bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thin Liquid Films: Instabilities of Driven Coating Flows on a Rough Surface
Authors: Kondic L. , Bertozzi A. 
Published: April 2011

AbstractThe flow of a thin layer of fluid on a solid surface is of considerable technological importance; many industrial applications, ranging from spin coating of microchips to the design of photographic film, are susceptible to often undesirable instabilities. We use a recently developed numerical scheme to analyze the problem of flow down an inclined plane, and concentrate on the case of completely wetting fluid characterized by a small precursor film height, b. In particular, we explore the role of imperfections of the solid surface, exploring the influence of the length scale of the surface roughness on the film stability and eventual pattern formation (fingers and rivulets). It is found that perturbations characterized by very short length scale do not influence considerably the film stability, in contrast to the perturbations specified by longer length scales. Further, we find that the role of imperfections becomes more pronounced at smaller precursor film thicknesses, b. We also analyze the effect of a time dependent body force on the film stability.
Diffusion in Two Dimensions in The Presence of Sinks
Authors: Lavine J. P. 
Published: April 2011

AbstractThe diffusion of electrons in two dimensions is investigated when the model space has one or more sinks. A random walk approach is used to follow each electron until it is trapped at a sink. The times to capture are combined to form the survival time distribution. This is found to decay exponentially with time for the cases considered here. The characteristic time for the decay depends directly on the model space area and inversely on the number of traps or sinks and the trap radius. Power laws with non-integers are found for all three parameter dependences.
Diffusion and Reactive Properties in Disordered Porous Media and in Confining Geometries
Authors: Levitz Pierre 
Published: April 2011

AbstractDisordered porous networks are important examples of confining geometries. A challenging problem is to couple the morphology and the topology of such disordered systems with the diffusion and the reactive properties of embedded fluids (gases or liquid) inside the porous medium. Looking at the properties of the self-diffusion propagator, we first discuss how the geometric confinement influences the molecular diffusion and how the coupling between interfacial geometry and transport evolves in space and time. In the long time regime, two specific situations are presented. First, we focus on transport properties inside a membrane-like disordered matrix, the sponge phase (symmetric or asymmetric). Second, we discuss some basic properties of the Knudsen diffusion. The particular coupling with the pore network geometry allows to analyse this transport process in term of the continuous time random walk formalism (C.T.R.W.). An interesting consequence for some specific disordered porous media or “low dimension” geometries is a transition from a Gaussian diffusion to a Levy walk. Finally, excitation and relaxation kinetics are discussed. More specifically, NMR relaxation of water inside a Vycor glass is investigated and a comparison with recent experimental results is presented.
Molecular Configurations and Solvation Forces in Confined Alkane Films
Authors: Wang Jee-Ching , Fichthorn Kristen A. 
Published: April 2011

AbstractWe review the results of two studies [1,2] aimed at clarifying the surface forces of con fined fluids. In the first study [1], molecular-dynamics simulations are used to study the influence of chain branching on the molecular configurations of alkane films physically adsorbed on a solid surface. The symmetric n-decane molecules exhibit strong layering, while t-butyl-hexane films have a novel pillared-layered structure, in which a few randomly distributed molecules orient themselves with the t-butyl end near the surface and the alkyl tail perpendicular to the surface. These molecules are surrounded by parallel, layered molecules. In the second study [2], we outline the development of a new NP‖AT ensemble method, with advantages for simulating confined fluids. For confined Lennard-Jones particles simulated with the new method, clear oscillatory solvation-force profiles and step-like dependencies of the number of confined molecules on surface separation were observed. As the parallel pressure increases, the oscillations in solvation forces are enhanced and tend to become repulsive.
Low Dielectric Constant Fluorocarbon Films
Authors: Lau K. K. S. , Gleason K. K. 
Published: April 2011

IntroductionChemical vapor deposition (CVD) continues to generate immutable interest as a method of producing thin fluorocarbon films. This impetus stems from both the process advantages of CVD and the extensive market potential for the resultant films. Fluorocarbon films find extremely diverse applications because of their unique electrical, chemical and surface properties. They are currently being evaluated, among other applications, as dielectric interconnects in microelectronic circuits1–3 and as passivation coatings in clinical devices.
Temperature Stability Of Plasma Polymerized Antiadhesive Coatings
Authors: Michaeli W. , Dahlmann R. , Fonteiner I. 
Published: April 2011

