bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Use of Mosaic Target for the Deposition of Ferroelectric Bismuth Titanate Thin Films
Authors: Ghosh P.K. , Azimi M.E. 
Published: April 2011

ABSTRACTIon beam sputter deposition using a Kaufman source is a well-established technique for fabricating thin films. This method has the capability for yielding smooth surfaces and depositing uniform films over a large area. We have used this technique, in the past, with a 5″ diameter target to deposit smooth ferroelectric bismuth titanate (Bi4Ti3O12) films. One of the major obstacles was fabricating the large target with the desired composition. To reduce cost by simplifying the target preparation process we developed a ‘mosaic’ target to deposit ferroelectric Bi4Ti3O12films. Films were deposited at different substrate temperatures. Measurements show that the post-annealing of the deposited films results in measurable ferroelectric properties and enhanced low field dielectric behavior in the films. The discussion will include the target fabrication, the observed properties of the resultant films, and the effect of the deposition and post-annealing temperatures on the film properties.
Preparation of PbZrxTi1−xO3 Films on Si Substrates Using SrTiO3 Buffer Layers
Authors: Tokumitsu Eisuke , Itani Kensuke , Moon Bum-Ki , Ishiwara Hiroshi 
Published: April 2011

ABSTRACTWe report the preparation of PbZrxTi1−xO3 (PZT) films on Si substrates with a SrTiO3 (STO) buffer layer. STO buffer layers and PZT films were formed on Si substrates by the electron-beam assisted vacuum evaporation technique and sol-gel technique, respectively. By evaporating a thin (8nm) metal Sr layer prior to the STO deposition, which deoxidizes the SiO2 layer at the Si surface, (100)- and (111)-oriented STO thin films can be grown on Si(100) and (111) substrates, respectively. It is shown that a strongly (100)-oriented PZT film is grown on STO(100)/Si(100), whereas a strongly (111)-oriented PZT film is obtained on STO(111)/Si(111). It is also found that the STO buffer layer remains intact even after the PZT deposition. Secondary ion mass spectrometry (SIMS) analysis showed that the STO barrier layer was effective in preventing diffusion of Pb into the Si substrate.
Growth of Ferroelectric PLT Thin Films on Various Single Crystal Substrates
Authors: Kang Y.M. , Ku J.K. , Baik S. 
Published: April 2011

ABSTRACTFerroelectric Pb1−xLaxTi1−x/4(x = 0 ∼ 0.28) epitaxial thin films were prepared on MgO(001), SrTiO3(001), and LaAlO3(001) single crystalline substrates using pulsed laser deposition. The change in lattice constants of PLT films by La concentration, x, was investigated systematically for each substrate. RBS studies revealed that the composition of PLT films is consistent with that of the targets. Lattice constants, degree of c-axis orientation, crystal quality of the PLT films were characterized by symmetric and asymmetric X-ray scans. The strain which occurred during the cubic to tetragonal phase transition seemed to be the major factor determining the c-axis orientation configuration, i.e., 90° domain structure and the crystal quality of PLT films.
Anisotropic Dynamic Strain Sensors Based on Ferroelectric PZT Films
Authors: Bakirov A.A. , Sviridov E.V. , Dudkevich V.P. 
Published: April 2011

ABSTRACTThe present paper deals with anisotropie dynamic strain sensors based on polycrystalline Pb(Zr0.53Ti0.45W0.01Cd0.01)O3 films. The films were deposited on ceramic substrates designed to operate at radiofrequencies. The planar interdigitated Al electrodes were deposited on the film surfaces. To pole the films the sawtooth monopolar pulses of the amplitude ranging from 5 · 107 to 8 · 107 V/m were used during the heating of the films from room temperature to 300 °C and the following cooling down to room temperature (Tc = 360 °C).
Processing Path and The Evolution of Crystallinity in Rapidly Solidified Glassy Alloys
Authors: Otooni M. A. 
Published: April 2011

