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5631 articles

A1218 – Reductive solid-state ion exchange as a way to vanadium introduction in BZSM and BBeta zeolites

A solid-state ion-exchange method is described that introduces vanadium into zeolites BZSM-5, BBeta and their deboronated by washing forms at 773K in hydrogen. Two types of vanadium species (vanadium ions in cationic position and VO2+ complex in a silanol nest) are identified when the amount of V2O5 is equivalent to the framework boron. The vanadium-loaded samples have been characterised by the methods of IR-KBr, FTIR and UV-Vis spectroscopies; temperature-programmed reduction/oxidation cycles (TPR/TPO).
R. Dimitrova, Y. Neinska, M. Mihalyi, G. Pal-Borbély, M. Spassova, Applied Catalysis A: General 266 (2004) 123-127

A1221 – The NO selective reduction on the La(1-x)SrxMnO3 catalysts

La(1-x)SrxMnO3 (x = 0, 0.1, 0.3, 0.5, 0.7) perovskite-type oxides (PTOs) were prepared by coprecipitation under various calcination temperature, and their performances for the NO reduction were evaluated under a simulated exhaust gas mixture. The X-ray diffraction (XRD) and thermogravimetric analysis were carried out to find the formation process of the perovskite. The NO reduction rate under different reaction temperature, the concentration of oxygen and the presence of hydrocarbon were observed by the input/output analysis. In the presence of 10% excess oxygen, the catalyst La0.7Sr0.3MnO3 calcined at 900°C showed a NO reduction rate of 61% at 380°C. The study of the reaction curves showed that C3H8 could act as the reducer for the NO reduction below 400°C. The NO reduction is highly affected by increasing the O2 concentration from 0.5 to 10%, especially at high temperatures when oxygen becomes more competitive than NO on the oxidation of C3H8, leading to a decrease of the NO reduction from 100% to zero at 560°C.
X. Wu, L. Xu, D. Weng, Catalysis Today 90 (2004) 199-206

A1220 – Synthesis, characterisation and rehydration behaviour of titanium(IV) containing hydrotalcite like compounds

Layered double hydroxides (LDHs) containing Mg2+, Al3+ and Ti4+ with varying molar ratios of Al3+/Ti4+ were prepared by coprecipitation at constant pH. Characterisation of the samples as synthesised and their calcined products by bulk chemical analyses, powder XRD, TG-DTA, FT-IR and diffuse reflectance spectroscopy, N2 physisorption and TPD of CO2 indicated well crystalline hydrotalcite like structures with Ti4+ in the brucite layer. The introduction of Ti4+ in the layer induced a distortion of the brucite like sheet which results in LDH precursors with decreased crystallinity. Calcination at 450°C gave rise to mixed oxides with poorly crystalline MgO type structures, which can be reconstructed to their original structure by exposure to an aqueous solution. Both, the surface area and the number of basic sites of calcined samples decreased with increase of the Ti4+ content in the samples. Substitution of Ti4+, either for Mg2+ or Al3+, increased the adsorption capacity of the calcined samples up to 20%, thus providing indirect evidence in favour of Ti4+ in the brucite layer.
N. Das, A. Samal, Microporous and Mesoporous Materials 72 (2004) 219-225

A1219 – Development of EVOH-kaolinite nanocomposites

This paper reports on a novel route to develop EVOH-kaolinite nanocomposites by a melt intercalation process and on some relevant nanocomposite properties as a function of composition. The kaolinite clay used is a very cheap raw material of the tile industry and as such needed to be refined and chemically modified prior to the melt intercalation step. The modification was carried out with dimethyl-sulfoxide, methanol and octadecylamine in order to increase the basal plane distance of the original clay by a factor of more than three. Melt blended nanocomposites were characterized by WAXS, TEM, DSC, TGA and oxygen transmission rate. From the early results, partial exfoliation and intercalation of the clay platelets was the dominant morphology attained. An increase in thermal resistance, glass transition temperature, crystallinity and barrier properties to oxygen were also observed for mass clay loadings below 8%.
L. Cabedo, E. Giménez, J.M. Lagaron, R. Gavara, J.J. Saura, Polymer 45 (2004) 5233-5238

A1222 – Behavior of selenium in the combustion of coal or coke spiked with Se

Selenium (Se) is one of the most volatile trace metals emitted from coal-fired combustors and will most probably be considered for regulation in the electric power industry due to its significant environmental impact. Novel technologies are needed to remove Se vapor. This requires first a clear understanding of the behavior of selenium in combustion. In this work, coal and coke samples spiked with Se were prepared and the effect of Se on combustion was evaluated in a thermobalance. Impregnation with Se had a negligible impact on the combustion of coke; this allowed a systematic experimental study of the vaporization, condensation, and association of Se through burning cokes spiked with Se. Capturing the aerosol in the combustion flue gas on a membrane filter, coupled with identification of the species present using X-ray photoelectron spectroscopy, was established as a useful approach for coal combustion. The high volatility of Se and its affinity for oxygen, as well as the effect of chlorine on its vaporization, supported our previous calculations. The dominant Se species were identified as atomic Se and SeO2, which also confirmed the thermodynamic predictions.
R. Yan, D. Gauthier, G. Flamant, and Y. Wang, Combustion and Flame 138 (2004) 20-29

A1223 – A simple method to synthesize NiO fibers

Nickel oxide fibers with diameters 1-2 µm and lengths up to 100 µm were synthesized by a simple pyrolytic decomposition method in NaCl flux with NiSO4 as precursor. X-Ray diffraction, X-ray photoelectron spectrum (XPS) and scanning electron microscopy (SEM) techniques were used to characterize these fibers. They have single-crystal structure, large aspect ratios and macroscopic quantity. Suitable precursor and molten NaCl environment are conjectured to be key factors in this method.
Y. Zhan, C. Yin, C. Zheng, W. Wang, and G. Wang, Journal of Solid State Chemistry 177 (2004) 2281-2284

A1224 – Synthesis and crystal structure of a new layered aluminophosphate [Al3P4O16][C6N3H17][H3O]

A new layered aluminophosphate denoted AlPO-AEPP has been synthesized under hydrothermal conditions using N-(2- aminoethyl)-piperazine (AEPP) as structure directing molecule. The compound, with the empirical formula [Al3P4O16][C6N3H17][H3O] crystallizes in the orthorhombic space group P212121 (No. 19) with a = 14.550(8) Å , b = 16.163(8) Å , c = 18.677(9) Å , Z =4; R1 = 0.0253 and wR2 = 0.0644. Inorganic sheets contain a 4 x 6 network previously found in a layered compound synthesized with 1,2-dimethylimidazole molecules. Layers stack in the ABAB sequence and are held together by doubly protonated organic molecules and H3O+ cations. AlPO-AEPP represents the second example of layered aluminophosphate for which protonated water acts as a co-template along with organic molecules.
A. Tuel, V. Gramlich, and Ch. Baerlocher, Journal of Solid State Chemistry 177 (2004) 2484-2493

A1227 – Structure, nonstoichiometry and magnetic properties of the perovskites Sr(1-x)CaxMnO(3-d)

The structural, thermal and magnetic properties of the perovskite-type alkaline-earth manganites of the series Sr(1-x)CaxMnO(3-d) (0 < x < 1) were investigated. SrMnO(3-d) forms a hexagonal perovskite lattice and shows a first-order transformation to a highly defective cubic high-temperature modification. By substituting Ca for Sr (x > 0.25) the hexagonal perovskite is suppressed and a cubic (or orthorhombic) lattice becomes stabilized for all temperatures. For x = 0.5 and 0.75 cubic perovskites with a large nonstoichiometry (e.g., d = 0.25 for x = 0.5) are obtained at 1400°C. The defective perovskites are prepared by either quenching from high temperature or by cooling in an inert atmosphere. The oxygen vacancies are easily filled by subsequent reoxidation at low temperature (400-600°C) and stoichiometric samples are obtained. Orthorhombic perovskites are formed at T < 1200°C with the nonstoichiometry d increasing with increasing temperature (e.g., d = 0.06 at 1000°C and d = 0.14 at 1200°C for x = 0.5). Slow cooling in air results in almost complete reoxidation (d = 0). CaMnO(3-d) is an orthorhombic perovskite with a large range of nonstoichiometry (0 < d < 0.30). The cubic to hexagonal phase transformation of the Sr-rich samples is accompanied by a large expansion of the lattice that is reduced by Ca substitution. The Ca/Sr-manganites are antiferromagnets with TN of 170 K for x = 0.5 and d = 0.02 and 120 K for x = 1 and d = 0.05.
J. Töpfer, U. Pippardt, I. Voigt, R. Kriegel, Solid State Sciences 6 (2004) 647-654

A1226 – Phase transformation and growth of mullite in kaolin ceramics

The phase transformation and growth of mullite (3Al2O3.2SiO2) in kaolin ceramics have been investigated using X-ray diffractometer, transmission electron microscope, select area electron diffractometer, energy dispersion spectrometer and differential thermal analysis. The mullite which was transformed from kaolin appears at 1050°C by XRD and tallies with DTA. The initial mullite crystal showed a plate-like morphology. The Al2O3 content in mullite crystal increased from 49.57 to 71.37 wt.% but the lattice parameters of a, b and c axes decreased from 8.085, 8.106 and 3.215 Å to 7.882, 7.974 and 2.946 Å , respectively, with the grain width increasing from 20 to 70 nm when the kaolin was sintered at 1300°C for 30 min. The nonisothermal activation energy of mullite crystallization in kaolin ceramics was 1182.3 kJ mol-1. The growth morphology parameters n and m were both about 2.0, indicating that the bulk nucleation was dominant in mullitization and the crystal growth was controlled by diffusion. Seemingly, this study has been attempted to provide an integrative presentation of the thermal-structural characterization together with detailed kinetic and mechanistic interpretations.
Y-F. Chen, M-C. Wang, M-H. Hon, Journal of the European Ceramic Society 24 (2004) 2389-2397

A1225 – New binuclear vanadium(III) and (IV) squarate species: synthesis, structure and characterization of [V(OH)(H2O)2(C4O4)]2 . 2H2O and (NH4)[(VO)2(OH)(C4O4)2(H2O)3] . 3H2O

Two new vanadium squarates have been synthesized, characterized by infrared and thermal behavior and their structures determined by single crystal X-ray diffraction. Both structures are made of discrete, binuclear vanadium entity but in 1, [V(OH)(H2O)2(C4O4)]2 . 2H2O the vanadium atom is trivalent and the entity is neutral while in 2, (NH4)[(VO)2(OH)(C4O4)2 (H2O)3] . 3H2O, the vanadium atom is tetravalent and the entity is negatively charged, balanced by the presence of one ammonium ion. Both molecular anions are bridged by two terminal m2 squarate ligands. 1 crystallizes in the triclinic system, space group P-1, with lattice constants a = 7.5112(10) Å , b = 7.5603(8) Å , c = 8.2185(8) Å , alpha = 106.904(8)° ; beta = 94.510(10)° ; gamma = 113.984(9)° while 2 crystallizes in the monoclinic system, space group C2=c; with a = 14.9340(15) Å , b = 6.4900(9) Å , c = 17.9590(19) Å and beta = 97.927(12)° : From the magnetic point of view, V(III) binuclear species show ferromagnetic interactions at low temperatures. However, no anomalies pointing to magnetic ordering are observed down to 2K.
C. Brouca-Cabarrecq, A. Mohanu, P. Millet, and J.C. Trombe, Journal of Solid State Chemistry 177 (2004) 2575-2583

A1230 – The effects of oxidative environments on the synthesis of CuO nanowires on Cu substrates

Copper foils are thermally oxidized at 400 and 500°C under various gaseous environments, including nitrogen, air and oxygen, with and without water vapor. The oxidized samples are examined using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It is found that the nanowires are formed exclusively from monoclinic CuO crystals under a gaseous atmosphere with a sufficiently high oxygen partial pressure. Thus, no nanowires are found in samples oxidized in nitrogen, with or without water vapor. A high density of uniform nanowires is formed in wet air, while only a small amount is formed in dry air. The CuO nanowires formed in pure oxygen have the highest density, with sizes of 50-100 nm in diameter and up to 15 µm in length. Our experiment shows that a high oxygen partial pressure enhances both the nucleation probability and the growth rate of the nanowires, while the effect of the water vapor is mainly to assist their nucleation. Their formation can be best explained on the basis of a vapor-solid growth mechanism.
C.H. Xu, C.H. Woo, S.Q. Shi, Superlattices and Microstructures 36 (2004) 31-38

A1229 – Synthesis and mixed conductivity of ammonium tungsten bronze with tunneling structures

The ammonium tungsten bronze has been prepared by soft-chemical synthesis method at ambient pressure. The hexagonal or cubic pyrochlore structure could be obtained from the same acidified tungsten system, depending upon the dissolution or not of the ammonium tungstate in the solvent before acidification. The complete dissolution leads to the hexagonal structure and the nondissolution gives the pyrochlore one. The powders were characterized by TG-mass spectroscopy, IR and SEM analyses. XPS results confirmed the presence of the mixed valence state of tungsten. Electrical properties of the compounds were studied by impedance spectroscopy from 25 to 110°C. They are characteristic of a mixed proton and electronic conductivity in both samples. IR and XRD results indicate that the bronze can be further reduced by hydrogen in the presence of water vapor at temperatures higher than 70°C, resulting in a co-inserted bronze Hx(NH4)yWO3.nH2O. It was concluded that water plays an important role on the process of the hydrogen oxidation of the as-prepared hexagonal bronze.
L. Huo, H. Zhao, F. Mauvy, S. Fourcade, C. Labrugere, M. Pouchard, J-C. Grenier, Solid State Sciences 6 (2004) 679-688

A1228 – Oxygen vacancy ordering and magnetism in the rare earth stabilised perovskite form of “SrCoO(3-d)”

We have demonstrated that SrCoO(3-d) can be stabilised into phase pure perovskite forms by the introduction of small amounts ~ 5% of certain rare earth ions (Sm3+-Yb3+). At the same doping levels, La3+ and Pr3+ crystallise with the same isostructural trigonal structure as Sr6Co5O15; while the Nd3+ composition shows a mixture of both structure types. Powder X-ray diffraction showed only a simple cubic perovskite structure, however, a combination of electron and neutron diffraction has revealed a tetragonal (P4/mmm) ap x ap x 2ap superstructure. Strontium and the rare earth ions are disordered over a single site, while the oxygen vacancies are localised on the apical O2 sites. Magnetisation measurements show that these materials undergo transitions to a spin-glass state at temperatures below 150 K, and that significant coupling occurs between the rare earth ions and the mixed Co3+/4+ ions. Magnetisation measurements as a function of applied field reveals that below the transition temperature ferromagnetic ordering takes place at relatively large fields.
M. James, D. Cassidy, K.F. Wilson, J. Horvat, R.L. Withers, Solid State Sciences 6 (2004) 655-662

