bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation, Characterization and Catalytic Activity of Niobium Oxynitride and Oxycarbide in Hydrotreatment
Authors: Kim H. S. , Sayag C. , Bugli G. , Djega-Mariadassou G. , Boudart M. 
Published: April 2011

ABSTRACTOxynitride and oxycarbide of niobium present metallic and acidic catalytic functions as evidenced by molecular probe reactions: isomerization of cyclohexane and hydrodenitrogenation of 1–4 tetrahydroquinoline. The proximity of the two functions leads to the concept of “dual site” by selective inhibition of the metallic and acid sites. Substitution of nitrogen of the oxynitride by carbon to form the oxycarbide produces a large enhancement of the metallic character of the surface. The oxynitride was shown to present a more acidic and a less hydrogenating activity as compared to the activity of the oxycarbide. Both compounds of niobium have been compared to molybdenum oxynitride.
Green Technology for the 21st Century: Ceramic Membranes
Authors: Anderson M. A. , Zeltner W. A. , Merritt C. M. , Anderson Professor Marc A. 
Published: April 2011

ABSTRACTThe nineties have brought us to an era of environmental crisis. We are faced with problems of air pollution, both indoor and outdoor, acid rain, water pollution, hazardous wastes, toxic landfills and leaking storage tanks in our soil, to name a few. Our rapid advances into the industrial and technological age have contributed to these problems. However, our advancing technology in the areas of remediation and such “green” engineering tools as ceramic membranes can certainly make a significant contribution in terms of environmental clean-up and a healthier world.
On the Stability of Mo2N During First-Stage Hydrocracking
Authors: Veen J. A. R. Van , Minderhoud J. K. , Buglass J. G. , Lednor P. W. , Thompson L. T. 
Published: April 2011

ABSTRACTAn unsupported sample of Mo2N has been subjected to a first-stage hydrocracking test. The evolution of the HDS and HDN performance indicated a transformation of Mo2N into MoS2. This was substantiated by XPS and TEM, the latter technique showing that the transformation is limited to only a few surface layers.
Characterization of a Catalytically Active Molybdenum Oxycarbide
Authors: Ledoux Marc J. , Delporte Pascale , Pham-Huu Cuong 
Published: April 2011

ABSTRACTA very active and selective molybdenum based catalyst for C6+ linear alkanes isomerization as been found. Physical characterization of this new active phase, such as XPS, XRD, MASN-MR and HRTEM is described.
Application of Defect Modeling to Materials Design
Authors: Spears Marlene A. , Tuller H.L. 
Published: April 2011

AbstractDefect chemical models have been found to be useful in establishing defect generation andtransport mechanisms, extracting thermodynamic data and deconvoluting contributions to the total electrical conductivity. In most cases, however, the utility of the approach has been limited due to the imposed simplifications made to make the analysis more tractable, e.g. the simplified neutrality relation and the elimination of defect associates. In thiswork, we treat more complex equilibria with the aid of numerical methods and illustrate how this approach can be used, not only to extractkey thermodynamic and kinetic data, but also to assist in the design and optimization of materials. Some specific examples with application to solid state ionics will be used to illustrate this approach.
Pulse Applications of Electrochemical Cells Containing Insertion Reaction Electrodes
Authors: Huggins Robert A. 
Published: April 2011

AbstractThere is a rapidly increasing interest in energy sources optimized to provide electrical energy at high power levels for short times. Applications include very short pulses for digital electronic devices, the somewhat longer power pulse demands of some implantable medical devices, and the much larger transient power needs in connection with vehicle traction.Several mechanisms can be used to provide short term energy, with fundamentally different characteristics and applicability to different types of transient output requirements.Four different electrochemical methods can be used to evaluate the critical materials parameters in insertion reaction materials that might be applicable to such applications, and spreadsheet techniques can be used to model the transient transport behavior of such electrodes under various conditions. LaPlace transform methods can then be used to convert information about the physical mechanisms and parameters of individual components into the dynamic response of an electrochemical system.
Non-Stoichiometry and Cation Tracer Diffusion Studies in the Magnetite-UlvÖSpinel Solution, (Fe,Ti)3-δO4
Authors: Aggarwal Sanjeev , Dieckmann Rudiger 
Published: April 2011