AbstractAtomic transport properties in rapidly solidified glassy alloys are not fully understood in spite of much experimental data on the subject. Nevertheless, a thorough understanding of these properties is of fundamental importance when studying the practical limits of the application of rapidly solidified glassy alloys.Several attempts are made in this paper to explain our experimental results on the mechanical flow properties near the transition temperature, Tr. These results are interpreted in the context of possible operating mechanisms such as diffusion and/or relaxation processes. Some inferences have been made on the nature of viscosity and its fluctuation near the transition temperature. The linear temperature dependence of the viscosity near the transition temperature is explained by invoking the free-volume concept for the viscosity of the glassy alloys.These results are used to provide appropriate data for the selection of feasible processing paths which will produce alloys with advanced thermomechanical properties.
Rapidly Solidified Nb Base Alloys With High Carbide Content
Authors: Sheftel Elena N. , Kaputkin Dmitry E. 
Published: April 2011

AbstractNb base alloys with high Zr and C contents possess high strengths at up to 1400°C, but their low-temperature ductilities are unacceptably low due to nearly continuous rough eutectic carbide net along grain boundaries. The net has been broken by rapid solidification (RS). The structure and microhardness of these alloys after RS as well as after consequent compacting and/or annealing have been studied.
Modelling of Two-Dimensional Grain Growth and Crystallization
Authors: Krakow William 
Published: April 2011

AbstractPC based computer programs have been developed to simulate twodimensional microstructural grain growth either by nucleation or transformation from an amorphous phase. By controlling the parameters of the rate of grain growth, nucleation rate, depletion zone size, and changes in these latter two variables most grain growth conditions can be achieved in practice. Several cases have been explored which include: constant nucleation rates, both increasing and decreasing rates, and the instantaneous saturation of nucleation sites. The evolution of domain sizes can be investigated which is dependent on the effective rate of nucleation during various stages of grain growth. Real time graphics displays are present the instantaneous growth parameters and their changes as well as information on fractional area growth.
Hall-Petch Basis for Assessing Alloy Strengthening
Authors: Armstrong Ronald W. , Douthwaite R. Michael 
Published: April 2011

AbstractThe Hall-Petch relation σ = σo + kl−½, provides for the separate consideration of friction stress strengthening within the polycrystal grain volumes through σo and grain boundary strengthening through the product of the microstructural stress intensity k and the reciprocal square root of the grain diameter l Smaller grain diameters are normally obtained at higher alloy contents as illustrated for yield strength results reported for different face-centered-cubic Al-Mg alloys. Results on Al-Li alloy give an interesting example of substantial grain boundary strengthening that is associated with reduced ductility of the material. More complete results reported for the Cu-Al system, allow an evaluation of the strengthening component dependencies on alloy composition, in particular, connecting with a predicted square root of grain boundary obstacle stress in k. The much studied Cu-Zn alloys bring out subtle changes in σo and k
Hall-Petch Analysis of Yield, Flow and Fracturing
Authors: Armstrong Ronald W. 
Published: April 2011

AbstractThe explanation for the grain size dependence of the polycrystal yield stress or cleavage stress of steel, investigated in complementary studies by Hall and Petch, is rooted in dislocation pile-up theory first described by Eshelby, Frank and Nabarro just a step away from previous theoretical work on the stress concentrating properties of cracks. Beginning from Cottrelllocking of dislocations at grain boundaries by carbon that is responsible for the pronounced yield point behavior and the grain size dependence of the yield strength of steel, the same concepts have been shown to apply for the complete stress/strain behavior of steel and other materials. Other mechanical properties such as fatigue strength show a similar dependence on grain size. A notable application of such grain size based considerations has been to the ductile-brittle transition and fracture toughness properties of steel and related materials — because refinement of grain size both strengthens a material and improves its fracture toughness. Early results for the polycrystal hardness dependence on grain size gave evidence that the strength benefits of grain size refinement ought to extend to ultrafine grain sizes.
Microsrtuctures and Electrical Characterization of CVD-W and Mo Films as Contacts in Photocells
Authors: Gesheva Kostadinka A. , Stoyanov G. I. , Stefanov R. , Vlakhov E. S. 
Published: April 2011