A1232 – Nitridation effects on the oxidation mechanisms of an ods Fe-Al intermetallic alloy

An ODS Fe-Al intermetallic alloy has been nitrided at low-energy high flux implantation diffusion at 400°C leading to the formation of hexagonal Al-N and alpha-Fe segregation. Its high temperature behaviour is subsequently evaluated under isothermal oxidation at 800°C. Microscopy techniques (SEM, TEM) will show that nitridation hinders aluminium outward diffusion and enhances iron outward diffusion giving rise to a layered structure.
F. Pedraza, J.L. Grosseau-Poussard, J.F. Dinhut, Applied Surface Science 233 (2004) 35-41

A1231 – Mesoporous FeAlMCM-41: an improved catalyst for the vapor phase tert-butylation of phenol

A range of iron and aluminum-containing mesoporous molecular sieves FeAlMCM-41 with different nSi/(nFe + nAl) ratios have been synthesized hydrothermally and characterized in detail by physicochemical methods, viz. X-ray diffraction (XRD), N2 adsorption, elementary analysis,UV-Vis, ESR and 27AlMASNMRspectroscopy.UV-Vis and ESR spectroscopy suggest that iron is present in tetrahedral coordination and imparts Bronsted acidity. The catalyst FeAlMCM-41 (nSi/nAl = 40; nSi/nFe = 40) showed superior performance in the acid-catalyzed tert-butylation of phenol employing tert-butanol as the alkylation agent. At a reaction temperature of 200°C, a phenol conversion of 70.1% and a selectivity of ca. 75% for 4-tert-butylphenol (4-TBP) were observed. The catalyst FeAlMCM-41(nSi/nMe = 50) shows a phenol conversion of 55.4% at a reaction temperature of 180°C, which is significantly higher as compared to AlMCM-41(56) and FeMCM-41(50). Over these catalysts, phenol conversions amounted to 35.9 and 21.1%, respectively.
A. Vinu, K. Usha Nandhini, V. Murugesan, W. Böhlmann, V. Umamaheswari, A. Pöppl, M. Hartmann, Applied Catalysis A: General 265 (2004) 1-10

A1234 – High-quality nickel manganese oxalate powders synthesized in a new segmented flow tubular reactor

High-quality nickel manganese oxalates have been prepared using an innovative approach for the production of homogeneous powders, the continuous Segmented Flow Tubular Reactor (SFTR). This new reactor is mainly composed of a mixer, a segmenter, a tubular section and a decanter. Mixed Ni-Mn oxalates are synthesized in the SFTR. The powders present controlled morphology, narrow particle size distribution, high purity and desired stoichiometry. Their characteristics are compared to those of powders obtained in a batch reactor. These oxalates are precursors for nickel manganites, used as negative temperature coefficient thermistor (NTC) ceramics.
S. Guillemet-Fritsch, M. Aoun-Habbache, J. Sarrias, A. Rousset, N. Jongen, M. Donnet, P. Bowen, J. Lemaître, Solid State Ionics 171 (2004) 135-140

A1233 – Study of the nanostructuration of ZrAu alloy near the ambient temperature by X-ray diffraction and thermal analyses

Spontaneous nanostructuration in air of the crystallized ZrAu alloy has been followed by X-ray diffraction using both synchrotron radiation and conventional laboratory X-ray source. This has allowed the study of the degradation of this compound from 25 to 150°C with an accurate step in time adapted to the very fast oxidation kinetic (2µm of oxide layer per day at room temperature). From these experiments the activation energy (Ea) of the mechanism has been determined by the way of an original approach consisting in the analysis of the temperature dependent evolution of the integrated intensity of a selected ZrAu diffraction peak. Furthermore, this activation energy has been compared with the one obtained from thermogravimetric analysis. The two independent techniques giving consistent information, average activation energy of 55 kJ mol-1 was associated with this unusual phenomenon. We have shown that no significant oxidation behavior is observed under pure oxygen below 100°C. The study of the phenomenon under pure oxygen, the microstructural analysis of the oxide layer and the study of the influence of relative humidity (RH) on the oxidation rate, allows us to attribute the oxidation mechanism to an atmospheric oxidation mechanism controlled by the dissociation of gaseous oxidative species at the alloy/air interface.
M. Isa, J-Ch. Valmalette, Ch. Muller, M. Lomello-Tafin, P. Gas, E. Elkaïm, Journal of Alloys and Compounds 373 (2004) 96-103

A1235 – Low-temperature heat capacity and thermal decomposition of crystalline [Er2(His.H+)(H2O)8](ClO4)6.4H2O

The heat capacities of rare earth complex with amino acid histidine, [Er2(His.H+)(H2O)8](ClO4)6.4H2O, were measured with an automatic adiabatic calorimeter from 79 to 320 K. Itwas found that therewas a sudden increment in heat capacity within the temperature range 182-190 K. Thermal decomposition behavior of the complex in nitrogen atmosphere was studied by thermogravimetric (TG) analysis, and a possible decomposition mechanism was suggested according to TG-DTG results.
X. Lan, Z-C. Tan, B. Liu, Z. Nan, L. Sun, F. Xu, Thermochimica Acta 416 (2004) 55-58

A1236 – Preparation of various color ultramarine from zeolite A under environment-friendly conditions

The ultramarine analogs of various colors have been prepared by calcination (mostly at 800°C) of the mixtures of zeolite A and sodium polysulfides or elemental sulfur and sodium carbonate. The color and structure of the products depend very much on alkalinity of the mixture. Low alkalinity leads to green products with retained LTA structure. Blue products with SOD structure are attained at high alkalinity. Alkalinity affects also the weight loss on heating (i.e. emission of volatile compounds) as well as the amount of salts removed on washing.
S. Kowalak, A. Jankowska, S. Laczkowska, Catalysis Today 90 (2004) 167-172

A1239 – Synthesis and crystal structures of a new (2,3-(CH3)2C6H3NH3)H2XO4 (X = P, As)

The aim of encapsulation of 2,3-dimethylanilinium cation in (H2XO4)n polymeric anion chains is to build acentric frameworks that are efficient for non-linear optical (NLO) applications. The synthesis and structures of two new inorganic-organic NLO crystals with general formula (2,3-(CH3)2C6H3NH3)H2XO4 (X = P, As) are reported. The magnitude of their second harmonic generations (SHG) responses was found to be between the KDP and urea. They crystallize with monoclinic unit-cells and are isotopic. We have determined the structure of phosphoric salt. The following unit-cell parameters were found: a = 8.866(3) Å, b = 5.909(6) Å, c = 10.644(5) Å, beta = 112.44(1)°, V = 515.5(5) Å3 and Dx = 1.412 g cm-3. The space group is P21 with Z = 2. The structure was refined with R = 0.041 (Rw = 0.057) for 1652 reflections with I > 3?(I). It exhibits infinite ((H2PO4)n)n- chains. The organic groups (2,3-(CH3)2C6H3NH3)+ are anchored between adjacent polyanions through multiple hydrogen bonds. Chemical preparation, crystal structure, calorimetric and spectroscopic investigation are described.
A. Rayes, C. Ben Nasr, M. Rzaigui, Materials Research Bulletin 39 (2004) 1113-1121

A1238 – Synthesis and crystal structure of a new o-ethylphenylammonium triphosphate [2-C2H5C6H4NH3]3H2P3O10

Chemical preparation and characterization by X-ray diffraction, IR, and NMR spectroscopies and thermal analysis of a new o-ethylphenylammonium triphosphate [2-C2H5C6H4NH3]3H2P3O10 are reported. This compound crystallizes in a monoclinic unit cell P21/n with the parameters: a = 17.670(1) Å , b = 8.558(8) Å , c = 20.100(2) Å , beta = 100.39(6)° , Z = 4, and V = 2990(4) Å3. Crystal structure has been solved and refined to R = 0.041 using 6857 independent reflections. In this atomic arrangement, layers built by (H2P3O10)3- groups are developed along (1 0 -1) direction. Between these layers are located the o-ethylphenylammonium entities which form hydrogen bonds with some external oxygen atoms of phosphoric groups.
W. Smirani, C. Ben Nasr, M. Rzaigui, Materials Research Bulletin 39 (2004) 1103-1111

A1237 – One-pot synthesis of dimethyl carbonate and glycols from supercritical CO2, ethylene oxide or propylene oxide, and methanol

Direct syntheses of dimethyl carbonate (DMC) and glycols (GCs) from supercritical (SC) CO2, epoxides (propylene oxide or ethylene oxide), and methanol were carried out using different solid catalysts prepared in this work. The effects of various conditions, such as reaction temperature, pressure, reaction time, molar ratio of the reactants, and the properties of the supports of the catalysts, on the conversion and yields were investigated. KI supported on ZnO (KI/ZnO) and KI/ZnO with K2CO3 (K2CO3-KI/ZnO) were very active and selective for the reaction after calcinations. At 423 K, all epoxides were reacted in 4 h; the yields of DMC and GC exceeded 57% when ethylene oxide was used, and the amount of the by-products was very small (0.2%). The K2CO3-KI/ZnO could be reused four times, and the yield and selectivity remained unchanged. No leaching of the active catalyst components was detectable at the experimental conditions, probably because the reaction was conducted in homogenous supercritical conditions, where non-corrosive CO2 was the main component in the reaction mixture. A mechanism of the reaction was proposed on the basis of the experimental results. This route may be an effective way to produce DMC and glycols in large-scale because it is simple, the raw materials are cheap, and the amount of by-products is very small.
Y. Chang, T. Jiang, B. Han, Z. Liu, W. Wu, L. Gao, J. Li, H. Gao, G. Zhao, J. Huang, Applied Catalysis A: General 263 (2004) 179-186

A1241 – Interaction between chitosan and alkyl beta-D-glucopyranoside and its effect on their antimicrobial activity

The interactions between chitosan and nonionic surfactant-alkyl beta-D-glucopyranoside (AG) in solid state and aqueous solution have been investigated by using FT-IR spectroscopy, thermal analysis, powder X-ray diffraction, viscometry and gel permeation chromatography (GPC). The FT-IR spectra demonstrated that interaction between -NH3+ and -OH groups of chitosan and -OH groups of AG occurred by electrostatic force or hydrogen bonding. Results of thermal analysis and X-ray diffraction indicated that higher orders of structure such as aggregation chain conformation etc and crystallinity of chitosan seemed changed by addition of AG. Results of viscometry and GPC showed that, in aqueous solution, AG most likely made the chitosan chains extend and disaggregate. Interestingly, antimicrobial activity of the dynamic association (mixed solution of chitosan and AG) was much higher than that of chitosan and AG separately. Minimum inhibition concentration (MIC) of dynamic association was 2-8 times lower than that of chitosan alone, and it could kill more microorganisms in a shorter time. The reasons for the enhanced antimicrobial activity of the dynamic association mixture are carefully discussed in terms of the interaction between chitosan and AG.
H. Liu, Y. Du, X. Wang, Y. Hu, J.F. Kennedy, Carbohydrate Polymers 56 (2004) 243-250

A1240 – Biocomposites based on plasticized starch: thermal and mechanical behaviours

The paper is focusses on the study of the thermal and mechanical behaviour of reinforced agro-materials. Various formulations based on plasticized starch matrix have been carried out, varying matrix formulation, filler content, fibres length and nature. Cellulose and lignocellulose fibres, which show unequal surface tensions, have been tested. After extrusion and injection moulding, the properties of these wheat starch-based biocomposites are analysed. Mechanical properties (tensile tests), thermo-mechanical properties (DMTA) and thermal degradation (TGA) are analysed. DMTA analysis shows important variations of main relaxation temperature, which can be linked both, to interactions resulting in a decrease of starch chain mobility and to a regular reinforcing effect. These results are consistent with the static mechanical behaviour, which vary according to the filler content (up to 30 wt%), fibre nature (cellulose vs. lignocellulose) and fibre length (from 60 µm to 1 mm). Besides, we have shown that the addition of cellulose fillers improves the thermal resistance of these biocomposites. Finally, we have tested the impact of the addition of biodegradable polyesters into these composites without significant effect on the postprocessing stability.
L. Averous, N. Boquillon, Carbohydrate Polymers 56 (2004) 111-122

A1242 – Evaluation of a sol-gel process for the synthesis of La(1-x)Srx MnO(3+d) cathodic multilayers for solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are electrical energy conversion devices with high efficiency and low pollution. In order to increase performances of SOFCs at intermediate temperature (700-800°C) and to decrease materials cost, an alternative sol-gel synthesis method has been investigated to deposit La(1-x)SrxMnO(3+d) (LSMx) as cathode thin films. Polycrystalline LSMx thin films were prepared by dip-coating using a polymeric solution. Lanthanum, strontium and manganese nitrates were used as raw materials. The viscosity of the solution was adjusted and the solution was deposited on polycrystalline ZrO2-8% Y2O3 ceramics. Prior to experiments, the substrate surface was eroded until a roughness of 20 nm and then cleaned with ethanol and dried. Film thicknesses were adjusted with the number of layers. Porosity and grain size of monolayers or multilayers were evaluated. Typical thickness of monolayer is 250 nm. A key parameter in the multilayer process was the intermediate calcination temperature (400, 700 or 1000°C) of each further layer deposition. A correlation between this intermediate temperature and morphology, thickness and porosity was found; porosity is ranging from 3 to 40% and thickness can reach 1 micron for multilayers. Concerning electrochemical performances, the best results were obtained for LSM0.4 multilayers with an intermediate calcination temperature (called Ti) of 400°C.
M. Gaudon, C. Laberty-Robert, F. Ansart, L. Dessemond, P. Stevens, Journal of Power Sources 133 (2004) 214-222

A1245 – Thermogravimetric kinetic model of the pyrolysis and combustion of an ethylene-vinyl acetate copolymer refuse

A kinetic study of the pyrolysis as well as the combustion of EVA copolymer refuse originating from the footwear industry was carried out by thermogravimetric analysis. Different runs were performed at heating rates between 5-20°C min-1 and atmospheres with different percentages of oxygen: 0, 10 and 20% (v/v). Pyrolysis and combustion processes can be simulated by two series reactions. The results obtained indicate that the second reaction begins when the first one is almost finished which implies that a good correlation is also obtained by simulation of the thermal decomposition of two independent fractions.
A.N. Garcia, R. Font, Fuel 83 (2004) 1165-1173

A1244 – Experimental and thermodynamic study of the high temperature microstructure of tantalum containing nickel-based alloys

