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5631 articles

A1116 – Thermoanalytical studies of Titanium(IV) acetylacetonate xerogels with emphasis on evolved gas analysis

Thermal decomposition of precursor xerogels for TiO2, obtained by gelling of acetylacetonate-modified titanium(IV) tetraisopropoxide (prepared at Ti-alkoxide:acetylacetone molar ratios of 1:1 (Ti-1) and 1:2 (Ti-2)) in boiling 2-methoxyethanol, was monitored by simultaneous TG/DTA/EGA-MS and EGA-FTIR measurements. Thermal degradation processes of Ti-1 and Ti-2 in the temperature range of 30-700°C consist of six mass loss steps, the total mass loss being 46.3% and 54.4%, respectively. EGA by FTIR and MS revealed release of H2O below 120°C; followed by evolution of acetone and acetic acid between approximately 100 and 320°C, and that of CO2 up to 560°C. Acetylacetone is evolved to a significant extent from sample Ti-2 at 120-200°C.
I. Oja Açik, J. Madarasz, M. Krunks, K. Tonsuaadu, D. Janke, G. Pokol and L. Niinistö, Journal of Thermal Analysis and Calorimetry 88 (2007) 557-563

A1120 – Crystal structure and thermal behaviour of (C14H16N)6P6O18.6H2O

Chemical preparation, crystal structure and thermal behaviour are given for a new organic-cation cyclohexaphosphate: ((C6H5CH2)2NH2)6P6O18.6H2O). This compound is monoclinic P21/m with the following unit-cell parameters: a = 10.752(4) Å , b = 24.029(9) Å , c = 13.348(4) Å , beta = 106.36(3)° and Z = 2. Crystal structure has been determined and refined to R = 0.041 using 2961 independent reflections. This structure can be described as a stacking of ribbons spreading parallel to the a-direction, formed by the P6O18 ring anions and the water molecules. The ribbons are interconnected by the dibenzylammonium proups.
O.S.M. El Mokhtar, M. Rzaigui, Materials Research Bulletin 39 (2004) 2219-2227

A1119 – Kinetic study of the thermal dehydration of borogypsum

In Turkey, a large amount of borogypsum waste is discharged by the economically important boric acid industry. Calcination of this waste provides a promising technique not only for recovering an economic value but also for reducing its environmental impact. The aim of this work is to study the thermal behavior of borogypsum, which contains gypsum crystals, boron oxide and some impurities under nonisothermal conditions in air atmosphere by using thermogravimetry and differential thermal analysis techniques (TG-DTA). Experiments were carried out at temperatures ranging from ambient to 773K at different heating rates. The temperatures of conversion from gypsum to hemihydrate and anhydrite states were determined. Various methods were used to analyze the TG and DTA data for determination of reaction kinetics. The activation energy and frequency factor were calculated for dehydration of borogypsum. Activation energy values of the main dehydration reaction of borogypsum were calculated to be approximately 95-114 kJ mol-1.
I.Y. Elbeyli, S. Piskin, Journal of Hazardous Materials B116 (2004) 111-117

A1122 – Deformation behaviour and oxidation resistance of single-phase and two-phase L21-ordered Fe-Al-Ti alloys

Single-phase Fe-Al-Ti alloys with the Heusler-type L21 structure and two-phase L21 Fe-Al-Ti alloys with MgZn2-type Laves phase or Mn23Th6-type t2 phase precipitates were studied with respect to hardness at room temperature, compressive 0.2% yield stress at 20-1100°C, brittle-to-ductile transition temperature (BDTT), creep resistance at 800 and 1000°C and oxidation resistance at 20-1000°C. At high temperatures the L21 Fe-Al-Ti alloys show considerable strength and creep resistance which are superior to other iron aluminide alloys. Alloys with not too high Ti and Al contents exhibit a yield stress anomaly with a maximum at temperatures as high as 750°C. BDTT ranges between 675 and 900°C. Oxidation at 900°C is controlled by parabolic scale growth.
M. Palm, G. Sauthoff, Intermetallics 12 (2004) 1345-1359

A1121 – Pyrolysis experiments and thermochemistry of mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB)

The thermal decomposition of two highly energetic materials, mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB), was investigated by thermogravimetric analysis and differential scanning calorimetry. Mass spectrometry and IR spectroscopy were used to identify the gaseous products. Decomposition appears in both cases to be initiated by the release of nitramine. The gaseous products after the exothermic decomposition are similar for MNB and DNB, but the decomposition temperature of MNB is significantly higher and leads to the formation of urea, biuret (imidodicarbonic diamide), triuret (diimidotricarbonic diamide), tetrauret (triimidotetracarbonic diamide), and cyanuric acid (S-triazine-2,4,6(1H,3H,4H)-trione).
J. Geith, G. Holl, T.M. Klapötke, J.J. Weigand, Combustion and Flame 139 (2004) 358-366

A1124 – Synthesis and characterization of low-temperature precursors of thorium-uranium (IV) phosphate-diphosphate solid solutions

Several compositions of new precursor of thorium-uranium (IV) phosphate-diphosphate solid solutions (Th(4-x)Ux (PO4)4P2O7, called beta-TUPD) were synthesized in closed PTFE containers either in autoclave (160°C) or on sand bath (90-160°C). All the samples appeared to be single phase. From XRD data and TEM observations, the diffraction lines matched well with that of pure thorium phosphate-hydrogenphosphate hydrate (TPHPH), Th2(PO4)2(HPO4).H2O, which confirmed the preparation of a complete solid solution between pure thorium and uranium (IV) compounds. TGA/DTA experiments showed that samples of thorium-uranium (IV) phosphate-hydrogenphosphate hydrate (TUPHPH) prepared at 150-160°C were monohydrated leading to the proposed formula Th((2-x)/2)U(x/2)(PO4)2(HPO4).H2O. The variation of the XRD diagrams versus the heating temperature showed that TUPHPH remained crystallized and single phase from room temperature to 200°C. After heating between 200°C and 800°C, the presence of diphosphate groups in the solid was evidenced. In this range of temperature, the solid was transformed into the low-temperature monoclinic form of thorium-uranium (IV) phosphate-diphosphate (alpha-TUPD). This latter compound finally turned into well-crystallized, homogeneous and single-phase beta-TUPD (orthorhombic form) above 930-950°C for x values lower than 2.80. For higher x values, a mixture of beta-TUPD, alpha-Th(1-z)UzP2O7 and U(2-w)ThwO(PO4)2 was obtained. By this new chemical route of preparation of beta-TUPD solid solutions, the homogeneity of the samples is significantly improved, especially considering the distribution of thorium and uranium.
N. Clavier, N. Dacheux, P. Martinez, V. Brandel, R. Podor, P. Le Coustumer, Journal of Nuclear Materials 335 (2004) 397-409

A1123 – Oxidation behaviour of Ag-containing TiAl-based intermetallics

The effect of alloy composition on the oxidation behaviour of g-TiAl alloys with silver additions was studied during exposure at 800°C in air. For this purpose, a number of Ti-Al-Ag alloys with systematic variation of the chemical composition was prepared by levitation induction melting. Subsequently, the alloys were isothermally and/or discontinuously oxidised at 800°C in air. The results showed that suitable silver additions can promote and stabilise formation of an alumina scale on g-TiAl up to the maximum test times of 12,000 h. An oxidation map was derived which allows defining which type of surface oxide is formed on various TiAl-Ag alloy compositions. This result can be applied in further work for development of oxidation resistant coatings for g-TiAl or/and Ti-based alloys.
L. Niewolak, V. Shemet, C. Thomas, P. Lersch, L. Singheiser, W.J. Quadakkers, Intermetallics 12 (2004) 1387-1396

A1125 – Synthesis and characterization of a NaSICON series with general formula Na2.8Zr(2-y)Si(1.8-4y)P(1.2+4y)O12 (0

In this work, we present the synthesis and the characterization of ionic conducting ceramics of NaSICON-type (Natrium super ionic conductor). The properties of this ceramic make it suitable for use in electrochemical devices. These solid electrolytes can be used as sensors for application in the manufacturing of potentiometric gas sensors, for the detection of pollutant emissions and for environment control. The family of NaSICON that we studied has as a general formula Na2.8Zr(2-y)Si(1.8-4y)P(1.2+4y)O12 with 0
A. Essoumhi, C. Favotto, M. Mansori, P. Satre, Journal of Solid State Chemistry 177 (2004) 4475-4481

A1126 – Synthesis and characterization of sodium titanates Na2Ti3O7 and Na2Ti6O13

Na2Ti3O7 and Na2Ti6O13 were synthesized by sol-gel method in order to obtain pure phases. Different heat-treatments were applied on powders and pellets of these materials. The effects were studied by XRD, dilatometry, TGA-DTA, SEM and electrochemical impedance spectroscopy. Pure Na2Ti3O7 was obtained at 973 K. Sintering at 1373K caused a partial decomposition into Na2Ti6O13. The Na2Ti3O7 powder sintered at 1273K showed polygonal microstructure. Na2Ti3O7 pellets sintered at 1323K for 10 h exhibited large structures. This latter microstructure decreased the electrical conductivity of Na2Ti3O7. Pure Na2Ti6O13 was obtained at 873 K. Sintering at 1073K caused a partial decomposition into TiO2 (rutile). Na2Ti6O13 pellets sintered at 1323K for 10 h exhibited common shrinkage behavior. This shrinkage process increased the electrical conductivity of this material. The presence of TiO2 resulted in a oxygen partial pressure dependence of the electrical conductivity.
A-L. Sauvet, S. Baliteau, C. Lopez , P. Fabry, Journal of Solid State Chemistry 177 (2004) 4508-4515

A1127 – Preparation of an anionicazo pigment-pillared layered double hydroxide and the thermo- and photostability of the resulting intercalated material

A large anionic pigment has been intercalated into a layered double hydroxide (LDH) host by ion-exchange of an Mg/Al LDHnitrate precursor with a solution of C.I. Pigment Red 48:2 (the calcium salt of 4-((5-chloro-4-methyl-2-sulfophenyl)azo)-3-hydroxy- 2-naphthalene-carboxylic acid), in ethane-1,2-diol. After intercalation of the pigment, the interlayer distance in the LDH increases from 0.86 to 1.72 nm. Infrared spectra and TG-DTA curves reveal the presence of a complex system of supramolecular host-guest interactions. The UV-visible diffuse reflectance spectra of C.I. Pigment Red 48:2 show marked changes after heating at 200°C and above, whereas there are no significant changes in the spectra of the intercalated pigment after heating at temperatures up to 300°C, showing that the thermostability is markedly enhanced by intercalation in the LDH host. The pigment-intercalated LDHs exhibits much higher photostability to UV light than the pristine pigment, in the case of both the pure solids and their composites with polypropylene, as shown by measurement of CIE 1976 L*a*b* color difference (?E) values.
S. Guo, D. Li, W. Zhang, M. Pu, D.G. Evans, X. Duan, Journal of Solid State Chemistry 177 (2004) 4597-4604

A1129 – Synthesis and structure determination of a novel lithium copper vanadate LiCu2VO4(OH)2

A novel lithium copper vanadate LiCu2VO4(OH)2 (I) and Volborthite Cu3V2O7(OH)2 are two phases obtained at 170°C by hydrothermal synthesis during the study of the CuO; V2O5; Li2O; H2O system. Compound (I) crystallizes in the orthorhombic system, with the space group P212121 (No. 19) and with the unit-cell parameters a = 9.6086(2) Å, b = 8.4482(2) Å, c = 5.8938(1) Å. The structure was determined from powder by an "ab initio" method using the EXPO software and refined with GSAS, a Rietveld refinement package. Wave-like layers of rutile-type copper chains sharing vertex with the neighbor chains, are linked into a three-dimensional framework by rows of alternating tetrahedra of vanadium and trigonal bipyramids of lithium which share edges and vertices with the copper octahedra.
D. Hoyos, J-L. Paillaud, J-L. Guth, Solid State Sciences 6 (2004) 1359-1364

A1128 – Synthesis of highly acidic and well ordered MgAl-MCM-41 and its catalytic performance on the isopropylation of m-cresol

Highly ordered mesoporous MgAl-MCM-41 materials with different nSi/n(Mg+Al) ratios have been successfully prepared using magnesium acetate, sodium aluminate and sodium silicate as the source of magnesium, aluminum and silicon, respectively. The samples are labeled MgAl-MCM-41(x) where x denotes the molar nSi/(nMg+nAl) ratio in the synthesis gel. The obtained materials have been characterized by powder X-ray diffraction, nitrogen adsorption, 27Al MAS NMR spectroscopy and AAS analysis. XRD and nitrogen adsorption measurements show that the hexagonal structure and textural parameters of the MgAl-MCM-41 materials are similar to MCM-41 materials. The wall thickness and pore diameter of the MgAl-MCM-41 samples can be controlled by varying the magnesium content in the synthesis gel. 27Al MAS NMR analysis clearly confirms that most of the aluminum in the calcined product occupies the tetrahedral coordination state. Temperature programmed desorption (TPD) of pyridine indicates that strong and medium acid sites of MgAl-MCM-41 are much larger as compared to AlMCM-41 and increase upon increasing the Mg content. The catalytic activity of MgAl-MCM-41 materials with different nSi/n(Mg+Al) ratios has been investigated using isopropylation of m-cresol with isopropyl alcohol. MgAl-MCM-41(20) shows more m-cresol conversion and higher selectivity towards 2,4-diisopropyl-5-methyl phenol (2,4-DI-5MP) as compared to the AlMCM-41(23) catalyst under optimized reaction conditions. Moreover, the above catalyst registers a very high m-cresol conversion and high selectivity of 2,4-DI-5MP at a very low reaction temperature of 200°C, due to strong acid sites generated by divalent Mg2+ ions incorporation in the silica walls.
A. Vinu, K. Ariga, S. Saravanamurugan, M. Hartmann, V. Murugesan, Microporous and Mesoporous Materials 76 (2004) 91-98

