in evidence. For this reason, in the tetragonal oxide under-layer (formed at the zirconium matrix – zirconium oxide interface) micro stress appears to be a fact that generates breakage of this internal under-layer. In this way, the corrosive agent may attack the zirconium alloy, leading to SCC initiation.
A1496 – In situ prepared PBSu/SiO2 nanocomposites. Study of thermal degradation mechanism
A series of nanocomposites consisted of poly(butylene succinate) (PBSu) and fumed silica nanoparticles (SiO2) were prepared using the in situ polymerization technique. The amount of SiO2 used directly affected the final molecular weight of the prepared polyesters. At a low SiO2 content (0.5 wt.%) the molecular weight obtained was higher compared to neat PBSu, however at higher concentrations this was gradually reduced. The melting point of the matrix remained unaffected by the addition of the nanoparticles, in contrast to the crystallinity, which was dramatically reduced at higher SiO2 contents. This was mainly due to the extended branching and cross-linking reactions that took place between the carboxylic end groups of PBSu and the surface silanols of the nanoparticles. Thermal degradation of the PBSu/SiO2 nanocomposites was studied by determining theirs mass loss during heating. From the variations of the activation energies, calculated from the thermogravimetric curves, it was clear that nanocomposites containing 1 wt.% SiO2 content had a higher activation energy compared to pure PBSu, indicating that the addition of the nanoparticles could slightly increase the thermal stability of the matrix. However, in PBSu/SiO2 nanocomposite containing 5 wt.% SiO2 the activation energy was smaller. This phenomenon should be attributed to the existence of extended branched and cross-linked macromolecules, which reduce the thermal stability of PBSu, rather than to the addition of fumed silica nanoparticles.
A1495 – Investigation of Fe-based oxyhydroxy-fluoride with hollandite-type structure
Well crystallized Fe-based oxyhydroxy-fluoride with the FeO(OH0.2F0.8)·0.2H2O chemical composition has been prepared from hydrolysis of Fe trifluoride under supercritical CO2 conditions. Investigation by Mössbauer spectroscopy and neutron diffraction show that this compound crystallize in the monoclinic symmetry (SG: I2/m, a = 10.447(7) Å, b = 3.028(2) Å, c = 10.445(4) Å, ? = 90.00(3)°). Taking into account the Fe–O(F) bond distances, F? anions are mainly located on the common vertices of Fe octahedra whereas OH? groups occupy mainly the shared edges of the Fe octahedra. Two various highly distorted octahedral sites have been identified with Fe–O/F bond distances varying from 1.90 Å to 2.31 Å. One Fe site is more distorted than in FeO0.8OH1.2·0.2Cl akaganeite because of the random distribution of F?/OH?/O2? in the vicinity of this Fe cation.
A1494 – About MX3 and MX2 (Mn+ = Mg2+, Al3+, Ti4+, Fe3+; Xp? = F?, O2?, OH?) nanofluorides
Several nanosized fluoro-compounds have been prepared by microwave-assisted solvothermal routes: Al3+-, Fe3+- and Ti4+-based oxyfluorides with the hexagonal tungsten bronze (HTB) framework, Ti4+-based fluorinated anatase, and rutile MgF2. The structural features have been determined using XRD and TEM analyses. The presence of OH? groups substituted for F? ions has been demonstrated for all of these nanofluorides. In Al- and Mg-based nanofluorides, the OH rate can be reduced by F2-direct fluorination. Furthermore, the higher the polarizing power of the cation, the higher the oxygen content. For cation with high formal charge, such as Ti4+ stabilized in a distorted octahedral site, the occurrence of O2?/OH?/F? anions in its vicinity as well as vacancies have to be mentioned. Finally coupling the microwave-assisted solvothermal route with the F2-direct fluorination allow preparing high surface area metal fluorides where the amount of oxygen is noticeable and contribute to create under-coordinated cationic species at the surface which can induce high Lewis acidity.
