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5631 articles

A0511 – TG/DTA/MS Study of the thermal decomposition of FeSO4.6H2O

The thermal decomposition of FeSO4.6H2O was studied by mass spectroscopy coupled with DTA/TG thermal analysis under inert atmosphere. On the ground of TG measurements, the mechanism of decomposition of FeSO4.6H2O is: i) three dehydration steps FeSO4.6H2O FeSO4.4H2O+2H2O FeSO4.4H2O FeSO4.H2O+3H2O FeSO4.H2O FeSO4+H2O ii) two decomposition steps 6FeSO4 Fe2(SO4)3+2Fe2O3+2SO2 Fe2(SO4)3 Fe2O3+3SO2+3/2O2 The intermediate compound was identified as Fe2(SO4)3 and the final product as the hematite Fe2O3.
P. Masset, J.Y. Poinso and J.C. Poignet, Journal of Thermal Analysis and Calorimetry 83 (2006) 457-462

A0514 – Decomposing or subliming? An investigation of thermal behavior of l-leucine

The thermal behavior of l-leucine under inert conditions was investigated by TGA, FTIR and TG-FTIR. The TG results showed that only one mass loss stage of more than 99% happened when l-leucine was under program heating with temperature ranging from 30 to 600°C. The apparent activation energy, pre-exponential factor and the most probable model function were obtained by using of master plots method. The results of kinetic study showed that the decrease in mass of l-leucine was due to subliming rather than decomposing. And this was proved by the FTIR spectrum analysis and the directly observed subliming phenomenon. The results of TG-FTIR experiments showed that there was only one stage of decomposition process that happened after the subliming of leucine. The gas products were CO2, NH3, CO and some organic compounds such as 3-methyl-1-butanamine, and the main primary decomposition was decarboxylation.
J. Li, Z. Wang, X. Yang, L. Hu, Y. Liu and C. Wang, Thermochimica Acta 447 (2006) 147-153

A0515 – Nanostructured C6B: A Novel Boron Rich Carbon For H2 Storage

We are proposing that a novel carbon, C6B, having a significantly large boron concentration (17 at %) in the lattice can be synthesized into novel carbon microstructures (keying on nanotubes). The unique nanostructure is one that is crenellated or puckered along the tube axis due the presence of these large boron concentrations. We are proposing to undertake a study in which these novel carbons are synthesized, H2 adsorption is measured and the mechanisms of adsorption are studied. We are also proposing that on the basis of this understanding the synthesis of these novel carbons can be scaled to allow for a commercially viable and responsive H2 storage material.
L.E. Jones, A. Cormack, J. Shelby, M. Lake and J. Howe

A0517 – Spectral and thermal studies of light lanthanide 4-chlorophthalates

Conditions for the preparation of light lanthanide 4-chlorophthalates were investigated and their composition, solubility in water at 295 K, IR spectra and thermal decomposition were determined. 4-Chlorophthalates of La-Nd(III) were prepared as complexes with general formula NaLn[ClC6H3(CO2)2]2, whereas compounds of Sm and Eu have general formula Ln2[ClC6H3(CO2)2]3.6H2O. During heating all complexes decompose to oxides with intermediate formation of oxochlorides. The carboxylate groups in the complexes studied are bidentate bridging (Sm, Eu) or bidentate chelating and bridging (La-Nd).
R. Kurpiel-Gorgol and W. Brzyska, Journal of Thermal Analysis and Calorimetry 85 (2006) 449-453

A0516 – Influence of particle size on the crystallization process and the bioactive behavior of a bioactive glass system

Bioactive glasses have attracted considerable interest in recent years, due to their technological application, especially in biomaterials research. Differential scanning calorimetry (DSC) has been used in the study of the crystallization mechanism in the SiO2-Na2O-CaO-P2O5 glass system, as a function of particle size. The curve of the bulk glass presents a slightly asymmetric crystallization peak that could be deconvoluted into two separate peaks, their separation being followed in the form of powder glasses. Also, a shift of the crystallization peaks to lower temperatures was observed with the decrease of the particle size. FTIR studies - that are confirmed by XRD measurements - proved that the different peaks could be attributed to different crystallization mechanisms. Moreover, it is presented the bioactive behavior of the specific glass as a function of particle size. The study of bioactivity is performed through the process of its immersion in simulated human blood plasma (simulated body fluid, SBF) and the subsequent examination of the development of carbonate-containing hydroxyapatite layer on the surface of the particles. The bioactive response is improved with the increase of the particle size of powders up to 80 ?m and remains almost unchanged for further increase, following the specific surface to volume ratio decrease.
Chatzistavrou X., Zorba T., Chrissafis K., Kaimakamis G., Kontonasaki E., Koidis P. and Paraskevopoulos K. M. Journal of Thermal Analysis and Calorimetry, Vol. 85 (2006) 2, 253-259

A0520 – Synthesis and crystal structure of [2-NH2-5-CH3C5H4N]4P4O12_6H2O

Chemical preparation, crystal structure, IR absorption and thermal analysis of a new cyclotetraphosphate [2-NH2-5-CH3C5H4N]4P4O12_6H2O are reported. This compound is triclinic P-1 with unit-cell parameters: a = 10.206(5), b = 11.778(1), c = 9.991(4) Å , a = 110.40(6), b = 117.74(6), g = 86.41(3)8, V = 989.1(8) Å 3, Z = 1, Dx = 1.445 g cm_3. The structure has been determined and refined to R = 0.034 and Rw = 0.044, using 3663 independent reflections. The P4O4_ 12 ring anions and water molecules form layers spreading around (a, b + c) planes via O-H_ _ _O hydrogen bonds. Between them are anchored 2-amino-5-methylpyridium cations, which establish H-bonds to interconnect the different adjacent layers and so contribute to the cohesion of the threedimensional network. Tautomerization of (C6H9N2)+ groups was evidenced in the present structure.
H. Hemissi, S. Abid, M. Rzaigui, Materials Research Bulletin 40 (2005) 2130-2138

A0519 – Crystal structure and characterization of [2,5-(CH3O)2C6H3NH3]4P4O12_2H2O

The preparation, crystal structure, TG-DTA analysis and spectroscopy investigation are reported for the 2,5-dimethoxy phenyl ammonium cyclotetraphosphate dihydrate [2,5-(CH3O)2C6H3NH3]4P4O12_2H2O. This new compound is triclinic P¯1 with unit cell dimensio
Z. Aloui, S. Abid, M. Rzaigui, Materials Research Bulletin 40 (2005) 2056-2063

A0518 – Comparative study of nanocrystalline Zr0.85Ce0.15O2 powders synthesised by spray-pyrolysis and gel-combustion methods

Zr0.85Ce0.15O2 nanopowders synthesised by gel-combustion and spray-pyrolysis methods were comparatively studied by means of X-ray diffraction, Raman spectroscopy, thermogravimetric and differential thermal analyses, specific surface area measurements, sca
G.E. Lascalea, D.G. Lamas, E. Djurado, E.D. Cabanillas, N.E. Walso e de Reca, Materials Research Bulletin 40 (2005) 2029-2038

A0521 – Synthesis, structure refinement and characterization of tetrahydrated acid gadolinium diphosphate HGdP2O7_4H2O

Synthesis and single crystal structure are reported for a new gadolinium acid diphosphate tetrahydrate HGdP2O7.4H2O. This salt crystallizes in the monoclinic system, space group P21/n, with the following unitcell parameters: a = 6.6137(2) Å , b = 11.4954(4) Å , c = 11.377(4) Å , b = 87.53(2)° and Z = 4. Its crystal structure was refined to R = 0.0333 using 1783 reflections. The corresponding atomic arrangement can be described as an alternation of corrugated layers of monohydrogendiphosphate groups and GdO8 polyhedra parallel to the (1 01) plane. The cohesion between the different diphosphoric groups is provided by strong hydrogen bonding involving the W4 water molecule. IR and Raman spectra of HGdP2O7.4H2O confirm the existence of the characteristic bands of diphosphate group in 980-700 cm-1 area. The IR spectrum reveals also the characteristic bands of water molecules vibration (3600- 3230 cm-1) and acidic hydrogen ones (2340 cm-1). TG and DTA investigations show that the dehydration of this salt occurs between 79 and 900°C. It decomposes after dehydration into an amorphous phase. Gadolinium diphosphate Gd4(P2O7)3 was obtained by heating HGdP2O7.4H2O in a static air furnace at 850°C for 48 h.
S. Hraiech, F. Chehimi-Moumen, M. Ferid, D. Ben Hassen-Chehimi, M. Trabelsi-Ayadi, Materials Research Bulletin 40 (2005) 2170-2179

A0522 – Characterization of the thorium phosphate-hydrogenphosphate hydrate (TPHPH) and study of its transformation into the thorium phosphate-diphosphate (b-TPD)

The preparation of thorium phosphate-diphosphate (Th4(PO4)4P2O7, TPD) was developed through the precipitation of thorium phosphate-hydrogenphosphate hydrate (Th2(PO4)2(HPO4).H2O, TPHPH) at 150-160°C in closed PTFE container or in autoclaves. FromEPMAanalyses andSEMobservations, the initial precipitate was single phase and multilayered. The behaviour of TPHPH (orthorhombic system with a = 21.368(2) Å , b = 6.695(1) Å and c = 7.023(1) Å ) was followed when heating up to 1250°C. It was first dehydrated leading to the anhydrous thorium phosphate-hydrogenphosphate (TPHP, orthorhombic system with a = 21.229(2) Å , b = 6.661(1) Å and c = 7.031(1) Å at 220°C) after heating between 180 and 200°C. This one turned progressively into the new low-temperature variety of TPD (called alpha-TPD, orthorhombic system with a = 21.206(2) Å , b = 6.657(1) Å and c = 7.057(1) Å at 300°C) correlatively to the condensation of hydrogenphosphate groups into diphosphate entities. These three phases (TPHPH, TPHPand alpha-TPD) exhibit closely related 2D layered structures, therefore different from the 3D structure of the thorium phosphate-diphosphate (high-temperature variety). This latter compound, now called beta-TPD, was obtained by heating alpha-TPD above 950°C. All the techniques involved in this study (XRD, Raman and R spectroscopy, 1H and 31P NMR) confirmed the successive chemical reactions proposed.
N. Dacheux, N. Clavier, G. Wallez, V. Brandel, J. Emery, M. Quarton, M. Genet, Materials Research Bulletin 40 (2005) 2225-2242

A0523 – Crystal structure, thermal analysis and IR spectroscopic investigation of (C6H9N2)H2XO4 (X = As, P)

Crystals of 2-amino-4-methylpyridinium dihydrogenmonoarsenate (C6H9N2)H2AsO4 and 2-amino-4-methylpyridinium dihydrogenmonophosphate (C6H9N2)H2PO4 have been prepared and grown at room temperature. These materials are isotypic with the following unit cell dimensions (C6H9N2)H2AsO4: a = 12.4415(5) Å , b = 6.8224(3) Å , c = 11.3524(5) Å , Z = 4, V = 963.60(6) Å 3; (C6H9N2)H2PO4: a = 12.4410(9) Å , b = 6.7165(3)Å , c = 11.3417(5) Å , Z = 4, V = 925.09(10) Å 3. The common space group is Pnma. The structure of these compounds has been determined by X-ray data collection on single crystals of (C6H9N2)H2AsO4 and (C6H9N2)H2PO4. Due to the strong hydrogenbond network connecting the H2XO4 groups, the anionic arrangement must be described as a linear organization. The chains composed by the (H2XO4)n_ n macroanion spread along the beta-direction, approximately centered by x = 0 and 1/ 2. All atoms of the structure, except one oxygen atom, are located in the mirror planes situated at y = 1/4 and 3/4, imparting an internal mirror symmetry to the anionic and the cationic entities. The linear macroanions are crossed by organic cations lying in mirrors perpendicular to the beta-direction; this atomic arrangement is then described by a threedimensional network of hydrogen bonds, built up by two types,O-H_ _ _O bonds inside the chains and N-H_ _ _Obonds linking adjacent chains. The thermal properties of both compounds are investigated as well as the IR properties supported by group theoretical analyses.
A. Chtioui, L. Benhamada, A. Jouini, Materials Research Bulletin 40 (2005) 2243-2255

A0524 – Calcium phosphate precipitation in catanionic templates

A simple and effective mean for controlling electrostatic interactions during mineral precipitation in water is the use of a "catanionic" template. Such strategy is used to precipitate calcium phosphate (hydroxyapatite or HAP) and obtain mesoporous materials. Mixtures of catanionic surfactants with phosphate head-groups (polyoxyethylene oleyl ether phosphate) and a quaternary ammonium (myristyl trimethyl ammonium bromide) are used in order to obtain a template with adjustable surface charge and test the "charge-matching" effect. This effect manifests by a strong dependence of the template shape on molar fraction, which governs the charge per unit area of the surfactant as well as the growth of inorganic network. We first explore the effect of high ionic strength and pH variation on phase diagram of template. A hexagonal structure is observed for anionic surfactant, and such organization is still preserved in the presence of large quantity of cationic component. Synthesis of HAP is then performed using independently various volume fractions of template and various mole fraction of anionic component in the template. For samples with low amount of surfactant and an excess of anionic component, TOC analysis shows more than 80% of the added surfactant is trapped in the precipitate. These samples display in SAXS three peaks that are characteristic of a hexagonal structure. Such structure, where the repetition distance is much lower than twice surfactant chain length, has not yet been described in surfactant selfassembly. This must be a monolayer microstructure, but symmetry group is not known since higher orders cannot be detected. The HAPtemplate hybrid structure disappears after calcination, and the BET surface of calcined powders is smaller than for HAP particles synthesized in homogeneous conditions.
B. Prélot, T. Zemb, Materials Science and Engineering C 25 (2005) 553 - 559

A0525 – Existence of superconductivity in the magnetic state of oxygen deficient RuSr2GdCu2O8 d (1212) system

We have investigated the superconducting properties of an oxygen deficient RuSr2GdCu2O8 d system. We bring out a new feature from the dc magnetization measurement seen both in the field-cooled as well as in the zero-field-cooled state. We propose to link this feature with the Meissner state of the superconducting phase. This stems from the complex situation arising from the simultaneous presence of signals corresponding to two different magnetic orders and of the diamagnetic signal of the superconducting phase. By separating out the contributions from the magnetic ordering, we find the visible presence of diamagnetic signal corresponding to the Meissner phase in this magnetically ordered system. However, signature of superconductivity, thus derived, is absent in a fully oxygenated system.
P.K. Mishra, R. Mishra, C.L. Prajapat, T.V. Chandrasekhar Rao, Physica C 433 (2005) 14-20