AbstractTungsten and molybdenum hexacarbonyls were used as precursors in chemical vapour deposition process for preparation of W and Mo thin films. Pyrolitical decomposition of these precursors proceeds at temperatures of 250–400°C. Thin films with thicknesses in the range of 0,02–1 μm were deposited on different substrates - bare or covered with CdTe glass, and monocrystalline Si. Microstructural studies performed by Reflection High Energy Electron Diffraction (RHEED) method showed that films deposited tend to grow textured. This is discussed as probably due to differences in the growth rate for various crystal planes. The sheet resistances of the as-deposited W and Mo films are in the range of 20–30 Ω/□ for thicknesses of 0.15 μm. After thermal annealing the resistance of W films drops to about 2 Ω/□ and for Mo films to about 9Ω/□. Decreasing in the resistivity of the films is tightly connected with the decreasing in the impurities concentration. These impurities are considered to be in the base of the observed behaviour of the temperature dependence of the electrical resistance of the films. The CVD-W and Mo films are studied as back contacts on CdTe layer in CdS/CdTe photocells. In the paper some preliminary results are presented for the sheet and contact resistances when CVD W and Mo films are deposited at lower temperatures on the surface of CdTe layers, deposited by closespaced sublimation method. The thin film materials, produced by CVD technology look promising with respect to the required high deposition rates and extremely wide deposition areas in the mass production of solar cells.
Tin Dioxide Films Prepared by a Rapid Chemical Vapor Deposition Method
Authors: Nishino Junichi , Ohshio Shigeo , Saitoh Hidetoshi , Kamata Kiichiro 
Published: April 2011

AbstractA rapid chemical vapor deposition method was studied for the preparation of tin dioxide films. The films were prepared under atmospheric-pressure on fused quartz and Si substrates at 200° to 600°C using bis(2,4-pentanedionato)tin as a source material. SnO2 films obtained at 300° to 600°C had polycrystalline rutile structures, while the film deposited at 200°C was amorphous judging from the XRD patterns. The deposition rate of SnO2 increased with increasing substrate temperature and vaporization temperature of the source material. The maximum deposition rate was 440 nm min−1. The transmittance of SnO2, deposited at Ts = 600°C, was more than 70% in the wavelength range 400–800 nm.
Chemical Vapor Deposited β-SiC for Optics Applications
Authors: Goela Jitendra S. , Pickering Michael A. , Taylor Raymond L. 
Published: April 2011

AbstractThe fabrication, properties and optics applications of transparent and opaque Chemical Vapor Deposited (CVD) β-SiC are reviewed. CVD-SiC is fabricated by the pyrolysis of methyltrichlorosilane, in excess H2, in a low-pressure CVD reactor. The CVD process has been successfully scaled to produce monolithic SiC parts of diameter up to 1.5 m and thickness 2.5 cm. The characterization of CVD-SiC for important physical, optical, mechanical and thermal properties indicate that it is a superior material for optics applications. CVD-SiC properties are compared with those of the other candidate mirror and window materials. SiC process/property relationships are discussed, emphasizing the differences in process conditions, microstructure, and properties between transparent and opaque CVD-SiC.
Frictional Forces in Thin Liquid Films
Authors: Urbakh Michael , Klafter Joseph , Daikhin Leonid 
Published: April 2011

ABSTRACTShear thinning of confined liquids is studied in the framework of the time dependent Ginzburg-Landau equation coupled to a shear-induced velocity field. Scaling relationship between the effective viscosity and the shear rate is analytically derived with an exponent which depends on the velocity profile within the liquid and on the boundary conditions. The velocity profile is derived in the limit of low shear rate. Thinning is observed for shear rates faster than typical liquid relaxation rates. Relevance to existing systems and predictions amenable to new experiments are discussed.
Surface Crystallization and Thin Film Melting in Normal Alkanes
Authors: Wu X. Z. , Shag H. H. , Ocko B. M. , Deutsch M. , Sinha S. K. , Kim M. W. , King H. E. , Sirota E. B. 
Published: April 2011

ABSTRACTNormal alkanes of carbon number n>14 exhibit surface crystallization at their liquid-vapor interface. This has been investigated with x-ray reflectivity, grazing incidence scattering and surface tension measurements. The structure and thermodynamics of the surface layer is consistent with a monolayer of the bulk rotator phase occurring at the surface above the bulk melting temperature. On the other hand, thin films of alkanes on SiO2, exhibit a reduction of the melting temperature. The surface crystalline phase is observed for carbon number n>14. The vanishing of surface phase for small n may be due to a transition from surface freezing to surface melting behavior. These measurements can yield the relative surface energies of the various phases.
Dynamics of Nanometer SiO2 Particles and their Coalescence Characteristics
Authors: Blaisten-Barojas Estela , Liu Ling , Zachariah Michael 
Published: April 2011

