bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Grain Size on Corrosion Fatigue of A537 Steel
Authors: Wang Qing , Song Yu-Jiu 
Published: April 2011

AbstractThe influence of grain size on corrosion fatigue behavior of A537 steel in 0.1M HCL solution has been studied. The results show that the increase of grain size can improve the corrosion fatigue crack growth resistance. But the change of crack growth rate da/dN with average grain diameter D is not monotonic. When D>40 μm, crack propagates little faster when grain is larger. When D>40 μm, crack propagates slower when grain is larger. According to the fractographic features, corrosion fatigue mechanism is anodic dissolution under fine grain condition but hydrogen embrittlement under coarse grain condition.
Grain Size Dependent Mechanical Properties in Nanophase Materials
Authors: Siegel Richard W. , Fougere Gretchen E. 
Published: April 2011

AbstractIt has become possible in recent years to synthesize metals and ceramics under well controlled conditions with constituent grain structures on a nanometer size scale (below 100 nm). These new materials have mechanical properties that are strongly grain-size dependent and often significantly different than those of their coarser grained counterparts. Nanophase metals tend to become stronger and ceramics are more easily deformed as grain size is reduced. The observed mechanical property changes appear to be related primarily to grain size limitations and the large percentage of atoms in grain boundary environments. A brief overview of our present knowledge about the grain-size dependent mechanical properties of nanophase materials is presented.
Formation of Amorphous and Nanocrystalline Phases in Mechanically Alloyed Zr-, Al-, and Mg-Base Transition Metal Alloys
Authors: Seidel M. , Eckert J. , Bauer H.-D. , Schultz L. 
Published: April 2011

AbstractZr-, Al-, and Mg-base transition metal alloys have been prepared by mechanical alloying and investigated by x-ray diffraction, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Amorphous phases with significant supercooled liquid region form directly during milling from the crystalline starting materials for Zr- and Mg-base alloys. For Albase alloys the formation of mixtures of amorphous and nanocrystalline phases is observed. The results are compared with data for melt-spun and quenched materials. Possible mechanisms for glass formation and crystallization are discussed.
Mechanical Properties of Nano-Scale Mechanically-Milled NiAl
Authors: Smith Timothy R. 
Published: April 2011

AbstractThis work reports on the mechanical properties of nanocrystalline NiAI materials. Mechanically- milled NiAl with and without Al2O3 additions was forged to 94% of the theoretical density of stoicheometric NiAl at < 0.5 Tm in air. Mechanical properties were investigated by microhardness measurements and the Miniaturized Disk-Bend Test (MDBT). Analysis of the hardness data indicates that most of the compression strengthening is due to the refined microstructure. MDBT results are consistent with tensile tests indicating that the tensile strength is controlled by the strength of grain boundaries.
Crack Velocity Measurements in Sea Ice
Authors: Gluschenkov Oleg , Petrenko Victor 
Published: April 2011

AbstractTo study crack dynamics in sea ice fast measurements of ice electrical resistance and an electromagnetic emission (EME) from cracks were used. The sample dimensions ranged from 0.05 to 30 meters. In a laboratory grown fresh water ice crack velocities varied from a few hundreds to a thousand meters per second while in the natural sea ice crack velocity was very low, about 10 m/s. This remarkable difference in the crack velocities is likely due to the dynamic resistance of unfrozen water in brine pockets and channels and to the high ductility of sea ice. It was found that the cracks propagate in ice discontinuously owing to the strong interaction with such microstructural elements as liquid inclusions and grain boundaries. The high sensitivity of the method allowed to detect nucleation of very first microcracks.
Preparation of Zinc Oxide Films by Low-Pressure Chemical Vapor Deposition Method
Authors: Nishino Junichi , Ohshio Shigeo , Kamata Kiichiro 
Published: April 2011

AbstractZnO and Al-doped ZnO films prepared using a low-pressure chemical vapor deposition (LP-CVD) method were studied. The films were prepared on fused quartz substrates using bis(2,4-pentanedionato)zinc and tris(2,4-pentanedionato)aluminum which are inexpensive and stable source materials. The highly c-axis oriented ZnO films were grown on the substrates above 500°C. The minimum electrical resistivity of ρ=6.5×10−5Ωm was obtained for the ZnO film, and of ρ = 3.5×10−5Ωm was obtained for the ZnO:Al film.
Visualization of Atmospheric Pressure Chemical Vapor Deposition and Powder Spray Pyrolysis by Laser Light Scattering
Authors: Mao Limin , Stewart Ogie , Reck Gene P. , Proscia James W. 
Published: April 2011