A0527 – Immobilization of heavy metals by calcium sulfoaluminate cement

Two types of calcium sulfoaluminate cement containing 20% and 30% phosphogypsum, respectively, were investigated for their ability in hazardous waste stabilization. Fourteen series of pastes were prepared, each containing the following soluble salt: Na2CrO4I4H2O; Na2Cr2O7I2H2O; CrCl3I6H2O; Pb(NO3)2; Zn(NO3)2I6H2O; ZnSO4I7H2O; and CdCl2I5H2O. The level of pollution was 0.069 mol of heavy metal per Kg of cement. The study has been carried out by means of X-ray diffraction, thermal analysis, scanning electron microscopy, mercury intrusion porosimetry, electrical conductivity, and leaching tests. Very good retention of lead, cadmium, zinc and trivalent chromium is observed. The retention of hexavalent chromium depends upon the nature of the binder: the cement containing 20% gypsum develops the best behaviour. This is explained by the microstructure of the hydrated paste: in the paste containing 30% gypsum, delayed ettringite precipitates and damages the hardened paste.
S. Peysson, J. Péra, M. Chabannet, Cement and Concrete Research 35 (2005) 2261 - 2270

A0526 – Mechanical properties and oxidation behaviour of two-phase iron aluminium alloys with Zr(Fe,Al)2 Laves phase or Zr(Fe,Al)12 t1 phase

Two-phase Fe-rich Fe-Al-Zr alloys have been prepared consisting of binary Fe-Al with a very low solubility for Zr and the ternary Laves phase Zr(Fe,Al)2 or t1 phase Zr(Fe,Al)12. Yield stress, flexural fracture strain, and oxidation behaviour of these alloys have been studied in the temperature range between room temperature and 1200°C. Both the Laves phase and the t1 phase act as strengthening phases increasing significantly the yield stress as well as the brittle-to-ductile transition temperature. Alloys containing disordered A2C ordered D03 Fe-Al show strongly increased yield stresses compared to alloys with only A2 or D03 Fe-Al. The binary and ternary alloys with about 40at.% Al and 0 or 0.8at.% Zr show the effect of vacancy hardening at low temperatures which can be eliminated by heat treatments at 400°C. At higher Zr contents this effect is lost and instead an increase of low-temperature strength is observed after the heat treatment. The increase of the high-temperature yield strength of Fe-40at.% Al by adding Zr is much stronger than by other ternary additions such as Ti, Nb, or Mo. Tests on the oxidation resistance at temperatures up to 1200°C indicate a detrimental effect of Zr already for additions of 0.1at.%.
F. Stein, M. Palm, G. Sauthoff, Intermetallics 13 (2005) 1275-1285

A0530 – Effect of silicon additions on the oxidation of a Ni-6 at.%Al alloy at 1273 K

The oxidation of four Ni-xSi-6Al alloys (x = 0,2,4 and 6 at.%) has been studied at 1273 K under 0.1 MPa O2. Silicon exerts the third-element effect by reducing the critical Al content needed for the transition from its internal to its external oxidation with respect to Ni-Al alloys. This result is interpreted by extending to ternary alloys Wagner s criterion for the same transition in binary alloys
Y. Wu, Y. Niu, Scripta Materialia 53 (2005) 1247-125

A0529 – Strengthening of iron aluminide alloys by atomic ordering and Laves phase precipitation for high-temperature applications

The ternary system Fe-Al-Ta allows the formation of the hard and brittle ternary Laves phase Ta(Fe0.5Cx,Al0.5Kx)2 with hexagonal C14 structure. The present study concentrates on Fe-Al-Ta alloys with small Ta contents between 2 and 6 at.% and various Al contents between 0 and 45 at.%. The phase equilibria in the ternary Fe-Al-Ta system at 1000°Care studied experimentally for determination of the solubility limits of Ta in iron aluminide matrices and types of phases and structures which may occur at high temperatures. It is observed that small amounts of Laves phase together with atomic ordering increase the yield stress and affect ductility in a complex way.
D.D. Risanti, G. Sauthoff, Intermetallics 13 (2005) 1313-1321

A0528 – Standard enthalpy of formation of La2Te3O9 and La2Te4O11

Lanthanum tellurites, La2Te3O9 and La2Te4O11, have been prepared by the solid state synthesis route and characterized for their phase and chemical compositions by XRD and ICP-AES analyses. The molar enthalpies of solution of La2Te3O9(s), La2Te4O11(s), La2O3(s) and TeO2(s) in 0.150 dm3 of 10.98 mol dm 3 HCl were measured using an isoperibol calorimeter. From these results and other auxiliary data the standard molar enthalpy of formation of La2Te3O9(s) and La2Te4O11(s) were derived to be ( 2814.6 ± 12.9) kJ mol 1 and ( 3116.5 ± 17.3) kJ mol 1, respectively, at 298.15 K which are the first reported thermodynamic data on these compounds at 298.15 K.
M. Ali(Basu), S.R. Bharadwaj, S.C. Kumar, D. Das, Journal of Nuclear Materials 347 (2005) 69-72

A0533 – TG and DSC studies of naturaland artificial aging of polypropylene

We study the evolution of thermal degradation of samples of polypropylene (PP), during their aging for two periods of 60 and 80 days. The study, using thermogravimetric analysis (TG) and differential scanning calorimetric (DSC) analyses, focused on two types of aging: the naturalone under the impact of the solar environment and the artificialone which was carried out by exposing the sample to radiations of a 100W commercial lamp. The comparative study of these two types of aging shows that the thermaldegradation of the PP increases as a function of time of aging. Indeed, for a same duration, this thermal degradation is more important in the artificialaging case than it is in the naturalone and is an increasing function of aging. The prolonged and continuous thermal effect produced by the lamp, in the case of the artificial aging, weakened the polymer and implies very important acceleration of the process of degradation. The results obtained during heating and cooling of the samples, using the DSC, show an evolution of the phase transition temperatures and the corresponding enthalpies of melting and crystallization.
M. Rjeb, A. Labzour, A. Rjeb, , S. Sayouri, Y. Claire, A. Périchaud, Physica A 358 (2005) 212-217

A0532 – Heterogeneous reduction of nitric oxide on synthetic coal chars

Model compounds, with a controlled heteroatoms content and well-defined functionalities, were used to study the release of nitrogen compounds from char combustion. In the present work, the mechanisms involved in NO-char heterogeneous reduction were studied with a synthetic coal (SC) char as carbon source. Another synthetic char (SN) without any nitrogen in its composition was also employed in these studies. Temperature programmed reduction (TPR) tests with a gas mixture of 400 ppm NO in argon and with isotopically labelled nitric oxide, 15NO (500 ppm 15NO in argon), were carried out. The gases produced were quantitatively determined by means of MS and FTIR analysers. Under the conditions of this work the main products of the NO-C reaction were found to be N2 and CO2. The main path of reaction involves the formation of surface nitrogen compounds that afterwards react with nitrogen from the reactive gas to form N2. It was observed that fuel-N also participates in the overall heterogeneous reduction reaction, although to a lesser extent.
C. Pevida, A. Arenillas, F. Rubiera, J.J. Pis, Fuel 84 (2005) 2275-2279

A0531 – Scaffolds for bone restoration from cuttlefish

Scaffolds of pure hydroxyapatite suitable for either direct clinical use or tissue-engineering applications were successfully produced via hydrothermal transformation of aragonite, obtained from fresh cuttlefish bones, at 200°C followed by sintering. Beyond low production cost, worldwide availability and natural-biological origin of raw materials, the produced scaffolds have ideal pore size and interconnectivity features suitable for supporting biological activities, such as bone tissue growth and vascularization. Bioactivity in vitro tests were excellent: (a) rapid and pronounced formation of hydroxyapatite occurred when the scaffolds were immersed in simulated body fluid (SBF), and (b) outstanding proliferation of osteoblasts was registered. The produced scaffolds can be machined and shaped very easily at any stage of processing. Therefore, these ceramic scaffolds can satisfy both bioactivity demands and the requirements for shaping of tailor-made individualized implants, especially for randomly damaged bones.
J.H.G. Rocha, A.F. Lemos, S. Agathopoulos, P. Valério, S. Kannan, F.N. Oktar, J.M.F. Ferreira, Bone 37 (2005) 850-857

A0534 – Novel bidentate phosphine modified Pd(acac)2/BF3OEt2 catalyst system for the homopolymerization of alkylnorbornenes and copolymerization with norbornene

The Pd(acac)2 + nPh2P(CH2)mPPh2 + 25BF3OEt2, n = 1-3, m = 1-6, catalyst system has been successfully employed for the homopolymerization of 5-alkyl-2-norbornenes and their copolymerization with norbornene. For this series, the most efficient catalyst system was Pd(acac) 2 + 2Ph2P(CH2)4PPh2 + 25BF3OEt2. The activity of the catalyst system is comparable to that of most active late transition metal catalysts described in the literature. Bidentate phosphines containing bridges larger than 1,4-butane are likely to act as monodentate ligands. The incorporations of flexible alkyl groups onto the main chain of norbornene, as well as copolymerization of 5-alkyl-2-norbornenes with norbornene, represent a useful method for lowering the glass transition temperature (Tg), i.e. improving the processability. The introduction of bidentate phosphine ligand to the Pd(acac)2 + 25BF3OEt2 system switched the carbocationic polymerization mechanism to the coordination Ziegler-Natta polymerization. The simplicity of this catalytic system composition might be of industrial importance.
G. Myagmarsuren, O.-Yong Jeong, Son-Ki Ihm, Applied Catalysis A: General 296 (2005) 21-29

A0536 – Polystyrenes with macro-intercalated organoclay. Part I. Compounding and characterization

Nanocomposites of polystyrene (PS) were prepared using a melt compounding or co-solvent method. Two commercial PS were used, and two organoclays-one prepared in this laboratory (COPS), and the other commercial Cloisitew 10A (C10A). The COPS is a product of clay intercalation with a copolymer of styrene and vinyl benzyl tri-methyl ammonium chloride. According to the XRD diffraction data, the clay platelets in COPS and its PNC with PS were relatively well dispersed, i.e. with the interlayer spacings of d001Z7-8 nm. By contrast, d001 in PNC prepared with C10A was only 4 nm. However, the number of clay platelets per stack in PS/COPS was found to be significantly larger than that in PS/C10A, viz. mZ3-12, compared to mZ2-6. The scanning and transmission electron microscopy indicated that in the PS matrix COPS existed in form of large, immiscible domains.
M. Sepehr, L.A. Utracki, X. Zheng, C.A. Wilkie, Polymer 46 (2005) 11557-11568

A0535 – Chemical reactions and structural phase transitions of sodalites and cancrinites in temperature dependent infrared (TIR) experiments

The infrared absorption of a solid highly diluted within an infrared transparent pellet (e.g., KBr, NaCl, etc.) is easily measured as a function of the temperature up to the melting point of the matrix. A disadvantage could be any interaction or chemical reaction between the matrix and the sample. However, such reactions and reactions within the embedded sample can be used in a systematical way for the investigation of the creation of new materials. Here, four types of working examples will be given. Starting with typical temperature dependent (TIR) investigations on the phase transition characteristics of a NaNO3-sodalite it is shown how this intrinsic property is effected by an exchange of Na/K between the matrix and the sodalite. Secondly, the effect of dehydration on NaB(OH)4-sodalite as studied in situ in the KBr pellet is considered. Thirdly, in situ investigations of the formation of new compositions within the family of cancrinites are described. Here, the effect of dehydration, and the combined exchange of Na/K and Cl/Br/NO3 of this typical microporous material is reported. Finally, the first steps of the soft chemically formed sodalite from the sol-gel liquid in the KBr container will be outlined briefly.
C.H. Ruscher, Microporous and Mesoporous Materials 86 (2005) 58-68

A0538 – Al-Pt MOCVD coatings for the protection of Ti6242 alloy against oxidation at elevated temperature

Results on isothermal oxidation at 873 K for 90 h of Al-Pt coatings on Ti6242 coupons are reported. These coatings were obtained by low temperature, low pressure metalorganic chemical vapor deposition using Me3(MeCp)Pt(VI) and dimethylethylamine alane. Three coating architectures were investigated, namely pure Al, Pt and Al sequential sublayers, and co-deposited Al and Pt. Oxidation kinetics revealed a strong transient oxidation regime followed by a diffusion driven parabolic one. Such coatings allow to decrease oxidation kinetics more than one order of magnitude compared with those of the bare Ti6242. Scanning electron microscopy, second ion mass spectrometry, X-ray diffraction and transmission electron microscopy revealed that these coatings present a rough surface morphology. They are dense, they develop scales composed of g-Al2O3 and y-Al2O3 and they prevent titanium diffusion from the alloy to the surface. It is concluded that coatings produced by this process show promise for use as effective protection against oxidation of Ti6242 alloys and consequently they may raise the maximum operating temperature tolerated by corresponding parts in helicopter turboengines.
M. Delmas, D. Poquillon, Y. Kihn, C. Vahlas, Surface & Coatings Technology 200 (2005) 1413 - 1417

A0537 – Characterisation of Ca- and Al-pectate gels by thermal analysis and FT-IR spectroscopy

Thermal analysis (TG-DTA) and FT-IR spectroscopy have been performed on calcium-pectate membranes to investigate their structure and the consequent variation caused by aluminium sorption. Calcium-polygalacturonate (Ca-PG) membranes, model systems of the soil-root interface, were exposed to aluminium solutions at different concentrations (25-800 lM). Three different pHs (3.50, 4.00 and 4.50) were chosen to study the influence of different aluminium species, such as [Al(H2O)6]3+, [Al(OH)(H2O)5]2+ and [Al(OH)2(H2O)4]+, on the structure of the Ca-PG membrane. The DTA profiles and FT-IR spectra showed how aluminium sorption induces structural modifications leading to a reorganisation of the chain aggregates and a weakening of the structure. Higher pH, that is, 4.00 and 4.50, and thus hydrolytic aluminium species and related higher calcium content maintain a more regular structure than at pH 3.50. At pH 3.50, both the effect of [Al(H2O)6]3+ and a major calcium release had a greater impact and thus induced a greater weakening of the structure.
T. Mimmo, C. Marzadori, D. Montecchio and C. Gessa, Carbohydrate Research 340 (2005) 2510-2519

A0539 – Hydrothermal synthesis and characterization of V2O3

V2O3 with spherical particles was hydrothermally synthesized (240°C, 48 h, autogenous pressure) as a single-phase material from a mixture of V2O5, 1,6-diaminohexane and H2O in the mol ratio 1:1:269. It was characterized by scanning electronic microscopy, X-ray powder diffraction, thermal analysis and electron paramagnetic resonance.
F. Sediri, N. Gharbi, Materials Science and Engineering B 123 (2005) 136-138