ABSTRACTVarious mechanisms of glassy transformations involving computational annealing were investigated by Molecular Dynamics simulations. Large clusters of silicon dioxide ranging from sub to nanometer size regime were considered. Silica is both a prototype ceramics and glassy material. Silica particles are fabricated in flow and flame reactors to design novel granular materials which depend strongly on the heating and cooling processes. During these processes extensive thermally driven relaxation in growing clusters allow for configurational changes from a liquid-like cluster to a glassy cluster. Crystal-like structures were investigated as well. Cooling rates comparable to experimental rates were achieved in these simulations. We find that the glass transition temperature decreases with decreasing cluster size. Calculations were performed by implementing a massively parallel particle decomposition schema of Molecular Dynamics with an excellent speedup and a significant decrease of complexity.
Molecular Dynamics Computer Simulations of Diffusion in Porous Silicates
Authors: Heffelfinger Grant S. , Pohl Phillip I. , Frink Laura J. D. 
Published: April 2011

ABSTRACTIn this work a newly developed dual control volume grand canonical molecular dynamics technique simulates the diffusion of gas in a cylindrical pore. This allows spatial variation of chemical potential and hence an accurate simulation of steady state pressure driven diffusion. The molecular sieving nature of imicroporous imogolite models and the Knudsen effect are discussed and compared with experimental data.
Dielectric Relaxation in Small Confining Geometries
Authors: Arndt M. , Kremer F. 
Published: April 2011

ABSTRACTBroadband dielectric spectroscopy (10−2 Hz – 109 Hz) is employed to study the molecular dynamics of the glassforming liquid salol (phenyl salicylate) being contained in (dielectric inactive) porous glasses with pore sizes of about 2.5 nm, 5.0 nm and 7.5 nm. Besides the bulk relaxation (I) of salol, two further dielectric loss processes are observed due to the geometrical constraint of the inner surfaces of the pores: the “interfacial relaxation” (II) and a Maxwell-Wagner polarization (III). The “interfacial relaxation” is assigned to the restricted dynamics of the molecules close to the inner surface of the pores. It shows a strong pore-size dependence for pores < 5 nm both in relaxation rate and dielectric strength.
Vesicles and Passages Between Lamellas inLαMembrane Phases
Authors: Golubović Leonardo 
Published: April 2011

ABSTRACTWe consider entropic effects of vesicles and passages confined between lamellas in fluid membrane lamellar (Lα) phases. We show that their presence induces attractive interactions between lamellas which strongly compete with steric repulsion in the vicinity of phase transitions from the lamellar to isotropic membrane phases. An interplay between steric repulsion and entropic interactions mediated by passages and vesicles determines the inter-lamellar distance reached at these transitions. This distance crucially depends on the membrane Gaussian bending rigidity constant.
Surfactant Self-Assemblies Near Contact Lines and their Effect on Wetting by Surfactant Solutions
Authors: Frank B. , Garoff S. 
Published: April 2011

ABSTRACTSurfactant self-assembly at the liquid-vapor, solid-liquid, and solid-vapor interfaces controls the wetting behavior of advancing surfactant solutions. While different surfactants exhibit different static and dynamic wetting properties, we show that these behaviors can be understood through an examination of microscopic structures driven by surfactant-surface interactions. We examine surfactant solutions exhibiting complete and partial static wetting as well as spreading by dendritic pattern formation and unsteady, stick-jump behavior. In each case, the observed behavior is related to the structure of the surfactant assemblies in the vicinity of the contact line.
Static and Dynamic Perturbations of Droplet Microemulsion by Confinement and Adsorption of Polymer
Authors: Lal Jyotsana , Farago Bela , Auvray Loic 
Published: April 2011