A1498 – From compressibility to structural investigation of sodium dodecyl
sulphate — Part 2: A singular behavior under pressure
Investigations were carried out to elucidate the compression behavior of a powdered surfactant, sodium dodecyl sulphate (SDS), based on a comparison with the main component of a detergent formulation, i.e. the chorine provider (DCCNa). The energetic analysis based on the compression cycles highlighted a lower compressibility of SDS compared with DCCNa, especially due to its worse packing ability, larger elasticity and bad cohesion ability. Also, it pointed out that the pycnometric density seemed to be overrun under pressure whereas a residual porosity had been evidenced in the expanded tablets. DSC/DTA analysis, Raman spectroscopy as well as powder X-ray diffraction refuted the hypothesis of a physico-chemical transformation of SDS under pressure. This was in accordance with the morphology of the SDS particles, quite unchanged after compression. The pycnometric density measurements have been improved; firstly, it allowed to properly express the compaction ratio of the ejected SDS tablets, and secondly, it led to conclude to a reversible intrinsic compressibility for pressures higher than 50 MPa, explained by the predominant elastic behavior of SDS.
A1497 – High-temperature oxidation of precipitation hardening steel
The oxidation of precipitation hardening (PH) steels is a rather unexplored area. In the present work an attempt is made to estimate the oxidation mechanism and the kinetics for a PH steel. For this purpose specimens of the material under examination were isothermally heated at 850, 900 and 950 °C for 15 h. The as-treated samples were examined with SEM and XRD, while kinetics was based on TGA results. From this examination it was deduced that a thick scale is formed on the substrate surface, which, regardless the oxidation temperature, is composed by different oxides arranged in the form of successive layers. Of course the distribution in the different layers is not uniform but the oxides of the minor elements tend to be gathered at certain layers. The layer close to the substrate is compact while the upper layer seems more porous. Regarding kinetics, the mathematical analysis of the collected data shows that the change of the mass of the substrate per unit area vs time is described by a parabolic law. Hence oxidation is impeded as the exposure time increases.
A1500 – The oxidation mechanisms of Cu54Ni45Mn1 (Constantan) tapes: Kinetic analysis
The kinetic parameters, namely the triplet activation energy EA, model function f(?) or g(?) and pre-exponential factor A of the oxidation of Constantan tapes in 1 atm of oxygen have been determined from both isothermal and non-isothermal thermogravimetry. For isothermal experiments, with temperatures ranging from 650 °C to 900 °C, the results from direct conversion of the weight increase as a function of the time and curve fitting, are compared with the isoconversion method. For the non-isothermal experiments, with heating rates from 1 °C/min to 20 °C/min, comparison is made between the Friedman differential method and the integral methods of Kissinger, Ozawa and Li and Tang. All methods give apparent activation energies with relative standard deviations as low as 3%. The results converge to the identification of three stages in the oxidation behaviour. A parabolic law for reaction extents ? below 15% with EA = 246 ± 7 kJ mol?1, ln A = 14.3, is followed by two linear stages with EA = 244 ± 4 kJ mol?1 and ln A = 15.3 for 0.18 < ? < 0.35 and EA = 228 ± 15 kJ mol?1, ln A ? 13 for ? > 45%, respectively
A1499 – The investigation of thermal decomposition pathways of phenylalanine and tyrosine by TG–FTIR
An online-coupled TG–FTIR evolved gas analysis (EGA) instruments have been used to identify and monitor the evolution of gaseous products during the thermal decomposition of phenylalanine and tyrosine in flowing N2 atmosphere up to 800 °C. The results indicate that the thermolysis processes of these two compounds are similar. For both of them the main primary decomposition steps are two competing paths: the direct decarboxylation and the concerted rupturing of C–C bonds. And the primary decomposition reactions also include deamination and dehydration. The main secondary reaction is the crack of cyclic dipeptide which also presents two competing pathways. The main gaseous products are NH3, H2O, CO2, CO, HNCO, HCN and some organic compounds. However, compared with tyrosine, the decomposition of phenylalanine is more complete and involves less secondary reaction. That is caused by their different thermal stability and decomposition temperature