A0540 – Synthesis study of alkaline-bearing rare earth phosphates with rhabdophane structure

"The synthesis mechanism of CsCaNd(PO4)2 from nitrates, carbonates and oxides of the different cations was investigated with the aim of immobilizing cesium. Two transitory phases, a monazite-type one, NdPO4, and a poorly crystallized cesium phosphate, CsCaPO4, were proposed to explain the formation of CsCaNd(PO4)2. Direct synthesis from NdPO4 and CsCaPO4 was thus carried out. It allowed to underline that within a 900-1000°C temperature range the rhabdophane structure, CsCaNd(PO4)2, was formed. However, the reaction was also found to be incomplete and this was assumed to be due to a lack of reactivity in concern with the high stability of monazite."
L. Campayo, F. Audubert, D. Bernache-Assollant, Solid State Ionics 176 (2005) 2663 - 2669

A0542 – Dehydration of tetrahydrate potassium pentaborate in fluidized bed

The dehydration of tetrahydrate potassium pentaborate was investigated in a fluidized bed reactor. The effects of reaction temperature, flow rate of the fluidization gas and particle amount were studied in detail. The optimum dehydration conditions of the studied reactor were determined at three temperatures (573 K, 598K and 623 K). In the process of dehydration, only tetrahydrate potassium pentaborate and KB5O8 were observed. The dehydration kinetics of tetrahydrate potassium pentaborate were also investigated at the same temperatures, and by applying the experimental data to the Shrinking-Core Model, it was found that the dehydration process is controlled by chemical reaction at the beginning period, and thereafter controlled by the diffusion through product layer.
G. Yang, Z. Li, Y. Zhang, Chemical Engineering and Processing 44 (2005) 1216-1220

A0541 – Rheological and mechanical comparative study of in situ polymerized and melt-blended nylon 6 nanocomposites

The rheological and mechanical properties of commercial neat nylon 6 and nylon 6 nanocomposites containing organically-modified montmorillonite (organoclays) produced by either in situ polymerization or melt-blending were investigated. The dynamic and steady shear, capillary and extensional viscosity of the neat nylon 6 and nylon 6 nanocomposite melts were studied, as well as the tensile properties of the solid material. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the organoclays were largely very well exfoliated, although the lateral size scale of the platelets was different for each material. The in situ polymerized nanocomposite exhibited higher melt viscosity and higher tensile ductility than the melt-blended nanocomposite which was related to improved dispersion and polymer-silicate interactions for this material. Scanning electron microscopy confirmed that the nanocomposite failure surfaces showed more evidence of brittle behavior than the failure surfaces of neat nylon 6, and also that agglomerates of organoclay could be seen easily in the fracture surface of the melt-blended nanocomposite, but not to the same degree as in the in situ polymerized nanocomposite. This is in addition to very fine, individually-dispersed silicate laminates that form in each case.
J. Tung, R.K. Gupta, G.P. Simon, G.H. Edward, S.N. Bhattacharya, Polymer 46 (2005) 10405-10418

A0544 – Mechanical properties and microstructure of high strength concrete containing polypropylene fibres exposed to temperatures up to 200°C

High strength concrete has been used in situations where it may be exposed to elevated temperatures. Numerous authors have shown the significant contribution of polypropylene fibre to the spalling resistance of high strength concrete. This investigation develops some important data on the mechanical properties and microstructure of high strength concrete incorporating polypropylene fibre exposed to elevated temperature up to 200°C. When polypropylene fibre high strength concrete is heated up to 170°C, fibres readily melt and volatilise, creating additional porosity and small channels in the concrete. DSC and TG analysis showed the temperature ranges of the decomposition reactions in the high strength concrete. SEM analysis showed supplementary pores and small channels created in the concrete due to fibre melting. Mechanical tests showed small changes in compressive strength, modulus of elasticity and splitting tensile strength that could be due to polypropylene fibre melting.
A. Noumowe, Cement and Concrete Research 35 (2005) 2192 - 2198

A0543 – Oxygen nonstoichiometry in La2Ni(M)O4+d (M = Cu, Co) under oxidizing conditions

The oxygen hyperstoichiometry of La2NiO(4+d), La2Ni0.9Co0.1O(4+d) and La2Ni0.8Cu0.2O(4+d) with K2NiF4-type structure was studied by thermogravimetric analysis and coulometric titration at 923-1223 K in the oxygen partial pressure range 8 x 10^(-5) to 0.6 atm. The p(O2)-T -delta diagrams can be described using a statistical thermodynamic approach, relating the strongly non-ideal behavior of lanthanum nickelate-based compounds to the coulombic repulsion of oxygen interstitials and interaction of holes localized on the B-site cations. The relationships between defect concentrations and chemical potentials were expressed analyzing the configuration probabilities via binomial distributions and using the corresponding number of states for the discrete Fermi-Dirac distribution. The results suggest that the distance between two interstitials cannot be shorter than the a parameter of K2NiF4-type unit cell. The repulsion of holes leads to similar phenomena, whilst the hole energy levels are determined by the interaction with other p-type charge carriers located in the second B-site cation coordination sphere. The sites occupied by nickel and copper cations in La2Ni0.8Cu0.2O(4+d) seem essentially equivalent from an energetic point of view, within the limits of experimental error. In the case of La2Ni0.9Co0.1O(4+d), however, the description of the p(O2)-T -delta diagram requires also to consider hole trapping by cobalt, which forms stable Co3+ existing in equilibrium with the electronic subsystem. The processes resulting in formation of oxygen vacancies and Cu+ states in the perovskite planes have no statistically significant effects on the oxygen nonstoichiometry. Doping-induced lattice expansion of La2NiO4-based phases favors the oxygen de-intercalation processes due to metal-oxygen bond weakening.
E.N. Naumovich, M.V. Patrakeev, V.V. Kharton, A.A. Yaremchenko, D.I. Logvinovich, F.M.B. Marques, Solid State Sciences 7 (2005) 1353-1362

A0545 – Kinetic parameters of a cyanate ester resin catalyzed with different proportions of nonylphenol and cobalt acetylacetonate catalyst

The isothermal cure of a dicyanate ester monomer has been investigated by differential scanning calorimetry (DSC) in the presence of different quantities of a catalyst system formed by nonylphenol (NP) and cobalt (II) acetylacetonate (Co(AcAc)2). Two sets of experiences were studied. Firstly, the NP composition was varied from 0 to 10 per hundred resin (phr) and secondly, the Co(AcAc)2 loadings were changed at 2 phr of NP. It has been observed that the cyanate conversion increases significantly after the first addition of the metal catalyst and, also, at the same time the thermal stability improves. Moreover, the kinetic data have been fitted with a second-order equation respect to the cyanate conversion in the kinetically conversion regime. Also, both the activation energies and the kinetic order respect to the NP and the Co(AcAc)2 have been determined.
C.M. Gomez, I.B. Recalde, I. Mondragon, European Polymer Journal 41 (2005) 2734-2741

A0547 – Spectroscopic properties of neodymium(III)-containing polyoxometalates in aqueous solution

The spectroscopic properties of the neodymium(III)-containing polyoxometalates (POMs) [Nd(PW11O39)2]11-, [Nd(PMo2W9O39)2]11-, [Nd(PMo4W7O39)2]11-, [Nd(PMo6W5O39)2]11-, [Nd(SiMo2W9O39)2]13-, [Nd(P2W17O61)2]17-, [NdW10O36]9-, [NdP5W30O110]12- and [NdAs4W40O140]25- are described. Absorption spectra of aqueous solutions of the complexes have been recorded and the transition intensities are parameterised in terms of the Judd-Ofelt intensity parameters ?? (? = 2, 4, 6). Marked differences were found between the luminescence lifetimes of the complexes of the type Nd(POM) and those of the type Nd(POM)2, due to a better shielding of the neodymium(III) ions from the bulk water molecules in the latter type of complexes.
S. But, S. Lis, R. Van Deunb, T.N. Parac-Vogt, C. Gorller-Walrand, K. Binnemans, Spectrochimica Acta Part A 62 (2005) 478-482

A0546 – Preparation and photocatalytic activity of ZnO/TiO2/SnO2 mixture

ZnO/TiO2/SnO2 mixture was prepared by mixing its component solid oxides ZnO, TiO2 and SnO2 in the molar ratio of 47171, followed by calcining the solid mixture at 200-1300°C. The products and solid-state reaction process during the calcinations were characterized with powder X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and Brunauer-Emmett-Teller measurement of specific surface area. Neither solid-state reaction nor change of crystal phase composition took place among the ZnO, TiO2 and SnO2 powders on the calcinations up to 600°C. However, formation of the inverse spinel Zn2TiO4 and Zn2SnO4 was detected at 700-900 and 1100-1200°C, respectively. Further increase of the calcination temperature enabled the mixture to form a single-phase solid solution Zn2Ti0.5Sn0.5O4 with an inverse spinel structure in the space group of O7 h Fd3m. The ZnO/TiO2/SnO2 mixture was photocatalytically active for the degradation of methyl orange in water; its photocatalytic mass activity was 16.4 times that of SnO2, 2.0 times that of TiO2, and 0.92 times that of ZnO after calcination at 500°C for 2 h. But, the mass activity of the mixture decreased with increasing the calcination temperature at above 700°C because of the formation of the photoinactive Zn2TiO4, Zn2SnO4 and Zn2Ti0.5Sn0.5O4. The sample became completely inert for the photocatalysis after prolonged calcination at 1300°C (42 h), since all of the active component oxides were reacted to form the solid solution Zn2Ti0.5Sn0.5O4 with no photocatalytic activity.
C. Wang, B-Q. Xu, X. Wangb, J. Zhao, Journal of Solid State Chemistry 178 (2005) 3500-3506

A0548 – Characterization of Al-Cu and Al-Cu-Mg mixed oxides and their catalytic activity in dehydrogenation of 2-octanol

Hydrotalcite (HT) type materials with different Cu:Mg:Al ratios were prepared. The samples were calcined at 450°C and when the layered structure was destroyed mixed oxides were formed. Such oxides were reduced under a flow of hydrogen gas at 300°C and their catalytic activity in dehydrogenation of 2-octanol was studied. High conversion and selectivity towards 2-octanone was observed. The samples without copper showed low conversion, but it increased with the copper content. The characterization of both precursors and reduced catalysts was carried out by XRD, XPS and diffuse reflectance. In the calcined samples, the XPS analysis detected Cu2+ in a CuAl2O4 spinel-like environment as well as CuO, while the reduced samples contained Cu0 and copper ions, such as Cu2+ and Cu+. Diffuse reflectance showed that the copper was present in two forms, the perfect and distorted octahedra. In the Al-Cu-Mg system, the copper was present in a cluster-like or bulk-like species, excepting the samples having a copper excess, where a spinel-like species was detected. By XRD, a greater structural ordering was observed in the samples containing a ratio Cu2+/Mg2+ 1 (Cu < 50% keeping in mind only cations M2+) and in those having a ratio (M3+/M3+ + M2+) approximately equal to 0.25; in this case other species were not detected.
M. Crivello, C. Pérez, E. Herrero, G. Ghione, S. Casuscelli, E. Rodriguez-Castellon, Catalysis Today 107-108 (2005) 215-222

A0549 – Influence of rare earth elements La, Nd and Yb on the acidity of H-MCM-22 and H-Beta zeolites

The influence of rare earth (RE) elements on the acidic properties of H-MCM-22 and H-Beta was studied by pyridine adsorption followed by infrared spectroscopy (FTIR) and n-heptane cracking, as a model reaction. The zeolites were submitted to ion exchange with rare earth nitrate solutions of La, Nd and Yb. The FTIR spectra of REH-MCM-22 indicate the presence of RE elements inside supercages and in the sinusoidal channels of the zeolite. After pyridine adsorption two additional bands are detected in REH-MCM-22 and REH-Beta, related to pyridine bonded to RE3+ cations. The n-heptane cracking reaction shows that the effect of rare earth elements is related not only to the acidity but also with the porous structure of both zeolites. In H-Beta zeolite, the presence of RE elements enhances the acidity of the catalysts. In H-MCM-22 zeolite, the most relevant effect of rare earth elements is on the shape selectivity that becomes more pronounced with the ionic radius of the RE elements. The nature of the coke deposited on the two materials shows distinct profiles that are also related to its porous structure.
A. Martins, J.M. Silva, C. Henriques, F.R. Ribeiro, M.F. Ribeiro, Catalysis Today 107-108 (2005) 663-670

A0552 – Gas phase photocatalytic removal of toluene effluents on sulfated titania

Photocatalytic removal of toluene in the gas phase was carried out over UV-illuminated sulfated titania materials in a cylinder-like continuous reactor. A series of (SO4)2- - TiO2 samples was obtained from the addition of H2SO4 on an amorphous titanium hydroxide gel synthesized according to a classical sol-gel procedure. The wide variety of materials led to varying photocatalytic behaviors depending strongly on the experimental synthesis parameters, having a determinant influence on the surface specific area, the crystallinity of the material, the crystallographic nature of TiO2, and the sulfate surface content. Optimization of the experimental parameters, such as the molarity of the sulfation solution, varying in the range 0.25-5 M leading to surface sulfate coverage of 2.5-14 wt%, and the calcination temperature ranging from 400 to 800°C, promoted enhanced photocatalytic performance toward toluene removal as compared with commercially available P25 TiO2 and sulfate-free sol-gel TiO2. The most efficient photocatalyst was obtained for a near-monolayer sulfate coverage corresponding to the presence of both TiO2 and well-dispersed SO4 2- with optimized contact between SO4 2- and TiO2 domains. Furthermore, a positive role of sulfates is attributed both to an electron transfer from titanium to sulfates, leading to a positive charge trap effect, and to better desorption of electron-rich sp2-bound carbon aromatic poisons, thus limiting deactivation.
E. Barraud, F. Bosc, D. Edwards, N. Keller, V. Keller, Journal of Catalysis 235 (2005) 318-326

A0551 – Solution syntheses of unsupported Co(Ni)-Mo-S hydrotreating catalysts

Highly dispersed Ni(Co)-Mo-S sulfides were prepared by simple room temperature solution reactions using nickel or cobalt salts and thiomolybdate precursors in the presence of nonionic surfactants. The products were characterized by X-ray powder diffraction, specific surface area measurements, and scanning and transmission electron microscopy. The evolution from amorphous pre-catalysts to highly dispersed sulfide catalysts during the activation step was studied by thermal analysis. Extended X-ray absorption fine structure measurements were carried out to elucidate the chemical environment of the transition metals in the precursors and the sulfided catalysts. The specific catalytic activities of the Ni(Co)-Mo-S systems in the hydrodesulfurization of thiophene and 4,6-DMDBT were up to six times higher than those of commercial alumina-supported systems.
D. Genuit, P. Afanasiev, M. Vrinat, Journal of Catalysis 235 (2005) 302-317