A1131 – Gas transport properties of starch based films

This paper deals with gas transport properties of starch based films. Oxygen permeability of plasticised starch, octanoated starch, starch- EVOH blend, and PE-starch multilayer was first studied. The best gas barrier properties of starch based films are generally obtained for low water and plasticiser contents. It was then shown that the interesting low permeability of these systems is due to the low solubility of gases. These results broaden the scope of starch gas transport properties, which are generally discussed in terms of mobility (i.e. gas diffusivity).
P. Dole, C. Joly, E. Espuche, I. Alric, N. Gontard, Carbohydrate Polymers 58 (2004) 335-343

A1130 – Synthesis and crystal structure of three-dimensional open-framework lanthanide oxalates containing either the guanidinium or tetramethylammonium ions

Single crystals of three new lanthanide oxalate complexes, (CN3H6)2[Nd(H2O)]2(C2O4)4.3H2O I, [N(CH3)4][Nd2(H2O)3](C2O4)3.5. 4H2O II and [N(CH3)4][Yb(C2O4)2] III, have been synthesized hydrothermally in presence of either the guanidinium or tetramethylammonium TMA ions. A relevant feature of III is the complete absence of water. For all the complexes, the three-dimensional framework structure is built up by the connections of the lanthanide and the oxalate units, forming cavities and channels where the guest species, guanidinium and TMA ions and free water molecules, are localized. Thus, the above complexes present a very open architecture. For I and II, the neodymium atoms are 9-coordinated, forming a distorted monocapped square antiprism while for III, the ytterbium atom is 8-coordinated forming a quite regular dodecahedron. For I, the dehydration process is partially reversible. All the complexes will be characterized by infrared spectroscopy and thermal analysis. I has been extended to other lanthanide forming a family, Ln = La-Eu.
J.C. Trombe, A. Mohanu, Solid State Sciences 6 (2004) 1403-1419

A1134 – Formation of CuO nanowires on Cu foil

We report the growth of CuO nanowires from copper foils oxidized in wet air at temperatures between 300 and 800°C. Within the temperature range of 400-700°C, the nanowires formed have two different morphologies, curved and straight, with diameters between 50 and 400 nm and lengths between 1 and 15 µm. The growth behavior can be understood in terms of kinetics involving short-circuit diffusion, the strength of the nanowires, and the thickness ratio of the oxide scale and the metal.
C.H. Xu, C.H. Woo, S.Q. Shi, Chemical Physics Letters 399 (2004) 62-66

A1133 – Thermal evolution and crystal structure of a polymeric complex: Pb3(3,5-dicarboxylatopyrazole)2(NO3)2.4H2O

Pb3(pdc)2(NO3)2.4H2O (pdcZdeprotonated 3,5-pyrazole-dicarboxylic acid) has been prepared and is stable up to 100°C. Above this temperature the hydration water loss is noted before 200°C. Until 360°C the material becomes amorphous during the decomposition of the organic ligand; at 365°C crystallization occurs and can be formulated as a mixture of PbO and lead oxynitrates, which subsequently recombines between 395 and 445°C into Pb6O5(NO3)2 over 570°C, the residue is essentially red PbO. Pb3(pdc)2(NO3)2.4H2O crystallizes in the monoclinic system, a=20.3688(7), b=6.4232(4), and c=18.1059(7) Å , beta=118.44(1)°, space group C2/c, Z=4. The structure displays an original polymeric coordination complex where the lead(II) is found in two different environments: (-Pb2-pdc-)N chains are identified along the [001] direction, while inter chains Pb2-pdc and Pb1-pdc links are bridging these chains in a layer like tridimensionnal structure, where pdc is acting as an hexadentate ligand.
F. Bentiss, P. Roussel, M. Drache, P. Conflant, M. Lagrenée, J.P. Wignacourt, Journal of Molecular Structure 707 (2004) 63-68

A1132 – Supercritical gas extracts from low-quality coals: on the search of new precursors for carbon materials

This paper studies the chemical composition of several supercritical gas (SCG) extracts and its influence on the thermal behaviour under carbonisation conditions. The extracts were obtained from a Spanish lignite (Mequinenza), a low-quality coal from the point of view of energy applications. The lignite was treated with toluene, ethanol (EtOH) and tetrahydrofuran (THF) as solvents under different supercritical temperature and pressure conditions. The extracts display high aliphatic nature and enhanced concentrations of oxygen functional groups, aided by the contribution of hydrogenation and oxygen incorporation reactions occurring in the SCG extraction with EtOH and THF. Thiophenic compounds are also present in great concentrations derived from the exceptionally high organic sulphur content of the parent coal. The carbonisation of the extracts renders anisotropic material with fine mosaic texture, as a consequence of the significant thermal reactivity inferred by the aliphatic and oxygenated groups. The size of the mosaic increases with the temperature of the SCG extraction and varies with the supercritical solvent in the order: toluene < EtOH < THF.
R. Garcia, A. Arenillas, F. Rubiera, S.R. Moinelo, Fuel Processing Technology 86 (2004) 205-222

A1137 – Development of polymer-ceramic composites for improved fire resistance

Materials that provide protection of lives and property from fire are highly desirable across many industries. Conventional polymers are generally completely consumed in a fire situation and require either halogenated additives that give off toxic and corrosive gases with large volumes of smoke or high filler loadings of non-halogen based additives in order to impart fire resistance. Attention has been shifted to the area of "ceramifiable" polymers as a means of improving passive fire protection, and silicones have been shown to possess desirable properties on firing, such as a slow burning rate without a flaming drip and low emissions of non-toxic smoke. However, the ceramic formed by firing silicones alone is very weak and powdery. Addition of certain inorganic fillers improves the strength, giving a near-net shape ceramic. The fire protection properties of silicone and silicone-based composites are investigated at temperatures up to 1100°C. The microstructure of the resultant ceramics has been studied and the mechanism for the conversion of silicone-based composites to ceramics is proposed.
L.G. Hanu, G.P. Simon, J. Mansouri, R.P. Burford, Y.B. Cheng, Journal of Materials Processing Technology 153-154 (2004) 401-407

A1136 – Mesoporosity in diatoms via surfactant induced silica rearrangement

Mesoporosity has been introduced into the micron-sized pore walls of diatoms. The technique used involves dissolution and rearrangement of diatomaceous silica, via interactions with the surfactant hexadecyltrimethylammonium bromide. The resulting biomineral possesses ordered hexagonal and disordered mesostructure, and has a BET surface area of 284 m2 g-1. Electron microscopy, X-ray diffraction and nitrogen adsorption studies have been used to confirm the presence of mesoporosity in the material, and the stability of the micron-sized diatom architecture under the reaction conditions.
C.E. Fowler, Y. Hoog, L. Vidal, B. Lebeau, Chemical Physics Letters 398 (2004) 414-417

A1135 – Catalytic degradation of expandable polystyrene waste (EPSW) over mordenite and modified mordenites

The performance of the several different modified mordenite zeolites in the degradation of expandable polystyrene waste (EPSW) was investigated in this study. The composition of the degradation products, especially the liquid fraction was compared to understand the role of H-mordenite and the effect of its modification through framework dealumination and metal impregnation. The degradation was carried out in a batch reactor at 360 and 400°C. The dealuminated mordenite with SiO2/Al2O3 ratio of 86 showed enhanced styrene/styrene dimer and styrene/ethylbenzene molar ratios at lower (360°C) and higher (400°C) temperature, respectively. This was attributed to the intermediate acid strength distribution generated on removal of framework aluminum by acid leaching. Modification of H-mordenite by metal impregnation substantially changed the acidic and catalytic properties in polystyrene degradation. The 0.64 wt.% phosphorous loading on H-mordenite showed improved EPSW conversion, styrene yield and SM/EB molar ratio at 400°C. The 0.32 wt.% phosphorous loading facilitated the improvement in SM/EB molar ratio with higher styrene selectivity than thermal degradation at 360°C.
V.R. Chumbhale, J-S. Kim, S-B. Lee, M-J. Choi, Journal of Molecular Catalysis A: Chemical 222 (2004) 133-141

A1141 – The prediction of the characteristics of some polysaccharides from molecular modeling. Comparison with effective behavior

Molecular modeling is a convenient technique to predict the behavior of polymers in solution as well as in the solid state; also, interaction with water and other small molecules can be examined. In our presentation, the main techniques used for molecular modeling of polysaccharides are briefly recalled and applied to different systems for which the chemical structure is known (allowing valuable description of the molecule). Then, experimental determination of the local conformation byNMRor of the global dimensions of galactomannan and chitosan chains by light scattering are compared with the corresponding predicted parameters with good agreement; interaction of amylose with water is studied by thermogravimetry and DSC and strongly interacting water are localized by molecular modeling. At end, modeling of crystalline and amorphous solids together with surface interactions is presented. For the first time, this paper demonstrates from a series of data obtained in our laboratory the validity of the molecular modeling approach proposed to predict the behaviour of polysaccharides in solution or solid state.
K. Mazeau, M. Rinaudo, Food Hydrocolloids 18 (2004) 885-898

A1140 – Semivolatile and volatile compounds in combustion of polyethylene

The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850°C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that alpha,omega-olefins, alpha-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC-MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.
R. Font, I. Aracil, A. Fullana, J.A. Conesa, Chemosphere 57 (2004) 615-627

A1139 – Effect of polysaccharides on the hydration of cement paste at early ages

This work deals with the relative efficiency of polysaccharides and their influence on cement hydration. Several parameters such as the structure, concentration, average molecular weight, and soluble fraction value of polysaccharides were examined. Cement hydration was monitored by isothermal calorimetry, thermogravimetry (TGA), and Fourier transform infrared (FTIR) spectroscopy. Results clearly show that retardation increases with higher polysaccharide-to-cement weight ratio (P/C). Low-molecular-weight starch showed enhanced retarding effect on the hydration of cement. The retardation effect of polysaccharides is also dependent on the composition of cement.
A. Peschard, A. Govin, P. Grosseau, B. Guilhot, R. Guyonnet, Cement and Concrete Research 34 (2004) 2153-2158

A1138 – Phase equilibria and primary crystallisation field for Sm(1+y)Ba(2-y)Cu3O7 at various p(O2)

Phase relations in the Sm-Ba-Cu-O system in air have been reconsidered and the topology at the liquidus surface has been consistently constructed from both new experimental investigation as well as critical review of literature data. Subsolidus phase equilibria near the superconducting Sm(1+x)Ba(2-x)Cu3O7 ("Sm123") phase have also been investigated at various oxygen partial pressures, revealing the strong influence of the oxygen chemical potential on the extension of the homogeneity region of the Sm123 phase. The decomposition temperature of Sm123 decreases rapidly from 1070°C down to 1010°C with the Sm excess x increasing from ~0 to ~0.5. For x > 0.5 the decomposition temperature is constant indicating an invariant reaction which marks the lowest temperature at which the Cu-rich melt is in equilibrium with both Sm123 and Sm2BaCuO5 ("Sm211"). For Cu-poor melts this temperature is 1030°C in air (0.21 bar O2). Implications of the results with respect to both sample growth during melt texturing and post annealing (decomposition of Sm-rich Sm123) in different atmospheres are being discussed. A p(O2)-T-diagram for equilibria containing Sm-rich Sm123 is derived.
C. Wende, B. Schüpp, G. Krabbes, Journal of Alloys and Compounds 381 (2004) 320-326

A1142 – Synthesis, crystal structures, and molecular hyperpolarizabilities of a new Schiff base ligand, and its copper(II), nickel(II), and cobalt(II) metal complexes

A new ligand (HL) obtained from the Schiff base condensation of 4-(diethylamino)salicylaldehyde with 4-nitroaniline is reported, with its nickel(II), copper(II), and cobalt(II) complexes. The crystal structures are reported for the four derivatives. While, Ni(II)L2 and Cu(II)L2 are centrosymmetric molecules, Co(II)L2 exhibits a pseudo-tetrahedral molecular structure. The quadratic hyperpolarizabilities (beta) of HL and Co(II)L2, measured by electric field induced second harmonic (EFISH) technique, are equal to 66 and 110 x 10^(-30) cm5 esu-1, respectively. Beside a geometric effect (pseudo-Td symmetry), the coordination of the metal center provides an intrinsic enhancement of the NLO response. In addition, an enhancement of the thermal stability of about 60° is found upon metal complexation.
P.G. Lacroix, F. Averseng, I. Malfant, K. Nakatani, Inorganica Chimica Acta 357 (2004) 3825-3835

A1143 – Studies on sacrificial and carbon deoxidation of niobium

The nature and extent of oxygen removal from Nb-C-O alloys on heating to 2273K under 2mPa vacuum has been investigated. Correlations have been given relating the vapour pressure ratios of CO, NbO(v) and NbO2(v) to the residual oxygen and carbon contents in niobium and the temperature of treatment. Experimental results of treating Nb pellets with initial oxygen content of 1.09wt% and added carbon corresponding to C/O ratios of 0-1.10 in a thermogravimetry unit up to 2273K under 2mPa have been explained on the basis of the relevant vapour pressure ratios. The deoxidation of Nb-C-O begins at 1650K and proceeds in three distinct steps consisting of both sacrificial deoxidation and carbon deoxidation. The first step is sacrificial deoxidation due to formation of NbO2(v), the second step is carbon deoxidation, and the final step is sacrificial deoxidation by NbO(v) vaporization. The extent of deoxidation in each of these steps depends on C/O ratio of the charge.
T.K. Roy, A. Awasthi, N. Krishnamurthy, International Journal of Refractory Metals & Hard Materials 22 (2004) 251-256

A1146 – Structural and electrical changes in NdSrNiO(4-d) by substitute nickel with copper

A novel series of the formula NdSrNi(1-x)CuxO4 d were synthesized for various values of x ranging from 0 to 1 in 1 atm of O2 gas flow using conventional solid-state methods and were characterized by powder X-ray diffraction and electrical resistivity measurements. The compounds have been shown to adopt the K2NiF4-type structure. The oxygen stoichiometry of the compounds was determined from thermo-gravimetric analysis (TGA). An analysis of the micro-structure of the neodymium strontium nickel copper oxide is described. All the samples were semi-conducting from room temperature down to 77 K. The effect of Cu2+ incorporation on the structural and electrical properties of NdSrNi(1-x)CuxO4 d, 0
H. Chaker, T. Roisnel, M. Potel, R. Ben Hassen, Journal of Solid State Chemistry 177 (2004) 4067-4072