AbstractCation diffusion in the spinel solid solution (Fe1-xTix)3-δO4 (0≤ x ≤ 0.3) was investigated at 1200 ºC as a function of oxygen activity, aO2 and cationic composition, x. At different cationic compositions, cation tracer diffusion coefficients, D*Me of Me = Fe and Ti were measured as a function of oxygen activity. Plots of log DMe vs. loga0 show V-shaped curves, indicating that different types of point defects prevail at high anc low oxygen activities. Thermogravimetric experiments were conducted, using a high resolution microbalance, to determine the deviation from stoichiometry in (Fe1-xTix)3-δO4 at 1200 °C. δversus log aO2 curves are S-shaped. An analysis of the oxygen activity dependences of thecation diffusion coefficients and the deviation from stoichiometry with regardto the point defect structure suggests that at high oxygen activities cation vacancies are the predominant defects governing the deviation from stoichiometry and the diffusion ofcations. At low oxygen activities, and at small values of x, cation interstitials determine the deviation from stoichiometry, while they dominate for 0 ≤ x ≤ 0.3 inthe cation diffusion.
Nonstoichiometry and Point Defect Structure of Olivines, (FexMg1-x)2SiO4
Authors: Tsai Tse-Lun , Dieckmann R. 
Published: April 2011

AbstractA thermogravimetric study was conducted on synthetic olivines (FexMg1-x)2SiO4' prepared either by a conventional ceramic methodor a sol-gel method, to determine the nonstoichiometry and the point defect structure. Measurements were carried out as a function of oxygen activity and cationic composition at elevated temperatures. To avoid the dissolution of transition metal components of the silicate into noble metal containers, commonly used in previous investigations, quartz containers were used. The analysis of the point defect structure of olivines based on the new experimental results is presented.
Study of Ac Conductivity in Dilute CeO2:Y3+ Ceramics
Authors: Vaysleyb A.V. , Lim B.S. , Nowick A.S. 
Published: April 2011

AbstractThe ac conductivity was studied for different compositions of CeO2 ceramics, undoped and doped with Y3+ ions in the composition range 1 to 12 atomic %Y over the temperature range from 50 K to 500 K. It was observed that in temperature range 300-400 K, the ac conductivity (as well as the real part of the dielectric constant, ε',) follows the universal power-law frequency dependence with exponent s ≈ 0.63. No systematic variation of s, either with temperature or with dopant concentration, was observed, although for nominally “pure” CeO2 no power-law regime was observed. The features of the ac behavior were explained on the basis of a percolation approach.
Xas Studies of Peo Based Polymer Electrolytes
Authors: Mcbreena J. , Yang X. Q. , Lee H. S. , Okamoto Y. 
Published: April 2011

AbstractX-ray absorption spectroscopy (XAS) has been very useful in elucidation the structure of polymer electrolytes, in particular ion-ion and ion-polymer interactions. Several examples are discussed. One is the use of XAS to study the effect of temperature on ion pairing. The other is the elucidation of the mixed cation effect on electrolyte conductivity. Several investigations have indicated abnormally high oxygen coordination numbers for cations. These are discussed.
Polyaniline: Influence of Polymerization Current Density
Authors: Skaarup Steen , Gunaratne L.M.W.K. , West Keld , Zachau-Christiansen Birgit 
Published: April 2011

AbstractPolyaniline has been synthesized in propylene carbonate by galvanostatic electrochemical polymerization at current densities between 16 and 1000 μA/cm2. Earlier results for polypyrrole have shown that low and high current density films have different properties: The films synthesized at low current density have a higher conjugation length and a more regular structure. The corresponding effect in PANI has been investigated by cyclic voltammetry and UV/visible spectroscopy. Simultaneous measurement of cyclic voltammograms and the absorbtion of selected spectral lines is used because of the complex nature of the PANI system which involves several redox systems as well as forms differing in the degree of protonation and morphology.The main result is that the method of galvanostatic synthesis at low current densities (-16 μA/cm2) produces polyaniline polymers of different, more conjugated and more regular structure than those prepared at higher current densities. The standard method of in situ layer-by-layer polymerization of conducting polymers during cyclic voltammetry often results in uncontrolled and unmeasured current densities of 0.5-2 mA/cm2 which produces a film that probably has a less regular structure containing more deviations from ideality.
Sensors for Acid-Base-Active Gases
Authors: Maier Joachim , Holzinger Michael , Sitte Werner 
Published: April 2011