A0550 – Effect of Cs impregnation on the properties of platinum in Pt/Na-BEA and Pt/Cs-BEA catalysts

The presence of alkali cations in zeolite framework provides peculiar basic properties that influence the characteristics and reactivity of supported metal particles. Particularly, the addition of increasing amounts of cesium in Pt/Na-BEA and Pt/Cs-BEA catalysts, by CsOH impregnation, leads to changes of the oxidation state and reducibility of Pt species present in the zeolite microporosity. For similar contents of impregnated Cs, the metal dispersion is higher in Pt/Cs-BEA than in Pt/Na-BEA series, showing that both the amount of Cs excess and the nature of the compensating cation affect the characteristics of the Pt species. In the case of Cs-overloaded Pt/Cs-BEA, the size of Pt nanoclusters is below 10 Å . The very small Pt nanoparticles in reduced Cs-overloaded Pt/Cs-BEA are particularly active in aromatization of nhexane.
E.R. Silva, J.M. Silva, P. Massiani, F.R. Ribeiro, M.F. Ribeiro, Catalysis Today 107-108 (2005) 792-799

A0553 – Formation of nanosized zirconia-supported 12-tungstophosphoric acid in mesoporous silica SBA-15: A stable and versatile solid acid catalyst for benzylation of phenol

A nanosized zirconia-supported 12-tungstophosphoric acid (TPA) in SBA-15 composite was prepared by wet impregnation of TPA/ZrO2 nanoparticles inside the mesoporous channels of SBA-15. The resulting composite material was calcined at 1123 K and characterized by elemental analysis, powder X-ray diffraction, nitrogen adsorption isotherms, transmission electron microscopy (TEM), scanning electron microscopy (SEM), solid-state 31P CP-MAS NMR, 29Si MAS NMR, UV-vis diffuse reflectance spectra, FTIR, TPD of ammonia, FTIR pyridine adsorption, and thermogravimetric analysis (TG-DTG). The synthesized TPA/ZrO2/SBA-15 showed a well-ordered hexagonal mesoporous structure and mesoporous support SBA-15 stabilized ZrO2-t (tetragonal) phase with crystal size in the range of 3-4 nm. SBA-15 was a better support than MCM-41 and MCM-48 because it retained its mesostructure even after high TPA loading and high calcination temperatures. Mesoporous silica support plays an important role in stabilizing the catalytically active tetragonal phase of zirconia, which gave the most active catalysts. The catalysts were examined for their catalytic activities in the liquid phase benzylation of phenol with benzyl alcohol and the catalyst 15 wt% TPA/ 22.4 wt% ZrO2/SBA-15 calcined at 1123 K was found to have high acidity and to be 10 times more active than neat TPA/ZrO2 under the reaction conditions studied in benzylation of phenol.
D.P. Sawant, A. Vinu, N.E. Jacob, F. Lefebvre, S.B. Halligudi, Journal of Catalysis 235 (2005) 341-352

A0555 – Synthesis and characterization of 2-amino-3-methylpyridinium dihydrogenomonoarsenate

A new crystal of 2-amino-3-methylpyridinium dihydrogenomonoarsenate has been prepared and characterized by X-ray crystallography, thermal analysis and spectroscopic studies. This compound crystallizes in the triclinic space group P1 with a = 7.2689 (2) Å , b = 8.0975 (2) Å , c = 8.3969 (4) Å, alpha = 77.09 (3)°, beta = 79.20 (3)°, gamma = 88.16 (2)°, V = 473.19 (3) Å 3, Z = 2. The crystal structure was solved and refined to R = 0.027 with 3375 independent reflections. The atomic arrangement can be described as (H2AsO4 )n polymeric chains anchoring the 2-amino-3- methylpyridinium cations through short hydrogen bonds. All the ring atoms of the organic entity are coplanar. The exocyclic N atom is an electron receiving center, which is consistent with features of imino resonance evidenced by bond lengths and angles. Solid-state 13C and 15N CP-MAS-NMR spectroscopies are in agreement with the X-ray structure. Ab initio calculations allow the attribution of carbons and nitrogen to the independent crystallographic sites.
A. Oueslati, A. Rayes, C. Ben Nasr, F. Lefebvre, Materials Research Bulletin 40 (2005) 1680-1689

A0554 – Preparation of plate-like nano alpha-Al2O3 using nano-aluminum seeds by wet-chemical methods

Alumina particles with plate-like shape were prepared successfully by a wet chemical processes with nano-size aluminum additive. The seed-effect of nano-size aluminum and its effect on the final alpha-Al2O3 particle size and shape were investigated. TEM, XRD, XPS, Zeta potential and DSC/TG were used to observe the microstructure of the alpha-Al2O3 particle and analysis this wet chemical processes. It was found that aluminum additive not only helps to produce the nano-size plate-like alpha-Al2O3 particles effectively but also reduces the formation temperature of alpha-Al2O3.
H. Lu, H. Sun, A. Mao, H. Yang, H. Wang, X. Hu, Materials Science and Engineering A 406 (2005) 19-23

A0557 – Carbon spheres prepared from zeolite Beta beads

Porous carbon beads were prepared from macroporous anion-exchange resin beads preliminary converted into resin-zeolite Beta composite or pure zeolite Beta spheres. Two synthesis procedures were used depending on the initial template employed. In a series of experiments, the resin from the resin-zeolite Beta composite was directly carbonized into carbon. In another series of experiments, the resin was removed by oxidation at 600°C leaving behind self-bonded zeolite Beta beads, which were filled with carbon by chemical vapor deposition (CVD) of propylene. As a final step for both procedures, the zeolite was dissolved in hydrofluoric acid. All the carbons prepared inherited the macroscopic spherical shape of the template spheres as well as the morphology of the primary particles building up the beads. The synthesis procedure and the carbonization temperature or the temperature for CVD of carbon employed influenced the ordering and the pore structure of the produced carbons. The carbons prepared by direct carbonization showed relatively low surface areas, less than 1000 m2 g-1, and no zeolite structural regularity. The samples obtained via CVD maintained the zeolite ordering with a periodicity of 11.7 Å and had surface areas of over 2000 m2 g-1."
L. Tosheva, J. Parmentier, V. Valtchev, C. Vix-Guterl, J. Patarin, Carbon 43 (2005) 2474-2480

A0556 – Aminopropyl-functionalized mesoporous silicas as CO2 adsorbents

A range of mesoporous silica substrates were functionalized with 3-aminopropyltrimethoxysilane to form hybrid products suitable for carbon dioxide adsorption. A dcylindrical poreT model was employed to characterize the extent of surface modification per unit substrate surface area and to permit its comparison on a common basis. The extent of surface functionalisation varied with substrate morphology. Combined DTA/TGA was used to characterise CO2 adsorption. Substantial reversible CO2 adsorption capacities were observed under anhydrous conditions (at 20°C). In the presence of water, CO2 capacity was enhanced, but the rate of desorption was diminished.
G.P. Knowles, J.V. Graham, S.W. Delaney, A.L. Chaffee, Fuel Processing Technology 86 (2005) 1435- 1448

A0559 – Hydrophobisation of active carbon surface and effect on the adsorption of water

A technique of surface hydrophobisation has been applied to two microporous carbonaceous adsorbents. A granular active carbon and an activated carbon fibre, both formerly chemically treated in order they preferentially present hydroxyl surface functions, were modified by action of vinyltrimethoxysilane (vtmos) in liquid phase. The resulting samples were characterised using sorption of nitrogen, FTIR, XPS and 29Si MAS-NMR spectroscopy, and elemental analysis. Their stability and heat treatment have also been investigated through thermal analysis. The efficiency of the hydrophobisation treatment was evaluated by static adsorption of water vapour and vapours of chlorinated volatile organic compounds (VOCs): dichloromethane and trichloroethylene. Grafting of the vtmos and development of a "coating" of polysiloxane onto the adsorbent induced a modification of the carbon surface but also a partial filling of the porosity. These modi- fications accounted for a decrease of both the amounts of water and VOC adsorbed by the hydrophobised materials. However, water uptakes were found to be much lower than those of the VOCs, evidencing an enhanced selectivity of the hydrophobised adsorbents toward VOCs.
F. Cosnier, A. Celzard, G. Furdin, D. Bégin, J.F. Marêché, O. Barrès, Carbon 43 (2005) 2554-2563

A0558 – Dependence of optical conductivity with delta in La2NiO4+d single crystals

"Optical conductivity and electrical resistivity of La2NiO4+d (d = 0.11 and 0.14) single crystals have been investigated for the (a, b) plane. Results show several changes of regime that are connected with the onset of spin and charge order, static or dynamic. A surprising contrast of data for both samples, in optical and electrical conductivity, is observed at lowest temperatures. In particular, a pronounced spin glass behavior is observed for d = 0.11. In the d = 0.14 sample, the progressive melting of the charge order scales with the temperature dependence of the oscillator strength of a "forbidden" mode related to folding to the Brillouin zone center of a mode for a wavevector q = (0.28, 0.28, 0) associated with the modulation of stripes."
N. Poirot, V. Ta Phuoc, G. Gruener, F. Gervais, Solid State Sciences 7 (2005) 1157-1162

A0561 – Elaboration, structural, thermal and vibrational studies of two new cadmium hybrid compounds: [Cd(OH)]2[O2C(CH2)2CO2], and [Cd3(OH)2][O2C(CH2)2CO2]2

"Two new cadmium hybrid inorganic-organic compounds have been hydrothermally prepared and structurally characterized using singlecrystal X-ray diffraction. [Cd(OH)]2[O2C(CH2)2CO2] ([CD1]) is Monoclinic P21/c, a = 10.12(2) Å, b = 5.554(5) Å, c = 6.134(3) Å, beta = 96.24(8)° and z = 2. [Cd3(OH)2][O2C(CH2)2CO2]2 ([CD2]) is Orthorhombic Pcca, a = 10.657(2) Å, b = 6.8610(3) Å, c = 16.949(3) Å, and z = 4. Both [CD1] and [CD2] have bi-dimensional inorganic networks pillared by carbon atoms of the succinate anions. [CD1] inorganic moiety is composed of a double layer of equivalent CdO6 octahedra sharing corners or edges. Smoothly corrugated mono-layers of CdO6 octahedra sharing corners or edges are present in the [CD2] inorganic moiety. Thermal as well IR spectroscopic studies are also presented. These hybrid compounds are stable up to 400°C under air flow."
A. Seguatni, M. Fakhfakh, N. Jouini, Solid State Sciences 7 (2005) 1272-1279

A0560 – Synthesis, crystal structures and properties of the trimetaphosphimates NaBa(PO2NH)3, KSr(PO2NH)3.4H2O, and NH4Sr(PO2NH)3.4H2O

The three double salts sodium barium tri-µ-imidocyclotriphosphate, NaBa(PO2NH)3 (1), potassium strontium tri-µ-imidocyclotriphosphate tetrahydrate, KSr(PO2NH)3.4H2O (2), and ammonium strontium tri-µ-imidocyclotriphosphate tetrahydrate, NH4Sr(PO2NH)3.4H2O (3), were synthesized by combining equimolar aqueous solutions of Na3(PO2NH)3.4H2O, K3(PO2NH)3, or (NH4)3(PO2NH)3.H2O, respectively, with the corresponding alkaline earth nitrate. In case of compound 1, suitable single crystals for X-ray crystal structure determination were solely obtained using gel crystallization in gelatine gels. The structures of 2 and 3 were found to be isotypic. All crystal structures were solved by single-crystal X-ray methods (1: C2/m, a = 1084.5(2), b = 1025.0(2), c = 796.2(2) pm, beta = 115.18(3)°, Z = 4, R1 = 0.023; 2: P21/n, a = 1087.2(2), b = 1049.6(2), c = 1191.2(2) pm, beta = 111.98(3)°, Z = 4, R1 = 0.025; 3: P21/n, a = 1088.4(2), b = 1048.5(2), c = 1196.9(2) pm, beta = 111.43(3)°, Z = 4, R1 = 0.025). In both structure types, the P3N3 rings of the trimetaphosphimate ions exhibit a chair conformation. In the crystal, the trimetaphosphimate ions act as mono and bidentate ligands of the alkali ions, and additionally as tridentate ones in case of the alkaline earth ions. Besides the oxygen atoms, the nitrogen atoms of the (PO2NH)3 3- rings contribute to the coordination of the cations as well. In 2 and 3, crystal water molecules complete the coordination of the metal ions. Extended hydrogen bonding reinforces the three-dimensional interconnection of the ions and the crystal water molecules in the structures of all three compounds.
S. Correll, S.n Sedlmaier, W. Schnick, Solid State Sciences 7 (2005) 1261-1271

A0564 – Kinetics of the thin films transformation Ti/Al multilayer y-TiAl

"Ti/Al multilayer thin films with nanometric bilayer thickness (period) were produced by d.c. magnetron sputtering. The kinetics from the Ti/Al nanolayers to the g-TiAl alloy is established based on differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. The kinetic study shows that the period (k) influences the formation of the ordered g-TiAl phase. For k =4 and k =20 nm the high diffusivity and reactivity lead to the formation of g-TiAl in a single step that includes the formation of disordered TiAl followed by an ordering process. On the contrary, for a multilayer with 200 nm period the formation of g-TiAl is preceded by the formation of Al3Ti. In both cases the activation energies (Ea) calculated can be compared with values reported in literature."
A.S. Ramos, M.T. Vieira, Surface & Coatings Technology 200 (2005) 326-329

A0563 – Synthesis and characterization of magnesium substituted biphasic mixtures of controlled hydroxyapatite/b-tricalcium phosphate ratios

"The present paper investigates the preparation of magnesium (Mg) substituted biphasic mixtures of different hydroxyapatite (HAP)/b-tricalcium phosphate (beta-TCP) ratios through aqueous precipitation method. The concentrations of added magnesium (Mg) were varied with the calcium in order to obtain constant (Ca+Mg)/P ratios of 1.67 ranging from 1.62+0.05, 1.58+0.09 and 1.54+0.13, respectively. The as prepared powders were calcined at different temperatures to study the phase behaviour and thermal stability. The powders were characterized by the following analytical techniques: TG-DTA, X-ray diffraction and FT-IR. The results have shown that substitution of Mg in the calcium-deficient apatites resulted in the formation of biphasic mixtures of different HAP/beta-TCP ratios after heating above 700°C. The ratios of the formation of phase mixtures were dependent on the calcium deficiency in the apatites with the higher deficiency having the strongest impact on the increased formation of beta-TCP and the substituted Mg was found to stabilize the beta-TCP phase."
S. Kannan, I.A.F. Lemos, J.H.G. Rocha, J.M.F. Ferreira, Journal of Solid State Chemistry 178 (2005) 3190-3196