A1501 – Thermochemistry of decomposition of RE2O2CO3 (RE = Sm, Eu)
Thermochemistry in the decomposition of samarium di-oxycarbonate, Sm2O2CO3(s) and europium di-oxycarbonate, Eu2O2CO3(s) was studied over the temperature regions of 755–987 K and 773–989 K, respectively. The equilibrium properties of the decomposition reactions were obtained by tensimetric measurement of the CO2(g) pressure over the biphasic mixture of RE2O2CO3(s) and RE2O3(s) at different temperatures (RE = Sm, Eu) and also by thermogravimetric analysis of the decomposition temperature at 1 atmosphere of CO2 pressure. The median enthalpy and entropy of the decomposition of the oxycarbonates were calculated by the second law analysis and their thermodynamic stabilities were derived. The results are discussed in the light of available thermochemical data of the compounds
A1505 – A study on isothermal kinetics of thermal decomposition of cobalt oxalate to cobalt
Thermal decomposition of cobalt oxalate (CoC2O4·2H2O) was studied using TG, DTA and XRD techniques. Non-isothermal studies revealed that the decomposition occurred in two main stages: removal of water and next decomposition of CoC2O4 to Co. Isothermal kinetic studies were conducted for the second stage of decomposition at six different temperatures between 295 and 370 °C in reducing (He + 15 vol% H2) atmosphere. Kinetic equation was found to obey g(?) = [?ln(1 ? ?)]1/n = kt relationship with varying values of n between 2 and 4. The variation of activation energy between 73.23 and 119 kJ mol?1 from the lowest to the highest temperature of decomposition indicated the multi-step nature of the process. SEM analysis revealed the formation of nano-size powder in this temperature range. Thermal decomposition at 550 °C for 30 min was found to be optimum condition producing fine size, non-pyrophoric and spherical powder in larger scale of production. Both hcp and fcc phases were present in the cobalt powder at room temperature.
A1504 – Mesoporous silica synthesis: Energetics of interaction between framework and structure directing agent
The thermodynamics of mesoporous silicas (MCM-41, MCM-48, SBA-15, and SBA-16) were studied by solution calorimetry at 323 K in 25% aqueous HF. The enthalpies of formation were determined for calcined mesoporous silica (MS) and organic structure-directing agent (SDA) occluded samples (SDA: n-hexadeciltrimethylammonium bromide or CTAB, Pluronic P123, and Pluronic F127). The following are the measured interaction enthalpies between the MS and SDA: MCM-41/CTAB, ÿ6.1 kJ/mol SiO2; MCM-48/CTAB, ÿ12.3 kJ/mol SiO2; SBA-15/P123, ÿ19.7 kJ/mol SiO2; SBA-16/F127, ÿ19.9 kJ/mol SiO2. Per unit surface area, these interactions are ÿ0.08, ÿ0.15, ÿ0.43, and ÿ0.40 J/m2, respectively. Though these SDA–frame-
work interaction energies are still small in magnitude, they are somewhat more exothermic than those in silica zeolite formation, reflecting the greater metastability of the MS materials and the role of the long chain SDA in stabilizing and space-filling the large pores. The cubic MS (SBA) show stronger SDA interactions than the hexagonal (MCM). The interaction energies confirm a complex landscape of many competing structures of similar energy; with the role of SDA kinetic in selecting a specific structure rather than energetic in strongly stabilizing a given state, as has already been noted for zeolites. The enthalpies of the calcined MS relative to quartz determined by HF solution calorimetry in this study are in excellent agreement with those determined previously by high temperature oxide melt solution calorimetry.
A1503 – Experimental investigations and thermodynamic description of the PbO–Fe2O3 system
The knowledge of the quinary Pb–Bi–O–Fe–Hg is necessary for understanding the degradation mechanisms of the T91 steel used as structure material in future ADS nuclear reactors. In this device, the steel will be in direct contact with the liquid spallation target (which is constituted by lead or lead-bismuth eutectic) surrounded by a reduced oxygen pressure atmosphere. In the present work, the characterization of the pseudo-binary PbO–Fe2O3 cut has been performed. In order to complete the available data in the literature, some experimental investigations by differential thermal analysis (DTA), isothermal annealing, powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) have been done. These results have allowed proposing a thermodynamic assessment using the Calphad method.