A1145 – The effects of synthesis pH and hydrothermal treatment on the formation of zinc aluminum hydrotalcites

Zn/Al hydrotalcites were synthesized by coprecipitation at increasing pH from 6.0 to 14.0, followed by hydrothermal treatment at 150°C for 7 days. The materials were characterized by X-ray diffraction (XRD), STEM, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), thermal analysis, infrared spectroscopy and Raman spectroscopy. The XRD analysis for the samples prepared between pH 9.0 and 12.0 showed a pattern typical of hydrotalcite, with a c-axis distance of ~22.6 Å . STEM showed that the pH of preparation affected the stability of the hydrotalcite and that instability, observed at pH 9.0, favored the formation of mixed phases when treated hydrothermally. It was also shown that treatment of a stable starting material increased the crystallinity and resulted in the formation of hexagonal plate-shaped particles. ICP-AES and thermal analysis showed that the Zn/ Al ratio and thermal stability increased with pH. Thermal analysis showed three major weight losses corresponding to the loss of interparticle water, interlayer water and dehydroxylation of the hydroxide layers and decarbonization of the interlayer region.
J.T. Kloprogge, L. Hickey, R.L. Frost, Journal of Solid State Chemistry 177 (2004) 4047-4057

A1144 – Synthesis and characterization of a new monophosphate [2,5-(CH3)2C6H3NH3]H2PO4

Chemical preparation, calorimetric studies, crystal structure and spectroscopic investigations are given for a new noncentrosymmetric organic cation monophosphate [2,5-(CH3)2C6H3NH3]H2PO4. This compound is orthorhombic P212121 with the following unit-cell parameters: a = 5.872(4); b = 20.984(3); c = 8.465(1) Å , Z = 4; V = 1043.0(5) Å3 and Dx = 1.396 g cm-3. Crystal structure has been solved and refined to R = 0.048 using 2526 independent reflections. Structure can be described as an inorganic layer parallel to (a; b) planes between which organic groups [2,5-(CH3)2C6H3NH3]+ are located. Multiple hydrogen bonds connecting the different entities of compound thrust upon three-dimensional network a noncentrosymmetric configuration.
K. Kaabi, C. Ben Nasr, M. Rzaigui, Journal of Physics and Chemistry of Solids 65 (2004) 1759-1764

A1148 – [Zn(3+x)V(2-x)O(7-3x)(OH)(2+ 3x)].2H2O and M[Zn(3-x)V2O7(OH)2]Cl(1-2x).(1+2x)H2O two families of zinc vanadates with structures related to the hexagonal structure of [Zn3V2O7(OH)2].2H2O

[Zn(3 +x)V(2-x)O(7-3x)(OH)(2+ 3x)].2H2O (I), with 0 < x < 0.66 and M[Zn(3-x)V2O7(OH)2]Cl(1-2x).(1 + 2x)H2O (II), with 0.15 < x <0.5, were obtained by hydrothermal synthesis at 170°C (24 h) from gels with the molar composition ZnCl2; aV2O5; bMOH; 228H2O, with M= Li, Na, NH4 or K for (I) and NH4 or Rb for (II); 0.2 < a <0.5 and 0.5 < b<6. The compounds of both families crystallize in the hexagonal system with a structure which can be related to the structure of [Zn3V2O7(OH)2].2H2O. Their Zn/V molar ratio can be determined from to the unit-cell parameter a0 by the linear relations Zn/V = 4.896 a0 - 28.124 (R = 0.988) for (I) and Zn/V = 15.302 a0 - 91.027 (with R2 = 0.992) for (II). In (I) the negative charges created by the substitution of vanadium with zinc in the tetrahedra of the pyrovanadate pillars connecting the octahedral sheets containing the zinc, are compensated by protonation of framework oxygen atoms. In (II) the negative charges, created by the removal of zinc in the octahedral sheet, are compensated by cations (NH4+ or Rb+) located between the pyrovanadate pillars. But in order to fill more completely the space, additional cations (NH4+ or Rb+) are incorporated in form of the chloride salt.
D. Hoyos, L. A. Palacio, J-L. Paillaud, A. Simon-Masseron, J-L. Guth, Solid State Sciences 6 (2004) 1251-1258

A1147 – New alkaline earth-zirconium oxalates M2Zr(C2O4)4 . nH2O (M=Ba, Sr, Ca) synthesis, crystal structure and thermal behavior

Three new alkaline earth-zirconium oxalates M2Zr(C2O4)4 . nH2O have been synthesized by precipitation methods for M=Ba, Sr, Ca. For each compound the crystal structure was determined from single crystals obtained by controlled diffusion of M2+ and Zr4+ ions through silica gel containing oxalic acid. Ba2Zr(C2O4)4 . 7H2O, monoclinic, space group C2/c, a = 9.830(2), b = 29.019(6), c = 9.178(2) Å, beta = 122.248(4)°, V = 2214.2(8) Å3, Z = 4, R = 0.0427; Sr2Zr(C2O4)4 . 11H2O, tetragonal, space group I41=acd, a = 16.139(4), c = 18.247(6) Å, V = 4753(2) Å3, Z = 8, R = 0.0403; Ca2Zr(C2O4)4 . 5H2O, orthorhombic, space group Pna21, a = 8.4181(5), b = 15.8885(8), c = 15.8885(8) Å, V = 2125(2) Å3, Z = 4, R = 0.0622. The structures of the three compounds consist of chains of edge-shared MO6(H2O)x (x = 2 or 3) polyhedra connected to ZrO8 polyhedra through oxalate groups. Depending on the arrangement of chains, the ZrO8 polyhedron geometry (dodecahedron or square antiprism) and the connectivity, two types of three-dimensional frameworks are obtained. For the smallest M2+ cations (Sr2+, Ca2+), large tunnels are obtained, running down the c direction of the unit cell, which can accommodate zeolitic water molecules. For the largest Ba2+ cation, the second framework is formed and is closely related to that of Pb2Zr(C2O4)4 . nH2O. The decomposition at 800°C into strontium carbonate, barium carbonate or calcium oxide and MZrO3 (M=Sr, Ba, Ca) perovskite is reported from thermal analyses studies and high temperature X-ray powder diffraction.
B. Chapelet-Arab, G. Nowogrocki, F. Abraham, S. Grandjean, Journal of Solid State Chemistry 177 (2004) 4269-4281

A1150 – Time-resolved photoluminescence analysis of distribution and migration ofterbium ions in zeolites X

The photoluminescence (PL) dynamics ofterbium-exchanged zeolites X was investigated upon laser excitation at 355 nm. The results evidenced the presence ofat least two terbium main environments with PL lifetimes varying between 391-411 and 753-770 ms. The two-site nature ofterbium distribution in zeolites X permitted a quantitative analysis ofthe migration process of terbium ions inside the pores and cavities upon dehydration in air at 200°C. Besides the increase ofthe PL lifetimes with about 30% and 80% compared to those ofthe hydrated zeolite, a fraction of almost 30% of terbium ions was estimated to migrate from the supercages to the neighboring sodalites or hexagonal prisms. Our results evidenced for the first time the capability of time-resolved luminescence spectroscopy in quantitatively tracking for the intrazeolitic migration of lanthanides.
C. Tiseanu, L. Frunza, M. Kumke, Physica B 352 (2004) 358-365

A1149 – Crystal structure, thermal, dielectric and vibrational studies of the [4-C2H5PyH]4[Sb2Cl10] crystal

Crystal structure of tetra(4-ethylpyridinium) decachlorodiantimonate(III), [4-C2H5PyH]4[Sb2Cl10], has been determined at 245 K by X-ray diffraction (tetragonal, space group P41212). DSC and dilatometric studies indicate a presence of two reversible phase transitions of the first order type, at 370/373 and 233/238 K (cooling/heating) with S = 4.0 and 10.1 J mol-1 K-1, respectively. Infrared spectra of polycrystalline [4-C2H5PyH]4[Sb2Cl10] have been studied in the temperature range 20-306 K. Substantial changes in the temperature evolution of frequencies of internal modes of the 4-ethylpyridinium cations near 233 K are due to the ordering of the cationic sublattice. The experimental results indicate that both phase transitions may be classified as the order-disorder ones.
B. Kulicka, R. Jakubas, A. Pietraszko, G. Bator, J. Baran, Solid State Sciences 6 (2004) 1273-1286

A1152 – CsF supported by alpha -alumina: an efficient basic catalyst

CsF supported by alpha- and gamma-alumina was characterized by DTG-DTA coupled with mass spectral analysis of the gases evolved by the solid, XRD, 19F NMR spectroscopy, and tested in the Michael addition of cyclohexene-2-one with nitroalkanes and in the synthesis of alkyl carbonates. After dehydration at low temperature, 19F NMR spectroscopy shows that F is in part as CsF when the support is alpha-alumina but only as Cs3AlF6 when the support is gamma-alumina. CsF is detected by XRD on alpha-alumina but not on gamma-alumina. On CsF/ alpha-alumina the Michael condensation of 2-cyclohexen-1-one with nitroalkanes can be achieved in a few minutes with an equimolar mixture of reactants. Cs/ alpha-alumina is also active after simple drying at 393 K, avoiding the usual activation at higher temperature. It is also surprisingly active for the transesterification of diethylcarbonate by different alcohols and diols with an activity nearly independent of the structure of the substrate.
J-M. Clacens, D. Genuit, B. Veldurthy, G. Bergeret, L. Delmotte, A. Garcia-Ruiz, F. Figueras, Applied Catalysis B: Environmental 53 (2004) 95-100

A1151 – TPO-TPD study of an activated carbon-supported copper catalyst-sorbent used for catalytic dry oxidation of phenol

Adsorption of organic pollutants in wastewater by carbon-based catalyst-sorbents followed by in situ catalytic dry oxidation of the adsorbed pollutants to regenerate the catalyst-sorbents at low temperatures is promising for the treatment of toxic and/or biorefractory wastewater streams. This paper investigates an activated carbon-supported copper catalyst-sorbent (CuO/AC) for catalytic dry oxidation of phenol at low temperatures in a TG/MS system through temperature-programmed oxidation (TPO) and temperature-programmed desorption (TPD). Phenol oxidation activities and ignition characteristics of the catalyst-sorbent were mainly discussed. The results indicate that the CuO/AC catalyst-sorbent has high catalytic activities for phenol oxidation and for AC ignition compared to the AC support itself; the initial oxidation temperature for phenol is about 190°C, which is 130°C lower than that for the AC. Consecutive adsorption-oxidation experiments show that the phenol adsorption capacity of the CuO/AC catalyst-sorbent decreases from an initial value of about 140 mg/g to a stable value of about 70 mg/g in 9 cycles, which is much better than the performance of activated carbon reported in the literature. TPD results indicate that phenol molecules adsorb on different types of active sites on AC and CuO/AC catalyst-sorbent. CuO plays an important role both in enhancing the affinity between phenol and CuO/AC catalyst-sorbent during phenol adsorption and in promoting catalytic activity for phenol oxidation.
J. Zhao, Z. Liu, D. Sun, Journal of Catalysis 227 (2004) 297-303

A1153 – Deposition of anatase on the surface of activated carbon

As part of a program looking into utilization of activated carbon prepared from waste material, titanium dioxide was deposited on the surface of active carbon (AC). This will be used in future work as potential photo-catalyst for treatment of chlorinated phenols in aqueous medium. Three different techniques were used: chemical vapour deposition (CVD), direct air-hydrolysis (DAH) and high-temperature impregnation (HTI) techniques. The total TiO2 deposited and amount crystallized into anatase TiO2 by each technique is estimated. The presonication was found useful in introducing part of the hydrolysis step within the small pores. The effect of each deposition procedure on surface area, porosity and thermal stability of the sample was studied by nitrogen adsorption, mercury intrusion, methylene blue (MB) adsorption and thermal gravimetric analysis. Surface texture of the potential catalysts was studied by electron microscopic techniques. Results showed that different procedures gave different yields of total and anatase TiO2. On the other hand, there was significant reduction, which may be due to TiO2 deposition, in porosity and surface area. The reduction in MB adsorption was proportional to anatase TiO2 but not to the total TiO2 deposited. Chemical vapour deposition gave more anatase TiO2 than the direct air-hydrolysis technique, which is thought to form the deposit within the micro-meso pores, and caused more porosity-surface area reduction. It is thought that TiO2 particles inside the pores have more opportunity to crystallize into the anatase form. The deposited layer of TiO2 apparently catalyzed slight weight loss at low temperatures but generally gave more thermal stability for the support. Non-activated carbon (C) was used and its thermal stability, porosity and surface area were not affected by TiO2 deposition. The deposition, in non-activated carbon, is thought to occur on external surface, which may be due to absence of large micropores.
A.H. El-Sheikh, A.P. Newman, H. Al-Daffaee, S. Phull, N. Cresswell, S. York, Surface & Coatings Technology 187 (2004) 284-292

A1155 – On structural phase transitions in 4-aminopyridinium fluoroborate, [4-NH2C5H5N][BF4]: differential scanning calorimetry, dielectric and infrared studies

Crystal structure of the 4-aminopyridinium tetrafluoroborate, [4-NH2C5H5N][BF4], has been determined at 293 K by means of X-ray diffraction as monoclinic space group, C2. The crystal shows a reach sequence of phase transition, four solid-solid transitions: at 250, 281, 388 and 485 K on heating. Most of the phase transitions, except that at 388 K, are clearly of first order and classified as an 'order-disorder' type. The rotational disorder both of cations and anions was studied by differential scanning calorimetry, dielectric and infrared spectroscopy. The low temperature phase transitions are associated with plastic crystal behavior.
O. Czupinskia, R. Jakubas, A. Pietraszko, Journal of Molecular Structure 704 (2004) 177-187

A1154 – Preparation of nanocrystalline Lu2O3:Eu phosphor via a molten salts route