AbstractBy means of microwave-assisted plasma polymerization it is possible to deposit polymer coatings on different surfaces such as plastics or metals. The surface tension can be influenced in a wide range. However, many applications require a high thermal stability of such low surface tension layers. Therefore, the influence of variations of the process parameters on temperature stability of such layers is examined. The produced layers were studied regarding their chemical and physical characteristics under temperature influence by means of contact angle measurements, xray photoelectron spectroscopy (XPS), thermo gravimetric analysis (TGA) combined with Fouriertransformed infrared spectroscopy (FTIR). Fluorine containing monomers offer good perspectives. Up to temperatures of approx. 200°C the antiadhesivity of these coatings is adjustable to values close to those of poly(tetrafluoroethylene) (PTFE).
Recent Measurements of Experiment Sensitivity to G-Jitter and Their Significance to ISS Facility Development
Authors: Herring R. A. , Tryggvason B. 
Published: April 2011

AbstractRecent experimental measurements of various microgravity experiments have been taken on the Mir and Space Shuttle under different conditions of microgravity using the Microgravity-vibration Isolation Mount (MIM). The results to date show a clear difference when the experimental measurements are taken from g-levels offered by the Mir and the Space Shuttle (non isolated) to g-levels offered by MIM (isolated) which have been reduced by two orders of magnitude. Concern for the International Space Station (ISS) experimental facilities arises when the quality of microgravity on the Mir and Space Shuttle (non isolated), which is believed to be not good enough, has been measured to be better than the ISS Requirement established by NASA for isolated racks, which will be significantly better than those racks not isolated.
High Growth Rate Metal-Organic Molecular Beam Epitaxy for the Fabrication of GaAs Space Solar Cells
Authors: Freundlich A. , Newman F. , Aguilar L. , Vilela M. F. , Monier C. 
Published: April 2011

AbstractRealization of high quality GaAs photovoltaic materials and devices by Metal-organic Molecular Beam Epitaxy (MOMBE) with growth rates in excess of 3 microns/ hours is demonstrated. Despite high growth rates, the optimization of III/V flux-ratio and growth temperatures leads to a two dimensional layer by layer growth mode characterized by a (2×4) RHEED diagrams and strong intensity oscillations. The not intentionally doped layers exhibit low background impurity concentrations and good luminescence properties. Both n(Si) and p(Be) doping studies in the range of concentrations necessary for photovoltaic device generation are reported. Preliminary GaAs (p/n) tunnel diodes and solar cells fabricated at growth rates in excess of 31µm/h exhibit performances comparable to state of the art and stress the potential of the high growth rate MOMBE as a reduced toxicity alternative for the production of Space 111-V solar cells.
Electronic Structure, Charge Transfer and Bonding in Intermetallics Using EELS and Density Functional Theory
Authors: Humphreys C. J. , Botton G. A. , Pankhurst D. A. , Keast V. J. , Temmerman W. M. 
Published: April 2011

ABSTRACTElectron energy loss spectroscopy and density functional theory have been used to show that there is a covalent component to the bonding in NiAl, CoAl and FeAl, between the transition metal atom and Al. There is no charge transfer and no ionic component to the bonding in NiAl and probably not in CoAl and FeAI. The bonding in non-stoichiometric NiAl is studied. Preliminary results are given for a Σ3 boundary in NiAl.
High-Temperature Phase Transformation in Cr Added TiAl Base Alloy
Authors: Abe E. , Niinobe K. , Nobuki M. , Nakamura M. , Tsujimoto T. 
Published: April 2011