Experiments and thermodynamic calculations were performed on three nickel-based alloys containing chromium, carbon and tantalum. Solidus and liquidus temperatures, and natures and surface fractions of the carbides after exposure for 100 h at 1000, 1100 and 1200°C were determined for each alloy. These results are compared with calculated results, using a thermodynamic database. Good agreement was generally found for the solidus temperatures but less good agreement for the liquidus ones. For alloys containing chromium carbides alone, carbide fractions and matrix compositions correspond to calculation results. But the presence of tantalum carbides in the third alloy was not predicted by calculations.
P. Berthod, L. Aranda, C. Vébert, S. Michon, Computer Coupling of Phase Diagrams and Thermochemistry 28 (2004) 159-166

A1243 – Formulation of muds for pelotherapy: effects of “maturation” by different mineral waters

Spa centres in northern Italy use clayey admixtures for the formulation of muds to be used in pelotherapy. The basic ingredient ("virgin" clay) is a dressed bentonitic geomaterial with mineralogical composition: smectite 60-70%, illite 5-10%, kaolinite 10-15%, quartz 5-10%, calcite 5-10% and feldspars 2-3%. The peloid muds are obtained by "maturation" of the virgin clay with mineral waters gushing out in situ which have different geochemistry: sulphureous, Ca-sulphate, Ca-Mg-sulphate and Br-I-salty (after the Italian regulation DPR 105/92). The maturation treatment is varying with respect to the mixing procedure and lasting time. Peculiar parameters have been tested to verify the effects of various maturation treatments, i.e., changes with respect to virgin clay. Formation of organic matter is due to the presence of microorganisms and algae in the maturation habitat. The < 2 µm fraction is generally decreased due to clay particles agglomeration. Mineralogical changes are mainly concerning the degradation of clay minerals, as smectite and illite, and subordinately to the dissolution of calcite. Cation exchange capacity (CEC), soluble salts, water retention, swelling index, activity, consistency parameters (WL, WP and PI), thermal behaviour and cooling kinetics are influenced by the geochemistry of mineral waters used for the maturation treatments but with some opposite trends for Br-I-salty water, and for sulphureous and Ca-sulphate waters, respectively. Noteworthy was the influence of high-pH value of the virgin clay on the pH of peloid muds (in fact, the pH of the used mineral waters is ranging around the natural value). Furthermore, the temperature reached by the peloid muds after 20 min of application (calculated after an innovative mathematical model) is influenced by water retention. An increase in plasticity index and a slower cooling are considered to improve the quality of the obtained peloid muds for pelotherapy. The observed different cation exchange behaviour and soluble salt content could be discriminant for either dermatological masks or thermal body cataplasms. A need of regulation (standard procedures) is suggested to certificate the clay geomaterials suitable for pelotherapy and also for drugs formulation.
F. Veniale, E. Barberis, G. Carcangiu, N. Morandi, M. Setti, M. Tamanini, D. Tessier, Applied Clay Science 25 (2004) 135-148

A1247 – Activation of pyrolytic tire char with CO2: kinetic study

Chars from old tire pyrolysis have been activated with CO2. The chars were obtained by pyrolysis of a waste tire sample in a fixed bed reactor at a temperature of 1000°C for 3 h. The pyrolytic char, basically the original carbon black plus the tire mineral matter, was ground and sifted to an average particle size obtaining different fractions that were used as raw material in the activation experiments. These experiments were performed in a thermobalance at different temperatures (850, 900, 950 and 1000°C) in order to determine the activation energy and pre-exponential factor, basic intrinsic kinetic parameters of the activation process. Experimental conditions were optimized to avoid internal and external mass transfer phenomena performing experiments with different particle sizes, at different flow rates and initial weights. Moreover, the tire char activation was found to be a first order reaction with respect to CO2. A kinetic expression for tire activation, based on the random pore model and the structural parameters of the pyrolytic char, was deduced. In addition, with this kinetic model it can also be explained the maximum in reaction rate observed experimentally at conversions around 40%.
R. Murillo, M.V. Navarro, J.M. Lopez, T. Garcia, M.S. Callén, E. Aylon, A.M. Mastral, J. Anal. Appl. Pyrolysis 71 (2004) 945-957

A1246 – Characterisation of model compounds and a synthetic coal by TG/MS/FTIR to represent the pyrolysis behaviour of coal

Coal pyrolysis is the initial, accompanying reaction of a number of coal conversion processes such as hydrogenation, combustion and gasification. However, because of the inherent complexity of coal composition, it is difficult to describe coal pyrolysis clearly. Single model compounds have been used before in order to provide additional insight into the complex processes that occur in the pyrolysis of coal. Yet the picture obtained is a simplified one and certain important aspects such as coal structure, interactions between different surface groups and cross-links are omitted. The approach used in this work involves the preparation of a synthetic coal, SC, with a known structure by curing a mixture of single, well-defined model compounds. By means of chemical characterisation, the SC was shown to contain the macroscopic features of a high volatile coal (proximate and ultimate analyses). FTIR characterisation revealed the presence of functional groups similar to those of coal in the structure of the SC. Temperature-programmed pyrolysis tests were performed in a thermobalance linked to a mass spectrometer and a Fourier transform infrared analyser (TG/MS/FTIR). The thermal behaviour of the synthetic coal (i.e., rate of mass loss and the evolution profiles of gaseous compounds during pyrolysis tests) is very similar to that of the high volatile bituminous coal which was used as a reference material. The great advantage of using SC lies in the fact that its composition and structure can be accurately determined and employed in subsequent applications in basic and mechanistic studies.
A. Arenillas, C. Pevida, F. Rubiera, R. Garcia, J.J. Pis, J. Anal. Appl. Pyrolysis 71 (2004) 747-763

A1249 – The phase diagram and tetragonal superstructures of the rare earth cobaltate phases Ln(1-x)SrxCoO(3-d) (Ln=La3+, Pr3+, Nd3+, Sm3+, Gd3+, Y3+, Ho3+, Dy3+, Er3+, Tm3+ and Yb3+)

Single phase perovskite-based rare earth cobaltates (Ln(1-x)SrxCoO3 d) (Ln=La3+, Pr3+, Nd3+, Sm3+, Gd3+, Dy3+, Y3+, Ho3+, Er3+, Tm3+ and Yb3+; 0:67pxp0:9) have been synthesized at 1100°C under 1 atmosphere of oxygen. X-ray diffraction of phases containing the larger rare earth ions La3+, Pr3+ and Nd3+ reveals simple cubic structures; however electron diffraction shows orientational twinning of a local, tetragonal (I4/mmm; ap x ap x 2ap) superstructure phase. Orientational twinning is also present for Ln(1-x)SrxCoO(3-d) compounds containing rare earth ions smaller than Nd3+. These compounds show a modulated intermediate parent with a tetragonal superstructure (I4=/mmm; 2ap x 2ap x 4ap). Thermogravimetric measurements have determined the overall oxygen content, and these phases show mixed valence (3+/4+) cobalt oxidation states with up to 50% Co(IV). X-ray diffraction data and Rietveld techniques have been used to refine the structures of each of these tetragonal superstructure phases (Ln=Sm3+-Yb3+). Coupled Ln/Sr and oxygen/vacancy ordering and associated structural relaxation are shown to be responsible for the observed superstructure.
M. James, D. Cassidy, D.J. Goossens, and R.L. Withers, Journal of Solid State Chemistry 177 (2004) 1886-1895

A1248 – Anomalous temperature effect on the hydrogen bond strength and phase transition in 2,4,6-trimethylpyridinium pentachlorophenolate.

The phase transition in 2,4,6-trimethylpyridinium pentachlorophenolate has been studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dielectric method as well as theoretical calculations. The crystal undergoes a first order phase transition of order-disorder type at 376 K. The transition to the high temperature phase causes anomalous hydrogen-bond shortening. Experimental and theoretical results show that the change in the mutual orientation of the phenol and pyridine rings is connected with the change of the hydrogen bond. Such an effect, which appears in the present simple hydrogen-bond complex, may be common also for the other hydrogen-bond complexes.
I. Majerz, R. Jakubas, Journal of Molecular Structure 694 (2004) 45-53

A1251 – Synthesis and characterization of Sr(1-x)LnxCoO(3-d), Ln = Y, Sm-Tm, 0.1< x < 0.5

Different perovskite-related phases have been found in an X-ray powder diffraction (XRD) and transmission electron microscopy study of the Sr(1-x)LnxCoO(3-d), Ln = Y, Sm-Tm, 0.1 < x < 0.5 systems. For the compositions Sr0.7Ho0.3CoO(3-d); Sr(1-x)EuxCoO(3-d) , 0.3 < x < 0.4; Sr(1-x)GdxCoO(3-d), 0.3 < x < 0.5; Sr(1-x)TbxCoO(3-d), 0.3 < x < 0.4; Sr(1-x)DyxCoO(3-d), 0.2 < x < 0.3 the formation of phases isostructural with the recently discovered perovskite related Sr0.7Y0.3CoO2.62, a ? 2 x aper, c ? 4 x aper (aper perovskite subcell) was observed. The crystal and magnetic structures of Sr0.7Dy0.3CoO2.62 were refined using neutron diffraction data (I4/mmm, a = 7.6280(8), c = 15.338(2) Å, Rp = 0.0332, RF2= 0.0447, X2 = 1.19). For x = 0.1 the XRD study indicates formation of cubic perovskites with all rare-earth cations. Electron diffraction and high resolution electron microscopy studies performed on Sr0.9Ln0.1CoO(3-d), Ln = Y, Eu, Dy, Ho revealed the presence of crystallites with brownmillerite (a ? ?2 x aper, b ? 4 x aper, c ? ?2 x aper), tetragonal perovskite (a ? aper, c ? 2 x aper) and Sr0.7Ln0.3CoO2.62 type (a ? 2 x aper, c ? 4 x aper) structures. For Ln = Sm, only XRD cubic perovskite phases were observed for all compositions, 0.1< x < 0.5. In the Sr0.5Eu0.5CoO(3-d) sample, crystallites of perovskite, tetragonal perovskite and Sr0.7Ln0.3CoO2.62 type were observed in the TEM study.
S.Ya. Istomin, O.A. Drozhzhin, G. Svensson, E.V. Antipov, Solid State Sciences 6 (2004) 539-546

A1250 – Thermodynamic stability of SrCeO3

Thermochemistry of the reaction between SrCO3 and CeO2 as SrCO3(s) + CeO2(s) = SrCeO3(s) + CO2(g) was studied over the temperature range 1113-1184 K. The equilibrium pressure of CO2(g) over the ternary phase mixture of SrCO3(s), CeO2(s) and SrCeO3(s) was measured at various temperatures using a tensimetric apparatus. The temperature dependence of the measured CO2(g) pressure could be represented as Log (pCO2 (Pa)) (± 0.04) = -11534 (± 750) / T + 13.1 (± 0.7) ; (1113 < T(K) < 1184). Tensimetric measurements were also carried out for the decomposition of SrCO3(s). The equilibrium vapor pressures of CO2(g) over the biphasic mixture of SrCO3(s) and SrO(s) could be represented as Log (pCO2 (Pa)) (± 0.01) = -11139 (± 263) / T + 12.72 (± 0.2) ; (1045 < T(K) < 1123). The observed CO2 pressures were compared with those obtained for reaction (1). Simultaneous thermogravimetric/differential thermal analysis experiments were carried out for reaction (1) and for the decomposition of SrCO3 in CO2 atmospheres. All these results were used to derive the thermodynamic properties of SrCO3(s) and SrCeO3(s).
A.N. Shirsat, K.N.G. Kaimal, S.R. Bharadwaj, and D. Das, Journal of Solid State Chemistry 177 (2004) 2007-2013

A1254 – Synthesis of TiO2 via hydrolysis of titanium tetraisopropoxide and its photocatalytic activity on a suspended mixture with activated carbon in the degradation of 2-naphthol

Titania (TiO2) photocatalysts are produced using hydrolysis of titanium tetraisopropoxide (TTIP) at 100-600°C. The powders are characterized by thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Anatase phase was obtained after calcination at 200°C. The anatase-rutile transformation takes place at temperatures higher than 400°C. Adding TiO2 powders prepared at 600°C to activated carbon (AC), exhibits much higher photocatalytic activity than commercial TiO2 (Degussa P-25) alone in degradation of 2-naphthol under the UV-irradiation with O2. This results shows that an optimum adsorption strength on the co-adsorbent (AC) is needed to improve titania's photoactivity in reactions of organic pollutant degradation in a shorter time.
S. Qourzal, A. Assabbane, Y. Ait-Ichou, Journal of Photochemistry and Photobiology A: Chemistry 163 (2004) 317-321

A1253 – Effects of cation exchange on the pore and surface structure and adsorption characteristics of montmorillonite

Ca-montmorillonite was exchanged with the metal cations, titanium, iron, and copper and the ion-exchange effects on the surface area, pore structure and adsorption property of the montmorillonite were studied. The changes in the pore structure and the surface roughness of the montmorillonite were first characterized based on the classical and fractal analyses of the nitrogen adsorption isotherms as well as the XRD and TGA/DSC patterns. Then, the adsorption isotherms of benzene, hexane, and cyclohexane were measured to identify how exchange process affected the adsorption characteristics of the montmorillonite. It was found that the ion-exchange processes could induce enormous changes in the surface and pore structure of montmorillonite and these changes could be interpreted with the coverture of the surface roughness (surface screening effect), the inhibition of the movement of nitrogen molecule into pores (pore blocking effect), and the interlamellar expansion of the montmorillonite (pore opening effect). The effect of alterations of the surface area and the pore structure on the adsorption characteristics of montmorillonite was discussed.
F-C. Huang, J-F. Lee, C-K. Lee, H-P. Chao, Colloids and Surfaces A: Physicochem. Eng. Aspects 239 (2004) 41-47

A1252 – Heat capacity and thermodynamic properties of pyrimethanil myristic salt (C26H41N3O2)

Pyrimethanil myristic salt was synthesized and its heat capacities were measured with an automated adiabatic calorimeter over the temperature range from T = (79 to 360) K.The melting point, molar enthalpy, ?fusHm and entropy, ?fusSm, of fusion of this compound were determined to be (321.84 ± 0.05) K, (56.53 ± 0.03) kJ.mol-1 and (175.64 ± 0.05) J.mol-1.K-1, respectively. The purity of the compound was calculated to be 98.99 mol% by using the fractional melting technique. The thermodynamic functions relative to the reference temperature, T = 298.15 K, were calculated based on the heat capacity measurements in the temperature ranges from T = (80 to 360) K. The TG-DTG results demonstrate that the mass loss of the sample takes place in one step with the maximum rate at T = 500 K, which was caused by evaporation of the sample.
M-H. Wang, Z-C. Tan, X-H. Sun, Y-F. Liu, H-F. Wang, L-X. Sun, T. Zhang, J. Chem. Thermodynamics 36 (2004) 477-482

A1255 – Degradation products of the process of thermal recovery of copper from lamina scraps in lab-scale fluidized bed reactor