A0562 – A simple kinetic analysis to determine the intrinsic reactivity of coal chars

"The intrinsic oxidation reactivity in air of an activated carbon char derived from bituminous coal was investigated using a new thermogravimetric analysis (TGA) method. Applying the new method, values of the Arrhenius activation energy E and pre-exponential factor A were estimated from TGA data obtained via heating samples at different constant rates. A novel statistical criterion was subsequently used to determine the heating rate at which optimum values of E and A were obtained. This is a valuable development, for in conventional non-isothermal TGA, while it is accepted that Arrhenius parameters vary with heating rate, there is no formal method for selecting one rate (and hence one set of values of E and A) over another. Using this new method, the following optimum values were obtained for the carbon at a heating rate of 25°C min-1: E=129.4 kJ mol-1 and ln(A/s-1)=10.4. These results are very similar to those calculated for the same material using more time consuming and less accurate isothermal TGA methods. It is therefore proposed that this new analysis method might be an improvement on conventional techniques to determine the intrinsic oxidation reactivity in air of coal chars."
E. Sima-Ella, G. Yuan, T. Mays, Fuel 84 (2005) 1920-1925

A0565 – Production and characterisation of activated carbon from wood components in powder: Cellulose, lignin, xylan

"The aim of this work was to characterise the activated carbon produced from wood and its basic components: cellulose, lignin and xylan (hemicelluloses). Two ways of activation were tested: simple pyrolysis under N2 and thermal treatment of the material impregnated with KOH (KOH-activation). Concerning the pyrolysis, simultaneous measurements of DTA-TGA allowed to compare the heat of reaction and the decomposition rate of the 3 wood components. Moreover it was shown that only the char from cellulose has a significant BET-surface area of pores. The KOH-activated carbons from wood and wood components were characterised by their BET surface area, their spectra in temperature programmed desorption (TPD) up to 1173 K and by their capacity to adsorb pollutant compounds in aqueous phase such as phenol and methylene blue. It was shown that the theoretical models of Langmuir and Freundlich satisfactorily fit to the adsorption isotherms of these pollutants, moreover most of the parameters of these theoretical models rank as the BET-surface area of pores."
L. Khezami, A. Chetouani, B. Taouk, R. Capart, Powder Technology 157 (2005) 48-56

A0566 – Sol-gel bonding of silicon wafers Part 1: Influence of the processing temperature on final bond morphology and interfacial energy

Sol-gel bonds have been produced between smooth, clean silicon substrates by spin-coating solutions containing partially hydrolysed silicon alkoxides. The two coated substrates were assembled and the resulting sandwich fired at temperatures ranging from 60 to 600°C. The sol-gel coatings were characterised using attenuated total reflectance Fourier transform infrared spectroscopy, ellipsometry, and atomic force microscopy, while the corresponding bonded specimens were investigated using scanning electron microscopy and cross-sectional transmission electron microscopy. Mechanical properties were characterised using both microindentation and tensile testing. Bonding of silicon wafers has been successfully achieved at temperatures as low as 60°C. At 300°C, the interfacial fracture energy was 1.55 J/m2. At 600°C, sol-gel bonding provided superior interfacial fracture energy over classical hydrophilic bonding (3.4 J/m2 vs. 1.5 J/ m2). The increase in the interfacial fracture energy is related to the increase in film density due to the sintering of the sol-gel interface with increasing temperature. The superior interfacial fracture energy obtained by sol-gel bonding at low temperature is due to the formation of an interfacial layer, which chemically bonds the two sol-gel coatings on each wafer. Application of a tensile stress on the resulting bond leads to fracture of the samples at the silicon/sol-gel interface.
C.J. Barbé, D.J. Cassidy, G. Triani, B.A. Latella, D.R.G. Mitchell, K.S. Finnie, K. Short, J.R. Bartlett, J.L. Woolfrey, G.A. Collins, Thin Solid Films 488 (2005) 153-159

A0568 – Re-investigation of synthesis of BaTiO3 by conventional solid-state reaction and oxalate coprecipitation route for piezoelectric applications

The formation of barium titanate powder by solid-state reaction and oxalate coprecipitation route is re-investigated by differential thermal analysis-thermo-gravimetry (DTA-TG) thermal analysis and high temperature X-ray diffraction (XRD). The temperature formation of the perovskite phase is lower for the chemical way than for the solid state one, and no intermediate product is detected. The obtained powder leads to ceramics with high dielectric and piezoelectric properties. For example the room temperature piezoelectric d33 coefficient is 260 pC/N (higher than the values usually published in the literature) and it shows a good stability under electrical solicitations. These properties make BaTiO3 (BT) a leadfree high performance material for piezoelectric applications.
L. Simon-Seveyrat, A. Hajjaji, Y. Emziane, B. Guiffard, D. Guyomar, Ceramics International 33 (2005) 35-40

A0567 – Sol-gel bonding of silicon wafers Part 2. Influence of the sol-gel chemistry on bond morphology and interfacial energy

Low temperature bonding of silicon wafers was achieved using sol-gel technology. The initial sol-gel chemistry of the coating solution was found to influence the mechanical properties of the resulting bonds. More precisely, the influence of parameters such as the alkoxide concentration, water-to-alkoxide molar ratio, pH, and solution aging on the final bond morphologies and interfacial fracture energy was studied. The thickness and density of the sol-gel coating were characterised using ellipsometry. The corresponding bonded specimens were investigated using attenuated total reflectance Fourier transformed infrared spectroscopy to monitor their chemical composition, infrared imaging to control bond integrity, and cross-sectional transmission electron microscopy to study their microstructure. Their interfacial fracture energy was measured using microindentation. An optimum water-to-alkoxide molar ratio of 10 and hydrolysis water at pH=2 were found. Such conditions led to relatively dense films (>90%), resulting in bonds with a fracture energy of 3.5 J/m2, significantly higher than those obtained using classical hydrophilic bonding (typically 1.5-2.5 J/m2). Ageing of the coating solution was found to decrease the bond strength.
C.J. Barbé, D.J. Cassidy, G. Triani, B.A. Latella, D.R.G. Mitchell, K.S. Finnie, J.R. Bartlett, J.L. Woolfrey, G.A. Collins, Thin Solid Films 488 (2005) 160-166

A0569 – Investigation of factors influencing catalytic activity for n-butane isomerization in the presence of hydrogen on Al-promoted sulfated zirconia

Two series of Al-promoted sulfated zirconia with 3 mol% Al2O3 content were prepared. In one case, zirconium-aluminum hydroxide has been aged at room temperature; in the other case, zirconium-aluminum hydroxide has been synthesized at 373 K under hydrothermal condition. For the two series of samples, the influence of the synthesis parameters such as ageing time, the amount of ammonia added, and zirconium concentration on catalytic activity for n-butane isomerization in the presence of hydrogen were investigated. Moreover, Alpromoted sulfated zirconia with a high surface area (174 m2/g) can be obtained by properly adjusting synthesis parameters under hydrothermal condition at 373 K. The catalytic data showed that this material had similar catalytic activity to a conventional Al-promoted sulfated zirconia with a low surface area (98 m2/g). The characterization of the samples revealed that the catalytic activity was directly correlated with sulfur content rather than surface area, sulfate density and the total number of Bronsted acid sites. The synthesis of the precursors of hydroxides before sulfation is a crucial step for catalytic activity of the samples in n-butane isomerization.
Y. Sun, S. Walspurger, B. Louis, J. Sommer, Applied Catalysis A: General 292 (2005) 200-207

A0571 – NH4F effect in post-synthesis treatment of Al-MCM-41 mesoporous materials

A series of Al-MCM-41 mesoporous molecular sieves, with Si/Al ratio in the range 15-40, were synthesized and characterized by XRD, N2 physisorption, DRIFT and 27Al and 29Si MAS NMR analysis. Al-MCM-41 samples were prepared by two procedures. (i) Synthesis at room temperature, following the procedure described by Gru¨n et al. including some variations. (ii) The as-synthesized samples obtained in (i) were suspended in 300 mL of NH4F 0.1 M for 34 h. Al-MCM-41 samples with high surface acidity were synthesized. The NH4F treatment contributed to enhance these acidic properties, leading to materials highly active in the vaporphase cumene conversion, studied as a catalytic test. The catalytic activity was related to tetrahedral or octahedral aluminum environments for non-fluorinated samples and fluorinated ones, respectively.
R. Luque, J.M. Campelo, D. Luna, J.M. Marinas, A.A. Romero, Microporous and Mesoporous Materials 84 (2005) 11-20

A0570 – Catalytic partial oxidation of methane to syngas over Ca-decorated-Al2O3-supported Ni and NiB catalysts

One wt% Ni and 1 wt% NiB catalysts supported on Ca-decorated g-Al2O3 (Ca-AlO) supports were prepared by conventional impregnation and chemical reduction methods. These supported catalysts were applied for the catalytic partial oxidation of methane (POM) to syngas. The two low-Ni-loading catalysts have shown high activity/selectivity for the POM, as good as those of 1 wt% Rh and 10 wt% Ni catalysts supported on commercial gamma-Al2O3 support (AlO). But their coking resistivity was remarkably better than that of 10 wt% Ni/AlO. The coke formation over these catalysts decreased in the following order: 10 wt% Ni/AlO > 1 wt% Ni/Ca-AlO > 1 wt% NiB/Ca-AlO ~ 1 wt% Rh/ AlO. The key factor in the improvement of the carbon resistance was to decrease the metallic Ni particle size through the lowering of Ni loading combined with the addition of B promoter. The low Ni loading has been achieved by covering the support with a CaAl2O4 layer, and decreasing the catalyst calcination temperature to ~723 K. The formation of crystalline carbon was greatly suppressed on the NiB catalysts due to the highly dispersed nature; such formation significantly improved the thermal stability of the Ni particles.
L. Chen, Y. Lu, Q. Hong, J. Lin, F.M. Dautzenberg, Applied Catalysis A: General 292 (2005) 295-304

A0573 – Solvent effects in the synthesis of CoAPO-5, -11 and -34 molecular sieves

Series of CoAPO-5, CoAPO-11 and CoAPO-34 molecular sieves have been synthesized starting from a synthesis gel varying in its amount of Co2+ and type of solvent molecule. Four protonic solvents have been investigated: water, ethanol, ethylene glycol and glycerol. The obtained crystalline materials were characterized with X-ray diffraction; diffuse reflectance UV-Vis-NIR spectroscopy; infrared spectroscopy; elemental analysis; electron microscopy microprobe analysis and thermo-gravimetrical analysis. It was found that the type of solvent has a strong influence on the crystallization behavior and the substitution degree of Co2+ for Al3+ in the framework of microporous aluminophosphates. Ethanol, ethylene glycol and glycerol seem to be the best solvents for the synthesis of single-phase and highly crystalline Co-rich CoAPO-34, CoAPO-11 and CoAPO-5 molecular sieves, respectively. By varying the type of solvent molecule, Co content and template amount in the synthesis gel it was possible to increase the substitution degree of framework Co2+ in microporous aluminophosphates. In this manner, around 10%, 25% and 36% of Al3+ could be replaced by Co2+ in the framework of CoAPO-11, CoAPO-5 and CoAPO-34, respectively. These substitution degrees are substantially higher than those for CoAPO materials synthesized in the presence of water.
W. Fan, R. Li, T. Dou, T. Tatsumi, B.M. Weckhuysen, Microporous and Mesoporous Materials 84 (2005) 116-126

A0572 – Evaluation of a new copper(II)-curcumin complex as superoxide dismutase mimic and its free radical reactions

A mononuclear (1:1) copper complex of curcumin, a phytochemical from turmeric, was synthesized and examined for its superoxide dismutase (SOD) activity. The complex was characterized by elemental analysis, IR, NMR, UV-VIS, EPR, mass spectroscopic methods and TG-DTA, from which it was found that a copper atom is coordinated through the keto-enol group of curcumin along with one acetate group and one water molecule. Cyclic voltammetric studies of the complex showed a reversible Cu2+/Cu+ couple with a potential of 0.402 V vs NHE. The Cu(II)-curcumin complex is soluble in lipids and DMSO, and insoluble in water. It scavenges superoxide radicals with a rate constant of 1.97 x 10^5 M-1 s-1 in DMSO determined by stopped-flow spectrometer. Subsequent to the reaction with superoxide radicals, the complex was found to be regenerated completely, indicating catalytic activity in neutralizing superoxide radicals. Complete regeneration of the complex was observed, even when the stoichiometry of superoxide radicals was 10 times more than that of the complex. This was further confirmed by EPR monitoring of superoxide radicals. The SOD mimicking activity of the complex was determined by xanthine/xanthine oxidase assay, from which it has been found that 5 Ag of the complex is equivalent to 1 unit of SOD. The complex inhibits radiation-induced lipid peroxidation and shows radical-scavenging ability. It reacts with DPPH radicals with rate constant 10 times less than that of curcumin. Pulse radiolysis-induced one-electron oxidation of the complex by azide radicals in TX-100 micellar solutions produced strongly absorbing (¨500 nm) phenoxyl radicals, indicating that the phenolic moiety of curcumin remained intact on complexation with copper. The results confirm that the new Cu(II)-curcumin complex possesses SOD activity, free radical neutralizing ability, and antioxidant potential. Quantum chemical calculations with density functional theory have been performed to support the experimental observations.
A. Barik, B. Mishra, L. Shen, H. Mohan, R.M. Kadam, S. Dutta,H.-Y. Zhang, K.I. Priyadarsini, Free Radical Biology & Medicine 39 (2005) 811 - 822

A0575 – Selective single-pot oxidation of cyclohexane by molecular oxygen in presence of bis(maltolato)oxovanadium complexes covalently bonded to carbamated modified silica gel

The bis(maltolato)oxovanadium complexes [VO(ma)2], cis-[VO(OCH3)(ma)2] and [VO(py)(ma)2] have been covalently bonded to carbamated modified silica gel and these systems are shown to serve as effective heterogeneous catalysts for cyclohexane oxidation by molecular oxygen without any additive. The [VO(ma)2] catalyst gives the best results which are further promoted in the presence of 2-pyrazinecarboxylic acid which acts as a co-catalyst, while picolinic acid proved to be almost inactive. The reaction occurs under mild conditions (175°C, 10 atm O2) forming two major products, cyclohexanol and cyclohexanone in a smaller amount, with a good selectivity. The TGA analysis of the catalyst shows that it is stable up to 273°C and inductive couple plasma (ICP) indicates a limited metal loss after 20 h use of the catalyst up to 175°C. The morphology of the catalyst was analyzed by SEM. Evidence is presented in favour of the involvement of a free-radical mechanism.
G.S. Mishra, A.J.L. Pombeiro, Journal of Molecular Catalysis A: Chemical 239 (2005) 96-102

