bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Assembled Hybrid Polymers
Authors: Rose Philip L. , Manziek Larry , Gallagher Michael K. 
Published: April 2011

ABSTRACTNovel copolymer composite resins have been synthesized using the surface assembled hybrid technology. Monodisperse polystyrene/DVB microspheres with diameters of 5.3 and 7.5 μm and polydisperse carbonaceous and acrylic microspheres with diameters ranging from 5–30 μm have been assembled onto the surface of styrene and acrylonitrile based gel and macroreticular resins.Carbonaceous adsorbents with holes of controlled diameter on their surfaces have been prepared using the surface assembling technique. Core-shell carbonaceous adsorbents with divergent surface chemistries have been prepared using this techniqueNovel catalytic materials have been made and are envisioned using the assembling technique to form short-diffusion path reactive systems. The range of surface functional groups include: strong acid, strong base, palladium, silver, gold and reductive amine-borane.
Synthesis and Characterization of Supported Metal Cluster Catalysts with Well-Defined Structures
Authors: Gates B. C. 
Published: April 2011

ABSTRACTNearly uniform supported metal clusters are the focus of this summary, which addresses their synthesis, characterization, and catalytic properties. Supported clusters represented as Ir4and Ir6were prepared on MgO powder by thermal decarbonylation of [HIr4(CO)11]−and [Ir6(CO)15]2−, respectively. The most useful characterization technique for supported clusters is extended X-ray absorption fine structure spectroscopy, but the structure data are limited by the precision of the coordination numbers (about ±20%). Ir4and Ir6clusters on supports catalyze hydrogenation of cyclohexene and of toluene, and they are catalytically distinct from larger iridium particles, although the reactions are structure insensitive (proceeding at about the same rate per exposed metal atom) when catalyzed by metal particles larger than about 1 nm. Thus the concept of structure insensitivity does not extend to supported metal clusters, which are regarded as quasi molecular.
Preparation of La1−xSrxMnO3 Perovskite Catalysts Supported on Ceramic Foam Materials
Authors: Ismagilov Z. R. , Podyacheva O.Yu. , Ketov A.A. , Bos A. , Veringa H. J. 
Published: April 2011

ABSTRACTThe new method of preparation of La1−xSrxMnO3 catalysts supported on ceramic foam materials was developed. The synthesized supported perovskite catalysts were examined by X-ray diffraction analysis and BET methods. It was shown that in coated samples there is a pure perovskite phase on the support surface up to temperatures of 1000°C.Unsupported La1−xSrxMnO3 catalysts were synthesized applying co-precipitation technique using La, Sr and Mn acetylacetonates and were studied by X-ray diffraction analysis. Temperature programmed reduction method revealed that catalysts contain 2 types of active centers: low temperature (α) and high temperature (β), the quantity of these centers and correlation between them depend on the value of x. It was shown that supported perovskite catalysts, similarly to the massive ones, maintain two types of active centers (α and β).The activity of La1−xSrxMnO3 on mullite foam was characterized in the methane oxidation reaction.
Laser Synthesis of Iron Nitride Nanoparticles from Pyrolysis of Fe(CO)5-NH3 System
Authors: Zhao X. Q. , Liang Y. , Zheng F. , Hu Z. Q. , Zhang G. B. , Bai K. C. 
Published: April 2011

ABSTRACTBy vapor-phase pyrolysis of Fe(CO) 5 and NH3 induced by CW CO2 laser, γ'-Fe4N and ε- Fe3N nanoparticles(≤35nm) were prepared in Ar and N2 atmospheres. In Ar, γ'-Fe4N accompanied by a little α-Fe was formed at low temperatures below 650°C, while higher temperatures favored the formation of γ-Fe. In N2 atmospheres, a mixture of Fe4N and Fe3N nanoparticles were obtained at high temperatures. In addition, the influences of synthesis parameters on the structure, morphology and magnetic properties of the nanoparticles were discussed.
Surface Properties of Molybdenum Nitride Thin Films
Authors: Lee Hyuek Joon , Mudholkar Mandar S. , Thompson Levi T. 
Published: April 2011