AbstractAtmospheric Pressure Chemical Vapor Deposition (APCVD) and powder spray pyrolysis are both pyrolytic thin film deposition techniques that are used to coat glass with thin films at atmospheric pressure. In the present study, the fluid dynamics of each process was investigated by laser light scattering. For each system, a 193 nm ArF excimer laser pulsed at 7 Hz was used for the analysis. In the case of the APCVD reactor, the difference in Rayleigh scattering between helium injected in the reactor and ambient air was used to characterize the process. For the powder spray process, laser scattering off the sprayed powder was used. The effect of various parameters is discussed.
Mixtures in Slit-Micropores with Pore-Walls Structured on Both the Atomic and Nanoscale
Authors: Curry J. E. , Cushman J. H. 
Published: April 2011

ABSTRACTThe grand canonical Monte Carlo method is used to study a binary mixture of Lennard-Jones atoms confined to various corrugated slit-micropores which are in thermodynamic equilibrium with their bulk phase counterpart. The micropore walls have the structure of the (100) face of an fcc lattice. In addition to this atomic scale structure, one wall possesses nanoscale structure in the form of rectilinear grooves (corrugation). The grooved surface divides the confined fluid film into two strip shaped regions. The confined film is studied in each region as a function of groove width, bulk phase composition, and the size of the wall atoms.
Dynamical Buckling Transitions of a Confined Colloidal Monolayer
Authors: Murray Cherry A. , Sprenger Wolfgang , Seshadri Raj , Cerise Jane E. 
Published: April 2011

ABSTRACTWhen a rigid two-dimensional triangular crystalline layer of colloidal spheres confined between two smooth repulsive walls is gradually given freedom to move out of plane, it buckles dynamically undergoing several Peierls transitions involving different soft phonon modes before forming a two layer crystal with square in-plane symmetry. We have mapped out the complex phase diagram of the buckling transitions as a function of sphere density and wall separation. Digital imaging is used to study the instantaneous particle positions and trajectories of the uniform, highly charged 0.3 μm diameter polystyrene spheres that comprise the crystalline layer in water suspension. Brownian motion of the spheres creates a true thermodynamic system with a real temperature, which is studied using video microscopy. We follow the collective dynamics of the system as well as individual particle motions and the motions and rearrangements of topological defects and domains. At sufficiently low sphere densities the system melts into a fluid. As the wall separation increases to the point of two layer formation we observe square symmetry in the fluid correlation volumes.
Depression of the Glass Transition Temperature in Ultra-Thin, Grafted Polystyrene Films
Authors: Keddie J. L. , Jones R. A. L. 
Published: April 2011

ABSTRACTWe have used ellipsometry to measure the glass transition temperature (Tg) of ultrathin films of polystyrene (PS) (less than 10 nm thick) obtained by grafting PS-COOH on the native oxide of Si. We find that Tg in these ultra-thin films is depressed from the bulk value by as much as, 35 K. This is in qualitative accord with our earlier results on thicker non-grafted films of PS.
Robustness of Methane Diffusion in Geometrically Restricted Molecular Sieve Pores
Authors: Nivarthi Sriram S. , Davis H. Ted , McCormick Alon V. 
Published: April 2011

ABSTRACTNMR measurements of sorbate mobility in zeolites are especially attractive because of their capability of measuring multicomponent and anisotropic self-diffusion. We have recently reported the application of the pulsed field gradient NMR technique using very large zeolite crystals to study how easily methane can diffuse when we attempt to slow its migration by crowding the pore space. Here we analyze the implications of these PFG NMR experiments involving (i) ethylene blocking of methane in zeolite NaY; and (ii) methane molecules trying to pass one another in the molecular sieve A1PO4-5.
Adsorption on Rough Surfaces
Authors: Segars Ronald , Piscitelle Louis 
Published: April 2011

ABSTRACTA new model for adsorption on rough surfaces is derived. The model predicts behavior regarding surface smoothing that agrees well with experimental observations. Computer simulations show the model capable of matching a wide variety of isotherm patterns with reasonable physical constants. These simulations also show that a significant error results in applying the standard BET equation to adsorption data obtained on rough surfaces.
X-ray Scattering Studies of Molecular Ordering Phenomena in Confined Films
Authors: Sinha Sunil K. , Tolan M. , Vacca G. , Lit Z. , Rafailovich M. , Sokolov J. , Lorenz H. , Kotthaus J. P. , Feng Y. P. , Grubel G. , Abernathy D. 
Published: April 2011