This paper presents experimental results dealing with a process for recovering copper in the scrap composite materials issued from electronic laminas industry. This environment-friendly process consists in the thermal treatment of scrap in a fluidized bed whose particles fix the harmful gases emitted by the organic glue gasification. A series of experiments was carried out in a thermobalance coupled to FTIR spectrometer and GC/MS with small lamina samples. These experiments demonstrated the thermal behavior of scrap composite materials, and identified the major degradation reaction gases. A series of experiments was performed with bigger scrap samples hung in a laboratory-scale fluidized bed coupled to FTIR and MS, at 350°C; the results confirmed those obtained in thermobalance. Experiments showed that a residence time lasting less than 5 min is sufficient to recover the metallic copper, and exhaust gases are not harmful.
P. Antonetti, Y. Flitris, G. Flamant, H. Hellio, D. Gauthier, B. Granier, Journal of Hazardous Materials B108 (2004) 199-206

A1256 – Effect of reactive element oxide coating on the high temperature oxidation behaviour of FeCrAl alloys

The influence of yttrium oxide coating (processed by the sol-gel method) on the oxidation behaviour of a commercial FeCrAl alloy (Kanthal A1) has been investigated during isothermal exposures in air at 1373 K. The scale growth kinetics of the uncoated alloy obey a parabolic rate law during the whole oxidation test, whereas the kinetic curves of the Y-coated specimen exhibit an initial transient stage for the first few hours, followed by a parabolic regime. The yttrium sol-gel coating deposited on the bare alloy does not provide the beneficial effect usually ascribed to reactive elements. No oxidation rate improvement of the coated alloy is observed, the parabolic rate constant values are strictly identical for both specimens. In situ X-ray diffraction reveals a marked influence of the reactive element on the composition of the oxide scale. The oxide layer formed on the yttrium-coated specimen comprised, in addition to a-alumina which is the main oxide also identified on the bare specimen, the presence of yttrium aluminates (YAlO3, Y3Al5O12) located in the outermost part of the layer.
R. Cueff, H. Buscail, E. Caudron, F. Riffard, C. Issartel, S. El Messki, Applied Surface Science 229 (2004) 233-241

A1257 – Simultaneous removal of SO2 and NOx from flue gas using a CuO/Al2O3 catalyst sorbent .I. Deactivation of SCR activity by SO2 at low temperatures

Deactivating effect of SO2 on selective catalytic reduction of NO by NH3 over a CuO/Al2O3 catalyst sorbent was examined in a fixedbed reactor. Transient experiment, DRIFT, elemental analysis, temperature-programmed techniques, and physical adsorption were used to evaluate the deactivation mechanism. Results show that SO2 greatly deactivates SCR activity of CuO/Al2O3 catalyst sorbent at temperatures of 200-300°C, and the deactivation is dependent on reaction temperature. The deactivating agents are ammonium sulfate salt and copper sulfate, formed during the reaction of NO-NH3-O2-H2O in the presence of SO2. Ammonium sulfate salt reduces the SCR reaction through pore filling and/or plugging, but can be removed by heat treatment at around 400°C. Copper sulfate deactivates the SCR either by pore filling and/or plugging or by its low SCR activity compared to CuO at low temperatures. Copper sulfate decomposes at temperatures greater than 660°C but can be converted back to CuO in NH3 at about 400°C.
G. Xie, Z. Liu, Z. Zhu, Q. Liu, J. Ge, and Z. Huang, Journal of Catalysis 224 (2004) 36-41

A1258 – Observation of a compensation relation for monomolecular alkane cracking by zeolites: the dominant role of reactant sorption

Monomolecular cracking of alkanes was investigated over zeolites of different structure types and after different treatments. Large deviations in apparent rates of reaction and apparent kinetic parameters were detected for zeolites of different structure types; smaller changes were observed within a structure type. The Si/Al ratio and different crystal sizes had no effect on turnover frequency; however, steaming of mordenite and ZSM-5 enhances the rate of reaction by a factor of 2-5 due to the formation of Lewis acid sites with enhanced heat of adsorption, although the number of Bronsted sites decreased. The apparent activation energies and preexponential factors showed a linear compensation relation in a Constable plot. Using the Langmuir-Hinshelwood kinetics formalism, the apparent kinetic parameters include enthalpy and entropy of adsorption and surface reaction terms. If the enthalpy and entropy of adsorption are linearly related, which is experimentally observed for unsteamed and steamed mordenite, then the apparent compensation effect implies that the observed differences in rate are dominated by differences in adsorption of the reactant in the pores of the zeolites, rather than by differences in acid strength. Zeolites with smaller pores show enhanced adsorption, and consequently the rate of reaction increases in the order H-Y < H-MOR < H-ZSM-5.
J.A. van Bokhoven, B.A. Williams, W. Ji, D.C. Koningsberger, H.H. Kung, and J.T. Miller, Journal of Catalysis 224 (2004) 50-59

A1259 – A calorimetric study of the acidity of bulk and silica-supported heteropoly acid H3PW12O40

The acid strength of bulk and SiO2-supported (10-60 wt%) H3PW12O40 (PW) is characterised by differential scanning calorimetry of ammonia adsorption in a gas-solid system and by microcalorimetry of pyridine adsorption in a liquid-solid system (cyclohexane slurry). In both systems, the strength of PW in terms of the heat of adsorption of NH3 or pyridine increases with increasing PW loading on silica, the bulk PW being the strongest acid. The temperature and the heat of NH3 desorption are shown to indicate the acid strength, in full agreement with the heats of NH3 adsorption. Attempts to measure the acidity of PW included in a sol-gel silica matrix have failed due to a large amount of water present in such systems.
E.F. Kozhevnikova and I.V. Kozhevnikov, Journal of Catalysis 224 (2004) 164-169

A1261 – Catalytic diesel particulate filter. Evaluation of parameters for laboratory studies

The definition of experimental methods to be employed in the lab-scale for catalytic activity measurements for soot oxidation with either powder or coated catalysts is necessary before industrial applications. Characterisations of carbon black, a model soot of constant composition, have proved that mechanical grinding weakly affects its structure. The nature of carbon black can be modified by oxidation with O2, H2O or H2O2 and confirmed by transmission electron microscopy (TEM). The temperature for half conversion of carbon (607-593°C after treatment) has revealed also the chemical stability of the structure. Molybdenum oxide is used as catalyst for the oxidation of carbon black. The reaction is greatly affected by the quality of the mixture between the two solid materials. For the preparation method by grinding, the effects of the amount of MoO3 and carbon black have been studied. At a high ratio of catalyst and carbon black (95/5), carbon black is well surrounded by MoO3 and the temperature for half conversion strongly decreases (from 607 to 459°C). This sample preparation condition can be adopted for the classification of catalysts.
Y. Nguyen Huu Nhon, H. Mohamed Magan, C. Petit, Applied Catalysis B: Environmental 49 (2004) 127-133

A1260 – Characterization of perovskite systems derived from Ba2In2O5 Part II: The proton compounds Ba2In2(1-x)Ti2xO(4+2x)(OH)y [0

The proton compounds Ba2In2(1-x)Ti2xO(4+2x)(OH)y [0
V. Jayaraman, A. Magrez, M. Caldes, O. Joubert, F. Taulelle, J. Rodriguez-Carvajal, Y. Piffard, L. Broh, Solid State Ionics 170 (2004) 25-32

A1263 – From molecules to materials: some examples in yttrium and lanthanide chemistry

Hydrolytic and hydrothermal transformations were applied to yttrium alkoxides, namelyY5O(OiPr)13, Y3(OtBu)9(tBuOH)2 and [Y8O6(OtBu)12]m. The resulting powders were characterized by XRD, TGA and transmission electron microscopy (TEM). Hydrolysis of the octanuclear oxo species gave nanocrystalline (5-6 nm) cubicY2O3 at 400°C by annealing of an oxohydroxide. Hydrothermal transformation in basic media (200°C, 10 h, 17 atm) of Y5O(OiPr)13 gave amorphousY2O3 as well as crystalline platelets and nanowires of Y(OH)3. Transformation into cubic yttria was achieved at 300°C. The lability of the M-OR bond allows easy formation of mixed-metal species, giving access to doped materials of high homogeneity and crystallinity, as shown by a Y2O3 matrix doped by Pr2O3. Modification of Y5O(OiPr)13 by polymerisable ligands provided molecular oxohydroxide aggregates that can be used for access to organic-inorganic materials by copolymerisation reactions.
L.G. Hubert-Pfalzgraf, S. Daniele, C. R. Chimie 7 (2004) 521-527

A1262 – X-ray diffraction, Raman study and electrical properties of the new mixed compound [Rb0.44(NH4)0.56]2HgCl4.H2O

Differential scanning calorimetry of [Rb0.44(NH4)0.56]2HgCl4.H2O material showed three anomalies at 340, 355 and 424 K, respectively. The room temperature phase has space group Pcma (a = 8.433(1) Å, b = 9.1817(9) Å and c = 11.954(1)). Phase II (T = 350 K) is disordered and exhibits orthorhombic symmetry (a = 8.456(13), b = 9.202(9) and c = 12.011(10) Å). Hydrogen bonding, the nature and the degree of structure (dis)order and the mechanisms of the transitions are discussed. The dielectric constant ?' at different frequencies and temperature revealed a phase transition at T = 340 K related to (NH4)+ reorientation and H+ diffusion, and a characteristic increase above 355 K, which might be due to loss of water of crystallization. Transport properties in this compound appear to be due to an Rb+ / (NH4)+ and H+ ions hopping mechanism.
M. Loukil, A. Kabadou, Ph. Salles, A. Ben Salah, Chemical Physics 300 (2004) 247-251

A1264 – Cyclodextrin-enhanced solubilization of pentachlorophenol in water

The solubilization of pentachlorophenol (PCP) by beta-cyclodextrin (beta-CD) and three of its most used derivatives, methyl-beta-cyclodextrin (MCD), hydroxypropyl-beta-cyclodextrin (HPCD) and carboxymethyl-beta-cyclodextrin (CMCD), has been investigated. The formation of soluble inclusion complexes between PCP and cyclodextrin (CDs) increases the aqueous solubility of PCP. Due to the ionizable nature of PCP, the effects of pH and ionic strength on the equilibrium complexation were evaluated. All CDs were found to form 1:1 inclusion complexes. Equilibrium constants calculated from solubility enhancement experiments revealed that the stability of the complexes was dependent on the polarity of the compound, on the ionic strength and on the cyclodextrin type. In general, weaker equilibrium constants were observed for PCP with beta-CD than with MCD or CMCD. For all CDs, the complexation or the solubilization efficiency of PCP (weak acid) depended on pH and ionic strength. Moreover, we observed that the solubility of the beta-CD/PCP complex was lower than that of the beta-CD molecule and dependent on the ionic strength of the solution. Although the equilibrium constant of PCP/CD complex was found to be higher at pH 3 than at pH 7 in water, extraction of PCP from porous media by a CD solution at neutral pH would be achievable due to the higher PCP aqueous solubility in neutral/basic media.
K. Hanna, Ch. de Brauer, P. Germain, Journal of Environmental Management 71 (2004) 1-8

A1266 – Proton conducting composite membrane from Daramic/Nafion for vanadium redox flow battery

A microporous separator (Daramic) was impregnated by soaking in a 5 wt.% Nafion solution to obtain a proton conducting composite membrane with modified properties for the vanadium redox flow battery (VRB). Nafion uptake by Daramic with thickness 0.25mm is 6.5 wt.%. Infrared spectroscopy (IR), thermogravimetric analysis (TGA) and ion exchange capacity (IEC) have also been carried out to confirm incorporation of Nafion into the Daramic membrane. The new Daramic/Nafion composite membranes give acceptable low electrical resistance, although the measured area resistances are higher for the composite membranes with different thickness than that for the untreated membranes. A reduction in water uptake of the membranes is observed after impregnation. Open circuit voltage measurement with time of the proton conducting composite membrane showed promising results compared with that of the untreated Daramic membrane when used in the VRB.
B. Tian, C.W. Yan, F.H. Wang, Journal of Membrane Science 234 (2004) 51-54

A1265 – Magnetic and Mössbauer study of some transition metal based nitroprussides

Susceptibility data of freshly precipitated nitroprussides TM[Fe(CN)5NO] n H2O (TM=Mn, Fe, Co, Ni, Cu) follow very well modified Curie-Weiss law down to T = 5K indicating paramagnetic state; nitroprusside (NP) containing Zn is diamagnetic with a sign of paramagnetic contribution. Deviation from Curie-Weiss law and magnetization measurements on MnNP, FeNP and CoNP below T = 5K can indicate ferrimagnetic ordering at low temperatures. A hysteresis behaviour in ZFC and FC magnetisation with the temperature of bifurcation Tb = 6K was found for CoNP and FeNP. Mössbauer spectra taken at room temperature (besides FeNP) consist of a single symmetric quadrupolesplit doublet with parameters delta and ? typical for Fe(II) ions in octahedral sites. A more complicated spectrum of FeNP is a consequence of different Fe environments.
M. Zentkova, M. Mihalik, I. Toth, Z. Mitroova, A. Zentko, M. Sendek, J. Kovac, M. Lukacova, M. Marysko, M. Miglierini, Journal of Magnetism and Magnetic Materials 272-276 (2004) e753-e754

A1270 – Synthesis of nanocrystalline Y2O3/Pr3+ from heterometallic alkoxide via sol-gel process

Y2O3/Pr3 + nanoparticulate powder has been prepared through a one-step hydrolytic sol-gel process using an yttrium praseodymium heterometallic alkoxide. The powder was characterized by TGA/TDA, XRD, TEM, XPS and photoluminescent experiments, which showed that a homogeneous and a highly crystalline material was obtained by calcination as low as 500°C.
S. Daniele, L.G. Hubert-Pfalzgraf, Materials Letters 58 (2004) 1989-1992

A1269 – Immobilization of tetravalent actinides in phosphate ceramics

Three phosphate-based ceramics were studied for the immobilization of tri- and tetravalent actinides: britholite Ca9Nd(1-x)AnIV(x)(PO4)(5-x)(SiO4)(1+x)F2, monazite/brabantite LnIII(1-2x)CaxAnIV(x)PO4 and thorium phosphate diphosphate beta - Th(4-x)AnIV(x)(PO4)4P2O7 (beta-TPD). For each material, the incorporation of thorium and uranium (IV) was examined through dry chemistry routes, using mechanical grinding of the initial mixtures then heating at high temperature (1373- 1673 K). The quantitative incorporation of thorium in the britholite structure was obtained up to 20 wt% through the coupled substitution (Nd3+; (PO4)3- <=>(Th4+; (SiO4)4-). On the contrary, the incorporation of uranium was limited to 5-8 wt% and always led to a two-phase system composed by U-britholite and CaU2O(5+y). The incorporation of Th and U(IV) was also examined in both matrices, beta-TPD and monazite/brabantite solid solutions. Homogeneous and single phase samples of beta-TUPD and (Th,U)-monazite/brabantite solid solutions were obtained using successive cycles of mechanical grinding/calcination. The three matrices were prepared in the pellet form then leached in 10^(-1) M or 10^(-4) M HNO3 at 363 K. The very low normalized dissolution rates confirmed the good resistance of the materials to aqueous alteration. Moreover, in over-saturation conditions, the formation of neoformed phases onto the surface of the pellets was evidenced for several sintered samples.
O. Terra, N. Dacheux, F. Audubert, R. Podor, Journal of Nuclear Materials 352 (2006) 224-232