ABSTRACTThe interaction of NH3 and CH3NH2 with the surfaces of f β-Mo16N7, γ-Mo2N, and δ-MoN films was investigated using thermal desorption spectroscopy. Ammonia temperature programmed desorption (TPD) spectra for the films were similar. Ammonia TPD (adsorption at ∼280 K) produced an NH3 peak at ∼360 K. Some of the NH3 decomposed into H2 and N2. Two H2 desorption peaks were produced: a low temperature peak due to recombination of surface hydrogen and a high temperature peak due to hydrogen that emerged from the nitride subsurface. The N2 desorption spectrum consisted of a peak at ∼340 K and several peaks in the range 500–900 K. The desorption kinetics depended on the structure and composition of the film. 15NH3 TPD experiments indicated that the low temperature N2 desorption peak was due to NH3 decomposition, while the origin of the high temperature peaks was the nitride itself. We believe that nitrogen desorption from the nitride was induced by the presence of hydrogen which altered the Mo-N bonding. Three different CH3NH2 decomposition processes were observed: complete decomposition of CH3NH2 into H2, N2 and C, partial decomposition into HCN, and simple C-N bond hydrogenolysis into CH4 and NH3. The decomposition pathways depended on the structural and compositional properties of the films. All three processes were observed for the β- Mo16N7 (400), β-Mo16N7 (203) and δ-MoN(002) films, while only trace amounts of HCN were detected for the γ-Mo2N(200) film, suggesting that the partial decomposition into HCN was not favored on this surface. The β-Mo16N7 (400) and δ-MoN(002) films had the high selectivities for simple C-N bond cleavage.
Palladium Carbide Formation in Pd/C Catalysts and its Effect on Adsorption, Absorption and Catalytic Behavior
Authors: Krishnankutty Nalini , Vannice M. A. 
Published: April 2011

ABSTRACTThe presence of PdCx, a metastable palladium carbide phase, was detected in Pd dispersed on high surface area carbon blacks using a Pd acetylacetonate precursor. TEM and XRD measurements indicated well dispersed Pd after reduction at 573 K; however, hydride formation and chemisorption of gases was suppressed on these catalysts and this was accompanied by lattice expansion of Pd as seen from XRD. Cleaning pretreatments with O2slightly contracted the Pd lattice and enhanced hydride formation and chemisorption, while a 673 K reduction gave normal hydride ratios and Pd lattice parameters although chemisorption was still suppressed. Pd lattice expansion and suppression of hydride formation and chemisorption are attributed to carbon atoms present both in the bulk and on the Pd surface. The performance of these catalysts in probe reactions was consistent with this model of C contamination of the Pd surface and bulk.
Dissolution-Recrystallization Processes of Nickel Hydroxide, The Active Material of the Ni/CD and Ni/H2Cells
Authors: Delahaye-Vidal A. , Sac-Epee N. , Portemer F. , Beaudoin B. , Figlarz M. , Jamin T. 
Published: April 2011

AbstractSeveral examples of dissolution-recrystallization processes at the nickel hydroxide electrode are reviewed. Some of them are very well known and have been studied for a few yearsin the case of Ni/Cd cells. The cycling of the ∝-type nickel hydroxide leads to the ∝→β transformation through dissolution of the a phase in the electrolyte (KOH) and recrystallization of the β phase from the solution. Further cycling of the resulting βex ∝phase causes an ageing effect which occursvia the solution (Oswald ripening). More recently, a strong ripening phenomenon has been observed by studying the behavior of nickel hydroxides cycling in Ni/H2cells. By simulating the ageing of charged and discharged materials under hydrogen pressure inKOH media, it has been shown that in the absence of voltage, hydrogen cannot be responsible for the strong ripening effect. Synergetic effects between hydrogen and voltage have to be considered.
Roughness Effect on the Lithium Diffusivity in WO3 Thin Films
Authors: Maaza M. , Gorenstein A. , Sella C. , Bridou F. , Pardo B. , Corno J. , Rogera G. , Bohnke O. , Julien C. 
Published: April 2011

AbstractIn this work, we investigate the influence of surface roughness on the kinetics of Li+ during the insertion process in the well-known electrochromic material WO3. Thin films 500 Å thick have been grown by rf-sputtering and annealed in therange of 25-350ºC. Grazing angle X-ray reflectometry shows that the film roughnessincreases considerably with thermal treatment. These measurements are correlated with chemical diffusion investigations obtained by electrochemical titration in Li/WO3 cells.
Electrochemical Study, Synthesis and Microstructural Characterization of Lithium and Sodium Inserted W18O49.
Authors: Cruz A. Martinez De La , Torres-Martinez Leticia M. , Garciaalvarado F. , Moran E. , Alario-Franco M. A. 
Published: April 2011