ABSTRACTWe have investigated a microstructure evolution of a Ti-48Al-3.5Cr (in at.%) alloy at high-temperatures (>1473K). In the alloy annealed at 1673K for 1.8ks, followed by air-cooling, a characteristic microstructure with a feathery fashion was uniformly formed. From a cooling-rate-controlling study, it was found that formation of the feathery structure is accomplished during continuous cooling from 1673K to 1573K, within the α+γ two-phase region. Transmission electron microscopy revealed that the feathery structure is composed of lamellar colonies (5–10µm) which are crystallographicaly tilted slightly (a few degree) with their neighbors. A surprising fact is that lamellae in each colony are mostly the γphase with few α2 phase less than 5% in volume. This suggests that the feathery structure is a metastable product and has not resulted from the α → α+γ transformation above 1573K. Instead, the feathery structure formation should be attributed to the non-equilibrium α → γtransformation which occurs at high-temperatures with a small degree of supercooling. We discuss this interesting phase transformation in terms of the α→γ massive transformation, based on the continuous-coolingtransformation (CCT) diagram constructed for the present alloy.
Iron Aluminide Composites
Authors: Schneibel J. H. 
Published: April 2011

ABSTRACTIron aluminides with the B2 structure are highly oxidation and corrosion resistant. They arethermodynamically compatible with a wide range of ceramics such as TiC, WC, TiB2, and ZrB2. Inaddition, liquid iron aluminides wet these ceramics very well. Therefore, FeAI/ceramic compositesmay be produced by techniques such as liquid phase sintering of powder mixtures, or pressureless meltinfiltration of ceramic powders with liquid FeAl. These techniques, the resulting microstructures, andtheir advantages as well as limitations are described. Iron aluminide composites can be very strong.Room temperature flexure strengths as high as 1.8 GPa have been observed for FeAl/WC. Substantialgains in strength at elevated temperatures (1073 K) have also been demonstrated. Above 40 vol.% WCthe room temperature flexure strength becomes flaw-limited. This is thought to be due to processingflaws and limited interfacial strength. The fracture toughness of FeAl/WC is unexpectedly high andfollows a rule of mixtures. Interestingly, sufficiently thin (<1 μm) FeAl ligaments between adjacentWC particles fracture not by cleavage, but in a ductile manner. For these thin ligaments the dislocationpile-ups formed during deformation are not long enough to nucleate cleavage fracture, and theirfracture mode is therefore ductile. For several reasons, this brittle-to-ductile size transition does notimprove the fracture toughness of the composites significantly. However, since no cleavage cracks arenucleated in sufficiently thin FeAl ligaments, slow crack growth due to ambient water vapor does notoccur. Therefore, as compared to monolithic iron aluminides, environmental embrittlement is dramaticallyreduced in iron aluminide composites.
Production and Characterization of Nanostructured Ti-Based Intermetallics
Authors: Calderónt H. A. , Garibay-Febles V. , Cabrera A. , Umemoto M. , Cabañas-Morenol J. G. , Tsuchiya K. 
Published: April 2011

ABSTRACTMechanical alloying and plasma assisted sintering are used to produce nanocrystalline Ti-Al alloys. Microstructural characterization and measurement of mechanical properties are reported. The alloys investigated include AITi+X and Al3Ti+X where X represents either Cr, Mn or Fe. Mechanical alloyed powders have a microstructure, which consist of an amorphous matrix containing small crystalline domains. Sintered specimens have a crystalline microstructure with nano-sized grains. Alloys based on AlTi-X are composed mainly of the phases α 2 (DO19) and γ (Ll0) distributed homogeneously in the form of nanograins (100–300 nm) resembling a globular structure. Al3Ti-X alloys show a cubic ordered phase (L12) with grain sizes ranging from 16 to 40 nm. Vickers hardness measurements of sintered alloys show a considerable increase with respect to as-cast alloys. Compression tests show a high mechanical strength of these alloys, although in the case of A13Ti-X, no ductility is found.
Characteristics of Ordinary ½⟨110] Slip in Single Crystals of γ-TiAl
Authors: Jiao S. , Bird N. , Hirsch P. B. , Taylor G. 
Published: April 2011