A1268 – Synthesis and crystal structure of [3,5-(CH3)2C6H3NH3]4P4O12.3H2O

Chemical preparation and crystal structure are given for a new cyclotetraphosphate: [3,5-(CH3)2C6H3NH3]4P4O12.3H2O. This compound is triclinic P1 with the following unit-cell parameters: a = 8.298(3); b = 8.299(3); c = 17.242(7) Å , alpha= 97.13(3); beta= 102.72(3); gamma= 64.55(3)°; Z = 1 and V = 1045.2(8) Å3. The crystal structure has been solved and refined to R = 0.040 using 6086 independent reflections. The atomic arrangement can be described as layers organization. Layers built by P4O12 ring anions, ammonium groups and water molecules parallel to the plan (001), between which the organic groups are located. Characterization by X-ray diffraction, IR absorption, and thermal analysis are described.
Z. Aloui, S. Abid, M. Rzaigui, Journal of Physics and Chemistry of Solids 65 (2004) 923-926

A1267 – Structure, phase transitions and molecular dynamics in 4-methylpyridinium tetrachloroantimonate(III), [4-CH3C5H4NH][SbCl4]

Crystal structure of the 4-methylpyridinium tetrachloroantimonate(III), [4-CH3C5H4NH][SbCl4], has been determined at 240 K by X-ray diffraction as monoclinic, space group, P21=n; Z = 8. Differential scanning calorimetry and dilatometric studies indicate the presence of two reversible phase transitions of first order type, at 335/339 and 233/289 K (cooling/heating) with ?S = 0.68 and 2.2 J mol-1 K-1, respectively. Crystal dynamics is discussed on the basis of the temperature dependence of the 1H NMR spin-lattice relaxation time T1 and infrared spectroscopic studies. The low temperature phase transition at 233 K of an order-disorder type is interpreted in terms of a change in the motional state of the 4-methylpyridinium cations. The phase transition at 335 K, probably of a displacive type, is characterised by a complex mechanism involving the dynamics of both the cationic and anionic sublattice. The 1H NMR studies show that the low temperature phase III is characterised only by the dynamics of the CH3 groups.
B. Kulicka, R. Jakubas, Z. Ciunik, G. Bator, W. Medycki, J. Swiergiel, J. Baran, Journal of Physics and Chemistry of Solids 65 (2004) 871-879

A1272 – 1-Pentene epoxidation in catalytic microfabricated reactors

Silicon-glass microreactors with TS-1 catalyst wall coatings were fabricated and used for 1-pentene epoxidation with hydrogen peroxide in continuous flow. Seeding of the microchannels before zeolite growth was necessary to obtain a small crystal size and a sufficient zeolite film thickness. Crystal size was further reduced by adjusting synthesis conditions and utilizing triethoxymethylsilane (TEMS) as a crystal growth inhibitor. Zeolite film morphology and crystal orientation did not show any significant effect on reactor performance. However, reaction rate was found to increase with decreasing TS-1 crystal size in the zeolite films and with increasing amount of tetrahedrally coordinated Ti(IV). Catalyst deactivation was observed, caused by the presence of organic compounds and Ti leaching from the microporous framework.
Y.S.S. Wan, J.L.H. Chau, K.L. Yeung, and A. Gavriilidis, Journal of Catalysis 223 (2004) 241-249

A1271 – Synthesis and characterization of metal carboxyalkylphosphonates hybrid materials

Several carboxyalkylphosphonate hybrid materials have been prepared under hydrothermal conditions: Mn2(OH)(O3PCH2CO2).1/2H2O, Mn2(OH)(O3PCH2CO2), Al3(OH)3(O3PCH2CH2CO2)2.3H2O, Pb5(O3PCH2CH2CO2)2(O3PCH2CH2COOH)2 and Pb3(O3PCH2CH2- CO2)2. The influence of some variables in the syntheses such as pH or metal/phosphonic acid molar ratios have been examined. Mn2(OH)(O3PCH2CO2).1/2H2O crystallizes in a triclinic cell with parameters a = 8.405 Å, b = 8.789 Å, c = 4.910 Å, alpha = 90.71°, beta = 98.58°, gamma = 103.68° and V = 348.6 Å3. Its dehydration lead to Mn2(OH)(O3PCH2CO2), which unit cell has also been determined: a = 8.307 Å, b = 8.322 Å, c = 4.940 Å, alpha = 103.31°, beta = 98.81°, gamma = 80.79° and V = 325.6 Å3. The diffraction data suggest a layered structure. Al3(OH)3(O3PCH2CH2CO2)2.3H2O crystallizes in a monoclinic unit cell with a = 10.534 Å, b = 7.880 Å, c = 10.320 Å, beta = 109.86° and V = 805.7 Å3. Its X-ray powder pattern and the spectroscopic data are consistent with a pillared layered structure. Finally, Pb5(O3PCH2CH2CO2)2(O3PCH2CH2COOH)2 is monoclinic with a = 11.889(1) Å, b = 12.746(1) Å, c = 9.835(1) Å, beta = 114.081(2)°, V = 1360.6(2) Å3, Z = 2, space group P21/c. Its structure has been solved from single crystal data, R1 = 0.069, and shows a pillared layered framework. There are two types of carboxyethylphosphonate chains, one being protonated which is pillaring the layers and the other chain is twisted and bonded to a unique inorganic layer through both carboxylate and phosphonate moieties. Thermal and IR data for these compounds are reported and discussed.
M.M. Gomez-Alcantara, A. Cabeza, M.A.G. Aranda, A. Guagliardi, J.G. Mao, A. Clearfield, Solid State Sciences 6 (2004) 479-487

A1275 – An investigation of Knoevenagel condensation reaction in microreactors using a new zeolite catalyst

New basic zeolite catalysts obtained by grafting amino groups onto NaX and CsNaX zeolites exhibit excellent catalytic activities for Knoevenagel condensation reaction between benzaldehyde and ethyl cyanoacetate (ECA), ethyl acetoacetate (EAA) and diethyl malonate (DEM). The CsNaX-NH2 catalyst also displays higher conversion compared to aminopropylated MCM-41. Knoevenagel condensation reaction in a CsNaX zeolite microreactor performed better than the traditional packed bed reactor (PBR) with an order of magnitude higher productivity (i.e. moles ethyl 2-cyano-3 phenylacrylate produced per hour for each gram catalyst). A nearly fourfold increase in reaction conversion was obtained for the microreactor when CsNaX-NH2 catalystwas used.Amembrane microreactorwas obtained by incorporating awater-selective, NaA membrane to the multi-channel microreactor. The selective removal of water byproduct during the reaction led to a 25% improvement in reaction conversion for both catalysts.
X. Zhang, E.S.M. Lai, R. Martin-Aranda, K.L. Yeung, Applied Catalysis A: General 261 (2004) 109-118

A1274 – Zr-substitution in LaNi5-type hydride compound by room temperature ball milling

High-energy ball milling at room temperature has been used to prepare the pseudo-binary compound La(1-x)ZrxNi5 (x = 0.5) in amorphous state. The stability of this phase has been investigated by XRD, DSC and DTA. It starts to crystallise into single-phase La0.5Zr0.5Ni5 alloy at 361°C and undergoes decomposition into LaNi5 and ZrNi5 above 670°C. Pressure-composition isotherm (PCI) curves of hydrogen absorption have been measured for crystalline La0.5Zr0.5Ni5 alloy and are compared to that of the binary LaNi5 and ZrNi5 compounds.
E. Msika, M. Latroche, F. Cuevas, A. Percheron-Guégan, Materials Science and Engineering B108 (2004) 91-95

A1273 – Oxidation behavior of TiNi shape memory alloy at 450-750°C

The isothermal oxidation behavior of a commercial TiNi shape memory alloy (SMA) in pure oxygen over the temperature range of 450-750°C was studied. The oxidation products were identified by X-ray diffraction (XRD). Characterization of the specimens after oxidation was conducted using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The oxidation kinetics at different temperaturewas studied, according to parabolic and logarithmic laws. The mechanism and activation energy of oxidation were discussed based on the oxidation kinetics. The spallation of the multi-layer scale formed during oxidation was analyzed by growth induced thermal stresses.
C.H. Xu, X.Q. Ma, S.Q. Shi, C.H. Woo, Materials Science and Engineering A 371 (2004) 45-50

A1276 – Experimental study of oxygen diffusion and permeation through YBa2Cu3O(7-x) membranes

The oxygen in-diffusion, out-diffusion, and permeability of layered perovskite-type-like YBa2Cu3O(7-x) (YBCO) were investigated by thermogravimetry, oxygen static adsorption, and oxygen permeability experiment. The results show that the oxygen in-diffusion at higher oxygen partial pressure is very faster, while the oxygen out-diffusion at lower oxygen partial pressure is relatively slow due to the formation of surface barrier. Oxygen permeation rate increases with temperature and arrives at 3.36 x 10^(-7) mol/s cm2 at 900°C for a YBCO membrane with thickness 1.00 mm.
D. Yang, H. Lu, H. Song, J. Mo, G. Li, C. Chen, Y. Guo, X. Hu, Journal of Membrane Science 233 (2004) 45-50

A1277 – Synthesis and characterization of three 5-(4-pyridyl)tetrazolato complexes obtained by reaction of 4-cyanopyridine with metal azides from aqueous solutions

Three metal complexes with the 5-(4-pyridyl)tetrazolate anion, (4-PTZ)- , as ligand were obtained by the reaction of 4-cyanopyridine with corresponding metal azides in aqueous solution. Isomorphic complexes of composition [M(4-PTZ)2(H2O)4] . 2H2O with M=Mn(II) (1) and Cd(II) (2) were obtained, whereas [Ca1.5((4-PTZ)2H)(N3)2(H2O)5](H2O)0.3 (3) was separated from calcium azide solutions. The IR spectra and the thermal behaviour of the complexes are measured and discussed. The single crystal X-ray diffraction revealed that the isomorphous structures of 1 and 2 consist of octahedrally coordinated metal centers, where two 4-PTZ anions act as monodentate ligands via their pyridine-N atoms in trans-positions. The structures also contain six water molecules, four act as monodentate ligands and the remaining two as lattice water molecules. Hydrogen bonds of the types O-H...O and O-H...N connect the mononuclear units to a three-dimensional network structure. The chain structure of complex 3 features octahedrally coordinated Ca(1); dinuclear subunits of pentagonal-bipyramidal Ca(2) centers; azide groups acting in end-on and endto- end bridging mode; a (4-PTZ)2H ligand in its zwitter ionic form coordinated via N(1) atom of the tetrazole ring to Ca(2), as well as lattice and ligand water molecules. Again, a complicated hydrogen bond system connects the chains of polyhedra to form a 3-D network structure.
F.A. Mautner, C. Gspan, K. Gatterer, M.A.S. Goher, M.A.M. Abu-Youssef, E. Bucher, W. Sitte, Polyhedron 23 (2004) 1217-1224

A1279 – Hydrophobic modification of silica nanoparticle by using aerosol spray reactor

Surface of commercial silica particle was hydrophobically modified with octyltriethoxy-silane (OTES) in an aerosol spray reactor. When the reactor temperature was higher than 250°C, one liquid droplet produced one agglomerated particle. However, when the reactor temperature was lower than 250°C, the original droplet shape was completely disappeared and particles were produced in a dispersed state. Based on the Fourier transform-infrared (FT-IR), thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM) results, competition between the evaporation of solvent and reaction of OTES with the silica surface was proposed to be responsible for the morphology dependency on the reactor temperature. Hydrophobicity of the modified particle was quantitatively measured by ethanol volume ratio (EVR) and contact angle. The hydrophobicity was increased as increasing the concentration of OTES and had the optimum point with the reaction temperature. It was found that the discrepancy of the hydrophobicity measured by the EVR and contact angle gave information on the degree of agglomeration of particles produced by the aerosol spray reactor.
Y.S. Chung, S.A. Song, S.B. Park, Colloids and Surfaces A: Physicochem. Eng. Aspects 236 (2004) 73-79

A1278 – Synthesis and structural characterization of a new layered chlorozincophosphate, Zn(HPO4)Cl.[H3N(CH2)6NH3]0.5

A new layered zinc-phosphate Zn(HPO4)Cl [H3N(CH2)6NH3]0.5 was synthesized in acidic conditions at room temperature. It crystallizes in monoclinic space group C2/c (No. 15) with the lattice parameters a = 21.826(3) Å, b = 9.452(7) Å, c = 8.780(1) Å, beta = 109.36(8)°, V = 1708.83(1) Å3, Z = 8, R = 0.036, Rw = 0.047. The structure of this compound is determined by X-ray diffraction and characterized with IR, TGA-DTA/DSC and NMR. The structure consists of inorganic layers, built by PO4 and ZnO3Cl tetrahedra interconnected by common oxygen atoms. The organic entities, located between these layers, perform the 3D cohesion through N-H...O or N-H...Cl hydrogen bonds.
A. Rayes, C. Ben Nasr, M. Rzaigui, Materials Research Bulletin 39 (2004) 571-580

A1280 – Carbon nanotubes produced by aerosol pyrolysis: growth mechanisms and post-annealing effects

Since the first observation of carbon nanotubes in 1991, their synthesis by different techniques has been extensively investigated. Recently, CVD-based methods have attracted much attention because of both their versatility and the quality of the nanotubes obtained. This work is focused on the aerosol pyrolysis process which is a catalytic CVD-based method involving pyrolysis of mixed liquid aerosols composed of both liquid hydrocarbon and catalyst precursor. This process generates clean and aligned multiwalled carbon nanotubes. To analyse and further understand the first nucleation and growth stages of nanotubes in the aerosol pyrolysis process, several samples composed of nanotubes starting to grow were prepared by flowing the aerosol in the reactor for short duration. Samples were analysed by SEM. First results indicate that the first stage involves the formation of a layer of catalyst particles in the [10-100] nm range on top of which nanotubes start to grow. An important issue for nanotube application is the control of their crystalline structure. Therefore, post-annealing treatments under flowing argon were performed on the as-synthesised multiwalled carbon nanotubes. The effects of such treatments on the structure of nanotubes are determined by a comparative HRTEM analysis and a thermogravimetric analysis under air. Results demonstrate that annealing treatment between 1700 and 2000°C is an efficient way to improve the structure of nanotubes and thus to make them more resistant against oxidative atmosphere.
M. Pinault, M. Mayne-L'Hermite, C. Reynaud, O. Beyssac, J.N. Rouzaud, C. Clinard, Diamond and Related Materials 13 (2004) 1266-1269