AbstractThe formation of lithium inserted W18O49 phases has been studied byelectrochemical methods. When lithium is inserted, several single phases LixW18O49 are observed in the range 0 ≤ x ≤ 40 between 3 and 1 V. Nevertheless the reaction is reversible only for x ≤ 22. Chemical reactions of W18O49 with different quantities of n-butyllithium have been carried out to isolate and characterize some of these phases. For Li17W18O49, this is ˜1:1 Li/W ratio, electron diffraction experiments clearly indicate that lithium produces a periodicity change, doubling the a, b and c cell parameters. On the other hand, when sodium is inserted in W18O49 two single phase regions NaxW18O49 are observed within the range 0 ≤ x ≤ 1.2 between 3 and 0.5 V.
Properties of LiV308 Cathode Materials Prepared from Gels by Spray-Drying
Authors: Saidi M. Y. , Olsen I. I. , Koksbang R. , Barker J. , Pynenburg R. , West K. , Zachau-Christiansen B. , Skaarup S. 
Published: April 2011

AbstractLiV308 powder has been prepared on a large scale by spray drying ofan aqueous gel. The material was further dehydrated at 150 and 350ºC. These materials were characterized by TGA, XRD and electrochemical methods. Materials dried at 150 and 350ºC, showed an unusual high reversible capacity, close to 4 Li per formula unit, and cycle well. The material dried at 350ºC is very similar to the crystalline LiV308 prepared by conventional high temperature synthesis.
Calculation of Defect Formation Energy from the Thermal Expansion Data for Lead Fluoride
Authors: Schuler Brenda J. , Aurora T. S. , Pederson D. O. , Day S. M. 
Published: April 2011

AbstractLead fluoride is a superionic conductor with the fluorite structure. Results of the measurement of linear thermal expansion of lead fluoride (reported earlier in literature) showed a large increase in the thermal expansion coefficient near 700 K where the ionic conductivity has been shown to exhibit a sharp increase. It is believed that thermally-generated defects in a crystal lattice affect the thermal expansion coefficient. This idea was applied in the present analysis to calculate the defect formation energy (Ef) by using the literature values of the coefficient of thermal expansion. It was assumed that the thermal expansion in excess of that produced due to the lattice anharmonicity (δ∝) is proportional to the concentration of defects (n). With this assumption, one may write: δ∝ = c nº exp(-Ef/kT), where c is a constant. For lead fluoride, a plot of ln(δ∝) versus (l/T) yielded Ef = 0.56 eV which is lower than the literature values. The assumptions in this analysis and the discrepancy in the result are discussed.
A Study of the Electrocatalytic Properties of SrCo0.8Fe0.2O3-δ by Impedance Spectroscopy
Authors: Pham Al Quoc , Jacobson Allan J. 
Published: April 2011

AbstractThe electrocatalytic behavior of the mixed electron - ion conductor SrCo0.8Fe0.2O3-δ, in the form of an electrode on YSZ, has been studied using impedance spectroscopy at low frequencies. The results suggest that the electrode process is dominated by the surface exchange at high temperatures and by the bulk oxygen diffusion at lower temperatures. No limiting current was observed in I-V measurements. The electrode polarization decreased with increasing current density. The creation of additonal oxygen vacancies in the electrode material is suggested to account for the better performance at the higher current densities.
Structural, Electrical and Optical Properties of Laser Deposited Thin Films of Srco0.8Fe0.2O3-δ
Authors: Zhang C. , Deng H. , Varon J. , Abeles B. , Yang Y. , Pham A.Q. , Jacobson A.J. 
Published: April 2011

AbstractThin film SrCo0.8Fe0.2O3-δ were made by pulse laser deposition. The electrical conductivity is thermally activated in the temperature 25-500 °C with an activation energy of 0.17-0.19 eV and is temperature independant from 500-800 °C. The optical absorption shows characteristic features which are interpreted qualitatively in terms of a simple band structure diagram.
Measurement of Partial Conductivities in Mixed Conductors Using Blocking Electrodes
Authors: Pham Al Quoc , Jacobson Allan J. 
Published: April 2011

AbstractThe blocking electrode method commonly used for the determination of the partial conductivities in a mixed ionic-electronic conductor has been suspected by several authors to give incorrect results in some cases. Experimental evidence illustrating the limitations of this method are presented. The resistance of three pellets of YSZ, the middle one playing the role of a “mixed” conductor, was studied by ac impedance spectroscopy. The imperfect contacts on a microscopic scale formed at the interface between the blocking electrodes and the sample were shown to give rise to additional resistances which cannot be separated from the total bulk resistance. The method was also used to study the conductivity of gold metal. Despite the presence of the ionically blocking electrodes an electronic current is observed. This electronic leakage current is due to the interaction with the gaseous environment, the mixed conductor playing the role of an electrode for the conversion of oxygen ions to electrons.
Synthesis, Characterization and Electrochemical Study of the Solid Solution LixNa0.875−δFe0.875Ti1.125O4 (0 ≤ δ ≤ 0.4, x ≥ 0)
Authors: Kuhn Alois , Garcia-Alvarado F. , Moran E. , Alario-Franco M.A. 
Published: April 2011