The paper reports on the course of decomposition of hydrated lutetium nitrate and lutetium chloride to Lu2O3 in the eutectic mixture of NaNO2 and KNO2. It was shown that a crystallographically pure phase of the cubic Lu2O3 is formed at temperature as low as 250°C. IR spectra revealed that the recovered powder contains some OH-contamination, however. The powders are characterized by crystallites sizes in the range of 18-30 nm in average. Emission and excitation spectra of Eu-doped powders show characteristic features for Eu3+ ion in an oxide host, which indicates that the procedure is appropriate for making activated nanoparticulate oxide phosphors. Most profound emission appears around 611 nm and the luminescence from the powder made starting with Lu(NO3)3 was noticeably higher compared to the product obtained from LuCl3. The excitation spectrum of Eu3+ emission at 611 nm contains a band related to the fundamental absorption of the lutetia host lattice, which indicates an existence of the host-to-activator energy transfer.
J. Trojan-Piegza, E. Zych, Journal of Alloys and Compounds 380 (2004) 118-122

A1156 – Pt-free sulphur resistant NOx traps

A thioresistant NOx trap based on CuO supported on sulphated zirconia mixed with a solid base is described. The rate of adsorption of NO at constant temperature and the amount of NO retained from a feed containing 750 ppm NO, 10% O2 and 5% water in nitrogen were measured. On badly dispersed CuO, the capacity for NOx adsorption does not decrease but slightly increases in the presence of 25 ppm SO2 in the feed. By contrast, a well dispersed Cu catalyst is irreversibly poisoned. The surface nitrates can be decomposed in air at 623 K. In a mixture, Ar + 1% H2, the nitrate is partly reduced to N2 at about 630 K, even after operation in the presence of SO2. The catalyst does not lose adsorption capacity after 10 cycles of adsorption-desorption and can be used in the temperature range 473-773 K. The resistance to SO2 depends also in part of the properties of the solid base.
J-M. Clacens, R. Montiel, H. Kochkar, F. Figueras, M. Guyon, J.C. Beziat, Applied Catalysis B: Environmental 53 (2004) 21-27

A1157 – New carbon multiwall nanotubes – TiO2 nanocomposites obtained by the sol-gel method

Carbon nanotubes-anatase nanocomposites obtained by the sol-gel method could be interesting materials due the semiconducting properties of TiO2. In the present study, nanotubes, produced by catalytic decomposition of acetylene, were covered with a TiO2 thin layer or with TiO2 nanoparticles obtained by the sol-gel method. In the sol-gel process, two different classical alkoxides were used: titanium tetra-ethoxide and titanium tetra-isopropoxide with or without addition of cetyltrimethylammonium bromide as surfactant. Thermal treatment removes organic moieties and allows TiO2 crystallization as anatase on the nanotubes surface. Without surfactant, the TiO2 crystallized as a thin film or as nanoparticles on the nanotubes surface. In the presence of a surfactant, the rate of anatase crystallization was observed to decrease.
A. Jitianu, T. Cacciaguerra, M-H. Berger, R. Benoit, F. Béguin, S. Bonnamy, Journal of Non-Crystalline Solids 345 & 346 (2004) 596-600

A1159 – Synthesis and characterization of IM-10: a new microporous silicogermanate with a novel topology

A novel GeO2 or (Si,Ge)O2 zeolite phase called IM-10 was obtained in the presence of the well-known hexamethonium ion as template and in fluoride media, from gels with Ge/Si molar ratios > 1. With decrease of the Ge/Si molar ratio, BEC-type zeolite and ITH-type zeolite were successively obtained. The recovered IM-10 samples were characterized by X-ray diffraction, SEM, elemental and thermal analysis, 19F MAS and 1H liquid (after dissolution of the samples in HF) spectroscopies. Due to the small crystal sizes (1-4 µm), the structure was determined from powder X-ray diffraction (of the GeO2 as-made sample) and refined by the Rietveld method. IM-10 is a new member of the clathrate family. It crystallizes in the tetragonal symmetry, the space group being P 4n2. The framework is made of F- -containing D4R units, bridged by GeO4 tetrahedra. The arrangement of the D4R units creates [6 20 4 2] supercages, each of them occluding one hexamethonium cation. Structural similarities exist between ASU-9 (AST), ASU-7 (ASV) and the new IM-10 zeolite with a novel topology (UOZ).
Y. Mathieu, J-L. Paillaud, P. Caullet, N. Bats, Microporous and Mesoporous Materials 75 (2004) 13-22

A1158 – Luminescence properties of ORMOSIL films doped with terbium complexes

Luminescence properties of sol-gel SiO2-TiO2 ORMOSIL films doped with various terbium complexes were studied. 3-(Trimethoxysilyl) propyl methacrylate and tetraisopropyl-orthotitanate complexed with methacrylic acid were used as sol-gel precursors for film deposition. In situ rare earth complexation was performed through the direct incorporation of TbCl3 and 1,10-phenanthrolin (Phen), phthalic acid (Phta), or 2,20-bipyridyl (Bipy) ligand in the sol-gel precursor solution. ORMOSIL coatings were deposited using the aerosol-gel process, which is an original deposition method based on the sol-gel polymerization of a liquid film produced from an ultrasonically sprayed aerosol. ORMOSIL films containing terbium complexes exhibited a strong green emission, which was intensified through post-treatment temperature optimization. The highest photoluminescence intensities were measured on films doped with Tb(Phen)3+ complex and heat treated at 150°C, while films doped with Tb(Bipy)3+ complex and heat-treated at the same temperature exhibited the longest lifetimes.
M. Trejo-Valdez, P. Jenouvrier, M. Langlet, Journal of Non-Crystalline Solids 345 & 346 (2004) 628-633

A1161 – Chiral matrix effect of optically active oxalate-based networks: controlled helical conformation of an organic chromophore

Optically active two-dimensional (2D) MIPS[MnIIMIII(C2O4)3] bimetallic networks with MIPS = 4-[4-methoxy-alpha-styryl]- N-isopentylpyridinium and M(III) = Cr, Co were obtained using as chiral inducing reagents the resolved (?)- or (?)-[M(III)(C2O4)3]3- building blocks. The correlation of the natural circular dichroism (NCD) of these 2D networks with their UV-vis properties demonstrates that the [Mn(II)M(III)(C2O4)3] anionic network has a chiral matrix effect on the MIPS+ cation: the choice of the con- figuration of the starting tris(oxalato)metallate(III) determines the helical conformation of the MIPS+ cation. Such a conformation of the cation sharply contrasts with the perfectly planar geometry observed by X-ray diffraction in MIPSBr.
M. Gruselle, B. Malézieux, S. Bénard, C. Train, C. Guyard-Duhayon, P. Gredin, K. Tonsuaadud and R. Clément, Tetrahedron: Asymmetry 15 (2004) 3103-3109

A1160 – Toluene disproportionation and coking on zeolites Y modified with Lewis-connected InO+ acid sites

The effect of introduction of Lewis acid sites on the reactions of toluene transformation and catalysts coking has been studied over parent (Si/Al = 2.5) and dealuminated (Si/Al = 3.7) Y zeolites modified with Lewis connected InO+ cationic acid sites. The catalysts with prevalent amount of Brönsted acid sites (less than 40% of protons exchanged by InO+) possess the typical for the proton directed reaction of methyl transfer upon toluene disproportionation long period of activation, the longer the higher the concentration of bridging protons. In contrast, at predominant Lewis sites concentration, the activation period disappear, an enhanced initial activity is observed, followed by deactivation on the expense of a rapid process of accumulation of strongly held reaction products and intermediates. Their further condensation leads to catalysts aging, the faster the higher the concentration of electron acceptor Lewis acid sites. A relation has been found between the initially accelerated processes of alkyl transfer and the reinforced formation of carbonaceous deposits over the In-modified catalysts.
V. Mavrodinova, M. Popova, R.M. Mihalyi, G. Pal-Borbély, Ch. Minchev, Journal of Molecular Catalysis A: Chemical 220 (2004) 239-246

A1163 – Effect of Zr-content on the oxidation and phase transformation of Zr-base amorphous alloys in air

The oxidation and phase transformation of three Zr-base amorphous alloys, Zr-20Cu-12Ni-10Al-5Ti (Zr53), Zr-30Cu-10Al-5Ni (Zr55), and Zr-15Cu-10Al-10Ni (Zr65), were studied over the temperature range of 300-500°C in dry air. Oxidation kinetics of these alloys generally followed a parabolic rate law at T > 350°C, but linear kinetics was obeyed at 300-350°C. It was found that Zr65 was the most oxidation-resistant alloy among the three alloys studied. Scales formed on the alloys during oxidation consisted of mainly tetragonaland monoclinic-ZrO2 (t- and m-ZrO2), and minor CuO and NiO (only detected in Zr53). The amount of m-ZrO2 formed strongly depends upon the alloy composition, exposure time, and temperature. TEM results showed that a significant amount of nano-grained Zr2Cu polycrystals formed beneath the amorphous oxide-scale in Zr53, indicating phase transformation has taken place. By contrast, Zr55 and Zr65 amorphous substrates transformed into Zr2Cu and ZrAl after oxidation.
H.H. Hsieh, W. Kai, R.T. Huang, M.X. Pan, T.G. Nieh, Intermetallics 12 (2004) 1089-1096

A1162 – Polytypes and polymorphs in the related Friedel’s salt [Ca2Al(OH)6]+[X.2H2O] halide series

Seven substituted Friedel's salt samples from the solid solution [Ca2Al(OH)6] + [Cl(1-x)Brx.2H2O] were synthesised by hydrothermal synthesis (x = 0, 0.23, 0.44, 0.57, 0.66, 0.78, and 1.0). These compounds, belonging to the layered double hydroxide family, present a structural phase transition from the rhombohedral HT-polymorph to the monoclinic LT-polymorph. The transition has been detected by differential scanning calorimetry and then characterized by X-ray diffraction. Rietveld analyses have been used to evaluate the structural modifications. The transition temperature is related to the ionic radius and the hydration enthalpy of the halide. As one goes from heavy to light halide, there is a strengthening of the water to halide hydrogen bonds that favours the LT-polymorph (with four short halide-to-water bonds) at the expense of the HT-polymorph (with six larger halide-to-water bonds) implying an increase of the transition temperature. The study has been enlarged to the analogous iodide compound.
G. Renaudin, J.-P. Rapin, E. Elkaim, M. François, Cement and Concrete Research 34 (2004) 1845-1852

A1164 – Adsorption of carbon dioxide by X zeolites exchanged with Ni2+ and Cr3+: isotherms and isosteric heat

The adsorption of CO2, at intervals of 30 K from 303 K was carried out on Mn+X zeolites (Mn+ = Ni2+ or Cr3+) exchanged at different degrees. The structural regularity of the zeolite lattice of NaX and the existence of well-defined cavities within which the adsorbate molecules are lodged suggest that it should be possible to use various isotherm equations. Several models were thus used to describe the experimental isotherms. The best fit of adsorption isotherm data is obtained with the Sips model. The Volmer model also describes satisfactorily the isotherms of CO2 adsorption by NaX, Ni(x)X, and Cr(x)X. Analysis of the isosteric heat reveals a character energetically heterogeneous for NaX and Ni(x)X samples exchanged at a higher degree of Ni2+ exchange and at low coverage. Specific interaction is also obtained between the adsorbate molecules and Cr(x)X exchanged at a lower degree. From these considerations, hypotheses will be advanced to describe the behavior of the adsorbed phase within zeolitic cavities.
A. Khelifa, L. Benchehida, Z. Derriche, Journal of Colloid and Interface Science 278 (2004) 9-17

A1166 – Synthesis, structure, and characterization of hybrid materials: [Ce(H2O)]2[O2C(CH2)2CO2]3 and [Sm(H2O)]2[O2C(CH2)2CO2]3 . H2O

The rare-earth dicarboxylate hybrid materials [Ce(H2O)]2[O2C(CH2)2CO2]3 ([Ce(Suc)]) and [Sm(H2O)]2[O2C(CH2)2CO2]3.H2O ([Sm(Suc)]) have been hydrothermally synthesized (200°C, 3 days) under autogenus pressure. [Ce(Suc)] is triclinic, a=7.961 (3)Å , b=8.176 (5)Å , c=14.32 (2)Å , alpha = 97.07° (7), beta = 96.75° (8), gamma = 103.73° (6), and z = 2. The crystal structure of this compound has been determined using 3120 unique single crystal data. The final refinements let the agreement factors R1 and wR2(F2) converge to 0.0138 and 0.0363, respectively. [Ce(Suc)] is built up from infinite chains of edge-sharing nine-fold coordinated cerium atoms running along [100]. These chains are interconnected by the carbon atoms of the succinate anions, leading to a three-dimensional hybrid framework. The cell constants of [Sm(Suc)], isotypic with monoclinic C2=c [Pr(H2O)]2[O2C(CH2)2CO2]3 . H2O ([Pr(Suc)]), were refined starting from X-ray powder data: a=20.275 (3)Å , b=7.919 (6) Å , c=14.130 (3) Å , and beta = 121.45° (1). Despite its lower symmetry, [Ce(Suc)] presents an important structural filiation with [Sm(Suc)]
A. Seguatni, M. Fakhfakh, M.J. Vauley, and N. Jouini, Journal of Solid State Chemistry 177 (2004) 3402-3410

A1165 – Seed-mediated synthesis of uniform ZnO nanorods in the presence of polyethylene glycol

Large quantities of ZnO nanorods have been synthesized by the seed-mediated method in the presence of polyethylene glycol at 90°C. The products are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The as-grown ZnO nanorods are uniform with a diameter of 40-70nm and length about 2 mm. The nanorods grew along the [0 0 1] direction. Possible roles of ZnO seeds and polymer in the growth of ZnO nanorods are also discussed.
X.M. Liu, Y.C. Zhou, Journal of Crystal Growth 270 (2004) 527-534

A1167 – Synthesis and optical absorption property of the Zn2TixSn(1-x)O4 (0

Zn2TixSn(1-x)O4 (0
C. Wang and B-Q. Xu, Journal of Solid State Chemistry 177 (2004) 3448-3453

A1169 – Multianvil high-pressure/high-temperature preparation, crystal structure, and properties of the new oxoborates Dy4B6O14(OH)2 and Ho4B6O14(OH)2