ABSTRACTA knowledge of the structural behavior of molecules confined in thin liquid films and the way in which they differ from bulk behavior is of great importance to a variety of technological applications. We discuss X-ray scattering studies of the conformation of liquid polymer wetting layers on laterally structured substrates in order to test theories of the conformality of the wetting layer to the substrate. Recent work on guided X-ray beams confined to the thin film opens up the possibility of detailed studies of ordering phenomena in molecular layers adjacent to solid surfaces. Recent experiments are discussed.
Microwaves for Reduction of Iron Ore Pellet by Carbon
Authors: Gomez Idalia , Aguilar Juan A. 
Published: April 2011

ABSTRACTResults of reducibility tests of reduction conducted on iron ore pellets by carbon are presented in this work. Work done is centered on reduction kinetics by carbon with conventional heat supply (heat transfer process) compared with reduction kinetics where heat is supplied by microwaves to whole volume. Ore used in this work is called “Alzada” which has reducibility characteristics well known, and is often used as standard for comparison. Importance of using actual pellet instead of dust is pointed. This work is part of a project related with microwaves for reduction of metallic oxides.
Experimental Study of a Reaction-Diffusion System in a Capillary: Complex Behavior of a Seemingly Simple System
Authors: Lin Anna , Yen Andrew , Koo Yong-Eun , Kopelman Raoul 
Published: April 2011

ABSTRACTWe study a reaction-diffusion system within the confines of a thin capillary tube. Xylenol orange and Cr 3+ are introduced into a capillary tube from opposite ends and meet in the middle forming a reaction front. Unequal initial concentrations of the reactants causes the center of the reaction front to move in time. Characteristics of the front such as the width of the reaction zone, w, the position of the center of the front, xf, the global reaction rate, R, and the local reaction rate, r(xf,t) are determined by continuously monitoring the product concentration in space vs. time. We observe crossover of the global rate from classical to non-classical behavior and a splitting of the reaction front.
Substrate-Dependent Features of Polyethylene Oxide (Peo) Adsorption from Aqueous Solution: Competitive Adsorption Versus Surface Relaxations
Authors: Santore M. M. , Rebar V. A. 
Published: April 2011

ABSTRACTThis work employed total internal reflectance fluorescence (TIRF) to examine the adsorption kinetics of polyethylene oxide (PEO) on silica from aqueous solution in controlled shearing flow. Studies with PEO, fluorescently labeled such that TIRF tracked the chain number on the surface, exhibited an overshoot in the early stages of adsorption. This overshoot was not seen with other polymers such as polyvinyl alcohol, and hydroxyethyl cellulose, possibly because these other polymers were labeled such that TIRF measured the interfacial mass. Indeed, reflectometry studies of PEO adsorption, sensitive to interfacial mass, showed no overshoot. This suggests that the overshoot results from the selectivity of the surface for high molecular weight populations within a polydisperse sample. Initially short chains adsorb because they diffuse to the surface quickly. At longer times, higher molecular weight chains reach the surface and replace the short chains. This evolution occurs as the mass coverage increases (according to reflectivity) but the number of adsorbed chains, and hence the TIRF signal decrease at long times. A study of the impact of the molecular weight distribution confirmed this hypothesis.Several complications to the molecular weight selectivity hypothesis, however, arose: First, the same PEO samples which overshot during adsorption on silica showed no overshoot on a polystyrene substrate. This suggested that the ability to overshoot was governed by the substratesegment interactions, even though the molecular weight distribution within the sample determined the overshoot shape. Further, the effect of transport conditions (wall shear rate, bulk polymer concentration) were not completely consistent with the molecular weight competition hypothesis, which was based on surface-solution equilibrium, taking into account transport-limited rates of adsorption. Finally certain runs, where the adsorption process was interrupted by solvent flow and later allowed to proceed, never reached the full coverage seen for uninterrupted runs. Hence, the surface coverage and possibly the chain configurations can depend on the history of the adsorption process, a feature which points to surface relaxations and non-equilibrium structures.
Initially Separated Reaction-Diffusion Systems
Authors: Taitelbaum Haim , Vilensky Baruch , Koo Yong-Eun Lee , Yen Andrew , Lin Anna , Kopelman Raoul 
Published: April 2011