AbstractThe calcium ferrite type structure of Na0.875Fe0.875Ti1.125O4[1] has double tunnels which are occupied by double rows of sodium atoms running along the b-axis. We have partially removed sodium from this compound at moderate temperatures with different oxidizing agents. Electrochemical studies show that the resulting materials, Na0.875Fe0.875Ti1.125O4 (0 ≤ δ ≤ 0.4), can reversibly intercalate lithium at potentials between 3.8 and 1 volt. At the lowest voltages, a compound containing ∼ 0.5 lithium per formula is formed. By chemical reaction of Na0.875Fe0.875Ti1.125O4 with n-butyllithium, the maximum lithium content also corresponds to Li0.5Na0.875Fe0.875Ti1.125O4. This suggests that many more than the one eighth of the empty sodium sites, per unit cell, of the parent phase are now being occupied by lithium.
Molecular Layer Processing of Polyaniline via the Use of Hydrogen Bonding Interactions
Authors: Stockton William B. , Rubner Michael F. 
Published: April 2011

AbstractMolecular layer-by-layer build-up on a variety of substrates is demonstrated for doped polyaniline (PAn) alternating with non-ionic water soluble polymers. The adsorption is enabled by the strong interchain interactions with PAn, such as hydrogen bonding. Multilayer build-up has been demonstrated with four distinctly different non-ionic water soluble polymers: poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA), poly(acrylamide) (PAAm), and poly(ethylene oxide) (PEO). Thus, non-ionic water soluble polymers containing a wide variety of functional groups such as amide, hydroxyl or ether groups can be used to successfully fabricate multilayer thin films with polyaniline. FTIR spectroscopy measurements show the PAn to be hydrogen bonded in these multilayer films. Conductivities for multilayer films are on the order of 1-4 S/cm for films doped with methane sulfonic acid. Conductivities on the order of 0.1 S/cm can be achieved for a single mixed layer self-assembled from a mixed solution of PAn/PVP or PAn/PAAm.
Performance of Polymer-Based Supercapacitors
Authors: Arbizzani Catia , Mastragostino Marina , Meneghello Luca 
Published: April 2011

AbstractSupercapacitors are now attracting much attention as an electric vehicle power source. The present study focuses on redox supercapacitors with electronically conducting polymers as electrode materials. Performance data of a symmetric supercapacitor based on p-doped poly(pyrrole), of an unsymmetric supercapacitor based on p-doped poly(pyrrole) and poly(3-methylthiophene), and of a symmetric sypercapacitor based on p- and n-doped poly(dithieno[3,4-b:3',4'-d]thiophene) are here compared.
Electrochromism and Photochromism of WO3 Thin Films
Authors: Lefrou C. , Marrot O. , Garot F. 
Published: April 2011

AbstractA photochromic effect is observed in WO3-based electrochromic devices with an ion-conducting polymer as electrolyte. Upon exposure to sun light, the electrochromic cells become blue. This is due to a change of color of the WO3 electrode. The photoeffect on this layer is due to a simultaneous insertion reaction (reduction) of the WO3 material and a photooxidation of water contained in the polymer. It is reversible and therefore not destructive for the complete device. The study of the transmittance and rest potential as a function of the time of exposure to light shows that a steady state is reached in c.a. 10 hours. The addition of U.V.-cut filters changes the reached steady-state, indicating that the photochromic effect is dependent upon the structure of the WO3 material.
High Rate Deposition of Nickel Oxide Electrochromic Thin Films by Reactive DC Magnetron Sputtering
Authors: Yoshimura Kazuki , Miki T. , Tanemura S. 
Published: April 2011

AbstractNickel oxide electrochromic thin films were prepared by reactive DC magnetron sputtering. As-deposited optical property and electrochromic behavior strongly depended on the target operation mode and the substrate temperature. In the condition of low oxygen flow ratio (∼1%), the deposition rate can be raised up to 40 nm/min at the power of 60 W. The sample with the deposition rate of 30 nm/min exhibited the best electrochromic performance when the substrate temperature was kept to 200°C-300°C during sputtering. The integrated luminous transmittance of the best sample could be controlled from 6.6% to 82.3%.
Proton Intercalation in γ-MnO2 from Ramsdellite to Groutite Through Groutellite
Authors: Chabre Yves , Pannetier Jean 
Published: April 2011