AbstractThe theoretical background for potentiometric and conductometric (bulk and surface) sensors is briefly discussed with regard to the usual application, viz. the detection of redox-active gases, and the importance of understanding chemical diffusion is stressed in this context. It is then shown how the analogous concept applied to acid-base interactions leads to powerful possibilities to measure partial pressures of acid-base active gases such as CO2, NH3 and H2O. Two examples of novel sensor principles are discussed: i) The response of the surface ionic conductivity of AgCl or CaF2 upon changes of partial pressures of (Lewis) basic or acid gases can be used to sense NH3 and BF3. ii) In the major part of the paper it is shown how the deliberate use of overall acid-base cell reactions in potentiometric arrangements leads to a fast and precise CO2-sensor. For this purpose, open reference electrodes based on Na2Ti6O13 or Na2SnO3 have been constructed. Owing to the criteria developed in the text the whole cell can be exposed to a CO2 and O2 containing atmosphere without the necessity of sealing. Detailed results are given.
Fabrication of V2O5 Thin Films and their Electrochemical Properties in Lithium Microbatteries
Authors: Julien C. , Gorenstein A. , Khelfa A. , Guesdon J.P. , Ivanov I. 
Published: April 2011

AbstractThin films of V2O5 were prepared using the flash-evaporation technique. Amorphous and polycrystalline samples were characterized by X-ray diffraction, Raman spectroscopy and XPS analysis. The electrical properties of the samples were determined. The effect of either deposition parameters or post-deposition treatments, i.e., annealing in various atmospheres and at different temperatures, on transport properties are presented.Electrochemical characteristics are evaluated in V2O5/LiCIO4-PC/Li microbatteries. The discharge curves present several voltage plateaus, similar to those already observed in cells with bulk V2O5 cathodes. Kinetics of lithium intercalation have been investigated as a function of the growth conditions of V2O5 films. Chemical diffusion coefficient and enhancement factor are calculated as a function of the degree of lithium intercalation. All the results are compared with previous reported results for bulk vanadium oxides. The relationship between the crystallinity of the films and their electrochemical features is also discussed.
Thin Film Fuel Cells
Authors: Van Dieten V.E.J. , Dekker J.P. , Schoonman J. 
Published: April 2011

AbstractIn recent years there has been an enormous increase in the application of thin film technologies in the fabrication of solid state electrochemical devices. Devices in which thin film components are utilized are,e.g.solid oxide fuel cells (SOFCs), thin film rechargeable batteries, and chemical gas sensors. Chemical vapour deposition (CVD) is one of the synthesis techniques for the fabrication of thin film components for solid state electrochemical devices. This paper will focus on the application of novel CVD techniques for the fabrication of the thin film components of one of these devices,i.e.the solid oxide fuel cell. A new SOFC design concept which uses only one gas phase synthesis method will be presented.
Thin-Film Electrolytes for Reduced Temperature Solid Oxide Fuel Cells
Authors: Visco Steven J. , Wang Li-Shun , Souza Selmar , Jonghe Lutgard C. De 
Published: April 2011