ABSTRACTCharacteristics of the A + B → C reaction-diffusion system with initially separated components are studied theoretically and experimentally. When the reaction is slow, the two species will mix before reacting. This leads to a series of crossovers from a rich initial behavior to an asymptotic time behavior. The crossovers depend on the system parameters, such as the diffusion coefficients and initial densities of the two species. In this paper we review our recent studies on this system. We elaborate on a theoretical study of momentum effects, and then focus on theoretical explanations of two experimental phenomena: 1) Non-universal and non-monotonic motion of the reaction front center. The latter occurs when one of the reactants has larger diffusion coefficient but smaller initial density. 2) Existence of more than one front. This occurs when two different transformations of the same reactant (on one of the sides of the system), react with the reactant on the other side with a different reaction constant - the majority slowly, but the minority much faster.
Chemisorption of Self Assembled Alkyl Thiol on Au(111)
Authors: Yeganeh M. S. , Dougal S. M. , Polizzotti R. S. , Rabinowitz P. 
Published: April 2011

ABSTRACTWe have used infrared-visible sum-frequency generation (SFG) to spectroscopically probe the interfacial structure of a self assembled monolayer (SAM) of alkyl thiol on a Au(111) surface. The SFG spectra of the CH3 group measured as a function of azimuthal angle indicates that sulfur atoms cannot be situated at sites of a single type, e.g., hollow or bridge, but must be in a mixed arrangement. SFG is also used to study the reconstruction of the gold substrate by alkyl thiol.
Dewetting of Polymer Bilayers: Morphology and Kinetics
Authors: Faldi Alessandro , Winey Karen I. , Composto Russell J. 
Published: April 2011

ABSTRACTThe kinetics of de-wetting a polycarbonate (PC) film from a poly(styrene-coacrylonitrile) (SAN) copolymer film was monitored using optical microscopy. Whereas the SAN layer was stable upon annealing at 190°C, the PC layer dewetted the SAN and formed holes whose diameter increased linearly with time. Auger electron spectroscopy measurements confirmed that PC was fully removed from the interior of the hole. Upon varying the AN content, the dewetting velocity was found to be a minimum near 0.27 weight percent AN. This result is consistent with the interfacial thermodynamics between PC and SAN. Atomic force microscopy was used to provide a unique image of the hole profile.
Monte Carlo Simulation of a Lattice Model of Microemulsions in Porous Media
Authors: Nowroozi Parisa , Sahimi Muhammad 
Published: April 2011

ABSTRACTMonte Carlo simulations are used to study various properties of a new lattice model of microemulsions. In particular, we calculate the critical exponent β of the order parameter (water concentration) and the correlation length exponent ν, and find them to be in excellent agreement with those of the 3D Ising model, and also in agreement with the experimental measurements. However, when the same exponents are calculated for the microemulsions in a porous medium, they do not agree with those of either the dilute or the random-field Ising model.
Direct Evidence of Surface Roughness in Small Metallic Particles
Authors: Yacaman Miguel Jose , Tehuacanero Samuel , Zorrilla Cristina , Diaz Gabriela 
Published: April 2011

ABSTRACTThe characterization of nanoparticles is of prime importance in catalysis. High Resolution Electron Microscopy coupled with image processing has produce a lot of new information on the detailed structure of the particles. In this paper we discuss the possibility of applying these techniques to the study of surface roughness.
Electronic and Structural Requisites for Catalytic Activity in Copper-Ruthenium Catalysts
Authors: Malaty M. , Singh D. , Vadel Noel , Gomez M.L. , Palmieri M. , Jansen S.A. , Lawrence S. 
Published: April 2011

ABSTRACTA system made by combining two non-alloying metals, ruthenium and copper, using alumina as a support was studied. This bimetallic supported catalyst has been used mainly in hydrogenolysis, dehydrogenation and oxidation reactions of hydrocarbons. The samples were characterized by Electron Paramagnetic Resonance Spectrometry (EPR) and X-ray Diffraction (XRD). These two molecular techniques are ideal for studying the electronic and structural changes of the samples at different temperatures and concentrations. Catalytic reactions were performed using the catalyst in the reduced and non-reduced forms on a series of catalytic hydrogenations. A correlation between the electronic, structural and catalytic properties has been made. A correlation of catalytic process to molecular phenomena has yield a better understanding of the catalytic site.
EPR Analysis of Copper Exchanged and Encapsulated Copper (SALEN) Complex in Zeolite - Y
Authors: Ulagappan N , Krishnasamy V 
Published: April 2011