ABSTRACTA study of the occurrence of ordinary slip in single crystals of Ti 54.5 at% Al with various orientations at different temperatures shows that the critical resolved shear stress is approximately the same for ¼⟨110] slip on {111} and {110} planes near the peak of the yield stress anomaly. However the shapes of the glide loops are quite different, suggesting that the order of relative mobilities of screw and edge dislocations is reversed in the two cases. The reason for this and its possible effect on the mechanism responsible for the yield stress anomaly of ½⟨110] {111} slip are discussed. Experiments on the thermal reversibility of the yield stress when either ordinary- or super- dislocation slip systems are operating at both temperatures have shown that the yield stress is reversible for the latter but not reversible in the former case.
Burner Rig Hot Corrosion of a Single Crystal Ni-48Al-Ti-Hf-Ga Alloy
Authors: Nesbitt J. A. , Darolia R. , Cuy M. D. 
Published: April 2011

ABSTRACTThe hot corrosion resistance of a single crystal Ni-48Al-1Ti-0.5Hf-0.2Ga‡ alloy was examined in a Mach 0.3 burner rig at 900C for 300 hours. The combustion chamber was doped with 2 ppmw synthetic sea salt. The hot corrosion attack produced a random mound morphology on the surface. Microstructurally, the hot corrosion attack appeared to initiate with oxide-filled pits which were often broad and shallow. At an intermediate stage, the pits increased in size to incorporate unoxidized Ni islands in the corrosion product. The rampant attack stage, which was observed only at sharp sample corners, was characterized by rapid inward growth of alumina in finger-like protrusions incorporating significant amounts of Al-depleted Ni islands. Aluminum consumption in the oxide fingers resulted in the growth of a γ' layer ahead of the advancing oxide fingers.
Clustered, Terraced And Mixed Surface Phases Of The Al70Pd21Mn9 Quasicrystal
Authors: Ledieu J. , Munz A. W. , Parker T. M. , McGrath R. , Diehl R. D. , Delaney D. W. , Lograsso T. A. 
Published: April 2011

AbstractThe five-fold surface of the Al70 Pd21 Mn9 quasicrystal has been studied using STM, LEED and AES. STM images from surfaces which have been sputtered and annealed to 875 K reveal 20-30 Å protrusions that have been identified by others as Mackay-type clusters. Higher-resolution images reveal substructures in these clusters having dimensions 2-3 Å. Longer annealing times at 875 K produced large areas having flat terraces which were imaged with atomic resolution. The LEED pattern from this surface has sharp spots on a low background, and AES indicates that the surface is deficient in Mn relative to the bulk. For surfaces annealed to 1050 K for less than 2 hours, STM images indicate that cluster and terrace phases coexist, and a third phase having aligned arrays of clusters is identified which appears to be intermediate between the cluster and terrace phases.
Symmetry Changes At The Surface Of Al70Pd20Mn10
Authors: Bolliger B. , Erbudak M. , Hensch A. , Kortan A.R. , Vvedensky D.D. 
Published: April 2011

AbstractSputtering with Ar+ ions induces structural phase transitions at the pentagonal surface of the icosahedral quasicrystal Al70Pd20Mn10. Sputtering at different temperatures changes the surface composition, thereby stabilizing different structures. At room temperature, the structure changes to body-centered cubic but, at elevated temperatures, it displays decagonal symmetry. In both cases, annealing the sample restores both the bulk composition and the icosahedral symmetry of the original surface.
Plastic Deformation of Approximants: Dislocations vs. Phason Lines
Authors: Klein H. , Feuerbacher M. , Schall P. , Urban K. 
Published: April 2011

AbstractDeformation experiments were performed on single crystals of the ξ-AIPdMn approximant in bending geometry at high temperature. Two different mechanisms of plastic deformation are shown to exist in this phase: one based on dislocations and another novel mechanism based on the motion of phason lines. Burgers vector and line directions of dislocations were determined. Phason lines are shown to build a periodic lattice. The interaction of a dislocation with the phason line lattice results in dislocations on another length scale. This meta-dislocation in the periodic phason line lattice has a Burgers vector of magnitude 165 Å. The relative importance of phason lines and dislocations for the plastic deformation is discussed as a function of the orientation of the sample with respect to the bending geometry.
Crystal Growth Of A Decagonal AI-Co-Ni Quasicrystal
Authors: Guo J.Q. , Sato T. J. , Kimura T. , Hirano T. , Tsai A. P. 
Published: April 2011