A1502 – Chemical preparation and thermal behavior of neodymium cyclotriphosphate pentahydrate NdP3O9·5H2O: A study by Controlled Rate Thermal Analysis (CRTA)
A new neodymium cyclotriphosphate pentahydrate powder, NdP3O9·5H2O, has been prepared using a classical chemistry method and characterized by X-ray diffraction and infrared spectroscopy techniques. The IR spectrum shows the characteristic bands of cyclotriphosphates as the triplet in the range 1055–1007–917 cm?1.The thermal behavior of the titled compound was also carried out using conventional thermal analysis techniques (TG and DSC) under air atmosphere and Controlled transformation Rate Thermal Analysis (CRTA) technique under constant water vapour pressure of 5 hPa. It was shown that thermal treatment in air, with linear heating rate of 10 K min?1, favourites the structure breakdown as soon as the release of water molecules starts. In this case an amorphous compound is obtained, which then crystallizes at 1073 K and gives the polyphosphate Nd(PO3)3. However, by CRTA technique at PH2O=5?hPa, the water molecules are eliminated with a lower rate which permits to save the initial structure up to an advanced dehydration step. The breakdown of the initial structure is immediately followed by the crystallization of the anhydrous polyphosphate Nd(PO3)3 phase in the temperature range 455 K < T < 793 K.
A1506 – Thermal stability investigation of organo-acid-activated clays by TG-MS and in situ XRD techniques
Organo-acid-activated clays were prepared with different surfactant contents by reaction of hexadecyltrimethylammonium hydroxide solution and acid-activated clays. The intercalated cations adopted different orientation in the interlayer spacing of the acid-activated clays and their thermal stability depended on the up taken amounts, acidity of the clay sheets and on the heating temperatures. The thermal stability of these materials was investigated using TG-MS, and followed by the in situ X-ray diffraction in nitrogen atmosphere. The clay sheets affected the decomposition of the surfactants, and as per consequence the thermal stability of the surfactants. TG-MS revealed that different types of water molecules were detected during the heating process with additional CO2, alkanes and alkenes species at temperatures above 200 °C. The interlayer spacing collapsed after completed degradation of the intercalated surfactants.
A1508 – Influence of oxygen concentration on the kinetics of cellulose wadding degradation
The kinetics of thermal decomposition of cellulose wadding was investigated from TG–MS experiments. Different oxygen concentrations in the atmosphere and several heating rates were used to study the influence of oxygen concentration on the mass loss of the sample and on the emission of gases. A shift and an amplitude variation of the DTG curves as well as an increase of the emission of gases such as CO and CO2 were observed. Then, a kinetic model was proposed to predict the mass loss of the cellulose wadding. Three stages were considered: the cellulose pyrolysis, the char oxidation and the decomposition of calcium carbonate. For the pyrolysis, the kinetic parameters were expressed according to the partial pressure of oxygen. For the char oxidation, a power law was used to account for the influence of oxygen whereas the other kinetic parameters were considered constant regardless of oxygen concentration. The decomposition of calcium carbonate was modelled by a first order influenced by the pressure of CO2.
A1507 – Study of inexpensive oxygen carriers for chemical looping combustion
Norwegian industrial tailings and by-products, as well as naturally occurring minerals and ores have been surveyed with the purpose of identifying candidate oxygen carrier materials for use in a chemical looping combustion process. Nine materials, based on manganese and/or iron oxide, were selected for an initial screening test; six were deemed promising and were hence investigated further. Thermogravimetric experiments were performed to investigate the oxygen capacity, the reaction kinetics and reversibility of the oxygen absorption reaction. A manganese ore with a reversible capacity of 4.9 wt% oxygen at 1000 °C was selected as the most promising for chemical looping combustion applications. This material was modified by addition of calcia to explore the possibility of enhancing the kinetic, catalytic and mechanical properties. The addition of excess calcium relative to manganese resulted in formation of calcium manganite and related phases. The oxygen capacity of the modified material was 4.5 wt% at 1000 °C, but it has potential advantages in terms of kinetics and chemical and mechanical stability relative to the pure ore.
A1509 – Conception, elaboration and characterization of silica-zirconia based nanostructured optical fibres obtained by the sol-gel process
This paper presents an original nanostructured optical fibre obtained by the sol-gel process. The studied fibre is composed with zirconia nanocrystals dispersed inside an amorphous silica matrix as core surrounded by a pure silica cladding. The conception and the elaboration of the fibre are described, as well as its structural and optical characterization. A preliminary study of the rheological properties of the initial silica-zirconia sol has been realized to determine the evolution of the sol behaviour as a function of the time .The introduction of ytterbium ions in the core composition is also investigated and the luminescence properties of the fibre are exposed and discussed.