A1282 – Synthesis of luminescent bioapatite nanoparticles for utilization as a biological probe

A europium-doped apatitic calcium phosphate was synthesized at low temperature (37°C) in water-ethanol medium. This apatite was calcium-deficient, rich in hydrogen phosphate ions, and poorly crystallized with nanometric sized crystallites. It is similar to the mineral part of calcified tissues of living beings and is thus a biomimetic material. The substitution limit of Eu3+ for Ca2+ ions in this type of bioapatite ranged about 2-3%. The substitution at this temperature was facilitated by vacancies in the calcium-deficient apatite structure. As the luminescence of europium is photostable, the doped apatite could be employed as a biological probe. Internalization of these nanoparticles by human pancreatic cells in culture was observed by luminescence confocal microscopy.
A. Doat, F. Pellé, N. Gardant, and A. Lebugle, Journal of Solid State Chemistry 177 (2004) 1179-1187

A1281 – Influence of mesoporosity on the sorption of 2,4-dichlorophenoxyacetic acid onto alumina and silica

Two SiO2 and three Al2O3 adsorbents with varying degrees of mesoporosity (pore diameter 2-50 nm) were reacted with 2,4-dichlorophenoxyacetic acid (2,4-D) at pH 6 to investigate the effects of intraparticle mesopores on adsorption/desorption. Anionic 2,4-D did not adsorb onto either SiO2 solid, presumably because of electrostatic repulsion, but it did adsorb onto positively charged Al2O3 adsorbents, resulting in concave isotherms. The Al2O3 adsorbent of highest mesoporosity consistently adsorbed more 2,4-D per unit surface area than did the nonporous and less mesoporous Al2O3 adsorbents over a range of initial 2,4-D solution concentrations (0.025-2.5 mM) and reaction times (30 min-55 d). Differences in adsorption efficiency were observed despite equivalent surface site densities on the three Al2O3 adsorbents. Hysteresis between the adsorption/desorption isotherms was not observed, indicating that adsorption is reversible. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy studies confirm that 2,4-D adsorption does not occur via ligand exchange, but rather via electrostatic interaction. The results indicate that adsorbent intraparticle mesopores can result in consistently greater 2,4-D adsorption, but the amount adsorbed is dependent upon surface charge and the presence of adsorbent mesoporosity. The data also suggest that when mineral pores are significantly larger than the adsorbate, they do not contribute to diffusion-limited adsorption/desorption hysteresis. Adsorbent transformations through time are discussed.
K.W. Goyne, J. Chorover, A.R. Zimmerman, S. Komarneni, and S.L. Brantley, Journal of Colloid and Interface Science 272 (2004) 10-20

A1284 – Structure and phase transitions in [(CH3)4P]3[Sb2Br9] and [(CH3)4P]3[Bi2Br9]

Two new phosphonium bromoantimonate(III) and bromobismuthate(III) [(CH3)4P]3[Sb2Br9] (PBA) and [(CH3)4P]3[Bi2Br9] (PBB) crystals have been synthesized and their structure determined by single-crystal X-ray diffraction. Both compounds are isomorphous in the room temperature phase and crystallize in the trigonal space group (polar), P31c: The structure consists of discrete [M2X9]3- anions and [(CH3)4P]+ cations. A sequence of structural phase transitions in PBA and PBB is established on the basis of differential scanning calorimetry and dilatometric studies. Two reversible phase transitions are found: (I <-> II) at 540/540 K and (II <-> III) at 193/195 K for PBA and (I <-> II) at 550/550 K and (II <-> III) at 205/207.5 K for PBB (on cooling/heating). The pyroelectric measurements of both compounds have confirmed the polar nature of phases (II) and (III). Proton spin-lattice relaxation time of polycrystalline PBA have been studied in temperatures 77-400 K. A dynamic inequivalence of two tetramethylphosphonium cations has been detected. A ferroelastic domain structure was found over the lowest temperature phase (III) of both crystals studied. The possible mechanisms of the phase transitions are discussed on the basis of the presented results.
M. Wojtas, R. Jakubas, Z. Ciunik, and W. Medycki, Journal of Solid State Chemistry 177 (2004) 1575-1584

A1283 – Elaboration and characterization of La2NiO(4+d) powders and thin films via a modified sol-gel process

Polycrystalline thin films of La2NiO(4+d) have been synthesized on yttria stabilized zirconia (YSZ) substrates by dip-coating using a polymeric sol. Crack-free films were obtained after sintering in air at temperatures ranging from 800°C to 1000°C. The microstructure, characterized by SEM, shows the formation of dense polycrystalline films with smooth surface and mean grains size of 140 nm, for films sintered at 1000°C. A correlation between grains size and non-stoichiometry in powders have been made in our processes. The thickness, evaluated for rugosimetry measurements, is thin (80 nm) and is a function of the viscosity of the sol. The higher the thickness, the higher the viscosity. As the non-stoichiometry level is controlled by the oxygen partial pressure, an evolution of non-stoichiometry in thin film has proposed. Then, it is possible by modifying synthesis and processing parameters to prepare thin films with a controlled microstructure (thickness, porosity and non-stoichiometry).
M-L. Fontaine, C. Laberty-Robert, F. Ansart, and P. Tailhades, Journal of Solid State Chemistry 177 (2004) 1471-1479

A1286 – Conductivity improvements to spray-produced LiFePO4 by addition of a carbon source

We present order-of-magnitude conductivity data for "carbon-included" lithium iron phosphate (LFP) powders lightly pelletised as used as cathodes in Li-ion batteries. The powders were synthesised by a spray pyrolysis method, with a short ameliorating sinter to optimise phase purity. Carbon was introduced into the materials by adding stoichiometric amounts of sucrose into the starting ingredients. We obtained X-ray diffraction patterns and electrical conductivity estimates for carbon contents of between 0 and 31 wt.%. The resultant conductivities spanned almost seven orders of magnitude.
S.L. Bewlay, K. Konstantinov, G.X. Wang, S.X. Dou, H.K. Liu, Materials Letters 58 (2004) 1788-1791

A1285 – Structural study of (U0.90Ce0.10)4O(9-d), an anion-excess fluorite superstructure of U4O(9-d) type

In the U-Ce-O system, a solid solution (U,Ce)O(2+x) of fluorite type containing anionic excess is known in a wide composition range.For high values of x; it transforms to a (U(1-y)Cey)4O(9-d) phase deriving from the beta-U4O(9-d) type [ordered anion-excess fluorite superstructure phase; I-43d space group; a = 21.7484(1)Å for y = 0.10].The crystal structure of (U0.9Ce0.1)4O(9-d) has been refined by the Rietveld method on a powder sample measured on D2B at ILL Grenoble.The structural model, proposed by Bevan et al.for beta-U4O(9-d) and not fully confirmed till now, has been verified. The structure is based on an ordered distribution of cuboctahedral clusters U6O37 inside a fluorite matrix. A preferential ordering of Ce4+ (and U4+) on the so-called "centaur polyhedra" with 10 coordination is proposed, on the basis of bond valence calculations.The structure so determined has the composition M64O143 (MO2.234) and no traces of excess anions, completing the supposed composition up to M4O9, could be detected.
C.Rocanière, J.P. Laval, Ph.Dehaudt, B.Gaudreau, A.Chotard, and E.Suard, Journal of Solid State Chemistry 177 (2004) 1758-1767

A1288 – Nitridation effect on the oxidation of a austenitic stainless steel AISI 304 at 900°C

This paper presents a study on the growth of oxides on a commercial chromia-forming alloy (austenitic stainless steel AISI 304), in air at 900°C. After the nitridation treatment performed, a gammaN solid solution is observed without any nitride formation in the alloy surface. In situ X-ray diffraction has been used to follow oxides evolution at the testing temperature. At the beginning of the oxidation test, Fe2O3 is formed together with Cr2O3 and Mn1.5Cr1.5O4. Nevertheless, Fe2O3 quickly becomes undetectable and appears again after 30 h oxidation. In the case of untreated specimens, four oxides are observed throughout the oxidation test: Cr2O3, Mn1.5Cr1.5O4, Fe2O3 and Fe7SiO10. Our results show that nitridation increased the high temperature oxidation resistance of the 304 stainless steel at 900°C.
C. Issartel, H. Buscail, E. Caudron, R. Cueff, F. Riffard, S. El Messki, S. Perrier, P. Jacquet, M. Lambertin, Applied Surface Science 225 (2004) 14-20

A1287 – Characterization of cobalt oxide supported on titania prepared by microwave plasma enhanced chemical vapor deposition

The microwave plasma enhanced chemical vapor deposition (MPECVD) was applied for the preparation of cobalt oxide supported on titania, CoOx/TiO2, starting from Cobalt(III) acetylacetonate, Co(acac)3 , (precursor) and TiO (support). The obtained CoOx/TiO2 materials were characterized by inductive coupled plasma-optical emissions spectroscopy (ICP-OES), thermogravimetric analysis-difference thermo analysis (TG/DTA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) investigations. Evidence is given that Co(acac)3 is evaporated and adsorbed on carrier surface in a first step and afterwards decomposed during the microwave-plasma treatment in oxygen atmosphere. As a function of the plasma treatment time and the cobalt content, cobalt oxide species with particle sizes between 2 and 10 nm were deposited on the support. As stated, the MPECVD method may allow, on the one hand, to prepare the CoOx/TiO2 materials with controlled particle size of cobalt oxide and, on the other hand, to avoid the use of salt solvents. This makes the method favorable in comparison with the preparation by impregnation.
A. Dittmar, H. Kosslick, J-P. Müller, M-M. Pohl, Surface and Coatings Technology 182 (2004) 35-42

A1291 – The effects of humidity on gas transport properties of sulfonated copolyimides

Hydrogen, oxygen and carbon dioxide transport properties are studied at various hydration rates for a large series of sulfonated copolyimides synthesized with a naphthalenic dianhydride, a sulfonated diamine and various non-sulfonated diamines. For all copolymers, the gas permeability coefficient decreases when the relative humidity increases in the range 0-70% and an increase of gas flux is observed at high hydration. The magnitude of the permeability coefficient variation depends on the gas polarity and on the copolymer composition. A detailed analysis of the gas transport properties at anhydrous state and of the water sorption mechanism as a function of the copolymers composition allows to explain all the gas permeability variations as a function of hydration.
F. Piroux, E. Espuche, R. Mercier, Journal of Membrane Science 232 (2004) 115-122

A1290 – Optical, thermal and defect studies on PbWO4 single crystals grown by the Czochralski method

The process parameters necessary for the growth of high-quality PbWO4 single crystals by the Czochralski method have been determined. If synthesis conditions are not optimal, colouration appears in the crystals. Optimised growth parameters are: seed pulling rate 2 mm/h and seed rotation rate 15 rpm. Detailed studies were carried out to identify the most suitable chemical etchant and etchant concentration. Etching with 0.5N NaOH at room temperature for 20- 30 min gave the best results (with minimal surface dissolution), revealing well-defined dislocations. Thermoluminescence (TL) and photoluminescence (PL) studies were also carried out for assessing the quality of the grown crystals. PL data for colourless crystals exhibit an emission peak with a full-width at half-maximum of 480 nm.
S. Ganesamoorthy, Indranil Bhaumik, A.K. Karnal, V.K. Wadhawan, Journal of Crystal Growth 264 (2004) 320-326

A1289 – Investigation of an as-sprayed NiCoCrAlY overlay coating. A thermoanalytical approach

A low pressure plasma sprayed (LPPS) NiCoCrAlY aircraft turbine blade overlay coating was investigated by differential thermal analysis (DTA). A pronounced irreversible endothermic reaction peak was observed at 975°C for the as-sprayed coating. No equivalent reaction is observed for the LPPS coating in the annealed state and in Ni-Co-Cr-Al (Ni:Co= 2:1) compositions after slowfurnace cool-down as well. The reaction scheme for the partial ternary AlNi-Cr-Ni system was taken as a reference standard for understanding the irreversible reaction, and was reexamined where necessary. The four-phase solid state reaction in the ternary system at 995°C, according to gamma-Ni + beta-NiAl --> gamma'-Ni3Al + alpha-Cr, is compared with the occurrence of the reaction observed at 975°C on the as-sprayed NiCoCrAlY coating material. It runs most likely according to gamma-Ni + gamma'-Ni3Al --> alpha-Cr + beta-NiAl. The reaction at 975°C is discussed in terms of metastable phase formation sequences.
K. Fritscher, C. Leyens, U. Schulz, Materials Science and Engineering A369 (2004) 144-150

A1293 – Synthesis and molecular structures of cobalt(II) beta-diketonate complexes as new MOCVD precursors for cobalt oxide films

Adducts of cobalt(II) 2,4-pentanedionate (acac) and 2,2,6,6-tetramethyl-3,5-heptanedionate (thd) with TMEDA (N, N, N', N'- tetramethyl-1,2-diaminoethane) and aminoalcohols, namely 1-dimethylamino-2-propanol (DMAPH) and 2-dimethylaminoethanol (DMAEH), have been synthesized and characterized by elemental analyses, FT-IR, 1H NMR, mass spectrometry and TGA. The molecular structures of Co(acac)2(TMEDA) (1) and [Co(acac)2(DMAPH)]2 (2) have been determined by single-crystal X-ray diffraction. 1 is monomeric while 2 is dimeric with two molecules linked by hydrogen bonds (O-H-O distance 2.708 Å av.). The most volatile and stable new adducts Co(acac)2(TMEDA) and Co(thd)2(TMEDA) have been studied as precursors for cobalt oxide deposition by liquid injection MOCVD in DME on monocrystalline LaAlO3 and Si substrates. Films were characterized by XRD and XPS. These preliminary MOCVD experiments showed that epitaxial Co3O4 films can be obtained by using both new precursors.
S. Pasko, L.G. Hubert-Pfalzgraf, A. Abrutis, J. Vaissermann, Polyhedron 23 (2004) 735-741

A1292 – Study of lanthanum orthophosphates polymorphism, in view of actinide conditioning

In order to perform researches on the substitution lanthanide-actinide in a view of actinide conditioning, a preliminary study of the polymorphism of lanthanum orthophosphates has been carried out by different techniques. LaPO4 formed by reaction of lanthanum nitrate with phosphoric acid contains 0.5 mol of water in open channel of the hexagonal structure (rhabdophane-type). The combination of thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction and 31P solid-state nuclear magnetic resonance clearly shows the different steps of the thermal treatment. The zeolitic water evaporates between 180 and 280°C. After heating up to 700°C, a monoclinic structure (monazite-type) is formed by compacting the chains of PO4 tetrahedron alternating with LaO9 polyhedron.
B. Glorieux, M. Matecki, F. Fayon, J.P. Coutures,S. Palau, A. Douy, G. Peraudeau, Journal of Nuclear Materials 326 (2004) 156-162