This paper reports about two new hydrogen-containing rare-earth oxoborates RE4B6O14(OH)2 (RE=Dy, Ho) synthesized under high-pressure/high-temperature conditions from the corresponding rare-earth oxides, boron oxide, and water using a Walker-type multianvil equipment at 8 GPa and 880°C. The single crystal structure determination of Dy4B6O14(OH)2 showed: Pbcn, a = 1292.7(2), b = 437.1(2), c = 887.3(2) pm, Z = 2, R1 = 0.0190, and wR2 = 0.0349 (all data). The isotypic holmium species revealed: Pbcn, a = 1292.8(2), b = 436.2(2), c = 887.1(2) pm, Z = 2, R1 = 0.0206, and wR2 = 0.0406 (all data). The compounds exhibit a new type of structure, which is built up from layers of condensed BO4-tetrahedra. Between the layers, the rare-earth cations are coordinated by 7+2 oxygen atoms. Furthermore, we report about temperature-resolved in situ powder diffraction measurements, DTA/TG, and IR-spectroscopic investigations into RE4B6O14(OH)2 (RE=Dy, Ho).
H. Huppertz, Journal of Solid State Chemistry 177 (2004) 3700-3708

A1168 – Diluted magnetic interactions in an oxygen-deficient perovskite cobaltite: magnetoresistance in the series SrCo(1-x)ScxO(3-d) (0

A series of the oxygen-deficient perovskite SrCo(1-x)ScxO(3-d) has been successfully prepared by using close ampoules for compositions in the range 0.05
A. Maignan, D. Pelloquin, D. Flahaut, V. Caignaert, Journal of Solid State Chemistry 177 (2004) 3693-3699

A1171 – Oxidation behaviour of a MoSi2-based composite in different atmospheres in the low temperature range (400-550°C)

The oxidation characteristics of a MoSi2-based composite within the temperature range of 400-550°C were investigated. The effects of temperature and water vapour on oxidation were examined. The oxidation kinetics were studied using a thermobalance, while the morphology and composition of the oxides were examined using XRD, ESEM/EDX, and SEM/EDX. The peak oxidation rates in dry O2 and O2 + 10%H2O were found to occur at temperatures of approximately 510 and 470°C, respectively. Within the temperature range of accelerated oxidation (400-500°C), the oxidation rate in O2 + 10%H2O was substantially higher than that in dry O2. At higher temperatures, the oxidation rate decreased, and the magnitude of the decrease was steeper and occurred at a lower temperature for O2 +10%H2O (510°C) than for O2 (550°C). Furthermore, the rate of depletion of molybdenum (Mo) from the oxide scales during oxidation increased with increasing temperature and water vapour content. It appears that Mo loss is a key process influencing the protective properties of the oxide layer on the MoSi2 composite. A potential mechanism for the different oxidation behaviours in O2 and O2 + 10%H2O is proposed.
K. Hansson, M. Halvarsson, J. E. Tang, R. Pompe, M. Sundbergd, J-E. Svensson, Journal of the European Ceramic Society 24 (2004) 3559-3573

A1170 – Mu-28: an open-framework fluorogallophosphate with a three-dimensional 12-membered ring channel system

A new three-dimensional (3-D) microporous fluorogallophosphate, named Mu-28, was obtained by hydrothermal synthesis. It was obtained in the presence of fluoride ions with 1,4-dimethylpiperazine as organic template. This new fluorogallophosphate, with chemical formula [Ga20P20O80(OH)6F6(H2O)4(C6H16N2)6] 8H2O, crystallizes in the monoclinic system space group P21 with the following unit cell parameters: a = 13.23(1) Å, b = 15.40(1) Å, c = 14.80(1) Å, beta = 95.10(9)° (Z = 1, R1 = 0.0435 [I>2?(I)]). Its structure was determined by single-crystal X-ray diffraction with the helpof 31P NMR spectroscopy. Mu-28 consists of a complex arrangement of GaO3(OH,F)(H2O)2, GaO4(OH)F and GaO4(OH)2 octahedra, GaO4F trigonal bipyramids and GaO3(OH,F) and PO4 tetrahedra. It displays a 3-D channel system delimited by 12-membered ring openings.
L. Josien, A. Simon-Masseron, V. Gramlich, F. Porcher, J. Patarin, Journal of Solid State Chemistry 177 (2004) 3721-3728

A1172 – Effect of maltose for the crystallization of tetragonal zirconia

A new method was used to prepare the tetragonal zirconia and high temperature X-ray powder diffraction (XRD) and thermo gravimetry and differential scanning calorimetry (TG-DSC) were employed to study the process of the formation and variation of crystal zirconia. The high temperature XRD results showed that [Nature 258 (1975) 703] during the formation of zirconia from zirconium hydroxide, the addition of maltose favored the phase transformation of zirconia from amorphous to tetragonal as the calcination temperature rises (from about 400 to 550°C), and then monoclinic zirconia gradually formed as the temperature increases (from about 550 to 846°C), [Appl. Catal. 71 (1991) 363] tetragonal zirconia would partly transform into monoclinic one during the annealing, and which implies that the suitable calcinations temperature for the preparation of tetragonal zirconia should be controlled lower than 550°C. In addition, it is suggested that the combination of high temperature XRD and TG-DSC is a powerful tool to approach the process of the formation of solid materials.
H-Y. Zhu, B. Liu, M-M. Shen, Y. Kong, X. Hong, Y-H. Hu, W-P. Ding, L. Dong, Y. Chen, Materials Letters 58 (2004) 3107-3110

A1174 – Defect chemical analysis of the electronic conductivity of strontium-substituted lanthanum ferrite

The electronic conductivity of La0.4Sr0.6FeO(3-d) is studied in the oxygen partial pressure range 10^(-5)300°C) which are in agreement with isobaric activation energies of the electronic conductivity at low temperatures (T<300°C).
E. Bucher, W. Sitte, Solid State Ionics 173 (2004) 23-28

A1173 – Oxygen isotopic effect on the IR reflectivity spectra of a La2NiO4.14 single crystal

Infrared reflectivity spectra measurements have been realised at T = 300 K on the oxygen-isotope exchanged single crystals (16O and 18O) of La2NiO(4+d) with d = 0.14. One of the main results lies on transfer of the spectral weight from the mid-infrared spectral range to the far-infrared range upon 18O substitution. This striking effect is studied in the framework of the harmonic oscillator concept by simulating the experimental data with a dielectric function model based on the generalisation of the Lyddane-Sachs-Teller relationship. It suggests that the lattice strongly influences the behaviour of the charge carriers in such 3d transition metal oxides.
B. Rousseau, J.M. Bassat, A. Blin, M. Silva de Oliveira, P. Odier, C. Marin, P. Simon, Solid State Sciences 6 (2004) 1131-1137

A1176 – Deposition of yttrium-based thin films on TA6V alloy substrates

Cathodic electrodeposition of yttrium containing thin films was realised on TA6V substrates from a Y(NO3)3 solution. Experimental conditions to obtain homogeneous and crack free thin films were determined. Subsequent thermal treatment led to an Y2O3 coating, expected to provide an increase of TA6Voxidation resistance at high temperatures. The steps occurring during the thermal treatment leading to Y2O3 were also investigated.
R. Siab, G. Bonnet, J.M. Brossard, J.F. Dinhut, Applied Surface Science 236 (2004) 50-56

A1175 – Evolution of several Ni and Ni-MgO catalysts during the hydrogenation reaction of adiponitrile

The changes of the surface properties of two bulk Ni (one commercial Raney-Ni and one prepared crystalline Ni) and two Ni-MgO catalysts were studied after the hydrogenation of adiponitrile in the gas phase at atmospheric pressure for 216 h at two different reaction conditions. Catalysts before and after the catalytic reaction were characterized by different techniques. Raney-Ni and Ni-MgO catalysts show an evolution of activity with the reaction time until reaching constant conversion and selectivity values. The metallic area decreases after reaction for all catalysts. Interestingly, this decrease is lower and the surface area slightly increases when using reaction conditions of high space velocity, which favour the desorption of condensation products and results in a certain disagglomeration of particles. The high hydrogenation ability of Raney-Ni and the basicity of Ni-MgO catalysts allow them to achieve much higher conversions than the bulk Ni catalyst prepared. The presence of defined octahedral particles, observed for the crystalline Ni and Ni-MgO catalysts by SEM, has been related to the constant high value of selectivity to 6-aminohexanenitrile (around 80%) maintained after 216 h of reaction at less hydrogenating conditions.
M. Serra, P. Salagre, Y. Cesteros, F. Medina, J.E. Sueiras, Applied Catalysis A: General 272 (2004) 353-362

A1178 – Synthesis of uniform diameter single wall carbon nanotubes in Co-MCM-41: effects of CO pressure and reaction time

The influence of the CO pressure and of the duration of catalyst exposure to CO was systematically investigated with respect to the carbon yield, selectivity, and diameter uniformity of single wall carbon nanotubes (SWNT) produced by CO disproportionation over Co-MCM-41 catalysts. The SWNT were characterized by Raman and near infrared (NIR) spectroscopy, while the state of the catalyst and the size of the metallic cobalt clusters were investigated by X-ray absorption spectroscopy (XAS). The experimental results suggest that both the selectivity to SWNT and the uniformity of their diameters are controlled by the relative rates of the following competing processes: cobalt reduction, nucleation of cobalt into clusters, and SWNT growth. It was found that reaction at low CO pressures leads to a wider distribution of diameters and lower SWNT selectivity. The duration of catalyst exposure to CO was found to strongly affect the SWNT selectivity at the early stages of SWNT growth, while it has a minor effect on the SWNT diameter uniformity.
Y. Chen, D. Ciuparu, S. Lim, Y. Yang, G.L. Haller, L. Pfefferle, Journal of Catalysis 226 (2004) 351-362

A1177 – High-temperature oxidation kinetics of NiAl single crystal and oxide spallation as a function of crystallographic orientation

Isothermal and cyclic high-temperature oxidation of NiAl single crystal samples are presented. Oxidations have been carried out at 900, 1050, 1100 and 1150°C on (1 0 0) and (1 1 0) oriented surface. Continuous thermogravimetry in cyclic conditions allows isothermal oxidation kinetics and spalling at each cycle to be followed. Oxidation kinetics are compared between (1 0 0) surface and (1 1 0) surface. (1 0 0) oriented surfaces appeared to oxidize slightly faster than (1 1 0) oriented surfaces. Experimental results of cyclic oxidation are compared to simulated results using a previously published statistical model. Spalling increases when the average oxide scale thickness increases with the number of cycles. Longer tests are necessary to study this evolution during the 'steady-state' but no critical oxide thickness was found.
D. Poquillon, D. Oquab, B. Viguier, F. Sénocq, D. Monceau, Materials Science and Engineering A 381 (2004) 237-248

A1180 – Thermal analysis of oxidised coals

The study has been performed on samples of high sulphur content Spanish brown coal Mequinenza and Polish flame coal Czeczot. The samples of raw coals and the coals oxidised by four different oxidising agents have been subjected to derivative thermogravimetry analysis (DTG). The results have shown that demineralisation has no effect on the temperature range of the maximum mass loss. The Czeczot flame coal has been shown to be characterised by a narrower temperature range of the main devolatilisation peak (380-500°C) than that of Mequinenza (320-500°C). The most pronounced structural changes in coal have been found to occur as a result of its oxidation by 5% nitric acid. After such a process of oxidation a new peak of devolatilisation appears with a maximum at 265°C, which can be assigned to the compounds having nitric groups in their structure.
R. Pietrzak, H. Wachowska, Thermochimica Acta 419 (2004) 247-251

A1179 – Synthesis and calorimetric study of rare earth complexes [RE(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3 (RE: Sm, Eu, Dy, Er)

The crystals of four complexes of rare earth perchlorate with DL-alpha-alanine and imidazole were synthesized and characterized. The components of them were determined to be [RE(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3 (RE: Sm, Eu, Dy, Er) by FT-IR, chemical, elemental and thermal analysis. The enthalpies of dissolution of [2C3H7NO2(s) + 3NaClO4(s)], [C3H4N2(s) + RECl3.6H2O(s)] and [3NaCl(s)], {[RE(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s)} were determined by a solution-reaction isoperibol calorimeter at T = 298.15 K, respectively. According to Hess's law, the standard molar enthalpies of reaction of four reactions, RECl3.6H2O(s)+ 2C3H7NO2(s)+ C3H4N2(s)+ 3NaCl(s) = [RE(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s) + 3NaCl(s) + 5H2O(l) (RE: Sm, Eu, Dy, Er) were determined to be 4.87 ± 0.20, 7.23 ± 0.19, 0.96 ± 0.27 and 12.88 ± 0.32 kJ mol-1, respectively. The standard molar enthalpies of formation of the four complexes at T = 298.15 K, ?fHm° {[Re(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3(s)} (RE: Sm, Eu, Dy, Er), were determined to be -(2448.1 ± 3.3), -(2360.3 ± 3.3), -(2451.8 ± 3.3) and -(2444.3 ± 3.3) kJ mol-1, respectively.
Y-M. Dan, H-G. Yu, Q. Long, A-X. Hou, Y. Liu, S-S. Qu, Thermochimica Acta 419 (2004) 169-172

A1181 – Effect of heat treatment on material characteristics and pseudo-capacitive properties of manganese oxide prepared by anodic deposition

Hydrous manganese oxide with amorphous structure is prepared by anodic deposition in manganese acetate solution. The effect of heat treatment (100-700°C) on the material characteristics of the oxides is investigated. The thermal property of the deposited oxide is examined by thermogravimetric and differential thermal analyses. Dehydration, organic-matter decomposition, oxidation and crystallization of the manganese oxide as a function of temperature are examined. Glancing angle X-ray diffraction, scanning electron microscope and X-ray photoelectron spectroscopy are carried out to explore, respectively, the crystal structure, surface morphology and chemical state of the oxide electrodes. It is found that the as-deposited manganese oxide, with an amorphous structure and fibrous feature, is further oxidized and tends to tangle with increasing annealing temperature (below 500°C). When the temperature uses above 500°C, the formation of crystalline oxide is confirmed. Cyclic voltammetry is also performed to evaluate the electrochemical performance of the oxide electrodes annealed at various temperatures. Excellent pseudo-capacitive behaviour of the oxide electrodes is revealed at a low annealing temperature (<200°C). The cyclic stability of the deposited manganese oxide is significantly improved by introducing proper heat treatment.
J-K. Chang, Y-L. Chen, W-T. Tsai, Journal of Power Sources 135 (2004) 344-353