A1510 – Couplage analyse thermogravimétrique et émission acoustique pour l’étude de la corrosion à haute température
Afin d'améliorer les connaissances du comportement à haute température des matériaux, le couplage de plusieurs techniques d'analyse physique in situ est une voie prometteuse. Dans ce but, des thermobalances ont été équipées d'un appareil spécifique de mesure des signaux acoustiques émis par les échantillons dont la variation de masse est continûment mesurée
sous diverses atmosphères représentatives de conditions industrielles. Les corrosions de surface à haute température sont à l'origine d'émission d'ondes acoustiques générées lors de
la croissance ou de la fissuration de couches formées. Des mesures simultanées in situ des variations de masse et des signaux acoustiques apportent donc des informations sur ces
mécanismes de corrosion haute température. L'application de cette méthodologie aux mécanismes d'oxydation, réduction ou attaque par les atmosphères carbonées (cokage) est
présentée dans ce document. Une perspective de ces études est de pouvoir établir des référentiels pour une éventuelle utilisation de l'émission acoustique pour l'étude de la corrosion des équipements fonctionnant à haute température
A1513 – CFD analysis of the modification of the furnace of a TG–FTIR facility to improve the correspondence between the emission and detection of gaseous species
A Fourier transform infrared spectrometer (FTIR) was coupled to thermogravimetric (TG) experimental equipment to determine the products of the thermal decomposition of several biomass samples both qualitatively and quantitatively. Working conditions for the TG device were simulated in a CFD model to analyse gas flux difficulties, embedding different models included in ANSYS FLUENT 12.1.4, including programming temperature control and devolatilisation kinetics, through User-Defined Functions. Based on the CFD results, an improvement to the experimental equipment was designed, simulated and implemented. A comparison between data from the original and the improved equipment was performed, including both experimental and simulated data.
A1512 – On the hydration of water-entrained cement–silica systems: Combined SEM, XRD and thermal analysis in cement pastes
The work described in this document focuses on the hydration of low water and low porosity SF-modified cement-based materials. The hydration of the clinker compounds was followed by X-ray diffraction (XRD), differential thermal analysis (DTA) and also by means of the thermo-gravimetric technique (TGA). This study was performed in three systems, each with a different composition namely a plain cement paste, a silica fume (SF)-modified cement paste and a water-entrained SF-modified cement paste with superabsorbent polymers (SAPs). In addition to the previous experiments, the microstructure of the systems was accessed by means of the scanning electron microscopy technique (SEM). This was primarily done with the purpose of supporting some ideas that have emerged when determining the hydration of these complex systems using the former techniques. However, in this manuscript only the results found through the TGA/DTA technique will be shown. Thus, in respect to the quantification of the CH phase developing in the system, the results taken by the TGA/DTA technique enable a more feasible description of the hydration of low water and low porosity SF-modified cement systems, including systems with water-entrainment by superabsorbent polymers. The results show that for cement-based materials with the physical nature of the systems that have been studied in this work, the pozzolanic activity is limited due to lack of water and/or space to accommodate additional hydration products, and as a consequence, a surplus of silica fume is to be found in the mature material. Due to either physical or chemical constraints, the system is not able to fully convert the calcium hydroxide into calcium silicate hydrate during the first month of hydration in sealed conditions. Additionally, in systems with water-entrainment by means of superabsorbent polymers, it is possible to observe the internal curing activity being promoted by this addition, which is translated by enhanced hydration of cement reactants. A model has been constructed from the empirical knowledge developed on the previous framework, which may be used in further research activities to study different formulations of SF-modified cement systems and also water-entrained cement-based systems
The objective of this study was to develop a methodology for the determination of the maximum sampling error and confidence intervals of thermal properties obtained from hermogravimetric analysis (TG), including moisture, volatile matter, fixed carbon and ash content. The sampling procedure of the TG analysis was of particular interest and was conducted with care. The results of the present study were compared to those of a prompt analysis, and a correlation between the mean values and maximum sampling errors of the methods were not observed. In general, low and acceptable levels of uncertainty and error were obtained, demonstrating that the properties evaluated by TG analysis were representative of the overall fuel composition. The accurate determination of the thermal properties of biomass with precise confidence intervals is of particular interest in energetic biomass applications.