ABSTRACTCopper exchanged and copper-(salen) complex encapsulated in zeolite-Y were prepared. The encapsulaled complex was analysed by TGA, DRS and IR, which confirms the presence of complex in zeolite. Both copper materials were examined by EPR spectra, and the calculated spin-Hamiltonian parameter indicates the copper complex is more covalent in character than NaCu-Y.
Selective Hydrogenation of Crotonaldehyde Over Cobalt Based Self-Supported Catalysts
Authors: Patil A. N. , Bañares M. A. , Lei X. , Fehlner T. P. , Wolf E. E. 
Published: April 2011

ABSTRACTComplex cobalt-carbonyl ligand based clusters of clusters are used as molecular precursors for self-supported model catalysts. These precursors consist of two metal layers: an outer of the complex Co-carbonyl ligands, and a core of metal (e.g. Co or Zn) carboxylate groups. Partial thermolysis at low temperature (LT) of these materials under hydrogen results in almost completely decarbonylated material with a mainly unchanged carboxylate metal core. Complete pyrolysis at higher temperatures (HT) in hydrogen leads to mixed metal environment. These materials were used as a heterogenous catalyst in the gas phase hydrogenation of crotonaldehyde. The maximum yield of 27 % of desired product crotyl alcohol was observed when HT-CoCo was used as the catalyst at 423 K. The catalyst activity and the crotyl alcohol selectivity remained unchanged over 2 days of operation. The bimetallic ZnCo catalysts showed lower selectivity to crotyl alcohol than the CoCo catalysts.
Synthesis and Properties of Lanthanide-Exchanged Preyssler's Heteropolyanions
Authors: Antonio Mark R. , Malinsky J. , Soderholm L. 
Published: April 2011

ABSTRACTNa+ in the Preyssler heteropolytungstate anion [NaP5W30O110]14− can be exchanged for a trivalent lanthanide ion. The potential significance of this new class of lanthanide heteropolyanions relates to their applications in catalysis science. This view follows from the fact that Keggin heteropolyanions and their free acids are used as heterogeneous solid catalysts and homogeneous solution catalysts. We describe synthetic conditions that lead to the incorporation of Ce3+ and Pr3+ within the Preyssler anion, and the coprecipitation of Ce3+ and the Preyssler anion. Initial studies indicate that the latter, coprecipitated, material deserves study for bifunctional catalytic activity.
EXAFS, XPS and TEM Characterization of SnO2-Based Emission Control Catalysts
Authors: Harrison Philip G. , Daniel Wayne , Lloyd Nicholas C. , Azelee Wan 
Published: April 2011

ABSTRACTCatalysts formed by sorption of Cr(VI) on to tin(IV) oxide have been investigated by EXAFS, XPS and TEM. The latter shows that uncalcined catalysts comprise uniform, homogeneous particles of dimensions 2nm which increase to 4nm on calcination at 400°C. Calcination at higher temperatures results in an increase in particle size to 20nm × 30nm at 600°C, ca. 60nm at 800°C, and 90–100nm at 1000°C. XPS data show the evolution of chromium(III) species upon calcination and both chromium(VI) and chromium(III) species exist at all calcination temperatures. Chromium K-edge XANES also shows the presence of tetrahedral chromium(VI) species at all calcination temperatures, but the relative abundance decreases with increase in calcination temperature. Corresponding EXAFS data indicate that the uncalcined catalyst contains sorbed four-coordinated {Cr2O7} species whereas calcination produces six-coordinated {CrO6} species together with some residual tetrahedrally coordinated chromium. EXAFS data show that adsorbed {Cu(H2O)6} is the copper(II) species present prior to calcination of CuII-SnO2 catalysts.
Co Oxidation by Bi2MoO6-γ(H) Catalyst
Authors: Galván D. H. , Avalos-Borja M. , Fuentes S. , Cota-Araiza L. , Cruz-Reyes J. , Castillón F. F. , Maple M. B. 
Published: April 2011

ABSTRACTWe present a study of a Bi-Mo catalyst, obtained by solid state reaction, for the oxidation of CO. Bismuth-molybdate catalysts form several phases (β3-Bi2Mo2O9, α-Bi2Mo3O12 and γ-Bi2MoO6, among others), depending upon the Bi/Mo ratio and the preparation method [1]. The γ-Bi2MoO6 phase is the one that is stable at high temperatures, according to the phase diagram, and is the one we used as catalyst for the conversion of CO [2].