A1182 – Effects of calcination temperature on performance of Cu-Zn-Al catalyst for synthesizing gamma-butyrolactone and 2-methylfuran through the coupling of dehydrogenation and hydrogenation

The results of the coupling process over Cu-Zn-Al catalysts show that the different calcination temperature has significant effect on catalytic performance. Lower temperature cannot facilitate the precursor to complete decomposition and higher calcination temperature will decline the surface area of the catalyst, which finally decline the yield for desired products. It is worth mentioning that the specific activities for BDO and furfural conversions are improved at high calcination temperature, but the simultaneous loss of surface area offsets the gain in specific activity and finally causes the decline in the overall activity of catalyst. In contrast to this, the specific activities for 2-methylfuran and tetrahydrofuran formation dramatically decrease when the calcination temperature reaches 750°C. This strongly indicates that the active sites of the catalyst for 2-methylfuran and tetrahydrofuran formation were significantly destroyed at calcination temperature higher than 750°C, and these sites are different from those for gamma-butyrolactone and furfuryl alcohol formation.
J. Yang, H-Y. Zheng, Y-L. Zhu, G-W. Zhao, C-H. Zhang, B-T. Teng, H-W. Xiang, Y. Li, Catalysis Communications 5 (2004) 505-510

A1184 – Oxidation treatments for SiC particles used as reinforcement in aluminium matrix composites

The present research is centred on the application of oxidation treatments to SiC particles to improve the casting processability of Al-SiC composites by means of a chemical interface control. If a continuous SiO2 layer is generated on the particle surface, the reinforcement particles can be incorporated in a molten aluminium matrix, and the degrading reaction of Al4C3 formation is replaced by other interfacial reactions which improve wettability, avoid particle consumption and increase interface strength. This work presents an optimisation study of the oxidation treatment conditions for SiC particles to obtain continuous adherent coatings which act as active barriers. The influence of particle sizes and treatment temperatures on the oxidation kinetics and barrier structure were evaluated. The capability of the protective barriers developed in the interfacial control was analysed by means of reactivity tests with molten aluminium, in comparison with unprotected particles. Both effects on local reactivity and mechanical interface properties were studied.
A. Urena, E.E. Martinez b, P. Rodrigo, L. Gil, Composites Science and Technology 64 (2004) 1843-1854

A1183 – Surfactant mediated nanoparticle assembly of catalytic mesoporous crystalline iron oxide materials

The first examples of a new mesoporous form of crystalline beta-FeOOH (akaganeite) were prepared by the surfactant-assisted method of nanoparticle assembly using FeCl3 as the precursor and a surfactant of either cationic cetylpyridinium or anionic dodecylsulfonate or nonionic Brij 56 as a hierarchical structure mediator. TEM images indicated the presence of a scaffold-like structure formed through the aggregation and intergrowth of rod-like akaganeite nanoparticles. The synthesized mesoporous akaganeite has a unimodal and very narrow pore size distribution with high surface area, which can be converted to mesostructured alpha-Fe2O3 (hematite) after degassing at 300°C. Bimodal pore size distributions could be obtained by increasing the synthetic temperature from 40 to 80°C. Mesoporous iron oxides with bicrystalline structure of akaganeite and hydronium jarosite were prepared when using dodecylsulfonate surfactant at 80°C. The surfactants were believed to play an important role in the formation of the hierarchical scaffold-like mesostructure.
Z-Y. Yuan, T-Z. Ren, B-L. Su, Catalysis Today 93-95 (2004) 743-750

A1185 – Influence of nitridation on the oxidation of a 304 steel at 800°C

This paper presents a study on the oxide growth on a AISI 304 chromia-forming alloy, in air at 800°C. After the nitridation treatment was performed on the steel surface, a gammaN solid solution is detected. In this case, no nitride formation in the alloy surface could be observed. In situ X-ray diffraction has been used to follow the oxides evolution at testing temperature. At the beginning of the oxidation test, CrN is formed together with Fe2O3. Nevertheless, Cr2O3 quickly appears and leads to a protective oxide scale formation growing according to a parabolic rate law. During oxidation in situ X-ray diffraction also shows that Fe2O3 is transformed into FeCr2O4. Our results show that nitridation increases the high temperature oxidation resistance of 304 steels at 800°C.
C. Issartel, H. Buscail, E. Caudron, R. Cueff, F. Riffard, S. Perrier, P. Jacquet, M. Lambertin, Corrosion Science 46 (2004) 2191-2201

A1188 – Effect of ZrO2 additions on sintering of SnO2-based ceramics

The effect of zirconia additions on sintering of CoO doped tin dioxide has been investigated in the temperature range 1100- 1250°C. A first study showed that the substitution of tin by zirconium reduces significantly the volatilisation rate of SnO2 for temperatures greater than 1400°C. It appeared that the zirconium content increase inhibits the densification kinetics of SnO2-based ceramics. Indeed, the relative density did not exceed 93% for a Zr content lower than 6 mol% in the Sn(1-x)ZrxO2 solid solution. This negative effect can be imputed to the elastic distortions caused by the introduction of Zr in the tin dioxide lattice. So, the diffusion rate of point defects such as oxygen or cobalt ions is lowered.
A. Maître, D. Beyssen, R. Podor, Journal of the European Ceramic Society 24 (2004) 3111--3118

A1187 – Solid state reactions of CeO2, PuO2, (U,Ce)O2 and (U,Pu)O2 with K2S2O8

Solid state reactions of CeO2, PuO2 and mixed oxides (U,Ce)O2 and (U,Pu)O2 containing different mol.% of Ce and Pu, were carried out with K2S2O8 at different temperatures to identify the formation of various products and to investigate their dissolution behaviour. X-ray, chemical and thermal analysis methods were used to characterise the products formed at various temperatures. The products obtained by heating two moles of K2S2O8 with one mole each of CeO2, PuO2, (U,Ce)O2 and (U,Pu)O2 at 400°C were identified as K4Ce(SO4)4, K4Pu(SO4)4, K4(U,Ce)(SO4)4 and K4(U,Pu)(SO4)4, respectively. K4Ce(SO4)4 further decomposed to form K4Ce(SO4)3.5 at 600°C and mixture of K2SO4 and CeO2 at 950°C. Thus the products formed during the reaction of 2K2S2O8 + CeO2 show that cerium undergoes changes in oxidation state from +4 to +3 and again to +4. XRD data of K4Ce(SO4)4 and K4Ce(SO4)3.5 were indexed on triclinic and monoclinic system, respectively. PuO2 + 2K2S2O8 reacts at 400°C to form K4Pu(SO4)4 which was stable upto 750°C and further decomposes to form K2SO4 + PuO2 at 1000°C. The products formed at 400°C during the reactions of the oxides and mixed oxides were found to be readily soluble in 1-2 M HNO3.
Meera Keskar, U.M. Kasar, K.D. Singh Mudher, V. Venugopal, Journal of Nuclear Materials 334 (2004) 207-213

A1186 – Chitosan kills bacteria through cell membrane damage

The bactericidal activity of chitosan (CS) acetate solution against Escherichia coli and Staphylococcus aureus was evaluated by the enumeration of viable organisms at different incubation times. Morphologies of bacteria treated with CS were observed by transmission electron microscopy (TEM). The integrity of the cell membranes of both species and the permeabilities of the outer membrane (OM) and inner membrane (IM) of E. coli were investigated by determining the release from cells of materials that absorb at 260 nm, changes in the fluorescence of cells treated with the fluorescent probe 1-N-phenylnaphthylamine (NPN) and release of cytoplasmic beta-galactosidase activity. In addition, the interaction of CS with synthetic phospholipid membranes was studied using gel permeation chromatography (GPC), UV-VIS spectrophotometery, Fourier-transform infrared spectroscopy (FT-IR) and thermal analysis. Results showed that CS increased the permeability of the OM and IM and ultimately disrupted bacterial cell membranes, with the release of cellular contents. This damage was likely caused by the electrostatic interaction between NH3 + groups of CS acetate and phosphoryl groups of phospholipid components of cell membranes.
H. Liu, Y. Du, X. Wang, L. Sun, International Journal of Food Microbiology 95 (2004) 147-155

A1190 – Preparation of spherical zirconia powder in microemulsion system and its densification behavior

The water droplets in the microemulsion system of cyclohexane/water/TritonX-100/hexyl alcohol can act as the nano-reactors which solubilize zirconium oxychloride and ammonia separately. The precipitation reactions will take place in the confined spaces determined by the droplets size. The minute original reactors help us obtain nano-size spherical zirconia amorphous powder with uniform diameter distribution and weak aggregate. Such powder begins to crystallize at the temperature about 475°C, and its shrinkage of densification will be elementarily finished from 1080 to 1280°C. The powder is formed by dry pressing process. The 99% relative density and 100% tetragonal phase can be obtained when the green body is sintered at 1400°C for 2 h.
T. Ma, Y. Huang, J. Yang, J. He, L. Zhao, Materials and Design 25 (2004) 515-519

A1189 – Incorporation of granite cutting sludge in industrial porcelain tile formulations

Granite wastes in the form of sludge, obtained from granite cutting industry, were incorporated in the batch formulations of porcelain tiles. The maximum possible substitution of sludge for feldspar was investigated. Samples of different formulations, in the form of pellets or extruded bars, were produced at both laboratory and pilot-plant scales and characterized throughout all the stages of the production process. The experimental results and their theoretical interpretation show that suitable incorporation of granite sludge can result in porcelain tiles with superior properties, in terms of water absorption (0.07%) and bending strength (>50 MPa). Sludge incorporation had negligible effect on density, shrinkage and plasticity during all stages of tile-production process, anticipating no modifications in the industrial production line.
P. Torres, H.R. Fernandes, S. Agathopoulos, D.U. Tulyaganov, J.M.F. Ferreira, Journal of the European Ceramic Society 24 (2004) 3177-3185

A1192 – Synthesis of nanocrystalline zirconia by amorphous citrate route: structural and thermal (HTXRD) studies

Nanocrystalline zirconia powder with a fairly narrow particle size distribution has been synthesized by the amorphous citrate route. The sample obtained has a high BET surface area of 89 m2 g-1. Rietveld refinement of the powder X-ray diffraction (XRD) profile of the zirconia sample confirms stabilization of zirconia in the tetragonal phase with around 8% monoclinic impurity. The data show the presence of both anionic as well as cationic vacancies in the lattice. Crystallite size determined from XRD is 8 nm and is in close agreement with the particle size determined by TEM. The in situ high temperature-X-ray diffraction (HTXRD) study revealed high thermal stability of the mixture till around 1023 K after which the transformation of tetragonal phase into the monoclinic phase has been seen as a function of temperature till 1473 K. This transformation is accompanied by an increase in the crystallite size of the sample from 8 to 55 nm. The thermal expansion coefficients are 9.14 x 10^(-6) K-1 along 'a'- and 15.8 x 10^(-6) K-1 along 'c'-axis. The lattice thermal expansion coefficient in the temperature range 298-1623 K is 34.6 x 10^(-6) K-1.
M. Bhagwat, V. Ramaswamy, Materials Research Bulletin 39 (2004) 1627-1640

A1191 – Thermal decomposition of the methoxide complexes MoO(OMe)4, Re4O6(OMe)12 and (Re(1-x)Mox)O6(OMe)12 (0.24 < x < 0.55)

The thermal decomposition of the methoxide complexesMoO(OMe)4 (I), Re4O6(OMe)12 (II) and (Re(1-x)Mox)O6(OMe)12 (0.24 < x < 0.55) (III) in hydrogen and nitrogen at T < 800°C and in air at temperatures T < 400°C have been monitored by thermal analysis, X-ray powder diffraction and scanning electron microscopy. Heating of I, II and III in air yields orthorhombic MoO3, ReO3 and amixture of these two phases, respectively. Thermal treatment of I and II in nitrogen, using heating rates of 20Kmin-1 or faster, yields the same products as in air, while applying slower heating rates of I and thermal treatment of III in nitrogen yield the tetragonal modification of MoO2 and (Re(1-x)Mox)O2 (with 0.24 < x < 0.55), respectively. Heat treatment of I, II and III in hydrogen yields fine powders of Mo, Re or a Re-Mo alloy (having the structure of the sigma-phase) at surprisingly low temperatures, around 520, 240 and 360°C for I, II and III, respectively.
G.A. Seisenbaeva, M. Sundberg, M. Nygren, L. Dubrovinsky, V.G. Kessler, Materials Chemistry and Physics 87 (2004) 142-148

A1193 – Adsorption of concanavalin A on the well-characterized macroporous chitosan and chitin membranes

Macroporous chitosan membranes were prepared by solvent evaporation method in the presence of silica particles which were used as a porogen. These membranes were cross-linked under alkaline conditions, using epichlorohydrin as the cross-linking agent. The macroporous chitin membranes were obtained by acetylating the chitosan membranes with acetic anhydride in methanol. SEM photographs showed a homogeneous pore distribution throughout the membranes with 16.1-17.9 µm average pore sizes. The adsorption and desorption properties of concanavalin A (Con A) on the membranes were investigated by fluorescence spectroscopy. The equilibrium adsorption time was found to be 2 h during the static adsorption experiments. The calculated adsorption rates for chitosan and chitin membranes were rad = 0.613 and 0.541 mg Con A/g dry membrane-minute, respectively at the initial protein concentration of 1.0 mg ml-1. The adsorption isotherms represented a monolayer of Con A at 0.5-2.0 mg ml-1 concentration range. The adsorption studies which were carried out at flow rate of 2 ml min-1 showed that adsorbed quantities of Con A decreased markedly in the presence of flow, and they were similar ( 14-15 mg Con A/g dry membrane) for both chitosan and chitin membranes. The fluorescence studies verified the absence of denaturation in the recovered Con A.
M. Gümüsderelioglu, P. Agi, Reactive & Functional Polymers 61 (2004) 211-220