AbstractThis paper presents an investigation of electrochemical proton intercalation in two chemically prepared MDs containing low amounts of structural defects and in a natural MD containing 89%of highly crystalline ramsdellite. XRD examination of equilibrated partly reduced synthetic samples confirms the formation of groutite as a final reduction product and, before mid-reduction, suggests the formation of a solid solution between ramsdellite and groutellite H0.5MnO2. In contrast, electrochemical spectroscopy hint at a two-phase process with an equilibrium potential at –60 m V vs Hg/HgO. The implication of the structural defects on these observations are discussed.
Pore Structure and Moisture Properties of Cement-Based Systemsfrom Water Vapour Sorption Isotherms
Authors: Baroghel-Bouny Veronique , Chaussadent T. 
Published: April 2011

AbstractThis paper presents results obtained for hardened cement pastes and concretes, ordinary and very-high-performance materials, concerning pore structure and moisture properties.Because of the inadequacy of classical pore investigation methods (mercury intrusion, nitrogenadsorption) to provide the exact pore network characteristics of cement-based systems, notably in the case of very-high-performance materials, a more pertinent type of experiment was carried out: water vapour desorption and adsorption measurements.From these experiments, isotherms were determined at hygrometrical equilibrium and at constant temperature (T = 23 °C) for every desorption/adsorption path. The analysis of these curves gives textural parameters in the mesopore range, not accessible by most of other methods. Thus, from the adsorption curve, the specific surface area accessible to water molecules was calculated by the B.E.T. method. The statistical thickness of the water film adsorbed on the solid surface was also determined. And finally, application of the B.J.H. method on the desorption branch provides relevant porosity values and pore size distribution of the hardened materials, and especially intrinsic characteristics of C-S-H hydrates.This makes it possible to point out the similarities and the differences between the materials, regarding microstructure and moisture properties, and to quantify the influence of mix parameters such as water-cement ratio or silica fume content.
Fracture Surfaces of Cement Pastes, Rocks, and Cement/Rock Interfaces
Authors: Mindess S. , Diamond S. 
Published: April 2011

AbstractStereo pair imaging in a scanning electron microscope was used to document the details ofthe topography of fracture surfaces at various degrees of magnification. The fracture surfaces had been produced by fracture testing of chevron-notched beam specimens according to ISRM Method I. The surfaces examined included the fracture surfaces of dolomite and andesite rocks, cement pastes with and without silica fume, the fracture surfaces from specimen prepared by casting cement paste on previously fractured rock specimen faces, and the fracture surfaces of mortars prepared using the same rock types and cement pastes. The principal topographic features of the various fracture surfaces are described.
Chemical Models for the Mechanisms that Influence the Nature and Structure of the Interfacial Transition Zone
Authors: Cocke D. L. , Mollah M. Y. A. , Lin T.-C. , Vempati R. K. , Hess T. R. 
Published: April 2011

AbstractThe chemical nature and microstructure of the interfacial transition zone (ITZ) are influenced by the interfacial mechanisms of hydration which are primarily controlled by surface and nearsurface phenomena. Recent works from our laboratory involving superplasticizers, metal anions that retard hydration and interaction with silicate based aggregates have established that the interfacial chemistry is of fundamental importance in understanding the mechanisms of CSH formation, surface chemical compound formation and mineralization of the interfacial transition zone and its interaction with the hydrated cement particles and the aggregate. A surface charge control reaction model that accounts for :he importance of calcium and other cations and anions will be outlined and used to discuss the interfacial physical chemistry of the ITZ and its ultimate chemical nature and structure.
Interface Transition Zone and the Elastic Modulus of Cement-Based Composites
Authors: Simeonov Peter I. , Ahmad S.H. 
Published: April 2011

AbstractThe influence of the Interface Transition Zone (ITZ) on the elastic modulus of concrete is demonstrated as a divergence of the experimental data from the general trend of the theoretical Hashin-Shtrikman bounds. This divergence is well related to the W/C of the composite. With reduction of W/C the influence of ITZ decreases and for values close to 0.4 and lower it is insignificant.The formation of the ITZ is characterized by a transfer of water from the matrix to the surface of the aggregates. As a result of this a highly porous ITZ is formed while the matrix remains with a reduced porosity. This process can also be described as a transfer of material properties. For some compositions the balance of this transfer can approach zero. The imbalance in this process is more pronounced at higher W/C.The effect of Interface Transition Zone can be successfully simulated by the help of recently derived Hashin's variational bounds for two-phase composites with imperfect interfaces.