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Conductivity Measurements (conductivity + measurement)
Kinds of Conductivity Measurements Selected AbstractsThe Uncertainty in SCHF-DT Thermal Conductivity Measurements of Lotus-Type Porous CopperADVANCED ENGINEERING MATERIALS, Issue 10 2009Hiroshi Chiba Abstract Lotus-type porous metals with many straight pores are attractive for use as heat-sinks because a large heat-transfer capacity can be obtained, due to the small diameter of the pores. In order to use lotus-type porous copper effectively as a heat sink, it is important to know the effective thermal conductivity considering the effect of pores on heat conduction in the material. Since these metals have anisotropic pores, a steady-state comparative longitudinal heat-flow method for measuring thermal conductivity, referring to an ASTM standard, is better than other methods. So far, the effective thermal conductivity of lotus-type porous copper has been measured by using specimens of different thickness (the SCHF-DT method). In this paper, the uncertainty in the effective thermal conductivity of a specimen measured using this method was evaluated by comparison between numerical analysis and current experimental data. The following conclusions were drawn: 1) The uncertainty showed good agreement with the uncertainty analysis; 2) The contribution of the thermal grease thickness was large, based on a combined standard uncertainty analysis; and, 3) The effective thermal conductivity perpendicular to the pores of lotus copper can be measured within 10% uncertainty by this method. [source] Proton Conductivity Measurements in Yttrium Barium Cerate by Impedance SpectroscopyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2002W. Grover Coors Proton-conducting solid-electrolyte perovskite ceramics based on acceptor-doped barium and strontium cerates have become the focus of extensive investigations as candidate materials for fuel cells that operate at moderate temperatures. To assess the suitability of a material for this application, it is necessary that bulk electrolyte conductivity be measured at the operating temperature. However, very little reliable published conductivity data exist above 600°C. Protonic conductivity in yttrium-doped barium cerate has been observed to be less at high temperatures than would be expected, based on the activation energy and preexponential for hydrogen transport at temperatures <300°C. Conductivity data obtained from impedance spectroscopy on BaCe0.9Y0.1O3,, over the extended temperature range of 100°,900°C are presented. An Arrhenius plot of the data shows two distinct linear regions, suggesting that two different rate-limiting processes occur in series with a break-over transition at ,250°C. The decrease in conductivity is apparently not due to dehydration. An activation energy for protonic transport of 0.26 eV, about one-half of the low-temperature value, is proposed, based on curve fitting of the high-temperature data. [source] Thermal and Electrical Conductivity Measurements on Aluminum FoamsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2003N. Babcsán Abstract Metal foams are one of the most interesting types of materials although there is limited information concerning their thermal and electrical conductivity. Closed cell different density Alporas foams are investigated, which has one of the most homogeneous cell size distribution recently. Comparative method has been chosen to determine the thermal conductivity of the samples in the function of the temperature at 30, 100, 200, 300, 400, 500,°C. For measuring the electrical conductivity of aluminium foams a special low frequency eddy current measuring apparatus was used. The ratio of thermal and electrical conductivity was calculated and shown an increasing function by the density of the foams. [source] Conducting and transparent SWNT/polymer compositesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 13 2006Urszula Dettlaff-Weglikowska Abstract Flexible, transparent and conducting poly(methyl methacrylate) (PMMA) composites films were prepared using SOCl2 functionalized SWNTs. Optical absorption spectra measured on composite films confirm that the composite preparation procedure preserves the electronic properties (position of the Fermi level) of the p-doped nanotubes in the polymer matrix. Due to the doping effect of SOCl2 the electrical conductivity of the composites is improved by a factor of 5. The light transmission of the composite films depends on the film thickness and on the nanotube concentration. The optical transmittance of visible light at 500 nm was found to be 92% for 0.1 wt% SWNT loading and 46% for 0.5 wt% SWNT loading. The thickness of the specimens was approximately 20 µm. Conductivity measurement of the thin films performed with the four lead method revealed values 3.5 × 10,3 S/cm and 4.7 × 10,1 S/cm, respectively. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis, characterization, and solution properties of some new organotellurium compounds based on di(cyclohexylmethyl)tellurideHETEROATOM CHEMISTRY, Issue 1 2007Ali Z. Al-Rubaie A new series of organotellurium(IV) compounds based on di(cyclohexylmethyl)telluride (1) (i.e., (C6H11CH2)2TeX2 and (C6H11CH2)2Te(R)X) was prepared by the reaction of compound 1 with halogens, N-bromosuccinimide, and alkyl halides. Phenylation of (C6H11CH2)2TeX2 with sodium tetraphenylborate gave di(cyclohexylmethyl)phenyltelluronium tetraphenylborate in good yield. Conductivity measurements in dimethylsulfoxide (DMSO) showed a considerable ionic character of these compounds and they behave as 1:1 electrolytes. 1H NMR studies in CDCl3 solution indicated that telluronium salts employed in this study are unstable toward reductive elimination. Reaction of di(cyclohexylmethyl)telluride, (C6H11CH2)2Te(CH3)I, and (C6H11CH2)2Te(PhCH2)Br with HgX2 (X = Cl or Br) afforded 1:1 complexes. All compounds were characterized by elemental analyses and spectroscopic data. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:93,99, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20240 [source] Properties of solid solutions of poly(ethylene oxide)/epoxidized natural rubber blends and LiClO4JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008C. H. Chan Abstract Solid solutions of blends of poly(ethylene oxide) (PEO) and epoxidized natural rubber (ENR) comprising 12 wt % of LiClO4 were studied. Two glass transition temperatures, corresponding to the Tgs of the constituents, confirm immiscibility of the polymers over the entire composition range. It turns out that the Tgs of both polymers slightly increase after addition of salt to the blends. This shift is approximately constant over the whole range of blend composition. Accordingly, Tg measurements reveal that the salt dissolves to approximately equal relative amounts in the two phases. The degree of crystallinity of PEO in blends with ENR descends only to a minor extent with ENR content. However, addition of salt leads first to decreasing crystallinity and second this decrease becomes more pronounced with the addition of ENR. It shows that under these experimental conditions the salt content in PEO increases as compared to ENR. As one expects, the rate of isothermal crystallization does not change in blends as long as PEO is in excess. The situation changes again when salt is added. The rate decreases in a certain range of crystallization temperatures when ENR is added, demonstrating that salt is favorably dissolved in PEO. Conductivity was measured in polymers comprising different salt concentrations. A power-law dependence of conductivity on salt concentration was found. It results that the mobility of charge carriers in PEO exceeds that of ENR by five orders of magnitude. Therefore, the conductivity in blends is primarily governed by PEO as long as PEO is in excess. Conductivity measurements reveal again that salt is preferably dissolved in PEO. The distribution coefficient is estimated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Electrochemical and optical properties of novel donor-acceptor thiophene-perylene-thiophene polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2008Sermet Koyuncu Abstract In this study, donor-acceptor type thiophene-perylene-thiophene monomers were synthesized and polymerized by both oxidative polymerization using FeCl3 as catalyst and the electrochemical process. UV,vis, FTIR, 1H NMR, and elemental analysis techniques were used for structural characterization. Thermal behaviors of these compounds were determined by using TGA system. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels and electrochemical and optical band gap values were calculated by using the results of cyclic voltammetry and UV,vis measurements, respectively. The number,average molecular weight (Mn), weight,average molecular weight (Mw), and polydispersity index (PDI) values of synthesized polymers were determined by size exclusion chromatography. Conductivity measurements of these polymers were carried out by electrometer by using a four-point probe technique. The conductivity was observed to be increased by iodine doping. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1974,1989, 2008 [source] Decorating Polypyrrole Nanotubes with Au Nanoparticles by an In Situ Reduction ProcessMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2009Jingjing Xu Abstract Au nanoparticle-decorated polypyrrole nanotubes (defined as PPy/Au nanocomposites) are prepared by an in situ reduction process. Polypyrrole (PPy) nanotubes are prepared by a self-degraded template method, and Au nanoparticles are deposited in situ by the reduction of HAuCl4. The size and uniformity of the Au nanoparticles that decorate the PPy nanotubes can be controlled by adjusting the experimental conditions, such as the stabilizers used and the reaction temperature. The morphologies and optical properties of the nanocomposites have been characterized by scanning electron microscopy, transmission electron microscopy, UV-vis, and FT-IR spectroscopy. Conductivity measurements show that the conductivities of the nanocomposites decrease with a decrease of temperature, and the conductivity,temperature relationship obeys the quasi-one dimensional variable range hopping model. [source] Structure, phase transitions and ionic conductivity of K3NdSi6O15·xH2O.ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2000-K3NdSi6O15·2H2O, its polymorphs Hydrothermally grown crystals of ,-K3NdSi6O15·2H2O, potassium neodymium silicate, have been studied by single-crystal X-ray methods. The compound crystallizes in space group Pbam, contains four formula units per unit cell and has lattice constants a = 16.008,(2), b = 15.004,(2) and c = 7.2794,(7),Å, giving a calculated density of 2.683,Mg,m,3. Refinement was carried out with 2161 independent structure factors to a residual, R(F), of 0.0528 [wR(F2) = 0.1562] using anisotropic temperature factors for all atoms other than those associated with water molecules. The structure is based on highly corrugated (Si2O52,), layers which can be generated by the condensation of xonotlite-like ribbons, which can, in turn, be generated by the condensation of wollastonite-like chains. The silicate layers are connected by Nd octahedra to form a three-dimensional framework. Potassium ions and water molecules are located in interstitial sites within this framework, in particular, within channels that extend along [001]. Aging of as-grown crystals at room temperature for periods of six months or more results in an ordering phenomenon that causes the length of the c axis to double. In addition, two phase transitions were found to occur upon heating. The high-temperature transformations, investigated by differential scanning calorimetry, thermal gravimetric analysis and high-temperature X-ray diffraction, are reversible, suggesting displacive transformations in which the layers remain intact. Conductivity measurements along all three crystallographic axes showed the conductivity to be greatest along [001] and further suggest that the channels present in the room-temperature structure are preserved at high temperatures so as to serve as pathways for easy ion transport. Ion-exchange experiments revealed that silver can readily be incorporated into the structure. [source] Organotin(IV) and organolead(IV) complexes as biocides and fertility regulators: synthetic, spectroscopic and biological studiesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2006Ashu Chaudhary Abstract Biocidal, antifertility and spectroscopic aspects of organotin(IV) and organolead(IV) complexes with amino acids(L) and 2,2-bipyridine(L,) are described with the support of elemental analysis, IR, 1H, 13C, 119Sn and 207Pb NMR spectroscopy. The spectral data suggest that the ligand L acts in a monodentate and ligand L, in a bidentate manner, coordinating through the nitrogen atoms. The complexes have been characterized on the basis of molecular weight determinations and conductivity measurements. The isolated products are coloured solids, soluble in dimethylsulfoxide (DMSO), dimethylformamide (DMF) and methanol. All the complexes are monomeric in nature, as indicated by their molecular weight determinations. Conductivity measurements in dry DMF show them to be non-electrolytes. The complexes have been screened against a number of fungi and bacteria to assess their growth inhibiting potential. The results are positive. In addition to these studies, the complexes show good antimicrobial properties as compared with their starting materials. The testicular sperm density, sperm morphology, sperm motility, density of cauda epididymis, spermatozoa and fertility in mating trials and the biochemical parameters of the reproductive organs of rats were examined and are discussed in detail. Copyright © 2006 John Wiley & Sons, Ltd. [source] Microchip electrophoresis in low-temperature co-fired ceramics technology with contactless conductivity measurementELECTROPHORESIS, Issue 14 2009Georg Fercher Abstract In this paper a novel micromachined contactless conductivity CE device produced in low temperature co-fired ceramics (LTCC) is introduced. The application of LTCC multilayer technology provides a promising method for the contactless detection of conductive compounds because of its increased dielectric constant compared with glass or plastics. The capacitive coupling of the excitation signal into the microchannel across the LTCC substrate is improved, resulting in better detection sensitivity. Two silver electrodes located externally at opposite sides at the end of the separation channel act as detector. Impedance variations in the channel are measured without galvanic contact between electrodes and fluid. Inorganic ions are separated in less than 1,min with this novel ceramic device. The limit of detection is 10,,M for potassium. [source] Determination of in-plane thermal conductivity of Nax Co2O4 single crystals via a parallel thermal conductance (PTC) techniquePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2008Xiaofeng Tang Abstract A novel parallel thermal conductance ("PTC") system was specifically developed to conduct the steady state thermal conductivity measurement on small size samples such as single crystals of Nax Co2O4 as reported here. The accuracy and reproducibility of the PTC system has been confirmed by measuring several standard reference materials. The in-plane thermal conductivity , of Nax Co2O4 single crystals grown by a NaCl flux method was measured from 10 K to 300 K and , was found to be ,5 W m,1 K,1 at 300 K. The phonon mean free path (MFP) is estimated to be lph , 9 Å at 300 K, which is comparable to the lattice constant but much smaller than the reported MFP of conducting carriers. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] DC conductivity studies in K3Na(SeO4)2 single crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2009G. Joseph Abstract DC electrical conductivity studies were carried out along the three crystallographic axes for Tripotassium sodium diselenate (K3Na(SeO4)2 or KNSe). Earlier studies of phase transition in this crystal show successive phase transitions at 334 K, 346 K, 730 K, and 758 K. In this paper we report the dc electrical conductivity measurements in the temperature region 303 K , 430 K along a, b and c , axes. An anomaly in conductivity was obtained around 341 K and another one around 333 K. These can be attributed as due to phase transitions in this crystal. A strong anomaly also has been observed along the c-axis and comparatively week one along a and b axes around 395 K for the first time. This can be due to newly observed phase transition in the crystal. DSC taken for the sample also shows endothermic peak supporting the occurrence of newly observed phase transition. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural, electrical and optical properties of Ge implanted GaSe single crystals grown by Bridgman techniqueCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2006H. Karaa Abstract Structural, optical and electrical properties of Ge implanted GaSe single crystal have been studied by means of X-Ray Diffraction (XRD), temperature dependent conductivity and photoconductivity (PC) measurements for different annealing temperatures. It was observed that upon implanting GaSe with Ge and applying annealing process, the resistivity is reduced from 2.1 × 109 to 6.5 × 105 ,-cm. From the temperature dependent conductivities, the activation energies have been found to be 4, 34, and 314 meV for as-grown, 36 and 472 meV for as-implanted and 39 and 647 meV for implanted and annealed GaSe single crystals at 500°C. Calculated activation energies from the conductivity measurements indicated that the transport mechanisms are dominated by thermal excitation at different temperature intervals in the implanted and unimplanted samples. By measuring photoconductivity (PC) measurement as a function of temperature and illumination intensity, the relation between photocurrent (IPC) and illumination intensity (,) was studied and it was observed that the relation obeys the power law, IPC ,,n with n between 1 and 2, which is indication of behaving as a supralinear character and existing continuous distribution of localized states in the band gap. As a result of transmission measurements, it was observed that there is almost no considerable change in optical band gap of samples with increasing annealing temperatures for as-grown GaSe; however, a slight shift of optical band gap toward higher energies for Ge-implanted sample was observed with increasing annealing temperatures. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Eight-Coordinate Endohedral Rhenium, Osmium and Iridium Atoms in Rare-Earth Halide Cluster ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2010Sina Zimmermann Abstract Endohedral (interstitial) atoms are essential for almost all of the rare-earth halide cluster complexes. Most of these contain octahedral clusters, some are isolated, but the majority exhibits condensation by common edges to structures of higher dimensionality. Higher coordination numbers of the endohedral atoms are rare. Four examples of extended cluster complexes with eight-coordinate endohedral atoms of sixth-period elements (Re, Os, Ir) are presented. In the quasi-isostructural, non-isotypic halides {ReGd4}Br4 and {OsSc4}Cl4, square antiprisms of gadolinium and scandium atoms, respectively, are connected by two common faces to chains, surrounded and loosely connected by halogenido ligands. The Re and Os atoms build a slightly bent chain with only little bonding interactions. Chemical bonding is dominated by endohedral atom,cluster atom and cluster atom,halide interactions. The same is true for the two scandium bromides {Ir3Sc12}Br16 and {Os3Sc12}Br16Sc, which contain chains of face-sharing square antiprisms and cubes in a ratio of 2:1. Metal,metal bonding is attested by short distances between those endohedral Ir and Os atoms, respectively, which center the square antiprisms (283 pm and 290 pm, respectively). Magnetic and conductivity measurements on {Ir3Sc12}Br16 reveal paramagnetism and a small-band-gap semiconductor. This is in accord with electronic structure calculations. [source] Some biophysical properties of castor oil esterified with some acid anhydridesEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 10 2008Mona A. Saied Abstract A series of castor oil adducts were synthesized by esterification of castor oil with acid anhydrides: phthalic, maleic and succinic anhydrides. The chemical structure of castor oil and the prepared adducts were characterized by means of IR and 1H,NMR spectroscopy. The number-average and weight-average molecular weights were measured by gel permeation chromatography. The electrical properties were studied through the