A1195 – Online evolved gas analyses (EGA by TG-FTIR and TG/DTA-MS) and solid state (FTIR, XRD) studies on thermal decomposition and partial reduction of ammonium paratungstate tetrahydrate

Ammonium paratungstate tetrahydrate (NH4)10[H2W12O42].4H2O (APT), a starting material in powder metallurgy of tungsten, has been subjected to a complex thermoanalytical study. The weight loss stages and the various heat effects have been followed by simultaneous thermogravimetry and differential thermal analysis (TG/DTA) in flowing 10% H2/Ar and 10% H2/He atmospheres up to 600°C. Meanwhile evolution of gaseous products has also been analyzed and monitored by both on-line coupled mass spectrometer (TG/DTA-MS) and infrared gas cell (TG-FTIR). In atmospheres containing 10% H2, the evolution courses of H2O and NH3 traced by these EGA-methods and the TG/DTA curves up to 380°C have been found quite similar to those of measured in air or in pure He. Effect of the reductive medium occurred above 380°C, where solid products of intermediate temperatures have been structurally evaluated by both FTIR spectroscopy and powder X-ray diffraction (XRD). Based on significant changes in XRD patterns, the only small exothermic heat effect observed at 420-440°C is assigned to the crystallization heat of a mixture of partially reduced tungsten oxide bronzes.
I.M. Szilagyi, J. Madarasz, F. Hange, G. Pokol, Solid State Ionics 172 (2004) 583-586

A1194 – Synthesis, crystal structures and properties of the bis-(trimetaphosphimato)-metallates Na4{Co[(PO2NH)3]2}.12H2O and Na4{Ni[(PO2NH)3]2}.12H2O

Tetrasodium-bis-(trimetaphosphimato)-cobaltate(II) dodecahydrate, Na4{Co[(PO2NH)3]2}.12H2O (1), and tetrasodium-bis-(trimetaphosphimato)- nickelate(II) dodecahydrate, Na4{Ni[(PO2NH)3]2}.12H2O (2), were obtained by the stoichiometric reaction of an aqueous solution of Na3(PO2NH)3.4H2O with the respective metal nitrate or halide. The structures of 1 and 2 were found to be isomorphous and were solved by single-crystal X-ray methods (1a: C2/c, a = 888.9(1) pm, b = 1901.8(2) pm, c = 1711.2(2) pm, beta = 104.59(1)°, Z = 4; 2a: C2/c, a = 894.4(1) pm, b = 1890.6(1) pm, c = 1723.6(1) pm, beta = 104.49(1)°, Z = 4). At low temperature a reversible phase transition occurs and the symmetry of the structure changes from C2/c to P21/n (1b: P21/n, a = 887.1(2) pm, b = 1900.1(4) pm, c = 1707.2(3) pm, beta = 104.59(2)°, Z = 4; 2b: P21/n, a = 890.3(1) pm, b = 1890.2(2) pm, c = 1713.3(2) pm, beta = 104.62(1)°, Z = 4). The phase transition is caused by a structural ordering of Na+ and H2O at low temperature. The P3N3 rings of the trimetaphosphimate ions exhibit a chair conformation. The trimetaphosphimate ions act as tridentate ligands. Thus, anionic complexes {M[(PO2NH)3]2}4- (M = Co, Ni) are formed. These structural elements are interconnected in the crystal by N-H...O and O-H...O hydrogen bonds and by coordination to Na+ forming a three-dimensional network. Upon heating, 1 and 2 loose their crystal water around 100°C and above 400°C new crystalline phases are formed, which have not been identified so far.
S. Correll, N. Stock, W. Schnick, Solid State Sciences 6 (2004) 953-965

A1196 – Benzene to phenol oxidation over iron exchanged zeolite ZSM-5

Zeolite ZSM-5 of different Si/Al ratio, templated and non-templated ones were modified with iron cations introduced by means of ionic exchange from aqueous solution and by solid state procedure. The modified samples calcined in the range of temperatures from 500 to 1000°C were applied for benzene to phenol hydroxylation. Interaction of benzene and N2O oxidant with Fe-ZSM-5 was searched by IR spectroscopy. The acidity of the samples was characterised by means of activity for cumene cracking and by IR spectra of adsorbed pyridine. Some correlations between oxidative activity, rate of deactivation and acidity of iron modified zeolites ZSM-5 were discussed.
A. Waclaw, K. Nowinska, W. Schwieger, Applied Catalysis A: General 270 (2004) 151-156

A1197 – Enhanced solubilization and removal of naphthalene and phenanthrene by cyclodextrins from two contaminated soils

The development of innovative methods for cleaning contaminated soils has emerged as a significant environmental priority. Herein, are investigated the effectiveness of cyclodextrin (CD) to solubilize and to extract organic pollutants from soils. The interactions in the cyclodextrin/pollutant/soil system have been studied "step by step" using two kinds of polycyclic aromatic hydrocarbons (PAH), naphthalene (Nap) and phenanthrene (Phe), cyclodextrins and soils. Inclusion complex formation of PAH with beta-cyclodextrin ( beta-CD) and hydroxypropyl-beta-cyclodextrin (HPCD) has been investigated and was proposed as a way to facilitate the pollutant removal from soil. Little effect of ionic strengthwas observed on CD complex formation for both compounds. The solubility of PAHin 50 g L-1 of HPCD was enhanced 20- and 90-fold for naphthalene and phenanthrene, respectively. Batch experiments were performed to study the adsorption-desorption of two PAH on two soils and the influence of CDs over these processes. These experiments were also conducted with a mixture of two PAH. The batch desorption results indicate that removal capacity of HPCD was higher than that of beta-CD. Phenanthrene was strongly sorbed on soils, this led to low desorption rates compared to that of naphthalene, whatever the extracting agent used. When HPCD solution was used as a flushing agent, 80% of naphthalene and 64% of phenanthrene recovery from soil were observed. For both compounds, the slowest desorption rate was found for the soil that had the greatest content of organic matter. CD sorption on soils, was relatively low and depended on soil type. The soil organic matter (SOM) could favor the retention of both CD and pollutant involving the extraction rate to be decreased. A competitive hydrophobic interactions of pollutant between SOM and CD molecules, and co-sorption were expected to be the mechanism for the inhibited desorption.
T. Badr, K. Hanna, C. de Brauer, Journal of Hazardous Materials B112 (2004) 215-223

A1198 – Influence of the coordination on the catalytic properties of supported W catalysts

Zirconia supported Wcatalysts were prepared using anionic exchange from a peroxo-tungstate solution and zirconium hydroxides of high surface areas. These solids contain about 20 wt%W, and retain a surface area of about 120 m2/g after calcinations in air at 873 K, temperature at which their acidity is maximum. Raman spectroscopy shows the presence of tetrahedral W at low temperature, sintered to polytungstates by calcination at 873 K and WO3 at 973 K. These catalysts are active for the oxidation of dibenzothiophene by hydrogen peroxide. The solids containing tetrahedral W cations show higher activity than clusters of WO3. The reaction can be performed with good oxygen selectivity with H2O2 in 2-butanol as solvent, or in decane with tert-butylhydroperoxide as oxidizing agent. The catalysts can be recycled without loss of performances.
F. Figueras, J. Palomeque, S. Loridant, C. Fèche, N. Essayem, G. Gelbard, Journal of Catalysis 226 (2004) 25-31

A1199 – Characterization of Co,Al-MCM-41 and its activity in the t-butylation of phenol using isobutanol

Co,Al-MCM-41 catalysts with various nSi/(nCo+nAl) ratios were synthesized and extensively characterized by low-angle XRD, TGA/DTG, BET, AAS, DRIFT, UV-Vis DRS and ESR. UV-Vis DRS and ESR studies reveal that cobalt in Co,Al-MCM-41 is highly symmetrical and occurs in tetrahedral coordination. Some of the cobalt atoms are transformed into the cobalt oxide form when nSi/(nCo + nAl) is increased to 20. t-Butylation of phenol with isobutanol was studied in the vapor phase as a model reaction at temperatures between 200 and 500°C. The products obtained were O-tert-butyl phenol (OTBP), 2-tert-butyl phenol (2TBP) and 4-tert butyl phenol (4TBP). O-Butenyl phenol (OBP) and 2-butenyl phenol (2BP) were also observed along with normal alkylated products. The phenol conversion drastically increased with temperature over all the catalysts. The activity of the catalysts followed the order of Co,Al-MCM-41 (20) > Co,Al-MCM-41 (50) > Co,Al-MCM-41 (80) > Al-MCM-41 (23). The influences of various parameters such as temperature, reactant feed ratio and feed rate, time on stream on conversion and products selectivity were studied and the salient results are discussed.
M. Karthik, A.K. Tripathi, N.M. Gupta, A. Vinu, M. Hartmann, M. Palanichamy, V. Murugesan, Applied Catalysis A: General 268 (2004) 139-149

A1201 – Bi17Yb7O36 and BiYbO3: two new compounds from the Bi2O3-Yb2O3 equilibrium phase diagram determination

Synthesis and thermal behavior investigation of Bi(1-x)YbxO1.5 materials (0.166 < x < 0.666) have been realized, in order to obtain the low temperature equilibrium phases. A plot of the Bi2O3-Yb2O3 equilibrium phase diagram is proposed. Two new compounds, structurally related to the d-Bi2O3 variety, are evidenced. Bi17Yb7O36 (x = 0.292) crystallizes in an orthorhombic cell with a = 16.259(2), b = 10.705(1), c = 5.487(1) Å . It transforms into the cubic d-Bi2O3 type variety over 855°C. Only this cubic form, easily quenchable in a metastable form, was reported up to now as a composition of a delta solid solution domain (delta). A narrow domain of orthorhombic solid solution (epsilon) could exist (0.275 < x < 0.305). A second compound BiYbO3 crystallizes in a triclinic cell with a = 8.487(1), b = 8.419(1), c = 9.928(1) Å , alpha = 86.03(1), beta = 111.29(1), gamma = 74.25(1)°. At 970°C, a peritectoïd transformation into a mixture of d and Yb2O3-based solid solution (Yb2O3-s.s.) occurs; this latter disappears at about 1200°C. This last event is easily reversible on cooling, whereas the first one is very sluggish. Consequently, for the composition domain x > 0.35, the samples cooled from the high temperature are generally constituted of a mixture of d-type phase and Yb2O3-s.s.
M. Drache, P. Roussel, J.P. Wignacourt, P. Conflant, Materials Research Bulletin 39 (2004) 1393-1405

A1200 – Bioengineering polyfunctional copolymers. VII. Synthesis and characterization of copolymers of p-vinylphenyl boronic acid with maleic and citraconic anhydrides and their self-assembled macrobranched supramolecular architectures

New boron-containing anion active functional copolymers are synthesized by complex-radical copolymerization of 4-vinylphenyl boronic acid and maleic or citraconic anhydrides with 2,2'-azobisisobutyronitrile as an initiator in DMF at 70°C under nitrogen atmosphere. Macrobranched derivatives of these copolymers are synthesized by the partial grafting with alpha-hydroxy,omega-methoxy-poly(ethylene oxide) and incorporation with poly(ethylene imine). Effect of H-bonding on the formation of self-assembled supramolecular macrocomplexes with higher crystallinity and thermal stability was observed and confirmed by FTIR, and 1H(13C DEPT-135( NMR spectroscopy, X-ray diffraction, DSC and TGA analyses of monomer, homopolymer, copolymer and grafted copolymer systems. Observed water solubility, biocompatibility and high density of acid groups in macromolecules allow these anion active B-containing copolymer systems for the developing new generation of effective antitumor agents, polymeric carriers for enzymes, gene delivery and boron neutron capture therapy.
G. Kahraman, O. Beskardes, Z.M.O. Rzaev, E. Piskin, Polymer 45 (2004) 5813-5828

A1202 – Kinetics of the pyrolysis and combustion of olive oil solid waste

The pyrolysis and combustion of solid residues from olive oil processing were studied by dynamic TG-DTG at heating rates between 5 and 20°Cmin-1 at atmospheric pressure. Two different atmospheres were used: on the one hand, an inert atmosphere (He) in order to study the pyrolysis of the material, and on the other hand an oxidative atmosphere (He:O2 in different ratios) to study its combustion. Pyrolysis follows a two parallel and independent fractions model, with kinetic parameters typical of holocelulose (12%) and lignin (48%). Combustion adds a third reaction to the model, which is cocurrent, due to the combustion does not start until the main devolatilization is finished, attaining kinetic parameters and reaction orders typical of a gasification reaction.
J. Jauhiainen, J.A. Conesa, R. Font, I. Martin-Gullon, J. Anal. Appl. Pyrolysis 72 (2004) 9-15

A1204 – LiIO3/SiO2 nanocomposite for quadratic non-linear optical applications

The present paper presents our work consisting of 'doping' SiO2 sol-gel matrices with 5-30% mass of LiIO3 nanocrystals. Indeed, bulk alpha-LiIO3 is known to be very efficient for second harmonic generation (SHG). Bulk nanocomposite samples have been first studied showing nanocrystallites with size ranging from 50 to 400 nm and SHG. Then dip and spin coating methods have been used to build thin layers. Being given that LiIO3 crystals present structurally a strong dipolar moment, non-linear optical (NLO) properties may be enhanced using Corona discharges to orientate nanocrystals. This paper relates the fabrication process and the structural and optical characterizations of bulk and thin layer material.
J.Teyssier, R. Le Dantec, C. Galez, Y. Mugnier, J. Bouillot, J-C. Plenet, Journal of Non-Crystalline Solids 341 (2004) 152-156