ABSTRACTThe effects induced on the structure and dynamics of dilute microemulsion droplets by the confinement of polymer chains inside the droplets and by the adsorption of polymer on the surfactant shells from the outer continous phase were studied. The local structure changes were observed by small angle neutron scattering (SANS). The curvature fluctuations and the size distribution of the droplets increase for both chains inside and outside by different possible mechanisms, an induced size polydispersity minimizing osmotic stresses in the first case, a lowering of the film rigidity in the second one. Neutron spin echo techniques (NSE) were also used to probe the shape fluctuations of the same droplets with and without polymer. A sharp characteristic peak due to the contribution of the 1=2 mode is exhibited by the spectrum of relaxation times as a function of wavevector q. The height of this peak is decreased with the addition of polymer. i.e. the fluctuation of the 1=2 modes are dampened with the addition of polymer. The effect on the elastic coefficient K of the surfactant layer will be discussed below.
Structural Characterization of Nanocrystalline Mo and W Carbide and Nitride Catalysts Produced by Co2 Laser Pyrolysis
Authors: Bi Xiang-Xin , Chowdhury K. Das , Ochoa R. , Lee W. T. , Bandow S. , Dresselhaus M. S. , Eklund P. C. 
Published: April 2011

ABSTRACTUsing both XRD and HRTEM lattice imaging, we have shown that CO2 laser pyrolysis (LP) produces nanoscale transition metal carbide and nitride catalysts, including cubic Mo2C, Mo2N, and W2N, which possess highly crystalline structures in their as-synthesized form In contrast, LP-produced W2C in its hexagonal phase is disordered. Clear lattice expansion, induced by the small crystallite size of the nanoparticles has been observed for LP-produced Mo2C particles, which have a typical crystallite size of 2 nm. No carbon coating was observed in HRTEM for LP-produced Mo2C particles. Furthermore, Mo=N and Mo=C bonding in Mo2N and Mo2C, respectively, were identified by an XPS measurement, which also reveals the presence of a thin oxide layer formed on the particle surface during the passivation process. Finally, the average crystallite sizes determined from HRTEM and XRD are in good agreement, indicating that the line broadening observed in XRD is due to the small crystallite size of the nanoparticles.
Effect of the Heat Treatment on the Lithium Insertion Process in MoO3
Authors: Yebka B. , Julien C. 
Published: April 2011

AbstractWe have studied the electrochemical characteristics of Li/MoO3-based batteries in relation with the morphology of the cathode-active material. The oxides and oxide-hydrates of molybdenum have been prepared with various degrees of heat treatement. The samples were characterized by X-ray diffraction, Raman spectroscopy, and conductivity measurements. The effect of the heat treatment on structural, optical and electrochemical properties are presented in this work. Thermodynamics and kinetics of lithium insertion were studied in MoO3 cathodes. Diffusion coefficients and enhancement factors were calculated as functions of the degree of lithium intercalation in the domain of the galvanic cell reversibility.
Complete Conductivity Spectra of Crystalline and Glassy Fast Ion Conductors Up to Far Infrared Frequencies
Authors: Cramer C. , Graeber R. , Ingram M.D. , Saatkamp T. , Wilmer D. , Funke K. 
Published: April 2011

AbstractComplete conductivity spectra have been taken of a lithium ion conducting glass of composition B2O3 · 0.56Li2O · 0.45LiBr and of lithium stabilized Na-β″-alumina, at various temperatures. — In the glass, it has forthe first time been possible to separate the hopping and vibrational contributions to theconductivity. The resulting hopping conductivity spectra display high-frequency plateaux similar to those known to exist in crystalline solid electrolytes like RbAg415 and Na-β-alumina. In the dispersive regime, the spectra are characterized bytwo different power-law exponents, p = 0.6 and q = 1.3. The data are evaluated by combined application of the jump relaxation model and the dynamic structure model. — Na-β″-alumina has pronounced high-frequency plateaux between about 200 GHz and 400 GHz. The hopping observed in the spectra can be decomposed into hops that are a priori unsuccessful and others that can be treated in terms of the jump relaxation model. The latter fraction is found to increase with increasing temperature.
A Comparative Study of LiMn204 From Various Sources
Authors: Oyang B. , Greenbaum S. G. , Boer M.den , Massucco A. , McLin M. , Shi J. , Fauteux D. 
Published: April 2011

AbstractA process recently developed at Arthur D. Little, Inc. has enabled the direct and rapid production of LiMOx intercalation cathode materials having specific and controlled geometric and topographic attributes. Results of a comparative study of the electrochemical and spectroscopic characteristics of LiMn204 from several commercial sources and LiMn204 prepared using our process are reported. Improved electrochemical performance observed for the LiMn204 cathode material produced using ADL's process are tentatively related to the small and uniform grain size and to the possible additional influence of electronic defects associated with surface states.