AbstractSolid oxide fuel cells produce electricity at very high efficiency and have very low to negligible emissions, making them an attractive option for power generation for electric utilities. However, conventional SOFC's are operated at 1000 °C or more in order to attain reasonable power density. The high operating temperature of SOFC's leads to complex materials problems which have been difficult to solve in a cost-effective manner. Accordingly, there is much interest in reducing the operating temperature of SOFC's while still maintaining the power densities achieved at high temperatures. There are several approaches to reduced temperature operation including alternative solid electrolytes having higher ionic conductivity than yttria stablilized zirconia, thin solid electrolyte membranes, and improved electrode materials. Given the proven reliability of zirconia-based electrolytes (YSZ) in long-term SOFC tests, the use of stabilized zirconia electrolytes in reduced temperature fuel cells is a logical choice. In order to avoid compromising power density at intermediate temperatures, the thickness of the YSZ electrolyte must be reduced from that in conventional cells (100 to 200 μm) to approximately 4 to 10 μm. There are a number of approaches for depositing thin ceramic films onto porous supports including chemical vapor deposition/electrochemical vapor deposition, sol-gel deposition, sputter deposition, etc. In this paper we describe an inexpensive approach involving the use of colloidal dispersions of polycrystalline electrolyte for depositing 4 to 10 μm electrolyte films onto porous electrode supports in a single deposition step. This technique leads to highly dense, conductive, electrolyte films which exhibit near theoretical open circuit voltages in H2/air fuel cells. These electrolyte films exhibit bulk ionic conductivity, and may see application in reduced temperature SOFC's, gas separation membranes, and fast response sensors.
Lithium Intercalation from Aqueous Solutions
Authors: Li W. , Dahn J. R. , Root J. H. 
Published: April 2011

AbstractLithium can be intercalated into a variety of materials using aqueous electrochemical methods, provided that certain criteria are met. The materials must be stable in concentrated Li+ aqueous solution and Li intercalation must take priority over hydrogen intercalation. We use X-ray and neutron diffraction, as well as electrochemical methods to investigate if lithium or hydrogen is intercalated into certain hosts. For example, spinel Li2Mn2O4 can be made from spinel LiMn204 by intercalating one Li per mole in an electrochemical cell with 1 M LiOH electrolyte. If the electrochemical reduction is carried out further, beyond one electron per mole, Mn(OH)2 is then formed, as we prove using neutron diffraction. By carefully selecting electrode materials and electrolyte composition it is possible to make rechargeable lithium-ion cells with aqueous electrolytes. For example, LiMn204/γ-Li0.36MnO2 can be selected as an electrode couple, and5 M LiNO3 in water as an electrolyte to make lithium-ion cells with aqueous electrolytes.
Nanostructured Organic/Inorganic Films from Poly (D-Lysine Hydrobromide) or Poly(N-Methyl.4-Vinyl Pyridinium Bromide) and Hectorite
Authors: Kleinfeld Elaine R. , Ferguson Gregory S. 
Published: April 2011

AbstractEstablishing the generality of any new preparative method is important for its future usefulness in applications of interest. In this paper, we build on results reported earlier for the formation of nanostructured ultrathin films from macromolecular precursors (a particular cationic polyelectrolyte and inorganic sheet silicate) by demonstrating that the method can readily be adapted to different polymers and more complex adsorption schemes. In particular, we used ellipsometry to monitor the regular growth of films incorporating poly(D-lysine hydrobromide) or poly(N-methyl-4-vinylpyridinium bromide) (PMVP) and hectorite. For the PMVP/ hectorite films, X-ray diffraction confirmed the presence of structural order by revealing a lattice spacing of 1.5 nm.
Microstructural Aspects of High-Performance Cement-Based Materials
Authors: Jiang W. , Roy D.M. 
Published: April 2011

AbstractThe goal of this research is to improve the physical properties, mechanical properties and durability of cement-based materials by controlling chemistry and processing to produce the desired microstructures and properties. An accompanying initiative is to establish the basic scientific understanding relating processing and microstructure with physical and mechanical behavior, for the future development of new, special purpose, high performance cement-based materials. The research involves both experimentation and theory elucidating fundamental strengthening mechanisms for materials such as warm-pressed, MDF, DSP, polymer, and fiber composites. SEM and computer image analysis were used. Of interest are creating process models that serve as a basis for real applications such as in the following areas: High-performance highway concrete, and the immobilization of radioactive waste.
Image Analysis of Fly Ash in the Characterization of the Shape of the Grains
Authors: Barrioulet M. , Cros H. , Husson B. , Ringot E. 
Published: April 2011