A1294 – Studies on bone marrow stromal cells affinity of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate)

The objective of this study is to investigate the biocompatibility of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) with bone marrow stromal cells in vitro. The adsorption of fibronectin on the material was studied by enzyme-linked immunosorbent assay. After bone marrow stromal cells were seeded and cultured on PHBHHx, their proliferation was investigated by MTT. Differentiation of the cells was assessed by measuring alkaline phosphatase activity and by histochemical assay. The wettability and thermal property of PHBHHx films were also studied by contact angle goniometer, thermogravimetry and differential scanning calorimetry, respectively. The results show that bone marrow stromal cells can attach, proliferate and differentiate into osteoblasts on PHBHHx films. These results suggest that PHBHHx has good affinity with bone marrow stromal cells and may have potential applications in bone tissue engineering.
M. Yang, S. Zhu, Y. Chen, Z. Chang, G. Chen, Y. Gong, N. Zhao, X. Zhang, Biomaterials 25 (2004) 1365-1373

A1296 – Synthesis of nanocrystilline ferrites by sol-gel combustion process: the influence of pH value of solution

The dried nitrate-citrate gels exhibit auto-catalytic combustion behavior, which can be used to synthesize the nanocrystalline ferrite powders. In this study, NiCuZn ferrite nanocrystalline powders with composition of (Ni0.25Cu0.25Zn0.5)O(Fe2O3)0.98 were synthesized by a sol-gel auto-catalytic combustion process. The influences of pH value of the precursor solution on the gel morphology, combustion behavior and crystallite size of synthesized powders were investigated with the help of scanning electron microscopy observation, thermal analysis, infrared (IR) spectra and X-ray diffraction technique. The experiments showed that the pH value of the mixed precursor solutions has a significant influence on the morphology of dried gels. The high porous precursors with network structure can be formed at high pH values after the solutions were dried at 135°C. With increasing pH value, the combustion rate is increased significantly. The as-burnt powders become uniform in size and the crystallites size is increased from 26 to 48nm with pH value increasing from 2 to 7. The combustion reaction mechanisms were put forward with the help of IR spectra and differential thermal analysis techniques.
Z. Yue, W. Guo, J. Zhou, Z. Gui, L. Li, Journal of Magnetism and Magnetic Materials 270 (2004) 216-223

A1295 – Characterization of the pores in hydrous ferric oxide aggregates formed by freezing and thawing

Hydrous ferric oxides (HFO) are efficient sorbents for inorganic and organic pollutants and therefore have great potentials in environmental science and engineering applications. Freezing and thawing of HFO suspensions leads to the formation of dense HFO aggregates. It facilitates the handling and increases the drying rate of HFO. In this study, we used a combination of pycnometry, gas adsorption (N2 gas, water vapor), and small-angle neutron scattering (SANS) to characterize the porosity and pore size distribution of dense HFO aggregates formed by freezing dialyzed HFO suspensions at -25°C and thawing them at room temperature. The crystallinity of the HFO, which was a 2-line ferrihydrite, was not affected by this treatment. Wet sieving and laser diffraction analysis showed that the dense HFO aggregates had a unimodal size distribution with an average diameter of 235 ± 35 µm. Increasing the freezing rate by cooling with liquid N2 (-196°C) resulted in much smaller aggregates with an average diameter of 20 µm. Adding NaNO3 electrolyte to the HFO suspensions prior to freezing also resulted in the formation of smaller aggregates. The dense HFO aggregates formed at -25°C had a porosity of 0.73 ± 0.02 11^(-1). SANS revealed a unimodal size distribution of pores, with an average pore diameter of 2.0 nm. The diameter of the HFO crystallites was estimated by transmission electron microscopy to be 1.9 ± 0.5 nm. Geometrical considerations taking into account the unit particle and average pore size suggest that the crystallites retain 1-2 layers of hydration water during the coagulation induced by freezing. Analysis by N2 gas adsorption showed that drying the dense HFO aggregates induced a reduction in porosity by about 25% and shifted the pore size distribution to smaller diameters. Rewetting during water vapor adsorption did not induce significant changes of the aggregate structure. The specific surface area of the dry HFO aggregates was between 320 and 380 m2 g-1.
A. Hofmann, M. Pelletier, L. Michot, A. Stradner, P. Schurtenberger, and R. Kretzschmar, Journal of Colloid and Interface Science 271 (2004) 163-173

A1298 – Adsorption of the quaternary ammonium salts on montmorillonite

Sodium montmorillonite SOMASIF® ME 100 (M) has been subjected to modification through ion-exchange reaction by a number of (alkyloxymethyl)dodecyldimethylammonium chlorides with the general formula [C12H25N+(CH3)2CH2OR]Cl-. The modified samples were studied by X-ray diffraction (XRD) technique, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), and thermogravimetric analysis. The basal spacing of unmodified montmorillonite, determined by XRD, was 1.227 nm and after modification it increased up to 1.557 nm (montmorillonite modified with dodecyldimethyl(dodecyloxymethyl)ammonium chloride). The FTIR studies revealed structural differences between the modified and unmodified montmorillonite samples. The IR spectra of the modified montmorillonite showed the C-C stretching bands (1468 cm-1) and C-H vibrations (near 2930 and 2856 cm-1). Results of the SEM study revealed a tendency towards lump formation and agglomeration of the organophilised particles of montmorillonite.
M. Kozak, L. Domka, Journal of Physics and Chemistry of Solids 65 (2004) 441-445

A1297 – In situ polymerization of interleaved monomers: a comparative study between hydrotalcite and hydrocalumite host structures

Vinyl benzene sulfonate (styrene sulfonate, VBS) and polystyrene sulfonate (PSS) were incorporated into Layered Double Hydroxides (LDH) by templating reaction. The two host structures investigated are Zn2Al(OH)6Cl. nH2O of hydrotalcite-type and Ca2Al(OH)6Cl.nH2O of hydrocalumite-type. The electrostatic binding between sulfonate groups of VBS and the inner-surface of LDH host structure evaluated by 13C CP-MAS NMR spectroscopy causes some shifts in the resonance lines. In situ polymerization of VBS molecules between LDH sheets is reached after soft heat treatment. Its completion requires a good matching between the layer charge density and the projected surface area of the guest molecule achieved by a ratio M2+ to M3+ of 2. For the pristine material, the change from Oh to Td aluminum site appears to be a collective process for the hydrocalumite, whereas it is more progressive for the hydrotalcite-type material. For the corresponding organoceramics, the site conversion before the breakdown of the lamellar structure is substantially reduced, and especially for PSS/LDH nanocomposite obtained by in situ polymerization. CaAl-VBS intercalate crystallizes in C2/c space group inducing a bilayer arrangement of VBS anions in the interlamellar space. Furthermore, distances between anionic sites allow an in situ zig-zag polymerization of syndiotactic type along the a axis. For hydrotalcite, the short Al3+-Al3+ distance at a?3 prevents also the formation of PSS other than syndiotactic. The thermal stability of the nanocomposites depends on the host structure but also on the synthesis pathway.
L. Vieille, E.M. Moujahid, C. Taviot-Guého, J. Cellier, J-P. Besse, F. Leroux, Journal of Physics and Chemistry of Solids 65 (2004) 385-393

A1301 – Synthesis and textural-structural characterization of magnesia, magnesia-titania and magnesia-zirconia catalysts

Several pure magnesium oxides together with some mixed systems (magnesia-titania and magnesia-zirconia) were synthesised, using the sol-gel technique. Chemical, textural and structural characterisation of the solids was carried out through a wide range of physical techniques. In all the cases, the presence of titanium or zirconium led to an increase in surface area as compared to pure magnesia. X-ray diffraction (XRD) revealed that no mixed phases were observed, but MgO (periclase), TiO2 (anatase) and ZrO2 (tetragonal) phases. As for mixed oxides, surface and bulk composition is quite similar in Mg-Zr system, whereas titanium tends to accumulate in the surface of Mg-Ti solids. The surface of the catalysts appears clearly carbonated as revealed by the XPS and diffuse reflectance infrared (DRIFT) spectra, revealing the basic character of the catalysts prepared.
M.A. Aramendia, V. Borau, C. Jiménez, A. Marinas, J.M. Marinas, J.A. Navio, J.R. Ruiz, F.J. Urbano, Colloids and Surfaces A: Physicochem. Eng. Aspects 234 (2004) 17-25

A1300 – Intumescent paints: fire protective coatings for metallic substrates

This study investigates the role of the binder in an intumescent paint. In fact, it is generally known that acid source, carbon source and blowing agent are the main ingredients of such a paint. However, since the binder may react with these ingredients, it is also a very important component of an intumescent paint. To begin with, the effect of the nature of the monomers composing the polymeric binder, on the chemical reactivity between the binder and the intumescent additives is investigated using thermogravimetric analysis, solid state NMR and FTIR analysis. It is found that the thermal stability increases when the copolymer is based on substituted styrene. Subsequently, the efficiency of protective behaviour of the intumescent coatings is evaluated varying the nature of the binder resin. It is found that the thermal insulation is greatly improved when using a mixture of a linear copolymer presenting a good reactivity with the acid source and a cross-linked copolymer as binder in the intumescent paint.
S. Duquesne, S. Magnet, C. Jama, R. Delobel, Surface and Coatings Technology 180-181 (2004) 302-307

A1299 – Effect of different thermal treatments on the self-assembled nanostructures of a styrene-butadiene-styrene star block copolymer

Time evolution of the lamellar self-assembling behaviour of a commercial styrene-butadiene-styrene (SBS) star block copolymer, submitted to two different thermal treatments under thermooxidative degradation conditions, is reported. A microphase separation process, leading to partially oxidized butadiene and polystyrene-rich copolymer, occurs in the block copolymer exposed at 150°C in air. The timing of the microphase separation depends upon previous thermal treatment, however, when the microphase separation takes place, the same evolution can be observed independently of the thermal treatment. The evolution of the morphologies has been observed by Tapping Mode Atomic Force Microscopy (TM-AFM). The evolution of the oxidation reactions and their influence on the molecular mass has been followed by thermogravimetric analysis (TGA) and gel permeation chromatography (GPC). Fourier transform infrared (FTIR) spectroscopy has been used to analyse the chemical changes involved in the nano/microphase separation process.
E. Serrano, A. Zubeldia, M. Larranaga, P. Remiro, I. Mondragon, Polymer Degradation and Stability 83 (2004) 495-507

A1303 – Copper-modified mesoporous MCM-41 silica: FTIR and catalytic study

Copper modified MCM-41 silica materials obtained by various preparation techniques are characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) and FTIR spectroscopy of adsorbed CO. The copper state in the samples is controlled by the preparation method used. The catalytic activity and selectivity of the samples in methanol dehydrogenation are also compared. The role of different copper species in the catalytic process is discussed.
T. Tsoncheva, Tz. Venkov, M. Dimitrov, C. Minchev, K. Hadjiivanov, Journal of Molecular Catalysis A: Chemical 209 (2004) 125-134

A1302 – Kinetics and formation mechanisms of the nanocomposite powder Ag-SnO2 prepared by reactive milling

A nanocomposite powder Ag-SnO2 was produced at room temperature by reactive ball-milling of mixtures of powders of silver bronze (Ag3Sn) and of silver oxide (Ag2O). Reaction kinetics were investigated for powders ground in air and under vacuum using X-ray diffraction (XRD) analysis, thermal analysis and 119Sn Mössbauer spectrometry. For these two milling conditions, all the results indicate a two-stage reaction path: oxidation of Sn to SnO from the decomposition of Ag2O under milling followed by oxidation of SnO to SnO2. In air, molecular oxygen contributes further to Sn oxidation, particularly to the oxidation of SnO to SnO2. Nevertheless, the reaction is found to be slower in air because of the formation of a surface barrier of silver carbonates from a reaction of Ag2O with the CO2 present in air.
N. Lorrain, L. Chaffron, C. Carry, P. Delcroix, G. Le Caër, Materials Science and Engineering A 367 (2004) 1-8

A1304 – Effects of metal oxide coatings on the thermal stability and electrical performance of LiCoCO2 in a Li-ion cell

A study is made of the effects of MgO and Al2O3 coatings on the electrical properties of LiCoO2 cathode material on the thermal stability (differential scanning calorimetry (DSC)) of the charged cathode, and on the safety characteristics of 18650 Li-ion cells. Powdery active material is coated with Mg or Al alkoxide solutions followed by heat treatment in air at temperatures between 300 and 800°C. The presence of the coating is confirmed by an elemental depth-profile analysis of the powder surface using secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). Both oxide coatings, especially the Al2O3 coating, substantially improve the charge-discharge voltage characteristics, rate capability, capacity and rate-capability retention on cycling and thermal stability of the LiCoO2 cathode. These beneficial effects are demonstrated in 18650 Li-ion cells.
H-J. Kweon, J.J. Park, J.W. Seo, G.B. Kim, B.H. Jung, H.S. Lim, Journal of Power Sources 126 (2004) 156-162

A1306 – Lattice thermal expansion of LaCo(1-x)CuxO3

Lattice thermal expansion studies on LaCo(1-x)CuxO3 (x = 0, 0.02, 0.05, 0.1, 0.3 and 0.5) were carried out by high temperature XRD from room temperature to 1173 K.Alinear increase in lattice parameterwas observed with increase in copper concentration indicating the substitution of copper in the lattice. The % volume thermal expansion (?V?100/V) increases with temperature. As the copper concentration increases from 0.0 to 30 mol.%, the % volume thermal expansion decreases from 5.98 to 4.522. The lattice and volume thermal expansion coefficients (TEC), alpha(a), alpha(c), and alpha(v) averaged between 298 and 1023 K are calculated using the HTXRD data. alpha(a), alpha(c), and alpha(v) decreased from 26.78 x x10^(-6) to 18.27 x 10^(-6) K-1, 27.81 x 10^(-6) to 24.56 x 10^(-6) K-1 and 82.45 x 10^(-6) to 72.9 x 10^(-6) K-1, respectively, as the copper concentration increased from 0 to 30 mol.%. The decrease in TEC with copper loading is due to the introduction of the covalent character of the Cu-O bond in the otherwise ionic nature of the La-O bond in LaCoO3. The larger decrease in alpha(a) as compared to alpha(c) confirms the substitution of more copper in the a-b plane rather than in the c-axis.
V. Ramaswamy, P. Awati, A.K. Tyagi, Journal of Alloys and Compounds 364 (2004) 180-185

A1305 – Valorization by thermal cracking over silica of polyolefins dissolved in LCO