A0574 – Synthesis of nano-scaled yttrium aluminum garnet phosphor by co-precipitation method with HMDS treatment

The present paper describes the process of preparing nano-scaled and well-crystallized cerium-doped yttrium aluminum garnet (YAG:Ce) crystalline phosphors synthesized by co-precipitation method with the addition of hexamethyldisilazane (HMDS) as OH-scavenging reagent. Thermal analyzer and X-ray diffractometer measurements showed that pure YAG phase could be got at the temperature of 900°C lower than that by solid-state method. It was also found that smaller size crystallites (?33 nm) were made after the HMDS treatment under the transmission electron microscope (TEM) observation. We inferred that it was achieved by reducing the surface condensing hydroxyl groups and by restricting the grain boundary motion due to second-phase particles pinning. Meanwhile, optical properties of YAG:Ce prepared in the present work were examined and showed that the photoluminescence intensity of the co-precipitated YAG:Ce crystallites plus HMDS treatment was better than those prepared by solid-state reaction or co-precipitation without any further treatment. It was proposed that the existing second-phase particles as well as higher specific surface area of nano-scaled YAG:Ce crystallites enhance the absorption of excitation.
Y-T. Nien, Y-L. Chen, I-G. Chen, C-S. Hwang, Y-K. Su, S-J. Chang, F-S. Juang, Materials Chemistry and Physics 93 (2005) 79-83

A0576 – Hydrophobisation of mesoporous y-Al2O3 with organochlorosilanes-efficiency and structure

y-Al2O3 materials with small mesopores are hydrophobised by reactions with organochlorosilanes in liquid media. The structure of the modified materials is studied by means of physisorption and high-resolution SEM. A good measure of the decrease in surface polarity can be obtained from BET-fits of the N2 isotherms. It was found that many pores become blocked by using chlorosilanes with bulky organic groups, while a more open structure is preserved for methylchlorosilanes. Using toluene as a solvent leads to a higher extent of modification than ethanol, as observed for methylchlorosilanes. Multifunctional organochlorosilanes (i.e. with 2 or 3 Cl-groups) are more reactive but also give rise to blockage of some of the microporous part as a result of polymerisation reactions. Mono- and difunctional methylchlorosilanes give the best results for alumina materials with small mesopores, preserving an open structure and leading to homogeneous modification. Modification with methylchlorosilanes in toluene leads to the lowest surface polarity. The results give clues for optimising the procedures for hydrophobisation of porous materials with small mesopores.
H.L. Castricum, A. Sah, M.C. Mittelmeijer-Hazeleger, J.E. ten Elshof, Microporous and Mesoporous Materials 83 (2005) 1-9

A0578 – The crystallization of an aluminosilicate glass in the K2O-Al2O3-SiO2 system

Objectives. The aims of the study were to explore the nucleation and crystallization kinetics of an aluminosilicate glass in K2O-Al2O3-SiO2 system and to characterize it. Objectives. A starting glass composition of wt%; 64.2% SiO2, 16.1% Al2O3, 10.9% K2O, 4.3% Na2O, 1.7% CaO, 0.5% LiO and 0.4% TiO2 was heated in an electric furnace and later quenched to produce glasses. The glass powders were heat treated using differing heat treatment schedules and quenched. Dta, Xrd, Eds and Sem analyses were used to characterize and explore the crystallization kinetics of the glasses. Results. Phase separation of the glasses was identified and characterized in the glasses. Tetragonal leucite, cubic leucite and sanadine glass-ceramics were produced. Fine leucite crystals (1 mm2) were crystallized with minimal matrix microcracking. Significance. Amorphous phase separation appeared to be an important precursor to nucleation and crystal growth in the alkali aluminosilicate glasses explored. It was possible to control the crystallization of tetragonal leucite and sanidine phases by selected heat treatment of glass powders and monoliths, resulting in the production of fine grained tetragonal leucite glass-ceramics.
M.J. Cattell, T.C. Chadwick, J.C. Knowles, R.L. Clarke, Dental Materials 21 (2005) 811-822

A0577 – Removal of the herbicide 2,4-dichlorophenoxyacetate from water to zinc-aluminium-chloride layered double hydroxides

Batch sorption studies were conducted to investigate the potential of [Zn-Al-Cl] layered double hydroxides (LDHs) for the removal of the herbicide 2,4-dichlorophenoxyacetate (2,4-D) from contaminated aqueous solutions. Experiments were performed at different pH values, initial pesticide concentration, solid/pesticide ratio and anion exchange capacity of LDHs. The LDH samples evaluated had very high retention capacity for 2,4-D whose removal was a rapid process, as a quasi-equilibrium state was reached after 1-h reactiontime. The adsorptioncanbe described by Langmuir-type isotherms, with an average affinity constant of 12.5L mmol 1. At initial 2,4-D concentrations between0.08 and 4 mmol L 1, the solids removed up to 98% of the pesticide. Physicochemical characterizationof the LDH solids, both fresh and after removal of 2,4-D, by X-ray diffraction, infrared spectroscopy and thermogravimetry, indicates that the retention of 2,4-D is done by adsorption on the surface of the solid for low 2,4-D concentrations. However, a combination of surface adsorption and interlayer ion exchange takes place when the 2,4-D concentration is high.
A. Legrouri, M. Lakraimi, A. Barroug, A. De Roy, J.P. Besse, Water Research 39 (2005) 3441-3448

A0580 – The influence of aluminum phosphates on graphite oxidation

Aluminum phosphates are of interest for use as inhibitors for the oxidation of carbonaceous materials. This investigation analyzes three aluminum phosphates of nominal compositions, Al2O3.P2O5, Al2O3.3P2O5, and Al2O3.9P2O5, in terms of thermal stability and efficacy to inhibit the thermal oxidation of graphite flake in pure oxygen. Temperature programmed oxidation reveals that the onset temperature for oxidation is increased by 75-100°C as a result of the aluminum phosphate treatments. Isothermal oxidation rate measurements show that while the overall oxidation rate constants are lowered by the aluminum phosphate treatments, the apparent activation energy remains constant (54-59 kcal/mol), which indicates that the reduction in rate constant with temperature is due to a lowering of the pre-exponential term.
Christopher R. Maier, Linda E. Jones, Carbon 43 (2005) 2272-2276

A0579 – Grafting luminescent metal-organic species into mesoporous MCM-41 silica from europium(III) tetramethylheptanedionate, Eu(thd)3

Mixed systems with Eu(III) beta-diketonates as optically active guest species, and mesoporous silicas MCM-41 as a host matrix have been investigated. The grafting of europium(III) onto the inner walls of unmodified MCM-41 has been achieved starting from Eu(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate), using two routes: wet impregnation (WI) at room temperature, and chemical vapour infiltration (CVI) at 185°C. In received hybrids, denoted Eu(thd)x@MCM-41, the same maximum yield [Eu]/ [Si] = 8.2 at% on average has been achieved with either methods. The molar ratio x = [thd]/[Eu] is 0.6 on average for WI samples, and 1.5 for CVI samples. In the latter, higher contents in thd compensate lower contents in silanols with respect to the former. Rationalizing the possible bonds exchanged at the silica surface leads to a great diversity of possible co-ordination schemes according to the expression ? [Si(OH)n-x(O)xEu(thd)3-x] (where ? means that surface species are considered). Chromophore neutral ligands phenanthroline (phen) or bipyridine (bipy) have been added to induce efficient Eu3+ luminescence under 270-280 nm excitation, via the antenna effect. For the most favourable case, (phen)yEu(thd)x@MCM-41, the emission intensity at 612 nm under excitation at 270 nm is 2/3 that for the genuine heteroleptic complex Eu(thd)3(phen). Moreover the hybrid material is stable up to 440°C.
A. Fernandes, J. Dexpert-Ghys, A. Gleizes, A. Galarneau, D. Brunel, Microporous and Mesoporous Materials 83 (2005) 35-46

A0582 – Solar synthesis of single-walled carbon nanotubes at medium scale

Single-walled carbon nanotubes were synthesized in gram quantities with a 50 kW solar reactor. Vaporization rate was in the range 6-15 g/h and two samples were collected for each run. The structure of the products was studied by SEM, TEM and Raman spectroscopy as a function of the buffer gas (helium or argon), the target length and the collected location. Good quality samples containing 1.2-1.6 nm diameter SWNTs were produced with helium at 450 hPa, 8 Nm3/h and a 15 cm target length using 2 at.% Ni and 2 at.% Co as catalyst. The material quality increased with the target length in helium. On the contrary, poor quality product was obtained whatever the target length in argon. TGA analysis showed that the best product purity was at least 35 wt%.
D. Luxembourg, G. Flamant, D. Laplaze, Carbon 43 (2005) 2302-2310

A0581 – Study of hygrothermal ageing of glass fibre reinforced PET composites

Hygrothermal ageing has been investigated on glass fibre reinforced polyethylene terephthalate (PET) composites using complementary techniques and a multiscale approach in order to identify the different steps of the material's degradation. For early ageing times (t!6 h), DMTA tests give evidence of the plasticisation of the PET matrix. GPC measurements and acid end group titration show that the chemical degradation step of the composites occurs immediately and that the main degradation mechanism is random chain scission. The changes in morphology resulting from hydrolysis, investigated through DSC and SAXS experiments, reveal a decrease in the long period that may result from the diffusion of oligomers out of the spherulites. The water uptake for long ageing times is attributed to an interfacial debonding which induces an osmotic pressure in this area. Photomechanical measurements highlight the development of microcracks within the aged material that induced an increase in the variation of material volume.
M.P. Foulc, A. Bergeret, L. Ferry, P. Ienny, A. Crespy, Polymer Degradation and Stability 89 (2005) 461-470

A0583 – Thermal analysis and spectroscopic characteristics of tetrabutylammonium tetrachloroferrate(III)

The IR, far-IR, Raman andM¨ossbauer spectra have been utilized to identify a newcompound consisting of a tetrachloroferrate(III) anion and a tetrabutylammonium cation [(C4H9)4N][FeCl4]. Its degradation has been studied by thermal analysis using TG, TG-MS, DTG and DTA, as well as DSC techniques. The measurements were run in static air and in argon atmosphere. Solid residues were identified by elemental analysis, far-IR and M¨ossbauer spectroscopy. The discussion was focused on processes proceeding during the first step of the thermal decomposition.
D. Wyrzykowski, T. Maniecki, A.Pattek-Janczyk, J. Stanek, Z. Warnke, Thermochimica Acta 435 (2005) 92-98

A0585 – Influence of grain size on the phase transition beta2 => epsilon in Bi4La2O9 material

This paper deals on a study realized in order to elaborate dense ceramic of Bi4La2O9 oxide conductor. A wet method in nitric media, usually favorable to obtain low grain size, did not allow to isolate the stable phases. Material with particle low size has been obtained by attrition treatment after conventional solid state powder synthesis. The decrease of particle size (ffi4 times), evidenced by X-ray diffraction and SEM, influences the reversibility of transitions between monoclinic e and rhombohedral b2 varieties on powder, as well as ceramics, leading to an improvement of the conductivity level of these ones after a thermal cycle.
M. Drache, N. Djelal, M.C. Steil, P. Roussel, P. Conflant, Materials Research Bulletin 40 (2005) 1599-1608

A0584 – Static and dynamic aspects of coupling between creep behavior and oxidation on MC2 single crystal superalloy at 1150°C

Creep tests were performed on thin wall specimens made of MC2 single crystal superalloy at 1150°C and under controlled atmosphere. The results highlight the deleterious oxidation effect on creep properties. The assumption that oxidation leads to a non-loadbearing affected zone is insufficient to explain the difference in creep rate that was noticed between tests performed under synthetic air and under hydrogenated argon, and cannot explain the decrease of the strain rate during the tests that were carried out with a change of atmosphere from synthetic air to hydrogenated argon. On the other hand, these experimental results are consistent with vacancy injection due to partial cationic oxidation, which accelerates the creep rate by promoting creep mechanisms controlled by diffusion. The anionic protective alumina scale formed under hydrogenated argon prevents this vacancy flux. The integration of this dynamic and long range oxidation effect in creep strain models is discussed.
S. Dryepondt, D. Monceau, F. Crabos, E. Andrieu, Acta Materialia 53 (2005) 4199-4209

A0587 – A thermodynamic approach for advanced fuels of gas-cooled reactors

For both high temperature reactor (HTR) and gas cooled fast reactor (GFR) systems, the high operating temperature in normal and accidental conditions necessitates the assessment of the thermodynamic data and associated phase diagrams for the complex system constituted of the fuel kernel, the inert materials and the fission products. A classical CALPHAD approach, coupling experiments and thermodynamic calculations, is proposed. Some examples of studies are presented leading with the CO and CO2 gas formation during the chemical interaction of [UO2±x/C] in the HTR particle, and the chemical compatibility of the couples [UN/SiC], [(U, Pu)N/SiC], [(U,Pu)N/TiN] for the GFR system. A project of constitution of a thermodynamic database for advanced fuels of gas-cooled reactors is proposed.
C. Guéneau, S. Chatain, S. Gossé, C. Rado, O. Rapaud, J. Lechelle, J.C. Dumas, C. Chatillon, Journal of Nuclear Materials 344 (2005) 191-197

A0586 – Solution preparation of the amorphous molybdenum oxysulfide MoOS2 and its use for catalysis

Acid condensation of aqueous MoO2S2 2 anion yields amorphous MoOS2 oxysulfide. This compound possesses tubular morphology and when freshly precipitated is soluble in polar organics such as acetone and ethanol. The ensemble of characterizations (IR, UV-visible, EXAFS spectroscopy) suggests that it contains cyclic or short linear oligomers of neutral molybdenum (V) oxysulfide MoOS2 core. Thermal decomposition of MoOS2 under inert atmosphere leads to the formation of a mixture of MoO2 and MoS2 phases. Promotion of MoOS2 with cobalt followed by sulfidation leads to highly active HDS catalysts.
Daisy Genuit, Igor Bezverkhyy, Pavel Afanasiev, Journal of Solid State Chemistry 178 (2005) 2759-2765