A1515 – Abnormal High Growth Rates of Metastable Aluminas on FeCrAl Alloys
Experimental evidence in high temperature oxidation of alumina-forming alloys has accumulated that the overall growth kinetics of the oxide scale are slower for 1000?C, where the stable ?-Al2O3 phase predominates, than for 900?C where metastable ? -Al2O3 and/or ?-Al2O3 polymorphs predominate. This intriguing behaviour has been unanimously related to the substantial
presence of twin boundaries and the cation vacancy network intrinsic to the metastable aluminas allowing faster diffusion than in the nearly close packed corundum structure. This paper shows that this abnormal growth rate accompanying the presence of stable alumina polymorphs in platelets or needle-like morphology is rather due to the formation of a corundum-alumina-rich compact layer from an outer metastable layer by the concomitant sintering at the intersection vertices of the platelets and secondary recrystallization in these platelets. These phenomena are illustrated from oxidation tests performed on thin FeCrAl foils in both a conventional muffle furnace (designed by AET) and thermogravimetric analysis furnace (TGA) over the temperature range of 800–1300?C using field emission scanning electron microscope (FEG-SEM), transmission electron microscope (TEM), electron probe microanalysis (EPMA),
atomic force microscope (AFM), grazing incidence X-ray diffraction (GIXRD) and image analysis (IA) techniques.
A1514 – Influence of water vapor pressure on the induction period during Li2SO4·H2O single crystals dehydration
The dehydration of Li2SO4·H2O single crystals at 80 °C has been studied by means of both isothermal thermogravimetry at 2.6, 3.6 and 4.6 hPa of water vapor and environmental scanning electron microscope. Thermogravimetric experiments allowed the determination of induction periods. Distributions of these isoconversion induction periods for a large number of single crystals showed that increasing the water vapor pressure produced a longer induction period. Moreover, the shape of the distributions of the induction periods over a large number of single crystals changed from one mode at 2.6 hPa to two modes at 3.6 and 4.6 hPa. Using an environmental scanning electron microscope, this result could be attributed to differences in nucleation rates at edges and faces of the single crystals.
A1519 – Influence of a Coating on Oxidation Resistance and Resistivity of a Chromia Former Alloy for High Temperature Vapor Electrolysis Application
Alloy 230 was studied as possible interconnect material for high temperature vapor electrolysis (HTVE) application. For such a use, the main important requirements are good corrosion resistance and a low area specific electrical resistance (ASR). The samples were oxidized at 800 °C for 250 h under cathodic (Ar–1 %H2–9 %H2O) and anodic (dry air) HTVE atmospheres. In situ ASR evolution of alloy 230 in both conditions was determined using a specific device. The influence of a LaCrO3 coating is also discussed in this study. It is shown that alloy
230 offers good corrosion resistance, improved by the presence of the coating. A calculation of the theoretical ASR is in good agreement with the experimental value obtained in anodic environment. For the cathodic condition, the ASR value is two orders of magnitude higher than the expected one, and this could be explained by the presence of hydrogen in the oxide layer. The LaCrO3 coating effect on ASR values remains unclear, but it appears to have at least an influence on its evolution over the test duration.
A1518 – Beneficial Effect of Pt and of Pre-Oxidation on the Oxidation Behaviour of an NiCoCrAlYTa Bond-Coating for Thermal Barrier Coating Systems
The oxidation behaviour of a thermal barrier coating (TBC) system is a major concern as the growth of the thermally grown oxide (TGO) layer on the bond-coating creates stresses that greatly favour the thermal barrier spallation. To delay the loss of the thermal protection provided, research has focused on the bond-coating composition and microstructure as well as on the parameters required for a suitable pre-oxidation treatment before the deposition of the ceramic top coat. Platinum is known to enhance the oxidation/corrosion resistance of MCrAlY
coatings. The effect of Pt on the oxidation behaviour of a NiCoCrAlYTa coating was assessed in this study. In addition, pre-oxidation treatments were conducted to determine if the oxidation behaviour of the modified NiCoCrAlYTa coating could be further improved.