AbstractFly ash from power stations is used as concrete additive to improve strength and durability. Surprisingly, studies of ashes of identical mineralogical composition from two different places have reported different results in terms of the rheological properties of the fresh material. The viscosity of the pastes made from these different fly ashes seems to be linked to the proportion of spherical and smooth-shaped grains found in them. A quantitative image analysis was carried out to characterize the shape of the grains of these two ashes from different geographical origins. The main result proves that the higher the glassy particle content of the fly ash, the more the hydraulic matrix is fluid.
Microstructure and Microchemistry of Calcium Sulfoaluminate Cement
Authors: AndaÇ Ö. , Glasser F.P. 
Published: April 2011

AbstractCalcium sulfoaluminate, 4CaO • 3Al2O3 • SO3, forms the basis of a new class of structural cements. Microstructural examination of commercial clinker is not easy because it is quite friable. However, backscattered imaging of impregnated clinker is successful and reveals an unusual pattern. The clinker has a sponge-like texture connecting better-sintered, denser regions. The microstructure is, however, very similar between regions of differing density. Irregular to equant, well-shaped crystals of 4CaO • 3Al2O3 • SO3 are enclosed in a matrix composed mainly of Ca2SiO4 together with a little titanium-rich, ferrite-like phase. The minor phases occluded within ferrite include oxide phases one of which concentrates Pb and Bi; the other, Cr, Fe and Ni. Other minor oxide phases in the matrix include lime, periclase, gehlenite and calcium sulfosilicate and probably bredigite. The crystal chemistry and elemental analyses of the individual phases are presented.
An Approach to Quantitative Image Analysis for Cement Pastes
Authors: Wang Yuting , Diamond Sidney 
Published: April 2011

AbstractCement paste microstructure as revealed in backscatter SEM presents a number of inherent difficulties that interfere with implementing quantitative image analysis. An approach to overcoming these difficulties is presented, involving gray scale segmentation coupled with application of a hole filling algorithm. Using this approach it is possible to isolate the unhydrated and hydrated portions of phenograins separately, and to combine them for analysis of combined phenograins. Pores and coarse calcium hydroxide masses may also be isolated for feature analysis. Results are reported on mature cement pastes prepared at two water:cement ratios (w:c 0.45 and w:c 0.30) and with and without superplasticizer. It was found that superplasticizer greatly reduced the content and the average size of “visible pores” and increased the content and the average size of coarse CH particles compared to corresponding plain pastes. The area per hydrated phenograin was much smaller in the lower w:c ratio pastes and higher in superplasticized pastes. Among the solid features measured, unhydrated cement particles had the smallest circularity values (at about 2.7) and were the most circular features; Hydrated phenograins had the largest circularity values (at 3.5) and were the most elongated features.
Distribution of Pore Sizes in White Concrete
Authors: Best G. , Cross A. , Peemoeller H. , Pintar M.M. 
Published: April 2011

AbstractNMR is used to study the evolution of the discrete distribution of proton magnetization fractions in hydrating synthetic white cement. The results at 100 hours hydration time are modelled using a trimodel pore size distribution. A good correspondence is found between the NMR analysis and SANS results reported in the literature.
Multitechnique Approach to Understanding the Microstructure of Cement-Based Systems
Authors: Cocke David L. , Yousuf M. , Mollah A. , Vempati R. K. , Hess T. R. 
Published: April 2011

AbstractThe chemistry of cement, its hydration and the development of microstructure in cement-based systems is extremely complex, and it becomes even more complex in the presence of additives. The elucidation of the mechanisms of these processes is a challenging problem and requires the applications of multiple techniques including the latest microscopic methods. The applications of molecular spectroscopies, surface spectroscopies and microscopies have helpeddevelop models and mechanisms for the retardation of cement setting by Zn, Cd and Pb, the chemical and structural effects of superplasticizers, and the interaction of hydrating cement with aggregates, selective sorbents and fillers. The results of these studies indicated that the inhibition of hydration is controlled by dispersion of various charges present in hyperalkaline solution in cement paste. According to this charge dispersal model, the Ca2+ ions from initial hydration form a tightly-bound bilayer with the negatively charged C-S-H surface. Consequent to this intrinsic process, the metalhydroxy or superplasticizer anions immediately surround the bilayer to constitute a trilayer which inhibits further hydration.