A0588 – Catalytic cracking of n-octane on small-pore zeolites

The small-pore zeolites Alpha (LTA), chabazite (CHA), NU-3 (LEV), Rho (RHO), Sigma-1 (DDR), ZK-5 (KFI) andZSM-58 (DDR) were hydrothermally synthesized and characterized by XRD, elemental analysis, 27Al MAS NMR spectroscopy and noctane adsorption. The Bronsted acid forms of the zeolites were used as catalysts for cracking of n-octane in a continuously operated fixed-bed reactor. For comparison, n-octane cracking experiments were performedon the medium-pore zeolite H-ZSM-5 (MFI) and the large-pore zeolite H-Beta (*BEA). In agreement with prior work on catalytic cracking of short-chain n-alkanes, it was foundthat the contribution of monomolecular Haag-Dessau cracking increases, as the pores are getting narrower. However, if a long-chain nalkane, such as n-octane, is usedas reactant, the typical products of both monomolecular and bimolecular cracking are observedon all 8-ring zeolites. For various small-pore zeolites, a pronounced influence of the pore dimensions was observed. Selectivities to C1 andC 2 products were shown to increase with decreasing size of the pore windows and increasing spatial constraints of the pore systems.
S. Altwasser, C. Welker, Y. Traa, J. Weitkamp, Microporous and Mesoporous Materials 83 (2005) 345-356

A0589 – Hydrothermal synthesis and characterization of a new inorganic-organic hybrid compound AMP[ZnCl3] (AMP = 2-aminomethylpyridinium)

A novel organic-inorganic hybrid complex [(2-NH2CH2C5H4N)ZnCl3] has been hydrothermally synthesized and characterized by single crystal X-ray diffraction, thermal analysis and spectroscopic studies. The compound crystallizes in the triclinic system, space group P 1, a = 7.5339(9), b = 7.589(2), c = 9.365(2) A ? , a = 104.55(2) , b = 97.22(1) , c = 87.88(2) , V = 513.6(2), Z = 2. In the title compound, the 2-aminomethylpyridine acts as a ligand covalently linked to Zn(II) cation to form a slightly distorted ZnCl3N tetrahedral environment. Each [Zn(C6H8N2)Cl3] unit is connected to one neighbor by a pair of hydrogen bonds between the apical chlorides and amine hydrogen atoms and to the other by a couple of p-p stacking interactions between the aromatic rings of the coordinated ligands forming a novel one-dimensional chain-like arrangement. The title complex is the first one that contains both coordinated and hydrogen bonded 2-aminomethylpyridine. Solid state 13C and 15N CP-MAS-NMR spectroscopies are in agreement with the X-ray structure. Ab initio calculations allow the attribution of carbons and nitrogen to the independent crystallographic sites. The Raman spectroscopy confirmed the presence of Zn-Cl and Zn-N bonds.
R. Kefi, C. Ben Nasr, F. Lefebvre, A. Durif, Inorganica Chimica Acta 358 (2005) 4075-4080

A0591 – An investigation of polypyrrole-LiFePO4 composite cathode materials for lithium-ion batteries

A series of polypyrrole-LiFePO4 (PPy-LiFePO4) composites were synthesised by polymerising pyrrole monomers on the surface of LiFePO4 particles. AC impedance measurements show that the coating of polypyrrole significantly decreases the charge-transfer resistance of LiFePO4 electrodes. The electrochemical reactivity of polypyrrole and PPy-LiFePO4 composites for lithium insertion and extraction was examined by charge/discharge testing. The PPy-LiFePO4 composite electrodes demonstrated an increased reversible capacity and better cyclability, compared to the bare LiFePO4 electrode.
G.X. Wang, L. Yang, Y. Chen, J.Z. Wang, Steve Bewlay, H.K. Liu, Electrochimica Acta 50 (2005) 4649-4654

A0590 – Arsenic removal by adsorption on iron(III) phosphate

Under natural conditions, arsenic is often associated with iron oxides and iron(III) oxidative capacity towards As(III) is well known. In this study, As(III) and As(V) removal was performed using synthesised iron(III) phosphate, either amorphous or crystalline. This solid can combine (i) As(III) oxidation by iron(III) and (ii) phosphate substitution by As(V) due to their similar properties. Results showed that adsorption capacities were higher towards As(III), leading to Fe2+ and HASO4 2- leaching. Solid dissolution and phosphate/arsenate exchange led to the presence of Fe3+ and PO4 3- in solution, therefore various precipitates involving As(V) can be produced: with Fe2+ as Fe3(AsO4)2.8H2O(s) and with Fe3+ as FeAsO4.2H2O(s). Such formations have been assessed by thermodynamic calculations. This sorbent can be a potential candidate for industrial waste treatment, although the high release of phosphate and iron will exclude its application in drinking water plants.
V. Lenoble, C. Laclautre, V. Deluchat, B. Serpaud, J-C. Bollinger, Journal of Hazardous Materials B123 (2005) 262-268

A0592 – Nano-structured SnO2-carbon composites obtained by in situ spray pyrolysis method as anodes in lithium batteries

In this paper, we report on a series of SnO2-carbon nano-composites synthesized by in situ spray pyrolysis of a solution of SnCl2.2H2O and sucrose at 700°C. The process results in super fine nanocrystalline SnO2, which is homogeneously distributed inside the amorphous carbon matrix. The SnO2 was revealed as a structure of broken hollow spheres with porosity on both the inside and outside particle surfaces. This structure promises a highly developed specific surface area. X-ray diffraction (XRD) patterns and transmission electron microscope (TEM) images revealed the SnO2 crystal size is about 5-15 nm. These composites show a reversible lithium storage capacity of about 590 mAh g-1 in the first cycle. The discharge curve of the composite indicates that lithium is stored in crystalline tin, but not in amorphous carbon. However, the conductive carbon matrix with high surface area provides a buffer layer to cushion the large volume change in the tin regions, which contributes to the reduced capacity fade compared to nonacrystalline SnO2 without carbon.
L. Yuan, K. Konstantinov, G.X. Wang, H.K. Liu, S.X. Dou, Journal of Power Sources 146 (2005) 180-184

A0593 – Homogeneously precipitated Lu2O3:Eu nanocrystalline phosphor for X-ray detection

Nanocrystalline Lu2O3 doped with 1 at.% of Eu was obtained precipitating hydroxide of lutetium with urea at 80°C from water solution and decomposing the hydroxide to oxide at 500°C. Polyvinyl alcohol was used to hinder the particles growth during precipitation. The average size of the fabricated particleswas 2-5 nm. Although at 500°C the hydroxide decomposed to Eu-doped Lu2O3 traces of OH impurities were present in the material unless heated at 1200°C. Radioluminescence was very poor for samples heated at 800°C or lower temperature. After heating the precipitated powder at or above 1200°C the efficiency jumped 45 times reaching 75% of the output from commercial microcrystalline Gd2O2S:Eu. The properties make nanocrystalline Lu2O3:Eu prepared in the described way a promising X-ray phosphor for planar digital medical imaging.
E. Zych, J. Trojan-Piegza, L. Kepinski, Sensors and Actuators B 109 (2005) 112-118

A0596 – Structure and magnetism in the oxygen-deficient perovskites Ce(1-x)SrxCoO3-d (x>0.90)

We have examined the structure and phase behaviour of strontium-doped Ce(1-x)SrxCoO3 d and found that the perovskite form is stabilised over a relatively narrow solid solution range (x > 0.85). A combination of electron, powder X-ray and neutron diffraction has revealed tetragonal superstructures of the basic perovskite unit; (I4/mmm) 2ap x 2ap x 4ap (x = 0.90) and (P4/mmm) ap x ap x 2ap (x = 0.95). Magnetisation measurements show ferromagnetic behaviour under applied magnetic fields. Low temperature neutron diffraction of Ce0.10Sr0.90CoO2.80 in zero field reveals a magnetic cell of dimension 2ap x 2ap x 4ap with an ordered cobalt moment of 1.7 B.M. at 25 K.
M. James, K.S. Wallwork, R.L. Withers, D.J. Goossens, K.F. Wilson, J. Horvat, X.L. Wang, M. Colella, Materials Research Bulletin 40 (2005) 1415-1431

A0595 – Hydrothermal synthesis, characterization and magnetic properties of (N4C6H21) (Co(H2PO4)(HPO4)2)

The title compound, (N4C6H21) (Co(H2PO4)(HPO4)2), was prepared hydrothermally (473 K, 10 days, autogenous pressure), in the presence of the tris(2-aminoethyl)amine as organic template. Its structure is built up from a network of four membered-rings, formed by the vertex linkages between [CoO4] and [H2PO4] tetrahedra with [HPO4] moieties hanging from the Co center. Hydrogen bonds involving the cobalt phosphate units and the triply protonated amine molecule, contribute to the stability of the structure. The IR spectrum shows bands characteristic of the (N4C6H21)3+ cations and the (H2PO4) and (HPO4)2 phosphate anions. The UV-Visible-NIR spectrum confirms the tetrahedral coordination of Co2+ ions. The TGA analysis indicates that the dehydration of (N4C6H21) (Co(H2PO4)(HPO4)2) occurs in one step. Magnetic measurements from 4.5 to 305 K show a weak antiferromagnetic character of this compound.
A. Dakhlaoui, S. Ammar, L.S. Smiri, Materials Research Bulletin 40 (2005) 1270-1278

A0594 – Structural and electrochemical characterisation of new oxide ion conductors for oxygen generating systems and fuel cells

Ba2In2 xMexO5+y (Me=V, Mo, W) solid solutions were investigated. Solid solution limits were found at x =0.5 and x =2/3 for V and Mo, W, respectively. Partial substitution for In led to the stabilisation of the Ba2In2O5 fast oxide ion conducting cubic form at lower temperatures. As for substitution by other cations with radius smaller than that of In3+, a decrease of the order-disorder transition temperature with the increase of substitution rate was observed. This was associated with a decrease in the conductivity with increasing cation substitution. Below 400°C, an uptake of water was observed for all the materials, which also makes them promising as proton conductors. However, in this paper, only the electrical properties at high temperature are reported.
A. Rolle, R.N. Vannier, N.V. Giridharan, F. Abraham, Solid State Ionics 176 (2005) 2095 - 2103

A0597 – Crystal structures and luminescence properties of [Eu(ODA).(phen).4H2O]+, [Tb(ODA).(phen).4H2O]+ and [Tb(ODA)3]3- (ODA: oxydiacetate, phen: 1,10-phenanthroline)

Two novel complexes of Eu(III) and Tb(III) with mixed oxydiacetate (ODA) and 1,10-phenanthroline (phen) ligands and a Tb(III) complex with homoleptic ODA were prepared and their crystal structures were determined: [Eu(ODA).(phen).4H2O]Cl.5H2O, monoclinic, P21/n, a = 12.3197(12) Å, b = 16.7992(17) Å, c = 12.6754(10) Å, beta = 107.981(8)°, V = 2495.2(4) Å3, Z=4, R(|F|) = 0.0324 for 5728 data; [Tb(ODA).(phen).4H2O]Cl.5H2O monoclinic, P21/n, a = 12.2846(13) Å, b = 16.7560(14) Å, c = 12.6681(11) Å, beta = 108.144(8)°, V = 2478.0(4) Å3, Z=4, R(|F|) = 0.0279 for 4364 data; Na3[Tb(ODA)3].8H2O monoclinic, Cc, a = 15.751(3) Å, b = 9.8030(14) Å, c = 18.189(4) Å, beta = 105.513(15)°, V = 2706.2(9) Å3, Z=4, R(|F|) = 0.0406 for 3435 data. In these structures, the rare earth ions satisfy ninecoordination via binding to tridentate ODA, bidentate phen or water molecules. The geometry of the nine-coordinate polyhedron is discussed in terms of the dihedral angle and the mean plane. Photoluminescence (PL) and excitation spectra of Eu(III) and Tb(III) complexes with mixed ODA and phen ligands and with homoleptic ODA are reported. The complexes of [Eu(ODA).(phen).4H2O]+ and [Tb(ODA).(phen).4H2O]+ excited by UV light produce very bright red and green emissions, respectively, via the nonradiative energy-transfer from phen to the metals. For [Eu(ODA).(phen).4H2O]+ and [Tb(ODA).(phen).4H2O]+, the quantum yields of the sensitized luminescence (Q= 6.6 and Q= 75.7%, respectively) are much greater than those of the nonsensitized luminescence (Q= 2.0 and Q= 21.0%, respectively).
Jun-Gill Kang, Tack-Jin Kim, Hee-Jung Kang, Sung Kwon Kang, Journal of Photochemistry and Photobiology A: Chemistry 174 (2005) 28-37

A0599 – High surface area submicrometer-sized h-SiC particles grown by shape memory synthesis method

A high surface area and non-microporous submicrometer-sized h-SiC material was successfully obtained according to the Shape Memory Synthesis (SMS) method. The attack by SiO vapors of a nanodiamond preform with sp3-bound carbon, at 1200-1300°C under dynamic vacuum, formed h-SiC nanoparticles by carboreduction of the SiO vapors. These h-SiC nanoparticles had a mean size distribution centered at 10 nm and a specific surface area of 140 m2/g. The high carbon to carbide conversion obtained and the location of the remaining unreacted carbon in the core of the h-SiC nanoparticles allowed a direct use of the material as a catalyst support without any stabilizing post-synthesis oxidative treatment. The material showed dispersive properties and a good resistance towards oxidation, due to the presence of a thick and partially oxidized protecting amorphous coating, preventing from the extensive oxidation of SiC into silica.
N. Keller, O. Reiff, V. Keller, M.J. Ledoux, Diamond & Related Materials 14 (2005) 1353-1360

A0598 – An integral method to determine variation in activation energy with extent of conversion

This paper proposes an integral method that uses local heating rates to evaluate the activation energy dependence on the extent of conversion. The method leads to consistent results with those from a differential isoconversional technique while regular integral isoconversional technique results in systematic errors in the activation energy with the extent of conversion. The method is validated from (1) simulated thermal analysis curves for a single reaction model, (2) simulated thermal analysis curves involving in two parallel reactions, and (3) non-isothermal dehydration of calcium oxalate monohydrate.
T. Wanjun, C. Donghua, Thermochimica Acta 433 (2005) 72-76

A0601 – Kinetic study of the pyrolysis of neoprene

Kinetics of neoprene thermal decomposition has been performed under dynamic conditions at different heating rates, between 5 and 80°C/ min in a TG apparatus. The same kinetic model has been applied simultaneously to runs performed at different heating rates and different atmospheres allowing a good correlation of the weight loss data. A mechanism based on three independent reactions has been used to model the thermal decomposition. The first reaction is of an order close to two, and the other two reactions are of order below one, similar to other plastic materials. Different alternatives for the mathematical treatment for fitting TG data were considered. The accuracy of the calculated kinetic parameters was studied by means of a sensibility analysis.
J.A. Caballero, J.A. Conesa, I. Martin-Gullon, R. Font, J. Anal. Appl. Pyrolysis 74 (2005) 231-237