permittivity, dielectric loss and conductivity measurements, which are considered to be in the range of electrical insulation. The electrical conductivity, which describes the ionic mobility of the systems, was found to be in the range of 10,9 to 10,12,S/cm. This indicates that castor oil and its esters could be used for antistatic applications. The viscosity,, and the activation energy,E,, obtained from the dependency of viscosity on temperature using the Arrhenius equation, were found to increase with increasing molecular weight of the system. The effect of different concentrations of castor oil and its esters on the growth activities of the sugar beet pathogens R.,solani and S.,rolfsii was studied through the determination of percent germination, average length of hyphal extensions, dry mass yield and the production of sclerotia. The obtained data indicate that the esterification of castor oil with anhydrides improves the antifungal activity. [source] Electropolymerization of a Bifunctional Ionic Liquid Monomer Yields an Electroactive Liquid-Crystalline PolymerADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Sungwon Lee Abstract The preparation and polymerization of a bifunctional imidazolium-based ionic liquid (IL) monomer that incorporates both a vinyl group and a thiophene moiety is reported. Potentiodynamic electropolymerization of the monomer produces an optically birefringent polymer film that strongly adheres to the electrode surface. Fourier transform IR spectroscopy shows that polymerization occurs through both the vinyl and thienyl groups. Cylic voltammetry (CV) is used to determine the polymer oxidation potential (1.66,V) and electrochemical bandgap, Eg, of 2.45,eV. The polymer exhibits electrochromism, converting from yellow in the neutral form (,max,=,380,nm) to blue in the polaronic state at 0.6,V (,max,=,672,nm) and to blue-grey in the bipolaronic state at 1.2,V (,max,>,800,nm). Topographic atomic force microscopy (AFM) images reveal isolated (separated) fibrils. Grazing-incidence small-angle X-ray scattering (GISAXS) studies indicate a lamellar structure with a lattice spacing of 3.2,nm. Wide-angle X-ray diffraction (WAXD) studies further suggest that the polymerized thiophene sheets are oriented perpendicular to the polymerized vinylimidazolium. The electrical conductivity, as determined by four-probe dc conductivity measurements was found to be 0.53,S cm,1 in the neutral form and 2.36,S cm,1 in the iodine-doped state, values higher than typically observed for polyalkylthiophenes. The structural ordering is believed to contribute to the observed enhancement of the electrical conductivity. [source] Conductive Nanostructures of MMX ChainsADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Alejandro Guijarro Abstract Crystals of [Pt2(n -pentylCS2)4I] show a transition from semiconductor to metallic with the increase of the temperature (conductivity is 0.3,1.4,S,·,cm,1 at room temperature) and a second metallic,metallic transition at 330,K, inferred by electrical conductivity measurements. X-ray diffraction studies carried out at different temperatures (100, 298, and 350,K) confirm the presence of three different phases. The valence-ordering of these phases is analyzed using structural, magnetic, and electrical data. Density functional theory calculations allow a further analysis of the band structure derived for each phase. Nanostructures adsorbed on an insulating surface show electrical conductivity. These results suggest that MMX-polymer-based nanowires could be suitable for device applications. [source] Conductivity and Methanol Permeability of Nafion,Zirconium Phosphate Composite Membranes Containing High Aspect Ratio Filler Particles,FUEL CELLS, Issue 4 2009M. Casciola Abstract Gels of exfoliated ,-zirconium phosphate (ZrPexf) in dimethylformamide (DMF) were used to prepare Nafion/ZrPexf composite membranes with filler loadings up to 7,wt.-% by casting mixtures of Nafion 1100 solutions in DMF and suitable amounts of 2,wt.-% ZrP gels in DMF. TEM pictures showed that the ZrPexf particles had aspect ratio of at least 20. All samples were characterised by methanol permeability (P) and through-plane (,thp) and in-plane (,inp) conductivity measurements at 40,°C and 100% RH. The methanol permeability of Nafion membranes containing in situ grown ZrP particles with low aspect ratio (Nafion/ZrPisg) was also determined. The methanol permeability and the swelling behaviour of the composite membranes turned out to be strongly dependent on the filler morphology. As a general trend, both permeability and swelling decreased according to the sequence: Nafion/ZrPisg > Nafion > Nafion/ZrPexf. The maximum selectivity (,thp/P,=,1.4,×,105,S,cm,3,s) was found for the membrane filled with 1,wt.