AbstractWe have grown a decagonal single quasicrystal with a size of centimeter order in an A172Co16Ni12 alloy by floating zone method at a growth rate of 0.5 mm/h. The single decagonal quasicrystal has been inspected by Laue X-ray as well as neutron diffraction, revealing a very high quasicrystalline quality. By quenching the liquid during growth, a flat solid-liquid interface has been directly observed. There exists solute redistribution at the growing solid-liquid interface. At steady state growth Al is enriched and Co, Ni are depleted in front of solid-liquid interface. Solute partition ratios of Al, Co and Ni were determined to be about 0.91, 1.57 and 1.08, respectively.
Porous Structure And High Electrical Resistivity Of AIPdRe Icosahedral Phase
Authors: Kirihara K. , Kimura K. 
Published: April 2011

AbstractMechanism of the structure formation of the I-phases, which is required for complete understanding of the origin of their high electrical resistivity and preparation of the high quality samples, is proposed. During annealing within 30 minutes, atomic difiusion of Al and Pd atoms from Al3Pd phase to Al07Re0.3 phase occurs and porosity is formed in the Al3Pd phase. It is supposed that the porosity formation results from Kirkendall effect.
Thermal Expansion And Grüneisen Parameters Of Quasicrystals
Authors: Edagawa K. , Kajiyama K. , Takeuchi S. 
Published: April 2011

AbstractTo investigate anharmonic phonon properties, thermal expansion measurements have been performed for icosahedral (i-) Al-Pd-Mn and decagonal (d-) Al-Cu-Co quasicrystals by X-ray diffractometry in the temperature range between 100 and 800K. The linear thermal expansion coefficient α(T) of i-Al-Pd-Mn is 1.1 × 10−5K−1 at 300K, which is about a half of that of pure Al phase. The measured α(T) of d-Al-Cu-Co coincides almost completely with that of i-Al-Pd- Mn and no appreciable anisotropy was detected between the tenfold periodic direction and a quasiperiodic direction perpendicular to it. The Grfneisen parameter γ(T), has been evaluated from the measured α(T) using the data of lattice specific heat and elastic moduli previously reported. The γ(T) values for the two phases are comparable to those for conventional metallic crystals and almost constant over the temperature range studied.
The Dodecagonal Quasicrystalline Telluride (Ta, V)1.6Te And Its Crystalline Approximant (TaV)97Te60
Authors: Reich C. , Conrad M. , Krumeich F. , Harbrecht B. 
Published: April 2011

AbstractThe dodecagonal (dd) quasicrystalline tantalum telluride dd Ta1.6Te and the crystalline approximant Ta97Te60have been modified by partly replacing tantalum by vanadium. The impact of the substitution on the structures has been studied by X-ray and electron diffraction and by high-resolution transmission electron microscopy. The layered-type approximant structure of Ta83V14Te60was determined by single crystal X-ray means. The partitioning of vanadium on 21 out of 29 crystallographically inequivalent metal sites is referred to, but not controlled by the Dirichlet domain volume available at the sites. A HRTEM projection of dd (Ta, V)1.6Te onto the dodecagonal plane is analysed with respect to the arrangement of (Ta, V)151Te74clusters on the vertices of an irregular aperiodic square-triangle tiling, the edge length of which corresponds to the distance between the centres of two such clusters. The clusters comprise about 1 nm thick corrugated lamellae which are periodically stacked by weak Te-Te interactions.
Effect of Network Elasticity on Nematic Liquid Crystal/Cross-Linked Polymer Phase Diagram
Authors: Nwabunma D. , Kyu T. , Pogue R.T. , Bunning T.J. 
Published: April 2011

ABSTRACTThe influence of elasticity on the phase behavior of a mixture of nematic liquid crystal (LC) and in-situ cross-linked polymer has been investigated. Unlike the phase diagram of the LC/pre-cured polymer, the experimental diagram of LC/cross-linked polymer phase supported by theoretical calculation showed no critical point. Instead, the binodal curve exhibits an upward asymptotic behavior as the LC volume fraction approaches unity due to domination arising from network elasticity, particularly at high LC volume fraction. An examination of the effect of cross-links segment length and network functionality on the phase diagram of LC/cross-linked polymer showed that the segment length between cross-links exerts a greater influence.