A study has been made of the cracking of polyethylene (PE) and polypropylene (PP) (which are the main components of post-consumer plastic wastes) dissolved in the Light Cycle Oil (LCO) product stream of a commercial Fluid Catalytic Cracking (FCC) unit. The cracking has been carried out on a mesoporous silica (pore size between 3 and 30 nm) in the 723-823 K range. This strategy for upgrading plastics and solvents together avoids heat transfer limitations and other problems inherent to the cracking of solid plastics. The polyolefins are transformed mainly into the components that make up the pool of gasoline (C5-C12). Furthermore, the incorporation of polyolefins has a synergistic effect on the cracking of LCO and causes a major decrease in the content of aromatics of the pool of gasoline and an increase in the content of olefins, paraffins and iparaffins.
J.M. Arandes, J. Erena, M.J. Azkoiti, D. Lopez-Valerio, J. Bilbao, Fuel Processing Technology 85 (2003) 125-140

A1308 – Thermal decomposition of zinc carbonate hydroxide

This study is devoted to the thermal decomposition of two zinc carbonate hydroxide samples up to 400°C. Thermogravimetric analysis (TGA), boat experiments and differential scanning calorimetry (DSC) measurements were used to follow the decomposition reactions. The initial samples and the solid decomposition products were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and laser particle size analyzer. Results showed that zinc carbonate hydroxide decomposition started at about 150°C and the rate of decomposition became significant at temperatures higher than 200°C. The apparent activation energies (Ea) in the temperature range 150-240°C for these two samples were 132 and 153 kJ/mol. The XRD analyses of the intermediately decomposed samples and the DSC results up to 400°C suggested a single-step decomposition of zinc carbonate hydroxide to zinc oxide with not much change in their overall morphologies.
N. Kanari, D. Mishra, I. Gaballah, B. Dupré, Mineral Processing and Environmental Engineering Team, Thermochimica Acta 410 (2004) 93-100

A1307 – Thermal stability of bulk and silica supported chromium trioxide

Thermal behavior of bulk CrO3 and supported CrO3/SiO2 catalysts on heating up to 1000°C in inert (Ar), oxidative (air, O2) and reductive (H2, CO) atmospheres was investigated by thermogravimetry (TG), differential thermal analysis (DTA) and mass spectroscopy (MS, SIMS). A two or three stage reduction pathway of unsupported CrO3 is or may be accompanied by simultaneous decomposition of intermediate CrOx phases (Cr3O8 and Cr5O12), which are eventually transformed into crystalline Cr2O3 at about 500°C. Entirely different behavior of supported CrO3/SiO2 is observed especially for low chromium content (up to 3% Cr). Oxidation at 500°C leads to catalyst surface covered with thermally stable chromate-like species (CrO4)2-. These highly dispersed Cr-oxo species are anchored to silica substrate in the form of chromate esters. The increase in Cr content leads gradually to di- or polychromate species, amorphous and finally crystalline alpha-chromia phases. For low loaded CrOx/silica reversible interconversions Cr(VI) <=> Cr(III) and Cr(VI) <=> Cr(II) seem to be accepted when hydrogen or carbon monoxide are used as the reducing agents. In the case of CO-reduced sample the reactivity of Cr(II) leads to Cr(III) formation as a result of interaction with water or hydroxyl groups. Catalytically active Cr(II) and Cr(III) sites are involved in water gas shift reaction above 500°C.
W.K. Jozwiak, W. Ignaczak, D. Dominiak, T.P. Maniecki, Applied Catalysis A: General 258 (2004) 33-45

A1309 – Dry-gel synthesis of zeolites [Al]EU-1 and [Ga]EU-1

The dry-gel conversion method using hexamethonium bromide (HMBr) as template allows to prepare zeolites [Al]EU-1 and [Ga]EU-1 (framework type EUO) with nSi=nAl ratios of 18-142 and nSi/nGa ratios of 12-86, respectively. The most critical parameters of the dry-gel synthesis of zeolites EU-1 are the amount of water present in the autoclave during the crystallization process and the contents of sodium cations and template molecules in the dry gel. Zeolites EU-1 with a high crystallinity were obtained with a water content in the autoclave of mH2O/mgel>0.67 and in the presence of a liquid water phase in the pores of the solid material during the conversion process occurring at T = 453 K. For a typical dry gel with an nSi/nAl ratio of 41, contents of sodium cations nNa/nSi and template molecules nHMBr/nSi of 0.3 and >0.11, respectively, are necessary to obtain zeolite [Al]EU-1 without impurities such as zeolite EU-2, amorphous phases, or alpha-quartz. The concentration of Bronsted acid sites as determined by 1H MAS NMR spectroscopy of dehydrated zeolites H-EU-1 shows a linear dependence on the contents of aluminum or gallium. The strength of the Bronsted acid sites in the obtained zeolites H-EU-1 was investigated by adsorption of 13C-2-acetone as probe molecule and application of 13C MAS NMR spectroscopy. The experimentally obtained chemical shifts of 13C-2-acetone adsorbed on zeolites H-[Al]EU-1 and H-[Ga]EU-1 of 214.9 and 213.3 ppm, respectively, indicate a higher acid strength of the aluminumcontaining zeolite in comparison with the gallium-containing material.
A. Arnold, M. Hunger, J. Weitkamp, Microporous and Mesoporous Materials 67 (2004) 205-213

A1311 – High-quality PbZr0.52Ti0.48O films prepared by modified sol-gel route at low temperature

Amodification of the methoxyethanol-based sol-gel route used for depositing high-quality PbZr0,52Ti0,48O (PZT) films at low temperature is reported. The modification consists of multiple distillations of Pb precursor after dissolving in 2-methoxyethanol and increasing the pyrolisis temperature after individual layer deposition. In addition, a large amount of PbO excess (20%) is used to maintain the stoichiometry of PZT films. As a result, the films processed at 500°C possess a dielectric permittivity of ~1900, a remanent polarization of ~30 µC/cm2 and a coercive field of ~60 kV/cm. The crystallization mechanism is discussed along with the possible applications of such films in microelectromechanical systems.
J. Perez, P.M. Vilarinho, A.L. Kholkin, Thin Solid Films 449 (2004) 20-24

A1310 – Synthesis and characterization of a new organic dihydrogenomonophosphate [3,5-(CH3O)2C6H3NH3]2(H2PO4)2

Chemical preparation, crystal structure, calorimetric studies and spectroscopic investigation are given for a new organic cation dihydrogenomonophosphate [3,5-(CH3O)2C6H3NH3]2(H2PO4)2. This compound is triclinic P1 with the following unit cell parameters: a = 9.030(6) Å , b = 16.124(5) Å , c = 8.868(3) Å , alpha = 75.04(3)8°, beta = 110.71(4)°, gamma = 104.61(1)°, Z = 4, V = 1148.0(1) Å3, Z = 2 and ?cal. = 1.454 g cm-3. Crystal structure was solved and refined to R = 0.04, 2752 independent reflections. The atomic arrangement can be described as inorganic layers of (H2PO4)- anions parallel to y = 1/2 planes, between which are located the organic groups. Solid-state 13C and 31P MAS-NMR spectroscopies are in agreement with the X-ray structure. Ab initio calculations allow the attribution of the phosphorous and carbon signals to the independent crystallographic sites and to the various atoms of the organic groups.
K. Kaabi, C. Ben Nasr, F. Lefebvre, Materials Research Bulletin 39 (2004) 205-215

A1312 – Structural characterization and antimicrobial activity of chitosan/betaine derivative complex

Complex of chitosan acetate (CSAC) with C12-C18 alkyl amido prophyl dimethylamine betaine (AAPDB) was prepared and characterized by Fourier transform-infrared (FT-IR), thermal analysis (TG, DTG and DSC), X-ray diffractogram. Results showed that complex formed mainly by the electrostatic interaction between NH3+ of CSAC and COO- of AAPDB. Minimum inhibitory concentrations (MICs) were evaluated against E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis and Candida albicans. Results showed that CS/AAPDB solution could or even more strongly inhibit growth of all the tested microorganisms, whereas CSAC could not inhibit growth of C. albicans and AAPDB could not inhibit growth of S. epidermidis, E. coli, P. aeruginosa. Relative inhibition times (RITs) of CS/AAPDB solutions with different concentration and ratio of CSAC and AAPDB were also investigated against the five microorganisms. Results showed that CS/AAPDB solutions with CCSAC + CAAPDB of 0.05% + 0.015%, 0.05% + 0.0075%, and 0.025% + 0.0075% showed higher antimicrobial activity. The relationship between complex formation and antimicrobial activity was discussed.
H. Liu, Y. Du, J. Yang, H. Zhu, Carbohydrate Polymers 55 (2004) 291-297

A1314 – Complex formation and degradation in poly(acrylonitrile-co-vinyl acetate) containing metal nitrates

Polymers containing metal-nitrates have been proposed as advantageous precursors for high temperature superconductors such as yttriumbarium- copper-oxide (YBCO). The advantage lies in using conventional polymer processing such as fiber spinning or microlithography before pyrolysis. This research investigated complex formation and degradation in poly(acrylonitrile-co-vinyl acetate) (P(AN-VA)) containing either yttrium nitrate (YN) or barium nitrate (BaN) and follows a similar investigation for copper nitrate. Complex formation was observed in P(AN-VA)/YN but not in P(AN-VA)/BaN. The exothermic nitrate degradation below the P(AN-VA)) cyclization temperature involved the release of NO3, a reaction with the nitrile group that disrupted cyclization, and, for BaN, P(AN-VA) degradation. For a P(ANVA)/ nitrate ratio of 2/1 there was no cyclization and the degradation temperature was reduced by about 200°C. The pyrolysis of P(ANVA)/ BaN yielded largely BaCO3, which is likely to impede the formation of YBCO.
M.S. Silverstein, Y. Najary, Y. Lumelsky, I. von Lampe, G.S. Grader, G.E. Shter, Polymer 45 (2004) 937-947

A1313 – Preparation and characterization of hybrid Nafion-silica membrane doped with phosphotungstic acid for high temperature operation of proton exchange membrane fuel cells

Nafion/silicon oxide (SiO2)/phosphotungstic acid (PWA) and Nafion/silicon oxide composite membranes were studied for the H2/O2 proton exchange membrane fuel cells (PEMFCs) operated above 100°C. The composite membranes were prepared by the recasting procedure, using Nafion solution mixed with SiO2 and PWA/SiO2 mixtures. The physico-chemical properties of these recast composite membranes were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, thermogravimetry-DTA (TG-DTA) and Fourier transform infrared (FTIR) spectroscopy. These results showed that SiO2 and PWA are compatible with the Nafion membrane. Furthermore, the incorporation of the SiO2 and PWA into the Nafion membrane could increase the crystallinity of the Nafion recast membrane and also improve the initial degradation temperature of the Nafion membrane. It was found that the composite membrane showed a higher uptake of water compared with the Nafion recast membrane. The proton conductivity of the composite membranes appeared to be similar to that of the native Nafion membrane at high temperatures and at 100% relative humidity (RH), however, it was much higher at low RH. When the composite membranes viz. Nafion/SiO2/PWA and Nafion/SiO2 were employed as an electrolyte in H2/O2 PEMFC, the higher current density values (540 and 320 mA/cm2 at 0.4V, respectively) were obtained than that of the Nafion 115 membrane (95 mA/cm2), under the operating condition of 110°C and at the humidified temperature of 100°C.
Z-G. Shao, P. Joghee, I-M. Hsing, Journal of Membrane Science 229 (2004) 43-51

A1316 – 1,4-Di(1,2,3,4-tetrazol-2-yl)butane as a precursor of new 2D and 3D coordination polymers of Cu(II)

A series of new coordination polymers of Cu(II) have been prepared in a reaction between copper(II) perchlorate or tetrafluoroborate salt and a novel ligand 1,4-di(1,2,3,4-tetrazol-2-yl)butane (bbtz). The compounds were characterised by an elemental analysis, TG measurements, IR, EPR and UV-Vis spectroscopy. Crystal structures of bbtz and five complexes of Cu(II) were determined by a single crystal X-ray diffraction measurement performed at 100 K. The composition and architecture of the obtained complexes strongly depend on the reaction conditions especially on the kind of solvent. Investigated complexes are composed of polymeric macrocations and non-coordinated anions. In all cases the bbtz molecules act as the bidentate ligand coordinated to metal(II) ions via N4, N4' nitrogen atoms from tetrazole rings. The complexes {[Cu(bbtz)2(MeOH)2]X2} (X=ClO4- , BF4- ) crystallise from methanol as 2D coordination polymers. In these compounds central metal ions are coplanar linked by molecules of bbtz and a coordination sphere is completed by axially coordinated solvent molecules. The complexes {[Cu(bbtz)3]X2} (X=ClO4- , BF4- ) were synthesised in EtOH/H2O solvent system and posses a common network topology. In this group of complexes each central atom is linked by ligand molecules to six other in plane arranged central atoms resulting in 2D networks. Reactions between Cu(II) salts and bbtz performed in absolute ethanol resulted in the formation of the next type of product. In {[Cu(bbtz)3](ClO4)2 . 2EtOH} neighboured copper(II) ions are linked by ligand molecules in the three directions what leads to the formation of 3D net. A crystal of this complex is composed of two mutually interpenetrated 3D networks.
R. Bronisz, Inorganica Chimica Acta 357 (2004) 396-404

A1315 – Vibrational study and crystal structure refinement of BaHPO4

X-ray single crystal structure of BaHPO4 is refined in the centric space group Pbnm (No. 62) with a = 4.609(1) Å, b = 14.195(3) Å, c = 17.214(5) Å, V = 1126.3(5) Å3, Z = 12 and a final R value of 0.036 for 1261 independent reflections. The atomic arrangement consists of anionic linear chains lying parallel to the a direction and strongly linked by hydrogen bonds. Two successive chains are separated by Ba2+ cations. A comparison of the anionic networks for some similar compounds is also given. The polarized Raman and infrared absorption spectra are investigated. A factor group analysis leads to determination of internal modes of the (PO4)3- anions. The vibrational study confirmed the strong H-OP hydrogen bonds to the phosphate groups and indicated a notable hydrogen bridges in BaHPO4 compound.
T. BenChaabane, L. Smiri, A. Bulou, Solid State Sciences 6 (2004) 197-204

A1317 – Hydrothermal syntheses and crystal structures of novel one- and two-dimensional organic-inorganic hybrid materials composed of paradodecatungstate-B clusters and [Cu(en)2]2+ complex groups

Novel one- and two-dimensional solids consisting of paradodecatungstate-B units linked via [Cu(en)2]2+ and/or [Cu(H2O)2]2+ bridging groups have been synthesized by the hydrothermal method and structurally characterized by X-ray crystallography, IR and chemical analysis.
B.Yan, N.K. Goh, L.S. Chia, Inorganica Chimica Acta 357 (2004) 490-494