-% ZrPexf: this value is seven times higher than that of Nafion. For the Nafion/ZrPexf membranes, the ratio ,inp/,thp increases with the filler loading, thus indicating that the preferred orientation of the ZrP sheets is parallel to the membrane surface. [source] Ionic dialysance: Principle and review of its clinical relevance for quantification of hemodialysis efficiencyHEMODIALYSIS INTERNATIONAL, Issue 2 2005Lucile Mercadal Ionic dialysance (D) is an online measured variable now available on several dialysis monitors to evaluate small-solute clearance. Based on conductivity measurements in the inlet and outlet dialysate, the principle of the measurement and the different measurement methods are described. Studies that have evaluated the reliability of ionic dialysance to assess dialysis efficiency are discussed. These studies are divided into two groups: the first comparing ionic dialysance to urea clearance and the second comparing Dt/V to Kt/Vurea, in which the uncertainties of the measurement of Vurea could have misrepresented the relationship between Dt/V and Kt/Vurea. When Kt/Vurea via the Daugirdas second-generation equation taking the rebound into account is considered, slight,even nonsignificant,differences are evidenced between Kt/Vurea and Dt/V. Therefore, ionic dialysance should be considered as a valid measure in future guidelines for dialysis efficiency. [source] Chirality Transfer in Imidazolium Camphorsulfonate Ionic Liquids through Ion Pairing EffectsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Karola Schneiders Abstract The paper describes our studies on ion pair interactions in ionic liquids (IL) using an asymmetric hydrogenation reaction as probe. Three different ionic liquids carrying prochiral keto-functionalized cations were hydrogenated in the presence of their chiral, enantiomerically pure counter-ion using an achiral heterogeneous ruthenium catalyst. For the hydrogenation of N -(3,-oxobutyl)- N -methylimidazolium camphorsulfonate (2), N -(3,-oxobutyl)imidazolium camphorsulfonate (4) and N -(5,-oxohexyl)- N -methylimidazolium camphorsulfonate (6) we found a strong dependency of the enantiomeric excess (ee in the cation) on the polarity of the solvent, the concentration of the IL and the structure of the IL. The highest ee values of up to 94% were found for the hydrogenation of 2 in ethanol. Interestingly, we observed that the ee (and consequently the strength of ion pair interaction) had a pronounced maximum for a certain concentration of the IL in the solvent depending on the nature of the solvent and on the substrate. Remarkably, the concentration leading to the maximum ee could be rationalized by independent determination of the degree of dissociation which was obtained by a combination of diffusion-ordered NMR spectroscopy and conductivity measurements. [source] Synthesis, characterization, and electrical properties of diazophenylene bridged Co, Ni, Cu, Ce, and Er phthalocyanine polymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Cemil Alkan Abstract In this research, diazophenylene bridged metal-phthalocyanine (Pc) polymers were produced from diazonium salt of 1,4-diaminophenylene and presynthesized 1,8,15,22-tetraamino metal-Pcs. 1,8,15,22-Tetraamino metal-Pc complexes of Co, Ni, Cu, Ce, and Er were obtained by reducing 1,8,15,22-tetranitro metal-Pc complexes synthesized from 3-nitrophthalic anhydride, urea, metal salt, and ammonium molybdate catalyst. Complexes and polymers were characterized by Fourier transform infrared (FTIR), ultraviolet,visible (UV,vis), and X-ray powder diffraction spectroscopes. X-ray analysis of the polymers showed that there were short-range orientations in the polymers. Thermal analysis of the complexes and the polymers were done by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) at a heating rate of 10°C min,1 under nitrogen atmosphere. Ash analysis was performed to determine the metal content of the polymers. Viscosimetry and ebullioscopy measurements of the soluble part of the polymers were done for molecular weight analysis of the soluble part in tetrahydrofuran (THF) at 25°C. Four-probe conductivity measurements on isothermal conditions revealed that the polymer samples showed 104 fold increases in their electrical conductivities when doped with iodine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Gas phase esterification of acetic acid with ethanol over MoO3 supported on AlPO4 and the effect of modification with phosphomolybdic acid and Ce4+ ionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2003Abd El-Aziz A Said Abstract A series of AIPO4,MoO3 (APM) systems with various molybdena loadings (5,50) mol %, same modified with phosphomolybdic acid (PMA) and cerium ions, were prepared by an impregnation method and calcined at 400 °C, except for the samples modified with PMA which were calcined at 350 °C for 4 h. The catalysts were characterized by TG/DTG, XRD, IR spectroscopy, N2 adsorption and electrical conductivity measurements. The surface acidity and basicity of the catalysts were determined by adsorption of pyridine and the dehydration,dehydrogenation of isopropyl alcohol. The catalytic esterification of acetic acid with ethanol was carried out in a convention fixed bed reactor. The results clearly revealed that the catalyst with a composition of 10 mol % MoO3 (APM10) was the most active and selective catalyst for the production of ethyl acetate. Moreover, the yield of ethyl acetate increases on addition of PMA into APM10 while it decreases on the addition of Ce4+ ions. These results were correlated with structure, semiconductivity and the acid,base properties of the prepared catalysts. Copyright © 2003 Society of Chemical Industry [source] EFFECT OF COMBINED UNDERWATER PROCESSING AND MILD PRECUT HEAT TREATMENT ON THE SENSORY QUALITY AND STORAGE OF FRESH-CUT CANTALOUPE MELONJOURNAL OF FOOD QUALITY, Issue 4 2010KAREN L. BETT-GARBER ABSTRACT Improvement of storage quality of fresh-cut cantaloupe using a combination precut heat treatment and a modified underwater cutting treatment was determined. Eating quality was evaluated using descriptive sensory analysis, and fruit integrity was measured with respiration, cell leakage and product weight loss. Treatments included (1) control (no treatment); (2) making the first longitudinal cut underwater; (3) mild precut heat treatment in a water bath at 60C for 60 min; and (4) combination of precut heat treatment and the underwater cutting methods. Precut heating and processing underwater resulted in more intense fruity/melon flavor compared to conventional processed fresh-cut fruit. Reduced electrolyte leakage and enhanced membrane integrity were observed in all three experimental treatments, as evidenced by lower conductivity measurements. The underwater cut and combined treatments significantly reduced respiration during fresh-cut storage, reflecting less physical stress and membrane damage. Weight loss was not significantly affected by any treatment during fresh-cut storage. PRACTICAL APPLICATIONS There is a steady increase in the consumption of fresh-cut produce. To enhance the storage quality of fresh-cut cantaloupe melon, two minimal processing techniques were examined separately and combined. The methods are mild heat treatment of the whole melon at 60C for 60 min then cooling to 4C for 24 h, cutting the cantaloupe in half and removing the seeds while submerged in a calcium chloride and water solution, and the combination of the two treatments. These methods are simple and can be utilized by small or large processors to maintain sensory quality and fruit integrity during storage. [source] Synthesis, properties, and sulfonation of novel dendritic multiblock copoly(ether-sulfone)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2008Sumiko Matsumura Abstract Multiblock copoly(ether-sulfone)s (PESs) bearing anchor units for the construction of dendritic blocks were synthesized by two-step reactions: (1) synthesis of PES block with both phenoxide end-groups; (2) chain extension and end-capping of the block by use of excess novel hexafunctional agent, hexakis(4-(4-fluorophenylsulfonyl)phenyl)benzene. The optimum average block length (n) and amount (x) of the hexafunctional agent used for the synthesis of high-molecular-weight PES without crosslinking were n = 26 and x = 2.6 equiv, respectively. The dendritic blocks in the PES were constructed by the aromatic nucleophilic substitution reaction of the activated aromatic fluoride groups on the anchor units using 4-tritylbenzenethiol. The clean substitution of the fluoride groups in the PES was confirmed by 1H NMR and 19F NMR. Three sulfonic acid groups were introduced on the pendant phenyl rings of the trityl groups in the PES by the reaction with chlorosulfonic acid. This is the first example of a dendritic PES bearing clusters of sulfonic acid groups only on the dendritic blocks. Cast films of presulfonated dendritic PES were strong and flexible, however, the membranes of sulfonated dendritic PES were brittle so that the conductivity measurements were not performed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6365,6375, 2008 [source] Synthesis of metal (Fe or Pd)/alloy (Fe,Pd)-nanoparticles-embedded multiwall carbon nanotube/sulfonated polyaniline composites by , irradiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006Kakarla Raghava Reddy Abstract Composites of multiwall carbon nanotubes (MWCNTs) and sulfonated polyaniline (SPAN) were prepared through the oxidative polymerization of a mixture of aniline, 2,5-diaminobenzene sulfonic acid, and MWCNTs. Fe, Pd, or Fe,Pd alloy nanoparticles were embedded into the MWCNT,SPAN matrix by the reduction of Fe, Pd, or a mixture of Fe and Pd ions with , radiation. Sulfonic acid groups and the emeraldine form of backbone units in SPAN served as the source for the reduction of the metal ions in the presence of , radiation. The existence of metallic/alloy particles in the MWCNT,SPAN matrix was further ascertained through characterization by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, ultraviolet,visible spectroscopy, thermogravimetric analysis, and conductivity measurements. HRTEM pictures clearly revealed the existence of Fe, Pd, and Fe,Pd nanoparticles of various sizes in the MWCNT,SPAN matrices. There were changes in the electronic properties of the MWCNT,SPAN,M composites due to the interaction between the metal nanoparticles and MWCNT,SPAN. Metal-nanoparticle-loaded MWCNT,SPAN composites (MWCNT,SPAN,M; M = Fe, Pd, or Fe,Pd alloy) showed better thermal stability than the pristine polymers. The conductivity of the MWCNT,SPAN,M composites was approximately 1.5 S cm,1, which was much higher than that of SPAN (2.46 × 10,4 S cm,1). Metal/alloy-nanoparticle-embedded, MWCNT-based composite materials are expected to find applications in molecular electronics and other fields. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3355,3364, 2006 [source] Synthesis and characterization of epoxidized polybutadiene/polyaniline graft conducting copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2004F. R. De Risi Abstract In this article the synthesis and characterization of an elastomeric conducting material, obtained by grafting polyaniline (EB) on commercial cis -1,4-polybutadiene (PB), are described. PB was first partially epoxidized in chloroform solution using meta-chloroperbenzoic acid (MCPBA). The conducting polymer was then grafted to the activated polybutadiene (EPB) via the aminolysis reaction between the polyaniline NH2 terminal groups and the oxirane rings. The material so obtained (EPBPAN) and the epoxidized intermediate product were characterized by 1H NMR, 13C NMR, Fourier transform infrared, and ultraviolet,visible spectroscopy, thermal and mechanical analysis, and electrical conductivity measurements. The effect of the sample deformation on conductivity also was analyzed. The HCl doping of the EPBPAN film induced crosslinking reactions, generated by the acid cleavage of unreacted oxirane groups. The electrical conductivity of the doped material reached values of about 10,5 ,,1 cm,1. The key characteristics of our elastomeric conducting material are its simple synthesis, its starting as a commercial product, and the solubility of its undoped form in a common low-boiling organic solvent like chloroform. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3082,3090, 2004 [source] Ni,YSZ Solid Oxide Fuel Cell Anode Behavior Upon Redox Cycling Based on Electrical CharacterizationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Trine Klemensø Nickel (Ni),yttria-stabilized zirconia (YSZ) cermets are a prevalent material used for solid oxide fuel cells. The cermet degrades upon redox cycling. The degradation is related to microstructural changes, but knowledge of the mechanisms has been limited. Direct current conductivity measurements were performed on cermets and cermets where the Ni component was removed. Measurements were carried out before, during, and after redox cycling the cermet. The cermet conductivity degraded over time due to sintering of the nickel phase. Following oxidizing events, the conductivity of the cermets improved, whereas the conductivity of the YSZ phase decreased. An improved model of the redox degradation mechanism was established based on the measurements. [source] Optical and Electrical Properties of Amorphous and Nanocrystalline (La0.8Sr0.2)0.9MnO3 Thin Films Prepared from Low-Temperature Processing TechniqueJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006Toshio Suzuki The results of a study on the optical and electrical properties of (La0.8Sr0.2)0.9MnO3 (LSM) thin films obtained by a polymeric precursor spin coating technique were presented. This method allowed preparation of optical quality thin films at annealing temperatures around 800°C. Amorphous and crystalline LSM thin films were studied by optical and electrical conductivity measurements. The energy-dependent absorption coefficients for the crystalline specimen were calculated from optical spectra and extra absorption was observed in the range of 1.8,2.5 eV with the exchange-gap excitation behavior in the 3,5 eV range. In comparison to the amorphous specimens, the electrical conductivity of the nanocrystalline specimen increased two to three orders of magnitude with decreasing activation energy. The charge carrier absorption model suggested an increase of the carrier concentration in the nanocrystalline specimen which may be a reason for the change in the electrical conductivity. [source] Microstructure,Property Correlations in Industrial Thermal Barrier CoatingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004Anand A. Kulkarni This paper describes the results from multidisciplinary characterization/scattering techniques used for the quantitative characterization of industrial thermal barrier coating (TBC) systems used in advanced gas turbines. While past requirements for TBCs primarily addressed the function of insulation/life extension of the metallic components, new demands necessitate a requirement for spallation resistance/strain tolerance, i.e., prime reliance, on the part of the TBC. In an extensive effort to incorporate these TBCs, a design-of-experiment approach was undertaken to develop tailored coating properties by processing under varied conditions. Efforts focusing on achieving durable/high-performance coatings led to dense vertically cracked (DVC) TBCs, exhibiting quasi-columnar microstructures approximating electron-beam physical-vapor-deposited (EB-PVD) coatings. Quantitative representation of the microstructural features in these vastly different coatings is obtained, in terms of porosity, opening dimensions, orientation, morphologies, and pore size distribution, by means of small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS) studies. Such comprehensive characterization, coupled with elastic modulus and thermal conductivity measurements of the coatings, help establish relationships between microstructure and properties in a systematic manner. [source] | ||||||||||||||||||||||||||||||||||