A0600 – Thermo-oxidative decomposition of polyvinyl chloride

Pyrolysis and combustion of polyvinyl chloride resin have been studied by thermogravimetric analysis. Nine different runs with about 5 mg sample mass have been carried out in three different atmospheres (He; He:O2 9:1; and He:O2 4:1) and heating rates (5, 10 and 20°C/ min). Adequate kinetic simplified models have been proposed and all heating rates have been simultaneously correlated with the same set of kinetic constants, obtaining good results. The pyrolysis model consists of one first reaction producing gases and solid residue followed by two parallel reactions of previous solid, whereas the combustion model adds a third parallel reaction with oxygen and three new combustion reactions to burn char formed in the three previous reactions. Different considerations have been taken into account during the optimization to achieve the best results. Parameters obtained have been discussed and also compared with others from literature.
I. Aracil, R. Font, J.A. Conesa, J. Anal. Appl. Pyrolysis 74 (2005) 215-223

A0603 – Assessment of tire devolatilization kinetics

In this paper, a kinetic study of the devolatilization of tire rubber has been performed in a thermobalance using nitrogen as carrier gas. The main operation variables have been studied including flow rate, particle size, final temperature and heating rate, observing that only temperature has a remarkable effect on tire rubber conversion. Kinetic parameters have been calculated and used to simulate all experimental curves including the ones obtained at different heating rates. In addition, an approximate tire rubber composition has been obtained by integrating the reaction rate versus temperature curves. The suitability of the kinetic parameters has been demonstrated in real conditions by performing experiments in a fixed bed reactor. Finally, the conclusions achieved from this study can be used not only for pyrolysis process design but also for the interpretation and modeling of the tire rubber combustion process.
E Aylon, M.S. Callén, J.M. Lopez, A.M. Mastral, R. Murillo, M.V. Navarro, Slawomir Stelmach, J. Anal. Appl. Pyrolysis 74 (2005) 259-264

A0602 – Pyrolysis of waste tyres in an atmospheric static-bed batch reactor: Analysis of the gases obtained

Scrap tyre pyrolysis was studied under nitrogen atmospheric pressure in order to analyse temperature influence on the global yields and the gas composition. A static-bed batch reactor was used to pyrolyse 300 g of shredded scrap tyres at temperatures from 400 to 700°C. The reactor was externally heated by means of electrical resistances, the heating rate being approximately 12 K min 1. Once the required system temperature was reached and stabilised, it was maintained for 4 h. The residence time of the gas in the reactor was calculated, with values falling between 1 and 1.5 min. Three phases were obtained after pyrolysis: solid (char), liquid (water and oils) and gas (light hydrocarbons, H2, CO and CO2). The product distribution and composition were studied as a function of the thermal treatment. Global yields were determined as follows: char, 47-63 wt.%, oils, 30-43 wt.%, and gas, 2.4-4.4 wt.%. It was observed that the liquid yield increases with temperature from 400 to 500°C. However, from 500°C on, this parameter remained almost constant. The solid yield followed an inverse trend to that observed for the liquid yield. On the other hand, the gas yield showed a slight continuous growth with temperatures ranging from 400°C (2.4 wt.%) to 700°C (4.4 wt.%). The gas phase was analysed off-line by gas chromatography. The main gases produced from the pyrolysis process were H2, CO, CO2 and hydrocarbons: CH4, C2H4, C3H6 and C4H8. It was observed that the fraction of light gases (H2, CO, CO2 and CH4) was greater at higher temperatures.
C. Berrueco, E. Esperanza, F.J. Mastral, J. Ceamanos, P. Garcia-Bacaicoa, J. Anal. Appl. Pyrolysis 74 (2005) 245-253

A0605 – Thermogravimetric study of different sewage sludges and their relationship with the nitrogen content

The pyrolysis and combustion of 17 sewage sludges were studied by thermogravimetry. The dynamic experiments were carried out at 10°C min-1, and three different behaviours were observed at the decomposition curves. One of them shows combustion and pyrolysis curves that are parallel until high temperatures, and so the combustion process can be considered as an oxidative pyrolysis. The DSC combustion curve shows that exothermic processes take place during most of the combustion run. The second behaviour shows combustion and pyrolysis curves that approximately coincide at low temperatures, but at high temperatures the combustion curve falls strongly, indicating that the combustion really occurs at high temperatures. The DSC curve shows that the exothermic process corresponds only to the combustion process. Some sludges with this behaviour show a combustion curve above the pyrolysis curve at a range of temperatures that also happens to BSA protein. The third behaviour is intermediate between the first and second behaviours, where the DSC curve shows exothermic processes during the first part and during the combustion of the char formed. Total nitrogen content, nitrogen content in decomposed fraction from combustion and a parameter that is associated to the decomposition of proteins were also studied and it was observed that there is a relationship between all of them and the type of behaviour in thermogravimetry.
M.F. Gomez-Rico, R. Font, A. Fullana, I. Martin-Gullon, J. Anal. Appl. Pyrolysis 74 (2005) 421-428

A0604 – Intensive pyrolysis of unsaturated organic precursors over acidified oxide surfaces

Carbon-like composite materials fabricated by non-catalytic heterogeneous pyrolysis (NCHP) of organic precursors over porous oxide supports are used in a variety of fields. The intensification of NCHP procedures for fabrication on a commercial scale is technically problematic. Direct intensification of operation parameters cannot be considered as the most effective method. For instance, an increase in support bed temperature often takes the pyrolysis process into the homogeneous reaction field, and greater gas space velocities and initial organic precursor concentrations lead to a rise in operating costs because of considerable losses of raw materials and increased power requirements. This paper describes an attempt to intensify non-catalytic heterogeneous pyrolysis procedures by optimizing the acid-base properties of the reaction agents (supports, precursors). A procedure of controlled acidification of the alumina support followed by thermal degradation of surface base salt was applied in order to cover the support surfaces with additional Lewis acid sites functioning as efficient host centres for precursor molecules. Unsaturated organic compounds, powerful Lewis bases, were used as the precursor agents. A probable elementary mechanism for non-catalytic heterogeneous pyrolysis of unsaturated organic precursors over an oxide surface reinforced by Lewis acids is proposed. The main characteristics of the composite hydrophobic materials produced by the NCHP technique using pre-acidified alumina samples-their chemical compositions, surface affinities to water, thermal stabilities in air, dynamic VOC adsorption and desorption capacities are presented and discussed. The elaborated composites are non-flammable in air until 600°C, whereas the thermal stability limit of activated carbons is situated in the 250-300°C range. As compared to activated carbons, these materials manifest really stable surface activities in VOC adsorption-desorption cycles.
L. Majoli, A. Evstratov, J-M. Guillot, J-F. Chapat, J-L. Le Loarer, J. Anal. Appl. Pyrolysis 74 (2005) 290-297

A0608 – Synthesis of indium phosphide nanoparticles via catalytic cleavage of phosphorus carbon bond in n-trioctylphosphine by indium

Nanocrystalline indium phosphide has been synthesized via catalytic cleavage of P-C bond in n-trioctylphosphine by indium nanoparticles at a temperature between 200 and 360°C under an atmosphere of argon. Indium chloride/sodium as well as indium(0) could be used as raw materials. The products were characterized by EDS, XRD, SEM, FESEM and PL techniques. XRD pattern of the obtained powder showed all the major peaks due to zinc blend indium phosphide with the sizes of 30-60 nm. FT-IR and TG/DTA studies indicated that InP particles were capped with TOP.
P.K. Khanna, K-W. Jun, K.B. Hong, J-O. Baeg, G.K. Mehrotra, Materials Chemistry and Physics 92 (2005) 54-58

A0607 – Pyrolysis of activated carbons exhausted with organic compounds

The regeneration of activated carbons used for the decontamination of water and wastewater polluted with organic compounds related to the pharmaceutical industry, has been studied in this work. To this end, the pyrolysis of exhausted activated carbons was performed in a quartz reactor. The influence of the pyrolysis of saturated activated carbons on their adsorptive capacities and porous structure was evaluated. Textural characterisation of the samples was carried out by helium density, and N2 and CO2 adsorption isotherms, at 196 and 0°C, respectively. Consecutive cycles of pyrolysis of activated carbons exhausted with phenol and salicylic acid, generated a widening of the microporosity, and a decrease in the apparent BET surface areas. The adsorptive capacities for phenol retention after a series of adsorption/ pyrolysis cycles were found to decrease drastically. In contrast, consecutive cycles gave higher salicylic acid adsorptive capacities, as compared to phenol. The DTG pyrolysis profiles of the samples saturated with salicylic acid appeared at lower temperatures than those of phenol, which showed two peaks, while those exhausted with salicylic acid only showed one. These results provide evidence of the different adsorption mechanisms of these two pollutants.
C.O. Ania, J.B. Parra, C. Pevida, A. Arenillas, F. Rubiera, J.J. Pis, J. Anal. Appl. Pyrolysis 74 (2005) 518-524

A0606 – Kinetic models for the pyrolysis and combustion of two types of sewage sludge

Pyrolysis and combustion of two types of sewage sludge have been studied. The two sludges considered, considering their thermal decomposition, have different behaviors when comparing pyrolysis and combustion TG runs of each sludge. In one case, the combustion can be considered as an oxidative pyrolysis, where the decomposition process is accelerated by the presence of oxygen. In the other case, the TG combustion run has two parts, the first one coinciding with the pyrolysis run and the second one with combustion of the char formed previously. For the pyrolysis of each sludge, three thermogravimetric runs at different heating rates (5, 15 and 30 K/min) were carried out to obtain a kinetic model, considering three parallel reactions. Following the simplex method, and with the same set of parameters for the three runs, and for each one of the three fractions considered, the values of pre-exponential factors, the apparent activation energies (103.9, 169.7 and 209.4 kJ/mol), the reaction orders and the maximum amount of volatiles were obtained. A discussion of the different values, in comparison with others obtained from literature is presented. Following a similar methodology, for the combustion of each sludge, two series of three runs at different oxygen concentrations (10 and 20%) and heating rates were carried out. For the sludge with oxidative pyrolysis behaviour, the scheme of three parallel reactions (as in pyrolysis) was appropriate for correlating the data, using the same values of activation energy, reaction order and maximum amount of volatiles evolved, and optimizing only the value of the pre-exponential factor, that is correlated with oxygen pressure. On the other hand, for the other sludge, with the first stage coinciding with pyrolysis and the second stage concerning the char combustion, the kinetic parameters of the second stage are obtained, with an apparent activation energy of 144.1 kJ/mol.
R. Font, A. Fullana, J. Conesa, J. Anal. Appl. Pyrolysis 74 (2005) 429-438

A0610 – Synthesis and NMR characterization of SAPO-35 from non-aqueous systems using hexamethyleneimine template

SAPO-35 was synthesized using hexamethyleneimine template in non-aqueous systems. X-ray diffraction and scanning electron micrograph analysis shows the synthesized sample is pure and well crystalline. Presence of four stages (1.6%, 0.8%, 7.8% and 8.4%) of weight loss is observed by TG/DTA analysis. FT-IR analysis in the framework region shows the presence of tetrahedral T-O-T vibrations is similar to the other known aluminophosphate molecular sieves. FT-IR spectrum in the -OH region shows stretching vibrations at 3631, 3604 and 3580 cm 1 can be assigned to OH groups in bigger cages near S6R, in bigger cages near D6R and those actually confined inside the D6R, respectively. The spectra for the as-synthesized sample show a single symmetrical 27Al MAS NMR line at d = 36.26 indicating the presence of a single tetrahedral aluminium species. Where as 29Si and 31P MASNMR shows the presence of two peaks in both at ( 89.9 and 95.15 ppm) and ( 34.01 and 40.45 ppm) due to the Si substitution of P present in two different locations in double 6 ring (D6R) and in single 6 ring (S6R). 27Al 3Q-MAS NMR shows two peaks for environmentally different tetrahedral aluminium atoms. This is the first time we are showing such a fact which is not observable using ordinary MAS NMR.
N. Venkatathri, Materials Research Bulletin 40 (2005) 1157-1165

A0609 – Organosilane-modified maghemite nanoparticles and their use as co-initiator in the ring-opening polymerization of -caprolactone

Hydroxyl and amino groups were introduced on maghemite nanoparticles surface by grafting of (3-glycidoxypropyl)trimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxy silane, in several solvents including water, toluene and N,N-dimethylformamide. Coating of maghemite particles by a biocompatible and biodegradable polyester, namely the poly( -caprolactone) was then achieved, by an aluminum isopropoxide-catalyzed ring-opening polymerization of -caprolactone initiated 'from' the maghemite particles surface. Silane and polymer coating were characterized by TGA and DRIFT spectroscopy. In this manner, nanocomposites containing up to 0.43 g of polymer per gram of maghemite were obtained.
C. Flesch, M. Joubert, E. Bourgeat-Lami, S. Mornet, E. Duguet, C. Delaite, P. Dumas, Colloids and Surfaces A: Physicochem. Eng. Aspects 262 (2005) 150-157

A0612 – Stability of poly(3-dodecylthiophene) upon doping and thermal de-doping

Poly(3-dodecylthiophene) (p3ddt) was prepared by oxidative polymerisation, doped with iodine, and characterised by surface resistivity, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), to study its stability and structural changes upon repeated doping and de-doping. The surface resistivity of p3ddt was greatly affected by the thermal de-doping temperature; at lower de-doping temperatures (<200°C), its conductivity gradually recovered with doping time; it would partially or completely lose conductivity above the de-doping temperature at 200°C. Both the pristine and doped p3ddt decomposed at around 350°C; the iodine uptake ability decreased while re-doping with the increase in heating temperature. XPS results revealed that doping and heating was accompanied by oxidation with the participation of oxygen. These structural distortions and chemical transformations may contribute to the increase in surface resistivity upon heating.
Jinwei Wang, Polymer Degradation and Stability 89 (2005) 15e20

A0611 – Synthesis, characterization and photocross-linking of copolymers of furan and aliphatic hydroxyethylesters prepared by transesterification

Mild experimental conditions were applied to the synthesis of furan-aliphatic photoreactive copolymers by bulk transesterification, which called upon potassium carbonate as the catalyst, reaction times of about 30 h and temperatures ranging from 95 to 120°C. The ensuing copolymers contained 3-10% of furan photoreactive monomer units, which absorbed at 308 nm, and had molecular weights of about 8000. They were semi-crystalline materials with glass transition temperatures of K51 to K62°Cand were stable up to 225°C. The irradiation in the near-UV of concentrated solutions or thin films of these copolymers resulted in their cross-linking and suggested their possible use as photoresists, particularly in offset printing plates.
E. Lasseuguette, A. Gandini, M.N. Belgacem, H-J. Timpe, Polymer 46 (2005) 5476-5483