A1203 – Mechanism of co-pyrolysis of coal-tar pitch with polyvinylpyridine

Co-pyrolysis of coal-tar pitch and poly(4-vinylpyridine) cross-linked with 25 wt.% of divinylbenzene (PVP) or the oxidized form of the co-polymer (PVPox) was studied as a possible way of manufacturing of carbonaceous materials enriched in nitrogen. Interactions of pitch with polymers were evaluated using thermogravimetry, elemental analysis, infrared spectroscopy in the DRIFT mode, X-ray photoelectron spectroscopy and optical microscopy. The tendency to depolymerization of PVP on heat treatment results in a little effect of the polymer on the thermal behaviour of the blend. PVPox is a stronger modifier of pitch carbonization behaviour and much more efficient source of nitrogen in the co-pyrolysis. The principal chemical interaction between pitch and PVPox is the dehydrogenative polymerization of pitch constituents induced by polymer oxygen groups. The oxidation of PVP does not affect the nitrogen functionalities transformation on pyrolysis.
B. Grzyb, J. Machnikowski, J.V. Weber, J. Anal. Appl. Pyrolysis 72 (2004) 121-130

A1206 – Vinyl acetate/butyl acrylate copolymers Part 2: Fire retardancy using phosphorus-containing additives and monomers

This study deals with the fire retardant performance of vinyl acetate (VA)/butyl acrylate (BA) copolymers using phosphorus compounds as additive or as co-monomer. First, VA/BA copolymer has been mixed with phosphorus additives from various sources: red phosphorus, organo-phosphates, organo-phosphonate, inorganic phosphate and an intumescent system (ammonium polyphosphate and pentaerythritol). The incorporation of 5 wt.-% phosphorus leads to VA/BA copolymers with improved fire properties whatever the source of phosphorus used. The best performance is achieved with the intumescent system. Second, VA and BA monomers have been copolymerised with phosphorus monomers (phosphate and phosphonate). Both systems present fire retardancy of interest. The better performance is achieved using phosphonate. Both systems are assumed to work in the condensed phase.
S. Duquesne, J. Lefebvre, G. Seeley, G. Camino, R. Delobel, M. Le Bras, Polymer Degradation and Stability 85 (2004) 883-892

A1205 – Intercalation of noble metal complexes in LDH compounds

Intercalation of iridium, platinum, and ruthenium complexes was carried out in [ZnAl], [MgAl], and [CuAl] LDHs structures by a new method of hydrothermal synthesis. Carbonate-free products were obtained. XRD, FTIR and EXAFS studies confirmed total anion exchange for Ir and Pt containing compounds. However, the geometry of local environment of iridium or platinum atom in the complexes appeared modified during intercalation. By thermal treatments metallic particles dispersed on oxide powder were obtained.
P. Beaudot, M.E. De Roy, and J.P. Besse, Journal of Solid State Chemistry 177 (2004) 2691-2698

A1209 – A new preparation method for the formation of gold nanoparticles on an oxide support

A preparation method for gold catalysts supported on alumina by a simple contact between a gold solution prepared with HAuCl4 as precursor and alumina over a narrow range of pH is described. This method, direct anionic exchange (DAE), differs from the mainly used method deposition precipitation generally used and presents the advantage that no gold is lost during the filtration and washing steps, the expected loadings of 2% is obtained. Gold particles size obtained by DAE is very sensitive to evolution and nature of the gold chloro-hydroxy species in the solution and on the surface of the support. According to the evolution of these species obtained by substitution of Cl- by OH- with increasing the pH value, the type of bonding complex-support is proposed. The surface of alumina is also sensitive to changes in pH of the solution. The formation of large particles of metal gold due to the presence of chlorine is put in evidence and can be limited by a treatment with ammonia solution. This washing procedure leads to some loss of gold with a final amount of 1.5%. Measurements of gold particle size by HRTEM are given as a function of preparation. A study of the activity in CO oxidation reaction is undertaken and correlated with TEM analysis.
S. Ivanova, C. Petit, V. Pitchon, Applied Catalysis A: General 267 (2004) 191-201

A1208 – A new mixed valence V(IV-V) and Li phyllosilicate: swelling, magnetic and conductive properties

This paper presents the synthesis and characterisation of a new V-Li phyllosilicate, Li2V0.95Si4O10(OH)1.24F0.76, under hydrothermal conditions. Part of the alkali is located in the interlayer spacing while the rest occupies the octahedral layer together with V(IV) and V(V). This silicate exhibits a mixed valence character and different properties, such as ferromagnetic order at low temperature, ionic conductivity and swelling upon exposure to moisture atmosphere. Thus, the basal spacing increases from 12.3 to 16.3 Å.
M. Richard-Plouet, C. Belcourt, S. Vilminot, Solid State Sciences 6 (2004) 875-878

A1207 – Preparation conditions of pure and stoichiometric NixFe(3-x)O4 bulk ceramics

The NixFe(3-x)O4 (0 < x <1) phases are spinels which are difficult to obtain under pure, dense and conductive ceramics forms. Treatment under inert atmosphere leads to a biphasic system of spinel and NiO monoxide. Treatment under air does not allow obtaining an optimised conductive ceramic because of oxidation during the cooling or quenching. Then, two step processes is proposed to obtain pure and stoichiometric nickel ferrites. At first, a treatment under air is carried out to synthesise dense and pure spinel ceramics. This treatment is followed by an annealing under inert atmosphere to reduce a part of Fe3+ and to form stoichiometric ferrites with semiconducting properties.
S. Corso, P. Tailhades, I. Pasquet, A. Rousset, V. Laurent, A. Gabriel, C. Condolf, Solid State Sciences 6 (2004) 791-798

A1211 – Synthesis of uniform diameter single-wall carbon nanotubes in Co-MCM-41: effects of the catalyst prereduction and nanotube growth temperatures

Catalyst pretreatment and CO disproportionation reaction conditions were observed to strongly affect the diameter uniformity of singlewall carbon nanotubes (SWNT) grown on Co-MCM-41 catalysts. The prereduction and CO disproportionation reaction temperatures were varied systematically while the carbon loading and the SWNT diameter uniformity were monitored by TGA, Raman spectroscopy, and TEM. The state of the catalyst during prereduction and the size of the cobalt clusters formed during the SWNT growth process were monitored by in situ XANES during the prereduction of the Co-MCM-41, and ex situ EXAFS of catalyst samples was performed after carbon deposition. These experiments allow development of correlations between the SWNT quality and the state of the catalyst. Control of the cobalt cluster size in the Co-MCM-41 catalyst is critical to the SWNT diameter control. The size of the cobalt cluster changes with both the prereduction and the SWNT synthesis temperatures. SWNT with a very narrow diameter distribution can be grown in Co-MCM-41 by controlling both the prereduction and the reaction temperatures.
Y. Chen, D. Ciuparu, S. Lim, Y. Yang, G.L. Haller, and L. Pfefferle, Journal of Catalysis 225 (2004) 453-465

A1210 – New effects during steam gasification of naphthalene: the synergy between CaO and MgO during the catalytic reaction

The catalytic activity of commercial CaO and MgO and their physical mixtures on the gasification reactions with steam was studied. Steam gasification of naphthalene as model reaction was selected and experiments in a laboratory scale reactor were performed. Carbon conversion for pure MgO and CaO was 54 and 62%, respectively. Every mixture showed a larger conversion than the weighted average of the pure compounds conversions; i.e., they exhibited catalytic synergy. The largest catalytic activity, reflected by the carbon conversion (79%), was obtained with a 10% CaO + 90%MgO mixture, which also showed the highest catalytic synergy (44.2%) among the assayed mixtures. Characterization of catalysts by XPS, XRD, SBET and DTG/DTA lead to conclude that formation of new phases, sintering, modification of dehydration or carbonation of the oxides in the mixture could not explain synergy, or basicity changes. Oxides forming the mixture have not been modified by the preparation or during the catalytic gasification. A catalytic cooperation between the two separated oxides is observed. Thus, synergy is attributed to MgO presence in the mixture, which inhibits formation of carbonaceous material as well as bidentate carbonate in the CaO surface, while promotes the formation of unidentate carbonate of lesser stability at the reaction temperature and in the presence of H2O(v).
N. Alarcon, X. Garcia, M.A. Centeno, P. Ruiz, A. Gordon, Applied Catalysis A: General 267 (2004) 251-265

A1213 – H2 absorption in amorphous and nanostructured Zr-based alloys under milling

We report on the mechanical hydriding of amorphous and nanostructured Zr-based alloys. The absorption process induces a demixing of the crystalline ZrH1.66 from the amorphous matrix with the concurrent formation of a less stable amorphous hydride. This phase releases the absorbed hydrogen at lower temperatures. No phase separation was observed in the nanostructured powders, which absorb hydrogen more quickly with respect to the amorphous structure through high diffusivity paths such as grain boundaries and free surfaces. Irrespective of the structural characteristics and the composition of the starting alloys, the absorption kinetics follows in both cases a well-defined sigmoidal trend. The conversion rate increases with the intensity of the milling treatment.
G. Mulas, S. Scudino, G. Cocco, Materials Science and Engineering A 375-377 (2004) 961-964

A1212 – The adjustment of hydrogen bonds and its effect on pyrolysis property of coal

Thermogravimetry (TG), in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) and on-line mass spectrometry (MS) were combined to study the effect of O-methylation and O-acetylation on the hydrogen bonds (HBs) in coal. A new method was proposed to compare the spectra of coal before and after the treatments by calibration of the band of kaolinite in coal. It was shown that both measures could reduce the amount of HBs in coal significantly (particularly the weak HBs), but neither of them could completely eliminate the HBs in coal because of the spatial resistance of three-dimensional structure in coal. It was proved that the stronger the hydrogen bonds formed by -OH groups, the less the extent to which they were reduced. The effect of O-acetylation is stronger than that of O-methylation on the reduction of HBs due to the low penetrability of the solvent used in the later treatment. Compared with the parent coal, both the pyrolysis temperature range and conversion of the treated coal increased, the initial decomposition temperature lowered, the decomposition rate accelerated and the composition of gas products was improved. Among the gases produced from the treated coal with these two methods, the amount of C1-C4 hydrocarbons increased, and CO2 and water reduced during pyrolysis compared with those of the raw coal.
D. Li, W. Li, H. Chen, B. Li, Fuel Processing Technology 85 (2004) 815- 825

A1214 – A novel macroporous structure of mesoporous titanias: synthesis and characterisation

Mesoporous titania materials with a novel macroporous structure have been synthesized by a one-step simple method in the presence of poly(ethylene oxide) surfactant. The three-dimensional, bicontinuous macroporous structures are in the interiors of the mesoporous titania particles with a uniform pore size gradient. The mesopores are disordered,wormhole-like, formed by the agglomeration of titania nanoparticles with anatase phase. The mesopore size can be modified from microporous to mesoporous range by tuning the synthesis time. The formation mechanism of the macro-mesostructured titanias is proposed.
T-Z. Ren, Z-Y. Yuan, B-L. Su, Colloids and Surfaces A: Physicochem. Eng. Aspects 241 (2004) 67-73

A1216 – Grafting 4f and 3d metal complexes into mesoporous MCM-41 silica by wet impregnation and by chemical vapour infiltration

Hybrid organic/inorganic materials have been prepared by reacting mesoporous MCM-41 silica with transition metal beta-diketonates, either by wet impregnation (WI) or by chemical vapour infiltration (CVI). Compounds obtained from Eu(III) or Gd(III) beta-diketonates, both by wet impregnation and by CVI, contain chemisorbed metalorganic species with strong Si-O-Ln bonding. Compounds prepared (by CVI only) from Cu(II) or Mn(III) beta-diketonates show a more complex absorption process than the lanthanides, since upon heating under dynamic vacuum they release part of the absorbed metal complex. Eu(thd)3 was more specifically used to prepare luminescent materials. It was used either alone, or with phenanthroline as an additional ligand in order to promote the so called 'antenna effect'.
A.N. Gleizes, A. Fernandes, J. Dexpert-Ghys, Journal of Alloys and Compounds 374 (2004) 303-306

A1215 – Comparison of different methods for characterizing multi-walled carbon nanotubes

Four complementary and independent methods are used to characterize nanotube samples: (i)TEM observation coupled with image analysis, (ii) nitrogen and krypton adsorption isotherm analysis, (iii) thermogravimetry and (iv) wide angle X-ray scattering. The methodology is discussed on the basis of two multi-walled carbon nanotube samples produced by the CCVD technique with very different reaction rates. It is shown that the total amount of deposited carbon is larger for the sample produced at the higher rate, that the fraction of nanotubes in the deposited carbon does not seem to be significantly different, but that the crystallinity of the nanotubes wall is larger for the sample produced at the lowest reaction rate.
C. Gommes, S. Blacher, N. Dupont-Pavlovsky, C. Bossuot, M. Lamy, A. Brasseur, D. Marguillier, A. Fonseca, E. McRae, J.B. Nagy, J-P. Pirard, Colloids and Surfaces A: Physicochem. Eng. Aspects 241 (2004) 155-164

A1217 – Synthesis and spectroscopic characterisation of chosen heteropolyanions and their Ln(III) complexes containing tetrabutylammonium counter ion

Synthesis and spectroscopic characterisation of tetrabutylammonium salts of heteropolyanions (NBu4HPAS) of Keggin's (NBu4)5H2PW11O39, (NBu4)6HPMo2W9O39, (NBu4)6H2SiMo2W9O39, (NBu4)4H3PMo2W9O39, (NBu4)6HPMo2W9O39, Dawson's type (NBu4)9HP2W17O61 and Preyssler heteropolyanion (NBu4)12[(Eu)P5W30O110] are presented. Extraction procedure has been selected as the best method for synthesis of compositions containing an organic counter anion. Elemental and thermogravimetric analysis, spectrophotometric determination of W and Mo, and FTIR spectra have been applied for analysis of the compositions obtained. The complexation studies were carried out with the use of Nd(III) and Er(III) absorption spectra (in the range of their hypersensitive transitions) and Eu(III) luminescence lifetime measurements. Threshold bootstrap computer-assisted target factor analysis (TB CAT) has been applied to evaluate the Nd(III) and Er(III) spectra in DMF and DMSO solutions and to estimate conditional formation constants for Ln(III)(NBu4HPAS)2 sandwich species (Ln(III)=Nd(III), Er(III)). Luminescence characterisation of the NBu4EuHPAS compounds concerning their intensity, quantum yield and luminescence lifetime of Eu(III) ion in non-aqueous solutions and solid are discussed.
S. Lis, S. But, G. Meinrath, Journal of Alloys and Compounds 374 (2004) 366-370